Foundation & Soil Investigation

FOR INTERNAL CIRCULATION ONLY

user’s manual of Construction

Soil Investigation&

Foundations

Construction ManagementPower Grid Corporation of India Limited

(A Government of India Enterprise)

DOCUMENT CODE NO. : CM/TL/SOIL INVESTIGATION & FOUNDATIONS/FINAL/98 OCT, 1998

CHAIRMAIN &

MANAGING DIRECTOR’S MESSAGE

It gives me immense pleasure to learn that Construction Management has come out with

further four volumes of User’s Manual of Construction : ‘Soil Investigation & Foundations’,

‘Pile & Well Foundations’, ‘Contracts Management’ and ‘Transformers & Reactors’.

The various changes in the wake of rapid advances in technologies and growing competition

on global basis has made it imperative to conceptualise the methods for optimizing our

resources; the 5M’s namely men, money, machines, materials and methods. They are the

basics to realize a construction project and time, cost & quality are its critical parameters.

The construction of transmission line is a wide canvas and complex in nature that needs a

multi disciplinary approach. However, no standard guidelines or manuals in consolidated

form are available for its various construction activities.

I compliment the Construction Management team for bringing out these manuals wherein

the main focus of the authors has been to combine the theoretical & practical aspects drawn

from their respective experience in transmission lines construction, academic institutions

and industry. An attempt has been made to explain the fundamentals in a simple & lucid

language. I am convinced that these manuals will act as guidelines and serve the needs of

our practicing Managers & site Engineers.

I should be our endeavour to follow these systems and procedures to enhance the quality of

construction management in transmission and quality power. More such User’s Manuals

covering the other related fields should be prepared for the benefit of the ultimate users at

our remote sites as well as for the younger generation inducted in POWERGRID.

(R.P. SINGH)

CONTENTS

SECTION-I

SOIL INVESTIGATION

SL. NO. DESCRIPTION PAGE NO.1.0 INTRODUCTION 11.1 PURPOSE OF SOIL INVESTIGATION 11.2 TYPE OF TESTING 31.2.1 BORING 31.2.2 SHELL AND AUGER BORING 31.3 SAMPLING 41.3.1 GENERAL 41.3.2 DISTURBED SAMPLE 41.3.3 UNDISTURBED SAMPLE 51.3.4 UNDISTURBED SAMPLING IN COHESIVE SOIL 61.3.5 UNDISTURBED SAMPLING USING PISTON SAMPLER 61.3.6 UNDISTURBED SAMPLING IN COHESIONLESS SOILS 71.3.7 TYPES OF SAMPLERS 71.4 INSITU PERMEABILITY TEST 71.4.1 PUMP-IN TEST 81.5 STANDARD PENETRATION TEST 91.6 STATIC CONE PENETRATION TEST 111.7 DYNAMIC CONE PENETRATION TEST 121.8 VANE SHEAR TEST 121.9 PLATE LOAD TEST 132.0 TRIAL PIT 152.1 GROUND WATER 182.2 ELECTRICAL RESISTIVITY TEST 192.3 FIELD INVESTIGATION ROCK 202.4 LABORATORY TESTING 242.5 REPORT 292.6 RATES & MEASUREMENTS 372.7 SPECIFIC REQUIREMENTS FOR GEOTECHNICAL

INVESTIGATION AT RIVER CROSSINGS

39

2.8 SUMMARY OF RESULTS OF LABORATORY TEST ON

SOIL AND WATER SAMPLES

40

2.9 TOOLS AND PLANTS FOR SOIL INVESTIGATIONS 423.0 GUIDELINES FOR CONDUCTING SOIL INVESTIGATION

IN TRANSMISSION LINE

44

SECTION-II

TOWER FOUNDATIONS

CHAPTER-1

GENERAL

SL. NO. DESCRIPTION PAGE NO.1.0 TOWER FOUNDATIONS1.1 LOADS, SAFETY FACTORS AND SETTLEMENT1.2 CLASSIFICATION OF SOILS1.3 PROPERTIES OF SOILS1.4 DATA FOR FOUNDATION DESIGN

CHAPTER-2

TYPES OF FOUNDATIONS

SL. NO. DESCRIPTION PAGE NO.2.0 INTRODUCTION2.1 TYPES OF FOUNDATION

CHAPTER-3

CLASSIFICATION AND STUB SETTING

SL. NO. DESCRIPTION PAGE NO.3.0 LINE CONSTRUCTION3.1 INVESTIGATION AND SURVEY3.2 TRANSPORTATION3.3 FOUNDATION3.4 PREPARATION OF FOUNDATION SITE3.5 TYPE OF FOUNDATION TO BE ADOPTED3.6 PIT MARKING3.7 SHORING AND SHUTTERING3.8 DEWATERING3.9 EXCAVATION IN ROCK3.10 PROCEDURE FOR SETTING STUBS OF SITE BY

COMBINED STUB SETTING

CHAPTER-4


SL. NO. DESCRIPTION PAGE NO.4.0 CONCRETE TYPE4.1 MIXES4.2 SIZES OF AGGREGATES4.3 GRAVEL SUB-BASE4.4 REINFORCEMENT4.5 FORM WORK4.6 MIXING, PLACING AND COMPACTING OF CONCRETE4.7 BACK FILLING4.8 CURING

CHAPTER-5

PROTECTION OF FOUNDATION

SL. NO. DESCRIPTION PAGE NO.5.0 CONCRETE TYPE5.1 UPLIFT RESISTANCE

5.2 REVETMENT5.3 BENCHING5.4 PROTECTION OF FOUNDATION AGAINST CHEMICAL

WATER5.5 MEASUREMENT OF VOLUME FOR REVETMENT AND

BENCHING

CHAPTER-6

CONCRETE TECHNOLOGY

SL. NO. DESCRIPTION PAGE NO.6.1 INTRODUCTION6.2 PROPORTIONING CONCRETE MIXTURES6.3 FRESH CONCRETE6.4 HANDING AND BATCHING CONCRETE MATERIALS6.5 BATCH PLANTS AND MIXERS6.6 READY MIXED CONCRETE6.7 MOVING AND PLACING CONCRETE6.8 CONSOLIDATING CONCRETE6.9 RECOMMENDED VIBRATION PRACTICES6.10 FINISHING AND CURING CONCRETE6.11 PLACING CONCRETE IN COLD WEATHER6.12 PLACING CONCRETE IN HOT WEATHER

CHAPTER-7

MECHANISED CONSTRUCTION

SL. NO. DESCRIPTION PAGE NO.7.0 INTRODUCTION7.1 MECHANICAL CONSTRUCTION EQUIPMENT & THEIR

APPLICATIONS7.2 WORK STUDY ON CONSTRUCTION EQUIPMENT7.3 PLANT PURCHASE VERSUS PLANT HIRE7.4 SAFETY PROGRAMME7.5 WHY MECHANICAL CONSTRUCTION EQUIPMENT?7.6 PRODUCTION OUT PUTS7.7 PRODUCTION TRIAL7.8 ECONOMIC LIFE

CHAPTER-8

STANDARD FIELD QUALITY PLAN

SL. NO. DESCRIPTION PAGE NO.

8.0 STANDARD FIELD QUALITY PLAN FOR TRANSMISSION

LINE PACKAGES

CHAPTER-9

GUIDELINES

SL. NO. DESCRIPTION PAGE NO.9.0 PIT MARKING9.1 STUB SETTING9.2 CONSTRUCTION MATERIALS9.3 INSTALLATION OF REINFORCEMENT STEEL & FORM

BOXES9.4 MIXING, PLACING AND COMPACTING OF CONCRETE

CHAPTER-10

CHECK FORMAT

SL. NO. DESCRIPTION PAGE NO.1.0 CHECK FORMAT FOR PIT MARKING2.0 CHECK FORMAT FOR FOUNDATION CLASSIFICATION3.0 CHECK FORMAT FOR STUB SETTING4.0 CHECK FORMAT FOR CONSTRUCTION MATERIALS5.0 CHECK FORMAT FOR INSTALLATION OF

REINFORCEMENT STEEL & FORM BOXES6.0 CHECK FORMAT FOR MIXING, PLACING AND

COMPACTING OF CONCRETEANNEXURE-IA : TOOLS & PLANTS FOR EXCAVATION,

STUB SETTING AND CONCRETINGANNEXURE-IB : MANPOWER FOR EXCAVATION, STUB

SETTING & CONCRETING GANGANNEXURE-IC : REINFORCED CONCRETE RETAINING

WALLS

SECTION-1

Soil Investigation

___________________________________________________________________________

SECTIONONE

___________________________________________________________________________

SOIL INVESTIGATION

Back to contents page

1.0 INTRODUCTION


An investigation of sill is essential for judging its suitability for the proposed

engineering works and for preparing adequate and economic design. In

general, the purpose of soil investigation is to obtain necessary information

about the soil and to know the engineering properties of soil which will be

affected.

Earlier, the soil investigation of locations of transmission line towers was not

very popular and general practice had been to adopt 4to 5 types of standard

design foundations for different classes of soils encountered. Only special

foundations in river beds necessitating huge volumes of concrete were

investigated for properties of soils. Now the soil investigation of normal

foundations is also felt necessary in good number of locations in the 400 kv

transmission lines which helps in better choice of standard foundation &

development of new designs to achieve overall cost, economy and minimise

chances of failure.

1.1 Purpose of soil investigation:


a) Technical Consideration

b) Economic Consideration

a) Technical Considerations : An inadequate design or a conservative

choice of standard foundation can lead to a failure causing long outage

of transmission line. In modern practice, a large variety of standardised

foundations are being pre-designed with different sets of properties

attached to forseeably encountered soils. Aarge varity of soils are

encountered as length of transmission lines are increasing with voltage

llevels going up. To obtain optimal choice of pre-designed standard

foundations,it is very much necessary to have a proper scientific

knowledgfe of properties of soil against the back-drop of increasing

sizes of towers, foundations, loads, thereby minimising the risk of fail-

ures of foundations.

b) Economic Considerations : Among site erection activities, the

foundations form the major chunk of the cost. The cost of foundations

constitures 50 to 70% of the toral cost of erection depending upon

terrain conditions. It forms 10 to 15% of the total cost of transmission

line. A considerable saving in the foundation cost can be achieved by

having detailed knowledge of soil properties and making wide usage of

them in designing the foundations in sufficient types and classification

of the foundations in field to match the most optimum size and type of

foundation.

1.2 Types of Testing :


1.2.1 Boring : Bore holes are generally taken at specified locations to obtain

information about the sub soil profile, its nature and strength and to collect soil

samples for strata identification and conducting laboratory tests. The minimum

diameter of the bore hole shall be 150 mm and boring shall be carried out in

accordance with the provision of IS:1892. Casing pipe is used in the bore hole

to support its side when a side fall is suspected to occur inside the borehole.

When casing pipe is used, it shall be ensured that its bottom end is at all times

less than 15cms above the bottom of the borehole and not below the level at

which the test has to be conducted or sampling has to be done. In case of

cohesion less soils the advancement of the casing pipe shall be such that it

does not disturb the soil to be tested or sampled. The casing shall be advanced

by slowly turning the casing pipe and not by driving.

1.2.2 Shell and Auger Boring: Cylindrical augers and shells with cutting edge on

teeth at the lower end can be used for making deep boring. Hand operated

rings are used for depths up to about 25m and the mechanized rings up to 50m.

Shell and auger boring can be used in all types of soil free from boulders. For

cohesion less soil below ground water table, the water table in the borehole

shall always be maintained at or above the ground water level. The use of

chisel bit is permitted in hard strate with SPT-N value greater than 100.Chisel

bits are also used to extend the borehole through local obstructions such as old

construction boulders, rocky formation etc. The various activities to be

conducted during the boring include standard penetration test, collection of

undisturbed and disturbed samples of soil at various depths, logging of

different layers of soil, depth of subsoil water and preparation of data sheets.

Further a series of tests have to be conducted on the disturbed and undisturbed

samples of soil at laboratory.


1.3 Sampling :


1.3.1 General :


(a) Sufficient number of soil samples shall be collected. Disturbed soil

samples shall be collected for field identification and conducting tests

such as sieve analysis, index properties, specific gravity, chemical

analysis etc. Undisturbed sample shall be collected to estimate the

physical strength and settlement properties of the soil. All the

accessories required for sampling and the method of sampling shall

confirm to IS:2132.

(b) All the samples shall be identified with date, bore hole and trial pit

number, depth f sampling etc. It is also essential to mark and arrow

pointing towards the top surface of the sample as the soil was in-situ.

Care shall be taken to keep the core samples and box samples vertically

with the arrow directing upwards . The tube samples shall be properly

trimmed at one end and suitably caped and sealed with molten paraffin

wax.

1.3.2 Disturbed Sample


a) Disturbed soil samples shall be collected in bore holes at regular

itervals.Jar samples weighing approximately 10N shall be collected in

boreholes at 0.5m intervals starting from a depth of 0.5 m below ground

level and at every identifiable change of strata to supplement the boring

records. Samples shall be immediately stored in air tight jars and shall fill

the jar as far as possible.

b) In elevated areas, if superficial material is available in plenty, then bulk

samples from a depth of about 0.5m below ground level shall be

collected to establish all the required properties to use it as a fill

material. Disturbed samples weighing about 250 N shall be collected at

shallow depths and immediately stored in polythene bags as per

IS:1892. The bags shall be sealed properly to avoid any change in

moisture content and they shall be kept in wooden boxes.

1.3.3 Undisturbed Sample :


In each borehole undisturbed sample shall be collected at every change of

strata and depths of 1.0 4.0 7.0,10.013.0,15.5m and water at regular intervals

of 3.0m and as directed by the Engineer. The depth interval between the top

levels of undisturbed sampling and standard penetration test shall not be less

than 10.m. Undisturbed samples shall be of 100m dia and 450 mm length.

Samples shall be collected in such a manner that the structure of the soil and

its moisture content do not get asserted. The specifications for the accessories

required for sampling and the sampling procedure shall conform to IS:1892

and IS:2132. Undisturbed sampling in sand shall be done using compressed air

technique mentioned in IS:8763. Thin walled sampler shall be used to collect

undisturbed samples by pushing the tube into the soil. The sampling tube shall

have a smooth finish on both surfaces and minimum effective length of

450mm. The area ratio of sampling tubes shall be less than 12.5%. However,

in case of very stiff soils, area ratio up to 20% shall be permitted. Area ratio

should be as low as possible. In no case it should be greater than 25%. The

inside clearance of the sampler should lie between 1 to 3 percent and the

outside clearance should not be much greater than the inside clearance.

1.3.4 Undisturbed Sampling in Cohesive Soil


Undisturbed samples in soft to stiff cohesive soils shall be obtained using a

thin walled sampler. In order to reduce the wall friction, suitable precautions

such as oiling the surfaces shall be taken.

1.3.5 Undisturbed Sampling using Piston Sampler


Undisturbed samples in very loose saturated sandy and silty soils and very soft

clays shall be obtained by using a piston system. In soft clays and silty clays,

with water standing in the casing pipe, piston sampler shall be used to collect

undisturbed samples. During this method of sampling expert supervision is

called for. Accurate measurement of the depth of sampling, height of sampler,

stroke and length of sample recovery shall be recorded. After the sampler is

pushed to the required depth, both the sampler cylinder and piston system shall

be drawn up together ensuring that there shall not be any disturbance to the

sample which shall then be protected from changes in moisture content.

1.3.6 Undisturbed Sampling in Cohesion less Soils


Undisturbed samples in cohesionless soils shall be obtained as per the

procedure given in IS:8763. Compressed air sampler shall be used to take

samples of cohesionless soils below water table.

1.3.7 Type of Samplers:


Samplers which shall be used commonly at sites are open drive sampler,

stationary piston sampler, and Rotary samplers depending upon the mode of

operation. Open drive types can be both the thick and thin wall samplers and

the stationary piston and the rotary types are thin wall sampler - depending

upon the area ratio (Fig.1 & Fig.2)

D22 - D12

Area ratio = ------------------- X 100 Percent D12

D3 - D1Inside Clearance = ---------------- X 100 percent

D1

D2 - D4

Outside Clearance = ---------------- X 100 percent

D4

1.4 In situ permeability test : In situ permeability test shall be conducted to

determine the water percolation capacity of overburden soil. The specification

for the equipments required for the test and the procedure of testing shall be in

accordance with IS: 5529, part -1. When it is required to carry out the

permeability test for a particular section of the soil strata above the ground

water table, bentonite slurry shall not be used while boring.


1.4.1 Pump-in test:


Pump-in test shall be conducted in the bore hole/trial pit by allowing water to

percolate into the soil. Choice of the method of testing shall depend on the soil

permeability and prevailing ground water level.

a) Constant Head Method ( in bore hole):

This test shall be conducted in boreholes where soils have a high

permeability i.e. it shall be allowed into the borehole through a

metering system ensuring gravity flow at constant head so as to

maintain a steady water level in the borehole. A reference mark shall

be made at a convenient level which can be easily seen in the casing

pipe to note down the fluctuations of water level. The fluctuation shall

be counteracted by varying the quantity of water flowing into the

borehole. The elevation of water shall be observed at every 5 minute

interval. When three consecutive readings show constant value, the

necessary observations such as flow rate, elevation of water surface

above test depth, diameter of casing pipe etc. Shall be made and

recorded as per the proforma recommended in IS:5529, PART-I,

Appendix-A.

b) Falling head method ( in bore hole)

This method shall ve adopted for relatively less permeable soils where

the discharge is small and where the soil can stand without casing. The

test section shall be seated by the bottom of the borehole and a packer

at the top of the test section. If the test has to be conducted at an

intermediate section of a prebored hole then, double packer shall be

used . Access to the test section through the packer shall be by means

of a pipe which shall extend to above the ground level. Water shall be

filled into the pipe upto the level marked just below the top of the pipe

and water allowed to drain into the test section. The water level in the

pipe shall be recorded at regular intervals as mentioned in

IS:5229,part-I, Appendix- B. The test shall be repeated till constant

records of water level are achieved.

1.5 Standard penetration Test :


The test shall be performed in a clean hole, 55 to 150 mm in diameter. A

casing or drilling mud shall be used to support the sides of the hole. The test

shall be conducted at depth of 2.0, 3.0, 5.0, 6.0, 8.0, 9.0, 11.0, 12.0, 14.0, m

and at 3.0m intervals and every change of strata and as per the direction of the

Engineer-in-charge. A standard thick wall split-tube sampler, 50.8 mm shall be

driven into the undisturbed soil at the bottom of the hole under the blows of a

65 kg drive weight with 75 cm free fall. The minimum open length of the

sampler should be 60 cm. The sampler shall be first driven through 15 cm as a

seating drive. It shall be further driven through 30cm or until 100 blows are

applied. The number of blows required to give the sampler 30 cm beyond the

seating drive, is termed as penetration resistance N. This test shall be

discontinued when the blow count is equal to 100 or the penetration is less

than2.5 cm for 50 blows whichever is earlier. At the location were the test is

discontinued the penetration and the number of blows shall be reported.

Sufficient quantity of disturbed soil samples shall be collected from the split

spoon sampler for identification and laboratory testing.

Following Tables give some of the empirical correlation of the soil properties

with the penetration resistance corrected for depth and for fine saturated sand.

Table (1) Penetraqtion resistance and Empirical correlations for cohesionless soils.

PenetrationResistance N

(Blows)

Approx.

(Degrees)

DensityIndex(%)

Description Approx.Moist

Density(t/m2)

-

4

10

30

50

25-30

27-32

30-35

35-40

38-43

0

15

35

65

85

Very Loose

Loose

Medium

Dense

Very dense

1.12-1.6

1.44-1.84

1.76 –2.08

1.76 –2.24

2.08 –2.40

Table (2) : Penetration resistance and empirical correlations for cohesive soils

PenetrationResistanceN (blows)

UnconfinedCompressive

Strength (t/m2)

SaturatedDensity(t/m3)

Consistency

0

2

4

8

16

32

0

2.5

5

10

20

40

-

1.6 - 1.92

1.76 -2.08

-

1.92 - 2.24

-

Very soft

Soft

Medium

Stiff

Very stiff

Hard

1.6 Static cone penetration test : Static cone penetration test shall be conducted

to know the soil stratification and to estimate the various soil propertie such

as density, undrained shear strength etc. The cone penetrometer shall be

advanced by pushing and the static forcr required for unit penetration shall be

determined. The test shall be conducted upto the specified depth or refusal

whichever is earlier. For this test ‘refusal’ means meeting a very hard strata

which can’t be penetrated at the rate of at least 0.3cm/sec even when the

equipment is loaded to its full capacity. The specifications for the equipment

and accessories required for performing the test, test procedure, field

observations and reporting of results shall conform to 1S: 4968, Part 111. Only

100 kN capacity mechanically operated equipment shall be used. At the

ground level, preboring upto 0.5 m depth shall be permitted if the overlying

strata is hard. Continuous record of the penetration resistance shall be

maintained.


1.7 Dynamic cone penetration test: Dynamic cone penetration test shall be conducted to

predict stratification, density, bearing capacity etc of soils. The test shall be conducted

upto the specified depth or refusal whichever is earlier. Refusal shall be considered when

the blow count exceeds 150 for 300mm penetration. The specification for the equipment

and accessories required for performing this test, test procedure, field observations and

reporting of results shall conform to 18:4968 Part-ll. The driving system shall comprise

of a 650 weight having a free fall of 0.75m. The cone shall be of 65 mm diameter

provided with vents for'continuous flow of bentonite slurry through the cone and rods in

order to avoid friction between the rods & soil. On completion of the test, the result shall

be presented as a continuous record of the number of blows required for every 300mm

penetration of the cone into the soil in a suitable chart supplemented by a graphical plot

of blow count for 300 mm penetration vs. depth.


1.8 Vane shear test: Field vane shear test shall be performed inside the borehole

to determine the undrained shear strength of cohesive soil -especially of soft

and sensitive clays, which are highly susceptible to sampling disturbance. The

vane shear test consist of four thin steel plates called vanes, welded

orthogonally to a steel rod (Fig.3) .The test shall be conducted by advancing

this four winged vane of s~itable size (as per the soil condition) into the soil

upto the desired depth and measuring the torque required to rotate the vane.

The torque shall be measured through a torque measuring arrangements such

as calibrated torsion spring, is attached to the steel rod which is rotated by a

worm gear and worm wheel arrangement. The specification for the equipments

and accessories required for conducting the test, the test procedure and field

observations shall correspond to IS: 4434. Tests mayalso be conducted by

direct penetration from ground surface. On completion of the test the results

shall be reported in an approved proforma as specified in IS: 4434, Appendix-

A.


1.9 Plate Load Test: Plate load test shall be conducted to determine the ultimate

bearing capacity of soil, and the load/settlement characteristics of soil at

shallow depths by loading a plane and leveled steel plate kept at the desired

depth and measuring the settlement under different loads, until a desired

settlement takes place or failure occurs. The specification for the equipment

and accessories required for conducting the test, the test procedure, field

observations and reporting of results shall conform to IS:1888. The test pit

shall be made five times the width of the plate. At the centre of the pit, a small

square hole shall be dug whose size shall be equal to the size of the plate and

the bottom level of which correspond to the level of actual foundation (Fig.4) .

The loading to the test plate shall be applied with the help of a hydraulic jack.

The reaction of the hydraulic jack shall be borne by either of the following two

methods:

a) Gravity loading platform method

b) Reaction truss method.

In case of gravity loading method a platform shall be constructed over a

vertical column resting on the test plate and the loading shall be done with the

help of sand bags, stones or concrete blocks. The general arrangement of the

set up for this method is shown in Fig. 5 & 6.

If the water table is at a depth higher than the specified test depth, the

groundwater shall be lowered and maintained at the test depth for the entire

duration of the test.

1.9.1 A seating load of 70 gm/sq.cm shall be applied and after the dial gauge

readings are stabilized , the load shall be released and the initial readings of

the dial gauges recorded after they indicate constant reading. The load shall be

increased in stages. These stages shall be 20, 40, 70, 100, 150, 200, 250, 300,

400, 500, 600 and 800 KN per sq.m. or as directed by the Engineer. Under

each loading stage, record of Time vs Settlement shall be kept as specified in

IS: 1888.

The load shall be maintained for a minimum duration of one hour or till the

settlement rate reduces to 0.02 mm/ min whichever is later. No extrapolation

of settlement rate from periods less than one hour shall be permitted.

1.9.2 Loading shall be carried out in stages as specified above till one of the

following conditions occurs.

a) Failure of the soil under the plate i.e. the settlement of the plate at

constant load becomes progressive and reaches a value of 40 mm or

more.

b) Total settlement of the plate is more than 40 mm.

c) Load intensity of 800 KN/Sq.m is reached without failure of the soil.

1.9.3 Dial gauge readings for settlement shall generally be taken at

1,2.25,4,6.25,9,16,25,60,90 and 120 minutes from the commencement of each stage

of loading. Thereafter the readings shall be taken at hourly intervals upto a further 4

hours and at two hours intervals thereafter for another 6 hours .

2.0 Trial pit


2.0.1 Trial pits shall be of minimum 2mx2m size at the bottom so as to permit easy access

for visual examination of walls of the pit and to facilitate sampling and insitu testing

operations. pits shall be upto 4 m deep or as per the directions of the Engineer.

Precautions shall be taken to ensure the stability of pit walls including provision of

shoring, if necessary, as per IS: 4453: Precautions shall be taken to prevent surface

water draining into the pit. Arrangements shall be made for dewatering if the pit is

extended below water table. Trial pits shall be kept dry and a ladder shall be provided

for easy access to the bottom of the pit. In-situ tests shall be conducted and

undisturbed samples shall be collected immediately on reaching the specified depth so

as to avoid substantial changes in moisture content of the subsoil. Arrangements shall

be made for barriers, protective measures and lighting necessary for the period the pits

remain open.

2.0.2 A note on the visual examination of soil strata shall be prepared. This should include

the nature, colour, consistency and visual classification of the soil, thickness of soil

strata, groundwater table, if any, etc.

2.0.3 Undisturbed samples shall be collected at 1.0, 2.0, 3.0 m depth and at the termination

depth in all the pits.

a) Chunk Samples

In cohesive soils, undisturbed samples of regular shapes shall be

collected. The samples shall be cut and trimmed to a suitable size

(0.3x0.3x0.3m). A square area (0.35x0.35m) shall be marked at the

centre of the leveled surface at the bottom of the pit. Without

disturbing the soil inside the marked area, the soil around this marking

shall be carefully removed upto a depth of 0.3Sm. The four vertical

faces of the soil block protruding at the centre to be trimmed slowly so

that its size reduces to 0.3mx0.3m. Wax paper cut to suitable size shall

be wrapped uniformly covered with two layers of thin cloth over all the

S exposed surfaces of the soil block and sealed properly using molten

wax. A firmly constructed wooden box of size 0.3Sx0.35x0.35m

(internal dimensions) with the top and bottom open shall be placed

around the soil block and held such that its top edge protrudes just

above the surface of the block. The space between the soil block and

the box shall be filled uniformly and tightly with moist sawdust. The

top surface shall also be covered with saw dust before nailing the

wooden lid to cover the box firmly taking care that the soil block is not

disturbed. The area of contact between the bottom portion of the block

and the ground shall be reduced slowly by removing soil in small

quantities using small rods, so that the block can be separated from the

ground slowly without disturbance. After inverting the wooden box

along with the soil block, the bottom portion shall be trimmed and

covered with wax paper, cloth and sealed with molten wax. A wooden

lid shall be nailed to the box after providing proper saw dust cushion

below it. An arrow mark shall be made on the vertical face of the

wooden box to indicate the top surface along wi th the coordinates and

depth of sampling .

b) Tube Samples

Undisturbed tube samples may also be obtained by means of a l00mm

diameter sampling tube with a cutting edge. The sampler shall be

slightly oiled or greased inside and outside to reduce friction. The

sampler shall be pushed into the soil and while doing so, soil around

the tube shall be carefully removed. In case it is not possible to push

the sample, it may be driven by light blows from a "monkey".

2.0.4 In each trial pit the soil in-situ density shall be determined by the sand

replacement method. The specifications, equipments, accessories required for

the test and test procedure shall be as per IS: 2720, Part- XXVIII. No separate

payment shall be made for this test.

2.1 Ground Water


2.1.1 One of the following methods shall be adopted for determining the ground water table

in bore holes as per IS: 693 5 and as per the lnstructions of the Engineer.

a) In permeable soils, the water level in the hole shall be allowed to

stablise after depressing it adequately by bailing. When the water level

inside the bore hole is found to be stable, the depth of water level

below ground level shall be measured. Stability of sides and bottom of

the bore hole shall be ensured at all times.

b) For both permeable and impermeable soils, the [following method

shall be suitable. The bore hole shall be filled with water and then

bailed out to various depths. Observations on the rise or fall of water

level shall be made at each depth. The level at which neither a fall nor

a rise is observed shall be considered as the water table elevation. This

shall be established by three successive readings of water level taken at

an interval of two hours.

2.1.2 In case any variation in the groundwater level is observed in any specific boreholes,

then the water level in these I boreholes shall be recorded daily during the course of

the field investigation. Levels in nearby wells, streams, etc., if any, shall also be noted

whenever these readings are taken.

2.1.3 Sub-soil Water Samples

a) Sub-soil water samples shall be collected for carrying out chemical

analysis thereon. Representative samples of groundwater shall be

collected when it is first encountered in bore holes before the addition

of water to aid boring or drilling.

b) Chemical analysis of water samples shall include determination of pH

value; turbidity, sulphate, carbonate, nitrate and chloride contents;

presence of organic matter and suspended solids. Chemical

preservatives maybe added to the sample for cases as specified in'the

test method/IS codes. This shall only be done if analysis cannot be

conducted within an hour of collection and shall have the prior written

permission and approval of the Engineer.

2.2 Electrical Resistivity Test


This test shall be conducted to determine the Electrical resistivity of soil

required for designing safety grounding system for the entire switch yard area.

The specifications for the equipments and other accessories required for

performing electrical resistivity test, the test procedure, and reporting of field

observations shall conform to 1S:3043. The test shall be conducted using

Wanner's four electrode method as specified in 1S:1892,Appendix-

B2.Unlessotherwisespecified, at each test location, the test shall be conducted

along two perpendicular lines parallel to the coordinate axes. On each line a

minimum of 8 to 10 readings shall be taken by changing the spacing of the

electrodes from an initial small value of 0.5m upto a distance of 10.0m.

2.3 Field Investigation Rock


2.3.1 Rock Drilling

a) Boring shall be continued in large hard fragments or natural rock beds

like but not limited to igneous, sedimentary and metamorphic

formations. The equipments, method and the procedure for drilling

operation shall conform to IS:1892. The starting depth of drilling in

rock shall be certified by the Engineer. The portion drilled in rock shall

be backfilled with cement and sand (1:3) grout.

b) Drilling shall be carried out with NX size tungston carbide (TC) or

diamond tipped drill bits depending on the type of rock and as per

IS:6926. Suitable type of drill bit (TC/Diamond) and core catchers

shall be used to ensure continuous and good core recovery. Core

barrels and core catchers shall be used for breaking off the core and

retaining i t when the rods are withdrawn. Double tube core barrels

shall be used to ensure better core recovery and to pick up cores from

layers of bed rock. Water shall be circulated continuously down the

hollow rods and the sludge conveying the rock cuttings to the surface

shall be collected. A very high recovery ratio shall be aimed at in order

to get a satisfactory undisturbed sample. Core of minimum 1.5m length

shall be aimed at. Normally TC bit shall be used. Change over to a

diamond bit shall require the specific written approval of the Engineer

and his decision whether a TC or a diamond bit is to be used shall be

final and binding on the Contractor.

c) No drilling run shall exceed 1.5m in length. If the core recovery is less

than 80% in any run the length of the subsequent run shall be reduced

to 0.75m. During drilling operations observations on return water, rate

of penetration, etc., shall be made and recorded as per IS:5313.

i) The colour of return water at regular intervals, the depth at

which any change of colour of return water is observed, the

depth of occurrence and amount of flow of hot water, if

encountered, shall be recorded.

ii) The depth through which a uniform rate of penetration was

maintained, the depth at which marked change in rate of

penetration or sudden fall of drill rod occurs the depth at which

any blockage of drill bit causing core loss, if any, shall be

recorded.

iii) Any heavy vibration or torque noticed during drilling should be

recorded together with the depth of occurrence.

iv) Special conditions like the depth at which grouting was done

during drilling fluid, observation of gas discharge with return

water etc., shall also be observed and recorded.

v) All the observations and other details shall be recorded as a

daily drill and reported in a proforma as given in IS:5313.

d) Core samples shall be extracted by the application of a continuous

pressure at one end of the core with the barrel held horizontally without

vibration. Friable cores shall be extracted from the barrel directly into

a suitable sized half round plastic channel section. Care shall be taken

to maintain the direction of extrusion of sample same as while coring

to avoid stress reversal.

e) Immediately after withdrawl from the core barrel, the cores shall be

placed in a tray and transferred to boxes specially prepared for the

purpose. The boxes shall be made from seasoned timber or any other

durable material and shall be indexed on top of the lid as per IS : 4078.

The cores shall be numbered serially and arranged in the boxes in a

sequential order. The description of the core samples shall be recorded

as per IS : 4464. Where no core is recovered, it shall be recorded as

specified in the standard. Continuous record of core recovery and RQD

to be mentioned in the corelog as per IS : 11315 Part-II.

2.3.2 Permeability Test

Permeability Test shall be conducted in bedrock inside the drilled holes by

pumping in water under pressure to determine the percolation capacity of the

rock strata. This test shall be conducted in uncased and ungrouted sections of

the drill hole and the use of bentonite slurry during drilling is strictly

prohibited when this test has to be conducted.

Clear and clean water shall be used for the purpose of both drilling and testing.

The equipments required and the procedure to be followed for conducting the

test shall conform to IS : 5529, Part-II. The length of the test section shall be

either 1.5m or 3.0 m as per field conditions and the directions of the Engineer.

The level of water table, if any, in the drill hole shall be recorded and the drill

hole shall be cleaned before beginning the test. Depending upon the depth of

the test section, single packer or double packer method shall be adopted. Care

shall be taken to see that all joints and connections are watertight during the

test.

a) Single Packer Method

This method shall be adopted when the bottom elevation of the test

section is the same as the bottom of the drill hole and where it is

considered necessary to know the permeability values during drilling

itself. This test shall be useful where the full length of the hoe cannot

stand uncased or ungrouted. The packer shall be fixed at the top level

of test section such that only the test section lies below the packer.

Water shall then be pumped through a pipe into the test section under a

particular pressure and maintaining it till a constant quantity of water

intake is observed. The amount of water percolating through the hole

shall be recorded at every 5 mm intervals. The test shall be repeated by

increasing the pressure at regular intervals upto a pressure limit as

specified in IS : 5529, Part-II. The details and observations during the

test shall be suitably recorded in a proforma recommended in IS : 5529,

Part-II, Appendix-B.

b) Double Packer Method

This method shall be used when the permeability of an isolated section

inside a drill hole has to be determined. Packers shall be fixed both at

the top and bottom of the test section such that their spacing is exactly

equal to the length of the test section.

2.4 Laboratory Testing


2.4.1 Essential Requirements

a) Depending on the type of sub strata encountered, appropriate laboratory

tests shall be conducted on soil and rock samples collected in the field.

Laboratory tests shall be scheduled and performed by qualified and

experienced personnel who are thoroughly conversant with the work. Tests

indicated in the schedule of items shall be performed on soil, water and

rock samples as per relevant IS: codes. One copy of all the laboratory test

data records shall be submitted to the Powergrid progressively every week.

Laboratory tests shall be carried out concurrently with field investigation

since initial laboratory test results could be useful in planning the later

stages of fieldwork. A schedule of laboratory tests shall be established by

the Contractor to the satisfaction of the Engineer within one week of

completion of the first borehole.

b) Laboratory tests shall be conducted using approved apparatus comply

in with the requirements and specifications of/'Indian Standards or

other approved standards for this class of work. It shall be checked that

the apparatus are in good working condition before starting the

laboratory tests./Calibration of all the instruments and their accessories

shall be done carefully and precisely. The tests shall be conducted at an

approved laboratory.

c) All samples, whether undisturbed or disturbed, shall be extracted,

prepared and examined by competent personnel properly trained and

experienced in soil sampling, examination, testing and in using the

apparatus as per the specified standards.

d) Undisturbed soil samples retained in lines or seamless tube /samplers

shall be taken out without causing any disturbance to the samples using

suitably designed extruders just prior to actual testing. If the extruder is

horizontal, proper support shall be provided to prevent the sample from

breaking. For screw type extruders, the pushing head shall be free from

the screw shaft so that no torque is app11ed to the soil sample in

contact with the pushing head. For soft clay samples, the sample tube

shall be cut by mean of a high speed hacksaw to proper test length and

placed over the mould before pushing the sample into it with a suitable

piston.

e) While extracting a sample from a liner or tube, care shall be taken to

see that its direction of movement is the same as that during sampling

to avoid stress reversal.

2.4.2 Tests

Tests as indicated in this specification and as called for by the Engineer shall

be conducted. These tests shall include but not be limited to the following.

a) Tests on Undisturbed and Disturbed Samples

- Visual and Engineering Classification

- Sieve Analysis and Hydrometer Analysis

- Liquid, Plastic and Shrinkage Limits

- Specific Gravity

- Chemical Analysis

- Swell Pressure and Free Swell index determination

- Proctor Compaction test

- California Bearing Ratio

b) Tests on Undisturbed Samples

- Bulk Density and Moisture Content

- Relative Density (for sand)

- Unconfined Compression Test

- Box Shear Test (in case of sand)

- Triaxial Shear Tests: (depending on the type of soil and field

conditions on undisturbed or remoulded samples )

i) Unconsolidated undrained,

ii) Consolidated Undrained Test with the Measurement of Pore

Water Pressure.

iii) Consolidated Drained.

- Consolidation

c) Tests on Rock Samples

- Visual Classification

- Moisture Content, Porosity and Density Specific Gravity Hardness

- Slake durability

- Unconfined Compression test (both saturated and at insitu water

content ) -Point load strength index

- Deformability test (both saturated and dry, samples)

d) Chemical Analysis of Sub soil water

2.4.3 Salient Test Requirements

a) Remoulded soil specimen, whenever desired, shall be fully reworked at

field density and moisture content . For conducting CBR test and

triaxial test for dyke and road material the sample shall be remoulded

to 95% of standard proctor density.

b) Triaxial shear test shall be conducted on undisturbed soil samples,

saturated by the application of back pressure. Only if the water table is

at sufficient depth so that chances of its rising to the base of the footing

are meagre or nil, the triaxial tests shall be performed on specimens at

natural moisture content. Each test shall be carried out on a set of three

test specimens from one sample at cell pressures equal to 100, 200 and

300 KN/sq.m. or as required depending on the soil conditions .

c) Effective stress triaxial shear test could be either consolidated drained

or consolidated undrained with pore water pressure measurement. The

test shall be conducted at cell pressure of 100,200 and 300 KN/ sqm.

increased in stages of 50 KN/sqm. ensuring complete consolidation at

each stage.

d) Direct shear test shall be conducted on undisturbed soil samples. The

three normal vertical stresses for each test shall be l00, 200 and 300

KN/sq.m. or as required as per the soil conditions .

e) Consolidation test shall have loading stages of 10, 25,50,75,100,200,

400and800KN/Sq.m. Rebound curve shall be recorded for all the

samples by unloading the specimen at the in-situ stress of the

specimen. Additional rebound curves shall also be recorded whenever

desired by the Engineer.

f) Chemical analysis of sub-soil shall include determination of pH value;

carbonate, sulphate (both SO3andSO4) , chloride and nitrate contents;

organic matter; salinity and any other chemical harmful. to the

foundation material. The contents in soils shall be indicated as

percentage ( % ) .

g) Chemical analysis of sub-soil water sample shall include the determination

of the properties such as colour, odour, turbidity, pH value and specific

conductivity both at 25 deg.C and chemical contents such as Carborates,

Surphates(both SO3 and SO4), Chlorides, Nitratesm Organic matter and any

other chemical harmful to the founmdation material. The contents such as

Sulphates, etc. shall be indicted as ppm by weight.

h) The lab CBR test shall be performed on undisturbed and remoulded

sample for soaked and unsoaked condition.

2.5 Report


2.5.1 General

a) On completion of all the field and laboratory work, the Contractor shall

submit a formal report containing Geological information of the region,

procedure adopted for investigation, field observations, summarised

test data, conclusion and recommendations. The report shall include

detailed borelogs, subsoil sections, field test results, laboratory

observations and test results both in tabular as well as graphical form,

practical and theoritical considerations for the interpretation of test

results, the supporting calculations for the conclusions drawn, etc.

Initially, the Contractor shall submit three copies of the report in draft

from for the Owner's review.

b) The Contractor's qualified Geotechnical engineer shall visit the Owners

Corporate office for a detailed discussion on the Owners comments on

his draft report. During the discussions, it shall be decided as to the

modifications that need to be done in the draft report. Thereafter the

Contractor shall incorporate in his report the agreed modifications and

after get ting the amended draft report approved, ten copies of the

detailed final report shall be submitted alongwith one set of

reproducibles of the graphs, tables, etc .

c) The detailed final report based on field observations, in-situ and

laboratory tests shall encompass theoretical as well as practical

considerations for foundations for different types of structures

envisaged in the area under investigation. The Contractor shall

acquaint himself about the type of structures, foundation loads and

other information required from the Engineer.

2.5.2 Data to be Furnished

The report shall also include but not be limited to the following :

a) A plot plan showing the locations and reduced levels of all field tests

e.g. boreholes, trial pits, static cone penetration tests, dynamic cone

penetration tests, plate load tests 1 etc. properly drawn to scale and

dimensioned with reference to the established grid lines.

b) A true cross section of all individual boreholes and trial pits with

reduced levels and coordinates shown in the classification and

thickness of individual stratum, position of ground water table, various

in-situ tests conducted and samples collected at different depths and

the rock stratum, if met with.

c) A set of longitudinal and transverse soil/rock profiles connecting

various boreholes in order to give a clear picture of the variation of the

subsoil strata as per IS:6065.

d) Geological information of the area such as geomorphology, geological

structure, lithology, stratigraphy and tectonics, core recovery and rock

quality designation, etc.

e) Past observations and historical data, if available, for the area or for

other areas with similar soil profile or with similar structures in the

surrounding areas.

f) Plot of Standard Penetration Test (N values both uncorrected and

corrected) with depth for identified areas.

g) Results of all laboratory tests summarised (i) for each sample (as per

Table-I) as well as (ii) for each layer along with all the relevant charts,

tables, graphs, figures, supporting calculations, conclusitions and

photographs of representative rock cores.

h) For all triaxial shear tests stress vs strain diagrams as well as Mohr’ s

circle envelopes shall be furnished. If back pressure is applied for

saturation, the magnitude of the same shall b~ indicated. The value of

modulus of elasticity, E shall be furnished for all tests alongwith

relevant calculations.

i) For all consolidation tests, the following curves shall be furnished :

e vs log p

e vs p and

Compression vs log t or

Compression vs square root of t (depending upon the shape of the plot

for proper determination of co-efficient of consolidation).

The point showing the initial condition (eo, po) of the soil shall be

marked on the curves.

j) The procedure adopted for calculating the compression index from the

field curve and settlement of soil strata shall be clearly specified. The time

required for 50% and 90% primary consolidation alongwith secondary

settlements, if significant, shall also be calculated.

k) For pressuremeter tests, the following curves shall be furnished :

Field pressure meter, creep and air calibration curves indicating Po' Pf

and Pi.

Corrected pressure meter and creep curves indicating Po, Pf', Pi

alongwith calculation for the corrections.

l) From the pressure-meter test results the values of cohesion, angle of

internal friction, pressuremeter modulus, shear modulus and coefficient

of subgrade reaction shall be furnished alongwith sample calculation.

Calculation for allowable bearing pressures and corresponding total

settlements, for shallow foundations and capacity calculation of piles in

various modes shall also be included.

2.5.3 Recommendations

Recommendations shall be given area wise duly considering the type of soil,

structure and foundation in the area. The recommendations shall include but

not be limited to the following :

a ) Type of foundations to .adopt for various structures, duly considering

the sub soil characteristics, water table, total settlements permissible

for structures and equipments. Minimum depth and width of

foundation shall also be recommended. The provision in relevant IS:

Codes indicated in clause 4.0 shall be considered.

b) For shallow foundations the following shall be indicated with

comprehensive supporting calculations.

i) Net safe allowable bearing pressure for isolated square footings

and continuous strip footings of sizes 2.0,3.0 and 4.0m at three

different founding depths of 1.0, 2. 0 and 4.0m below ground

level considering both shear failure and settlement criteria,

giving reasons for type of shear failure adopted in the

calculation.

ii) Net safe allowable bearing pressure for raft foundations of

widths greater than 6m at 2.0m , 3.0m and 4.0m below ground

level considering both shear failure and settlement criteria.

iii) rate and magnitude of settlement expected of the structure.

iv) Net safe bearing capacity for foundation sizes mentioned above,

modulus of subgrade reaction, modulus of elasticity from plate

load test results alongwith time settlement curves and load

settlement curve in both natural and log graph, variation of

Modulus of subgrade reaction with size, shape and depth of

foundation.

c) If piling is envisaged, the following shall be indicated with

comprehensive supporting calculations:

i) Type of pile and reasons for recommending the same

duly considering the soil characteristics.

ii) Suitable founding strata for the pile.

iii) Estimated length of pile for 500 KN (400 mm dia), 750

KN (450 mm dia), 1000 KN (500 mm dia) and 4500

KN (1070 mm dia) capacities. End bearing and

frictional resistance shall be indicated separately.

iv) Magnitude of negative skin friction, if any, to be

considered in pile design.

2.5.4 Additional Recommendations

a) Coefficient of permeability of various sub soil and rock strata based on

in-situ permeability tests.

b) Cone resistance, frictional resistance, total resistance, relation between

cone resistance and Standard Penetration Test N Value, and settlement

analysis for different sizes of foundation as specified based on static

cone penetration test.

c) Electrical resistivity of sub-soil based electrical resistivity tests

including electrode spacing vs cumulative resistivity curve.

d) Suitability of the soil for construction of roads and pavements, their

stable slopes for shallow and deep excavations, active and passive

earth pressures at rest and modulus of elasticity as a function of depth

for the design of underground structures.

e) Suitability of locally available soils at site for filling and back filling

purposes.

f) If expansive soil is met with, recommendation on removal or

retainment of the same under the foundation etc. shall be given. In the

latter case, detailed specifications of any special treatment required

including specifications for materials to be used, construction method,

equipments to be deployed, etc. shall be furnished.

g) Protective measures based on chemical nature of soil and ground water

with due regard to potential deleterious effects on concrete, steel and

other building materials, etc. Remedial measures for sulphate attack

and acidity shall be dealt in detail. Susceptibility of soil to termite

action and remedial measures for the same.

h) Susceptibility of sub soil strata to liquifaction in the event of

earthquake. If so, recommendation for remedial measures.

i ) Any other information of special significance like dewatering schemes,

etc. which may have a bearing on the design and construction ,

j) Recommendations for additional soil investigation beyond the scope of

the present work if the Contractor considers such investigation is

necessary.

2.6 Rates and Measurements


The clauses below shall apply for item rate contracts only. They shall not be

applicable to turn key and lumpsum contracts, except for work beyond the

scope of such contracts.

2.6.1 Rates

a) The item of work in the Schedule of Quantities describes the work very

briefly. The various items of the Schedule of Quantities shall be read in

conjunction with the corresponding sections in the technical

specifications including amendments and additions, if any. For each

item in the Schedule of Quantities, the bidder's rates shall include for

the activities covered in the description of the item as well as for all

necessary operations in details described in this technical specification.

b) The unit rates quoted shall include minor details which are obviously

and fairly intended, and which may not have been included in these

documents but are essential for the satisfactory completion of the work.

c) The bidders quoted rates shall be inclusive of providing all plant

equipments, men, materials, skilled and unskilled labour; making

observations establishing the ground level and coordinates at location

of each borehole, test pit, etc. by carrying levels from one established

bench mark and distances from one set of grid lines furnished by the

Owner. Also, no extra payments shall be made for conducting the

Standard Penetration Test; collecting, packing, transporting of all

samples and cores; recording of all results and submitting them in

approved formats.

d) No claims shall be entertained if the details are shown on the released

for construction drawings differ in any way (e.g .location and depth for

tests, number of tests, etc.) from those shown on the tender drawings.

2.6.2 Measurements

a) All measurements shall be in SI Units.

b) Lengths shall be measured in meters (m) correct to two places of

decimals. Areas shall be worked out in square meters (m2) and volume

in cubic meters and which may not have been included in these

documents but are essential for the satisfactory completion of the work.

c) The bidders quoted rates shall be inclusive of providing all plant

equipments, men, materials, skilled and unskilled labour; making

observations establishing the ground level and coordinates at location

of each borehole, test pit, etc. by carrying levels from one established

bench mark and distances from one set of grid lines furnished by the

Owner. Also, no extra payments shall be made for conducting the

Standard Penetration Test; collecting, packing, transporting of all

samples and cores; recording of all results and submitting them in

approved formats.

d) No claims shall be entertained if the details are shown on the released

for construction drawings differ in any way (e.g. location and depth for

tests, number of tests, etc.) from those shown on the tender drawings.

2.6.2 Measurements

a ) All measurements shall be in SI Units

b) Lengths shall be measured in meters (m) correct to two places of

decimals. Areas shall be worked out in square meters (m2) and volume

in cubic meters (m3), rounded off to two decimals.

c) Certain tests have to be conducted in bore holes, trial pits, etc. Such

boreholes, trial pits, etc., shall be measured only once and not again

just because of a tests are conducted therein.

2.7 Specific Requirements for Geotechnica1 investigation at River Crossings


The entire soil investigation work shall be carried ~ out in accordance with the

relevant parts of the specification for geotechnical investigation. Standard

Penetration test at River Crossings and special locations shall be carried out at

the interval of 2.0, 3.0, 5.0, 7.0, 10.0 and thereafter at the rate of 3m intervals

to 40m. However in each bore holes undisturbed samples shall be collected at

every change of strata and at depths as follows: 1.0m, 4.0m, 7.0m, 11.0m and

thereafter at the rate of 3m intervals up to 38m. The spacing between the top

levels of undisturbed sampling and standard, penetration testing shall not be

less than 1.0m. The boreholes shall generally be executed to, specified depth

as per specifications or as shown in the drawing. If refusal strata is reached

(i.e. SPT-N Value is greater than 100 continuously for 5m depth) the borehole

may be terminated at shallower depth i.e. at 5m in refusal strata.

2.8 Summary of Results of Laboratory Tests on Soil and Water Samples

B

O

R

E

H

O

L

E/

T

RI

A

L

PI

T

N

O.

D

E

P

T

H

(

m

)

T

Y

P

E

O

F

S

A

M

P

L

E

DENSITY

(KN/Cu.m.)

Bulk Dry

W

A

T

E

R

C

O

N

T

E

N

T

(

%

)

PARTICLE SIZE (%) CONSISTANCY

PROPERTIES

SOIL

GRAVEL SAND SILT CLAY L.L. P.L. P.I. CLA

SSIF

ICA

TIO

N –

IS

D

E

S

C

R

I

P

T

I

O

N

S

P

E

C

I

F

I

C

G

R

A

V

I

T

Y

Notations :

I. For type of sample II. For Strength TestDB Disturbed Bulk Soil sample PMT Pressuremeter TestDP Disturbed SPT soil sample SCPT Static Cone Penetration TestDS Disturbed Samples from cutting edge UCC Unconfined Compression Test

Of Undisturbed soil sample VST Vane Shear TestRM Remoulded soil sample Tuu Unconsolidated Undrained Triaxial TestUB Undisturbed soil sample Tcu Consolidated UndrainedUS Undisturbed Soil Sample by Sampler Triaxial Test with Pore PressureW Water Sample Ted Consolidated Drained Triaxial Test

(Note : 1. Replace T by D for Direct Shear Test)

STRENGTH TEST CONSOLIDATION TEST

TYPE C ec pc Cc P mv Cv

SHRINKAGELIMIT(

%)

SWELL TEST COMPACTION TEST

S. Pr F S M.D.D. O.M.C. C.B.R.

RELATIVEDENSITY(%)

PERMEABILITY (m/hour)

REMARKS

III. For Others Cv Coefficient of consolidation (sq.m./hr)LL Liquid Limit (%) MDD Maximum Dry Density (KN/Cu.m.)PL Plastic Limit (%) OMC Optimum Moisture Content (%)PI Plasticity Index (%) CBR California Bearing Ratio (%)C Cohesion (KN/Sq.m.) IV. For Chemical Test Angle of Internal friction (degrees)S. Pr. Swelling Pressure (KN/Sq.m.) pH pH valueFSI Free Swell Index (%) Cl Chlorine Contentec Initial Void Ratio SO3 Sulphate ContentPf Preconsolidation Pressure (KN/Sq.m.) NO4 Nitrate ContentCc Compression Index CO3 Carbonate ContentP Pressure range (KN/Sq.m.)Mv Coefficient of volume compressibility (Sq.m./KN)

2.9 Tools and Plants for Soil Investigations.


A. Sampling, S.P.T.

i) Tripod

ii) Shell and Augar

iii) Augar and wash boring

iv) Pump

v) Casing

vi) Chaintong

vii) Drill rod

viii) Pipes

ix) Monkey weight (For S.P.T.)

x) Winch (Man/Mechanically operated)

xi) Cathead

xii) Sockets

xiii) Samples

a) Open drive thin wall sampler

b) Tube Sampler

c) Split Spoon Sampler

d) Piston sampler (Bishop Sampler)

xiv) Polythin Packet

B. Other Test Apparatus

i) Vane Shear (4 blade vane)

ii) Dynamic cone (50mm and 65 mm diameter with apex angle 60 Deg.)

iii) Static cone (apex angle 60 Deg. & bore diameter 35.7 mm)

C. Pressure Meter Test

i) Menard Pressuremeter

D. Rock Drilling

i) Rotary drilling Machine with supporting equipments

a) Casing

b) Drilled

c) Core Barrel

d) Drilling bid (T. C bit/Diamond bit)

E. Resistivity Test

i) Meggar Test

F. Other Equipments

i) Power Winch

ii) Pulley

iii) Chain

iv) Buckets

v) Tents, water drums, camping cots, tables, chairs & petrox.

G. Transport Requirement

i) Motor Cycle

ii) Jeep

H. Safety Equipments

i) Safety Helmets

ii) First Aix Box

iii) Hand Gloves

iv) Shoes

NOTE :

a) The quantities and capacities of the equipments will depend upon the nos. of

bore hole, depth of the bore hole and completion schedule.

b) Additional equipments may be required depending upon site conditions.

3.0 Guidelines for Conducting Soil Investigation in Transmission Line


Provision is made in Tower Package Specification for conducting soil

investigation at various tower locations. However, it was observed in past that

there were doubts about the selection of locations for conducting soil

investigation. In view of the above to facilitate the procedure, the locations

where the soil investigation is to be conducted are described below :

The soil investigation is to be conducted at the following locations :

1. Fissured rock is encountered with sub-soil water within 1.5 meter

depth from ground level.

2. Hard rock in combination with sub-soil water within 1.5 meter depth

from ground level.

3. Fissured rock in combination with water is encountered at the bottom

of the pit with black cotton soil at top.

4. Hard rock is encountered at the bottom with water and black cotton

soil at top.

5. Dry pure sand encountered in the pit.

6. Predominantly silty sand mixed with clay or other soils (without sub-

soil water).

7. Pure sand encountered with sub-soil water.

8. Predominantly silty sand mixed with clay or othersoils encountered

with sub-soil waters.

9. Pure clay encountered with sub-soil water.

10. If soil considered bad/trencherous.

11. At the locations falling in back waters of a tank or reservoirs where

there will be stagnation of water.

12. River crossing locations.

13. Tower used with 18M/25M extensions for power line crossings.

14. Railway crossings.

Soil investigation may be done at the locations mentioned above. It is

not required to be done at the locations wherever soil could be easily

classified and one of standard approved types of foundations could be

adopted.

SECTION-II

Tower Foundation

CHAPTER-1

General

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CHAPTERONE

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GENERAL


1.0 Tower Foundations


The tower foundations cost approx. 10 to 30 percent of overall cost of tower,

or 5 to 15 percent of the cost of transmission lines, depending on the type of

soil.

Experience shows that while an inadequate foundation may lead to collapse of

tower, an over design may prove very uneconomical. It is a good practice to

check the tower for permissible deflection at the top. Since differential

foundation settlement also causes tower deflection at the top, and if the total

deflection at the top of the tower is to be restricted, the permissible deflection

has to be carefully apportioned between the structure deflection and that

caused by the differential foundation settlement.

The design of a safe and economical foundation is based on soil properties,

knowledge of soil structure interaction and settlement analysis of tower

foundation.

1.1 Loads, Safety Factors and Settlement


1.1.1 Loads

The loads on foundation are determined from an analysis of the tower. The

foundation is called upon to resist the following types of forces :

(i) Uplift

(ii) Downwards

(iii) Lateral load and

(iv) Overturning moment

The basic vertical forces are derived from the deadweight of the tower and the

conductors. The wind contributes to the horizontal force on the tower,

producing not only shear force (lateral load) on the foundation, but also an

uplift on the windward side of the structure and a downthrust on the other. The

uplift or the compression forces are of primary concern in tower foundation

design as shown in fig. l. In the case of the heavy angle and terminal

structures, however, one pair of legs will be permanently subjected to

compression and the other pair to uplift, due to the permanent heavy loads

imposed by the deviation of the line. In this case, it is the general practice to

design all the four footings to withstand both types of loading.

1.1.2 Safety Factors

The foundations are generally designed for factor of safety which are 10 percent in excess of

those adopted for towers. Accordingly, the overload factors assumed in the design are 2.2

under normal conditions and 1.65 under broken-wire conditions. However, IS:802-1977 (Part

III), relating to transmission line tower foundations, does not make any distinction with regard

to factors of safety as between towers and foundations.

1.2 Classification of Soils


The design of the tower foundation depends on the nature of loading and the

type of soil that supports the foundation. The soils are broadly classified as:

i) Sandy soil (loose, medium and dense),

ii) Clayey soil (soft, medium and stiff),

iii) Clayey sand (sandy clays, silty clays, clayey and silty sand), mixed soil.

iv) Rock (soft, medium and hard)

The following laboratory tests are usually conducted from the soil samples

collected:

i) Visual examination and other identification tests.

ii) Determination of in-situ density (r).

iii) Determination of strength parameters, namely, cohesion C and angle of

internal friction 0, settlement characteristic such as rate of settlement

(D/t), compression index Cc etc. and

iv) Determination of; elastic properties-Modulus of compressibility (k),

coefficient of lateral subgrade reaction (C), etc.

Among the field tests, the Standard Penetration Test (SPT) is extensively

adopted. In the Standard Penetration Test (SPT), a 64 Kg weight is dropped

76 cm to drive a sampling spoon into the ground. The no. of blows required to

push the spoon to a given depth is corelated with a no. of soil properties. The

advantage of SPT is that it is relatively quick, simple and inexpensive; but it is

also subjected to many kind of errors. Also, correlations of SPT measurements

with those of soil stress and other parameters are not particularly reliable.

In the Standard Core Penetration test, a shaft with a conical tip is slowly

pushed into the ground while electrical transducers measure both tip pressure

and side friction. The SCPT generally gives more accurate measurement than

the SPT. It is also a faster method to identify problem soils.

The SPT value N obtained from the field, is corrected for overburden pressure

in accordance with the chart shown in Fig. 2. The SCPT gives the point

resistance qc and side friction fc.

The SPT value N and the SCPT value qc are related as shown in table (1)

below. Table (1) - Correlation between SPT value N and SCPT value qc

Soil Type q/n

Clays 2.0

Silt, sandy silt and slightly cohesive silt and mixture 2.0

Clean fine to medium sands and slightly silty sands

Coarse

3-4

Sands and sands with little gravel 3-6

Sandy gravels and gravel 8-10

1.3 Properties of Soil


The following soil properties are used in the design of different type of

foundations:

1. Density

2. Relative density Dr

3. Angle of internal friction for sandy soil

4. Unconfined compressive strength Cu and cohesion C for clayey soil.

5. Modules of compressibility Es

6. Coefficient of lateral subgrade modules (C for sand and k for clay)

7. Poisson's Ratio n

8. Compressive strength of rocks s

9. Ultimate bond strength of rock-anchor interface.

Table below gives the above properties and classify the soils and rocks.

1.4 Data For Foundation Design


The following data are usually required for a proper selection of type of

foundation, its design and construction:

1. Route map showing proposed layout of tower and topography.

2. Selection of soil pits for soil data.

3. Selection of sites for SPT.

4. General layout of the tower and the loads at the foundation level.

5. Meteorological data " wind, earthquake and frost penetration

particulars.

6. Max. allowable settlement at the base of the tower considering the

permissible deflection at the top as H/140.

7. In the case of river crossings:

a. A site plan with details of crossing of at least 90m upstream and

downstream from the central line of the crossing.

b. Outline of banks.

c. Direction of flow of water.

d. Alignment of crossing and location of towers.

e. A cross section of the river at the proposed site of crossing, showing

bed-line, banks, ordinary flood level, low water level, the highest

flood, estimated depth of scour etc.

f. The maximum and mean velocity of water current.

Notes:

1. For non-cohesive soils the value of safe bearing capacity are to be

reduced by 50 percent if the water table is above or near the base of

footing.

2. The values of safe bearing capacities do not take into effect the shape

and size of footing, cohesion C, angle of internal friction 0, effect of

eccentricity, the SPT value N, etc. Hence, the values are to be

considered as average and approximate.

3. For other types of soil such as black cotton and peat, soil investigations

have to be necessarily carried out for determining the safe bearing

capacity.

Table (2) Relation between N, c, Dr, for sandy soil

Description SPT value (N) Density ()gm/cc

Relativedensity Dr

Angle ofinternal friction

Very loose 0-4 1.1 to 1.6 0-15 <28

Loose 4-10 1.45 to 1.85 15-35 28-30Medium 10-30 1.75 to 2.1 35-65 30-36Dense 30-50 1.75 to 2.25 65-85 36-41

Very Dense >50 2.1 to 2.4 85-100 >41

Table (3) Relation between N value, and unconfined compressive

strength Cu and cohesion C for clays

Consistency SPT Value N Unconfinedcompressivestrength C

kg/cm2

Cohesion Ckg/cm2

Reductionfactor for sidefriction a of

bore pileSoft 0-4 0-0.5 0-0.25 0.7

Medium 4-8 0.5-1.0 0.25-0.5 0.5Stiff 8-15 1.0-2.0 0.5-1.0 0.4

Very stiff 15-30 2.0-4.0 1.0-2.0 0.3Hard >30 >4.0 >2 0.3

Table (4) Safe bearing capacity

Type of rocks/soils Safe bearingcapacity Kg/cm2

RocksRocks hard without lamination such as granite 33Laminated rocks such as sand stone 16.5Rock desposits such as shale 9.0Soft rock 4.5Non-cohesive soils

Gravel, sand and gravel, compact and offering high resistance topenetration when excavated by tools

4.5

Coarse sand, compact and dry 4.5Medium sand, compact and dry 2.5Fine sand, silt (dry lumps easily pulverized by the fingers) 1.5Loose gravel or sand gravel mixture loose coarse to medium sand, dry 2.5Fine sand, loose and dry 1.0Cohesive soilsSoft shale, hard or stiff clay in deep bed dry 4.5Medium clay, readily indented with a thumb nail 2.5Moist clay and sand clay mixture which can be indented with strongthumb pressure

1.5

Soft clay indented with moderate thumb pressure 1.0Very soft clay which can be penetrated several inches with the thumb 0.5Black cotton soil or other shrinkable or expansive clay in dry condition(50 percent saturation)

1.5

Table (5) Modulus of compressibility E, and Poisson’s ratio for soils

Soil type Modulus of compressibilityE. kg/cm2

Ratio

ClayVery soft 3-30 0.1- 0.5Soft 20-40Medium 45-90Hard 70-200Silt 20-200 0.3-0.35SandSilty 50-200Loose 100-250 0.2-0.4Dense 500-1,000GravelLoose 500-1400 Reliable dataDense 800-2000 Not available

CHAPTER-2

Types of Foundations

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CHAPTERTWO

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2.0 Introduction


The foundation are classified as shallow or deep based on Df/B ratio

Where Df = Depth of foundation and B = Breadth of foundation

If Df / B<l, then the foundation is considered shallow and if Df / B>l, it is

classified as a deep foundation. Piles are classified as deep foundation. Even

though footing may have greater depth than the breadth in some

circumstances, they are Created as shallow foundations for the analysis of

bearing capacity. This approximation leads to a conservative estimate of the

factor of safety and is, therefore, adopted for convenience and ease in

calculations.

2.1 Types of Foundation


This foundation work requiring excavation and backfill operation is quite

satisfactory from design point of view. The knowledge of soil mechanics and

the necessity of erecting towers on a variety of soils have made it possible and

necessary for the designer to adopt new innovations and techniques. As a

result several types of tower foundations have been derived and successfully

used. Some of the more common types of foundation, mainly for broad based

towers are briefly described below.

(a) Concrete Pad and Chimney type (Fig.3)

This is the most common type of footing used in India and some

countries of the continent. It consists of a plain concrete footing pad,

the size and depth of which are decided either on the basis of bearing

area necessary for transmission of vertical downward load or from

consideration of the amount of holding power required to resist the

uplift force. The stub angle is taken inside and effectively anchored to

the bottom pad by cleat angle and keying rods; and the muff or the

chimney with stub angle inside works as a composite member. The

pad may be either pyramidal (Fig.3a) or stepped (Fig.3b).

(b) Steel Grillage (Fig.4)

Steel grillage can be of various designs. Generally it consists of a layer

of steel beam as pad for the tower leg by means of heavier joints or

channels resting cross-ways on the bearing beams.

Grillage footings require much more steel than a comparable concrete

footing but erection cost is only a fraction of that of the concrete

footing resulting in often economical and always quicker construction.

Other advantages are that the complete foundation can be purchased

from the manufacturer of towers alongwith the tower members.

The chief objection to earth grillage is that the steel may be easily attacked by corrosive

constituents of the soil, and that the periodical excavation necessary for

purposes of maintenance would loosen the soil and consequently lessen the

anchorage until the earth consolidates again.

(c) Concrete spread footings

There are several types of concrete spread footings which can be designed for

tower foundations. The two most common types of these are shown in

(Fig. 5). In the slopping pedestal type the centroid of the base is in line with

the batter of the tower legs and footing pedestals, reducing the additional

overturning moment to that caused only by the horizontal component of the

load in the lowest diagonal above the top of the pedestal.

(d) Augured Foundation (Fig.6)

The cast in situ reinforced concrete augured footing has been extensively used

in U.S.A., Canada and many countries in the continent. The primary benefits

derived from this type of foundations are the saving in time and manpower.

Holes can be driven upto one meter diameter and six meter deep. The truck

carrying the power augur is usually a cross country type of all wheel drive.

Usually, stiff clays and dense sands are capable of being drilled and standing

up sufficiently long for concreting works and installation of stub angle or

anchor bolts, whereas loose granular material may give trouble during

construction of these footings. Ben-tonite slurry or similar material is

sometimes used to stablize the drilled hole.

(e) Grouted rock footing (Fig. 7)

Grouted rock footings or rock anchors are suitable in the areas with

rock outcrops.

The anchoring strength will depend on the bond between the grout and

the surface of the anchor rods/bars. Anchor strength can be

substantially increased by provision of mechanical anchorages, such as

use of eye-bolt, fox-bolt or threaded rods as anchoring bars or use of

keying rods in case of stub angle anchoring. The effective anchoring

strength should preferably be determined by testing.

(f) Precast Concrete Foundations (Fig.8)

Due to difficulties inherent in getting good quality concrete in the

isolated tower locations, attempts have been made to manufacture

foundations either reinforced or prestressed in the'.factory. In Russia

and some other Europian countries, precast reinforced spread footing

of the type shown in (Fig. 8) is reported to have been successfully used.

Primary advantages of the prefabricated foundations are: (i) better

control over quality of concrete and workmanship (ii) saving in labour

cost and (iii) repeated use of formworks and more economical use of

materials of construction due to working under factory condition.

Major handicaps in the use of prefabricated foundations are, however,

the limitations of transport and handling facilities available for

installations of the completed footings at the site.

(g) Pile Foundations (Fig. 9)

When the soil has a poor bearing capacity or the foundation is to be

located on filled up soil, pile foundation may be adopted.

The downward vertical load on the foundations is carried by the piles

through skin friction or bypoint bearing while the uplift is resisted by

the dead weight of the concrete in piles and pile caps with appropriate

correction for floatation plus the pullout value of the piling. For

carrying heavy lateral loads, batter piles may be advantageously used.

Piles may be of different type such as driven-precast piles, bored piles

with or without under reams.

(h) Special Types of Footings (Fig. 10)

There can be several other types of tower foundations made of mass

concrete block foundation (Fig.10), tubular pile, pressed steel anchor,

etc., apart from a variety of special footings. Each of these, under

certain conditions, can do the job better than any other that could be

conceived. The suitable type of foundations will, above all, be

influenced by the forces to be accommodated, the sub soil condition,

transportation and the available construction facilities.

(i) Raised Foundation

In case the foundation is surrounded by stagnant/flood water for a long

time of the year, raised chimney foundations are to be adopted so that

steel parts are not corroded. In this case chimneys are generally raised

by about 500mm above the HFL.

(j) Shallow Depth Foundation:

Whenever the normal depth foundations cannot be constructed at site

due to excessive seepage of heavy sub-soil water then reduced depth

foundations are to be adopted. However, in all above cases engg.

approval is prerequisite. In such locations soil investigation to be

carried out to ascertain the properties of the soil for the design of the

foundation.

CHAPTER-3

Classification and Stub Setting

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CHAPTERTHREE

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CLASSIFICATION AND STUB SETTING


3.0 Line Construction


Transmission line construction comprises the following phases:

(i) Investigation and survey

(ii) Transportation

(iii) Foundations

(iv) Tower assembly

(v) Stringing

3.1 Investigation And Survey


In the earlier section on line surveys, the various aspects relating to

investigation and survey have been covered in detail.

3.2 Transportation


The weight of materials and equipment required for building a transmission

line tower may total several hundred tonnes, while construction sites are

usually scattered over a wide area. Logistic operations thus become a major

factor in these projects. Especially in mountainous terrain, road transportation

facilities are poor and effective temporary construction routes are limited. All

material transport shall be undertaken. in vehicles suitable for the purpose and

free from effect of any chemical substances. Tower members should be loaded

and transported in such a manner that these are not bent in transit and sharp

bend corners are not opened up or damaged.

3.3 Foundation


The construction of tower foundations shall be in accordance with IS

4091:1979 and Power Grid specifications.

3.3.1 Check Survey

This will be conducted to make a check on detailed survey and to locate the

peg marks and the tower positions on ground conforming to the survey charts.

In the process it is necessary to have the pit centres marked according to the

excavation marking charts. The levels, up or down, of each pit centre with

respect to the centre of the tower location shall be noted and recorded for

determining the amount of benching or earthwork required to meet design

requirements of the foundation.

If the levels of the pit centres be in sharp contrast with the level of the tower

centre (say beyond a slope of 1:4), suitable "leg extension" may be deployed as

required.

3.4 Preparation of Foundation Site


3.4.1 After tower spotting is done during check survey, it is often the case that the

area within the base of the tower is found uneven in level. Minor variation in

level can be ignored but variations in level of more than 60 cms are to be dealt

with benching the area to the reference level of centre peg. The foundation

shall be placed at the design depth with reference to the centre peg level. The

area below the centre peg shall be back filled to get a leveled surface. If the

level of back filling is considerably high, the filled area shall be enclosed by a

revetment wall to prevent erosion.

3.4.2 In Hilly areas the difference of levels in the four legs is generally very high

resulting in large quantity of benching and massive revetment walls, which

will be very uneconomical. In these cases special hillside extensions are

provided to place the four legs at different elevations.

3.5 Type of Foundation to be Adopted


3.5.1 The following standard types of foundation are approved in Powergrid for

adoption in transmission lines for different towers:-

i) Normal dry

ii) Wet

iii) Partially submerged

iv) Fully submerged

v) Dry fissured rock

vi) Wet fissured rock

vii) Hard rock foundation.

viii) Black cotton soil foundation

3.5.2 The above foundations are designed for the corresponding predominantly

prevalent soils in the pits. However, there will be cases where a combination

of soils in the pits may be observed and correct classification of the standard

foundations is required to be done.

3.5.3 Type of foundations to be adopted with reference to the soils and sub-soils

waters encountered in the pits are indicated in Table-1 to 3. Foundations may

be classified and adopted accordingly. In certain classifications of soils with

sub-soil waters (items 6(b) and 7(b) of Table-1, items 1(b) and 2(c) of table 2

and items 1,2 & 3 of Table 3) standard foundations cannot straight away be

adopted.

3.5.4 If the soil conditions differ with the four legs of the same tower necessitating

adopting of different types of approved foundation for the different legs of the

tower, classification of foundations may be done for each of the pits as

required by the actual soil conditions in the pits.

3.5.5 If site feels that soil encountered at any of the locations do not tally with the

description of soils given in the Annexure enclosed or if the soils are

considered very bad/tracherous, foundations may not be decided at such

locations by the site. Classification of the foundations of such locations may

be done in consultation with Corporate Engineering department. If the

locations fall in the back water of any river, tank or reservoir, the depth of the

back water at those locations and the duration of the stagnation of water at

those locations is to be ascertained and foundation to be decided after studying

the detailed soil report.

Table (1) Adoption of Foundations in Different Soils

Sl. No. Types of Soil Encountered Type of Foundation to be Adopted(1) (2) (3)1. a) In good soil

b) Where black cotton soil does not extent

beyond 30% of the depth from top with good

soils thereafter

Normal dry

c) Silty sand mixed with clayey soil (In all the

above cases water table is not encountered in

the pit)2. a) In paddy fields and sugar cane fields.

b) Where black cotton soil exceeds 30 and

extends up to 45% from the Ground level and

good soil thereafter.c) Where sub-soil water is encountered in the

pit beyond 1.5 m from ground level.

Wet

d) Where silty sand mixed with clayey soil and

water encountered in the pit beyond 1.5 m

from ground level.3. a) Where black cotton soil extends upto 60% of

the depth from G.L. and good soil thereafter.b) Where sub-soil water is encountered in the

pit between 0.75m depth and 1.5m depth

from ground partially level.

Partially Submerged

c) Where silty sand mixed with clayey soil and

water table in the pit is between 0.75m depth

and 1.5m depth from ground level.4. a) Where sub-soil water is encountered in the

pit within 0.75m depth from ground level.b) Where silty sand mixed with clayey soil and

water table in the pit is within 0.75 m from

G.L.

Fully Submerged

5. a) Where normal soil encountered with fissured

rock at the bottom without the presence of

water.

b) Where fissured rock is predominant in the pit

without the presence of water

Dry fissured rock

c) Where hard rock thickness at the bottom of

the pit is less than 2.0m6. a) Where fissured rock is encountered with sub

soil waster after 1.50m depth from ground

level

Wet fissured rock

b) Where fissured rocks is encountered with

sub-soil water within 1.5m depth from

ground

Soil investigation is to be properly

conducted at this location and the

contractor has to develop new fdn.

Design based on soil report and get

approved from Engg. Deptt.7. a) Wherever hard rock is encountered and the

thickness of hard rock layer below the

bottom of fdn. Is more than 2 meter

Hard rock

b) Wherever hard rock is encountered with sub-

soil water

Soil investigation is to be

conducted at this location & the

contractor has to develop new fdn.

Design based on soil report and get

approved from Engg. Deptt.8. Wherever black cotton soil extends beyond 60% of

the depth from ground level.

Black cotton soil fdn.

Table (2) Black cotton soil in combination with rock

Sl. No. Types of Soil Encountered Type of Foundation to be Adopted(1) (2) (3)1. Black cotton soil with fissured rock

combinationa) If fissured rock is encountered at the

bottom of pit (with black cotton soil at top) for

a depth of not less than 1000mm or the

thickness of the bottom slab concrete of dry

fissured rock foundation whichever is less.

Dry fissured rock foundation as per

approved drg. may be adopted with

wet chimneys because of black

cotton soil encountered in the top

portion of the pit.

b) If fissured rock in combination with

water is encountered at the bottom of the pit

with black cotton soil at the top.

Wet fissured rock foundation is to be

adopted.

2. Black Cotton Soil with hard Rock

Combinationa) If the hard rock is encountered at the

bottom of the pit (with black cotton soil at top)

and the thickness of the hard rock layer below

foundation is more than 2m.

Hard rock fdn. Design to be adopted

with wet chimneys because of the

black cotton soil encountered in the

top portion of the pit.b) If hard rock encountered at the bottom

of the pit with black cotton soil at the top and

hard rock layer depth is less than 2m.

Fissured rock foundation design to be

adopted with wet chimneys because

of the black cotton soil at the top.c) If hard rock is encountered at the

bottom with water and black cotton soil at top

and hard rock layer depth is less than 2m.

Wet fissured rock foundation as per

approved drgs. are to be adopted.

Table (3) Sand in Combination with Sub-soil water

Sl. No. Types of Soil Encountered Type of Foundation to be Adopted(1) (2) (3)1. Predominantly sand mixed with clay or other

soil (without sub-soil water)

Dry sandy soil foundation may be

adopted.2. Predominantly sand mixed with soils

encountered with sub soils water in the pits

FS/Wet sandy soil foundation may be

adopted depending on water table.3. Pure sand encountered with sub-soil water

inside the pit

Same as above

Table (4) Clay Mixed with Silty Sand

Sl. No. Types of Soil Encountered Type of Foundation to be Adopted(1) (2) (3)1. Pure clay encountered without water Dry black cotton foundation may be

adopted.

2. Predominantly clay mixed with silty sand

encountered with sub-soil water in the pits.

Wet black cotton foundation may be

adopted.3. Predominantly silty sand mixed with clay

encountered with sub-soil water.

Normal fdn. Based on the water table

classification can be adopted.

Note : To facilitate foundation classification a check format has been developed and

enclosed at Chapter-10 (Page Nos. 130, 131 & 132).

3.6 Pit Marking


3.6.1 The relevant drgs., Profile duly approved should be available at site with each

working gang.

3.6.2 The following tools and plants (T&P) should be available with each working

gang:-

i) Ranging rods with flag

ii) Dumpy level with stand.

iii) Survey umbrella

iv) One second theodolite and stadia method with calibrated levelling

stares.

v) Engineer's chain of 30 m length with 10m marking intervals.

vi) Stones, Wooden Pegs, nails, spade, pick axe etc.

3.6.3 Reference Level

The reference level is the level at the centre peg of the foundation location.

The depth of all the four pits are to be measured from this reference point. The

reduced level of the centre peg to be measured correctly and to be verified with

the profile drg.

3.6.4 Pit marking shall be carried out according to the pit marking chart.

The design office will furnish the site with an excavation pit marking chart or

excavation plan which gives the distance of pit centres, sides and corners with

reference to centre point of tower. The distances are measured and each pit

boundaries are marked in the field by means of spade or pick axe along the

sides of the pit.

3.6.5 In case of open cut foundation the pit sizes shall be determined after allowing

of 150 mm all round. No margin is necessary in case of undercut foundation.

The depth of excavation at the pit centre shall be measured with respect to

tower centre level.

3.6.6 While excavating care should be taken that earth is cut vertically/Tapered/In

steps as per the site requirement to avoid any mishap during excavation. A

typical excavation chart is enclosed. The proceeding and succeeding span on

both sides of the centre of location shall be measured correctly and verified in

order to ensure the exact location of the centre peg. For tangent towers pits are

to be marked along the centre line through previous location and next location.

3.6.7 For angle towers pit marking is done along the bisection of angle of deviation.

While carrying out this work the angle of deviation and type of tower is to be

tallied with the profile. The bottom of the excavated pit shall match with

originally marked pit plan.

3.6.8 The land mark and topography around the location should be carefully

observed and tallied with the approved profile. The distinct feature shown in

the profile drg. should normally match with prevailing site conditions.

3.6.9 On a slopy ground, care should be taken to take only horizontal distances

from-centre to centre as per the pit marking charts. Excavation of the pits upto

the desired level shall be done with respect to centre level of the pit.

3.6.10 The excavated earth shall be dumped on the outer edges of the pits away from

the base of the tower to a minimum distance equal to the depth of the pit to

avoid collapse of the free standing sides of the pit during excavation or

concreting.

3.6.11 For the sake of reference the pits of the towers shall be designated as shown in

the figure (Fig. 11).

3.7 Shoring and Shuttering


3.7.1 Shoring and shuttering shall be done keeping in view the requirements given

in IS 3764:1966

3.7.2 In pits excavated in sandy soil or water bearing strata and particularly black

cotton soil where there is every likelihood of pits collapsing, shoring and

shuttering, made out of timber planks 30-35 mm thickness or steel frames of

adequate strength to suit the requirement, will be provided.

3.7.3 Sand Bedding/stone bedding will be provided in foundations of marshy and

wet Black Cotton foundations.

3.8 Dewatering


3.8.1 Dewatering shall be carried out manually or by mechanical means power

driven pumps to facilitate excavation and casting of foundation. The pumps

shall be suitable for handling mud water.

3.8.2 In areas where sub-soil water recoupment is heavy and where water cannot be

controlled even by use of power driven pumps well point system is used for

controlling water. In this system a grid of pipes are laid around the area where

the pits are excavated and the system is very effective in pumping operation.

The pit can be excavated avoiding risk of collapse of earth. This will ensure

proper quality of concreting.

3.8.3 Another method is by drilling bore holes of a deeper pit much below

foundation level for pumping out water by ordinary pumps. Number of

boreholes depend on the volume of sub soil water.

3.8.4 In areas where sub-soil water recoupment is very rapid and water cannot be

controlled, shallow foundations will be useful.

3.9 Excavation in Rock


For excavation in hard rock, blasting can be resorted to. Reference shall be

made to statutory rules for blasting and use of explosives for this purpose. No

blasting is permitted near permanent work or dwellings. Blasting shall be so

made that pits are excavated as near to the designed dimensions as practicable.

3.9.1 The work of blasting in rock is carried out in three separate operations.

(a) Drilling of holes to hold explosive charge.

(b) Charging of the drilled holes

(c) Fixing the charge

(a) Drilling of Holes to hold explosive charge

i) Drilling of holes to hold the explosive charge may be done either

manually or with an air compressor as per the requirement at the site.

ii) The equipment for hand drilling is simple but requires more man hours

and generally consists of a set of Jumpers or Drills which are usually

made from 22 mm diameter hexagonal steel bars.

iii) The jumpers are 1m, 1.25m and 1.5m long and are suitably shaped.

They must be tempered when sharpened. A 2 Kg. hammer is used for

striking the jumper, which is given a slight rotation after each blow.

The rate of progress by this in hard rock is 25 to 41 cm per hour.

iv) When large quantity of rock is required to be excavated, an air

compressor is used for drilling the holes.

(b) Charging of the Drilled Holes

The charge consists of gelatine and detonator. Either half or a full gelatine is

used as per the requirement. Detonator is normally pressed into the gelatine

after making a hole in the gelatine with stick. Detonator is to be pressed into

the gelatine till it is completely embedded in the gelatine. Then this assembly

is placed into holes drilled.

(c) Fixing the Charge

The detonator leads are first interconnected to form a circuit and later the ends

of this circuit are connected to the exploder with separate wires. The exploder

is kept in a sheltered spot. To fire the shot the exploder handle is rotated at a

high speed.

3.9.2 Procedure in case of Misfired Shots

(i) The misfired shot should not be touched.

(ii) One should not approach a misfired shot until atleast 15 minutes have

elapsed and all connections and' handle removed from the exploder.

(iii) A second hole is to be drilled at a safe distance from the first in such a

direction as well to keep the boring tool clear of the hole.

(iv) Thus second hole is to be charged and fired.

(v) The debris is to be searched thoroughly for unexploded detonator.

3.9.3 Additional Precautions

To protect the persons and animals from injuries from flying debris depending

on situation the numbers of holes to be drilled should be less deep and the pit

should be covered with a steel plate. Such controlled blasting is an exception if

the transmission line is kept away from villages and inhabited areas.

3.10 Procedure for setting Stubs at site by Combined Stub Setting


In the foundations of transmission line towers, a stub, generally of cross

section of leg member of super-structure, is embedded in the foundation

concrete at the same angle as that of superstructure main leg slope. To achieve

this, there are three methods of setting the stubs in the pits for correct slope

and alignment.

i) By using templates for individual stubs.

ii) By using bottom section of tower as template.

iii) By using a stub setting template common for all stubs.

i) By using templates for individual stubs

For setting the stubs of towers' having hill side extensions or very broad base it

becomes unwidely and uneconomical to use the combined template. The stubs

are set separately using individual stub templates to maintain the slope. A

steel channel or beam section of sufficient length to pass over the sides of the

pits is used. A cleat .is welded to this to maintain the leg slope.

After roughly aligning the individual templates with reference to centre peg,

the stubs are fixed to the welded cleats. The stubs are aligned diagonally with

the help of a theodolite stationed at from centre peg and adjusted by measuring

diagonals. They are finally levelled precisely with the help of dumpy level.

ii) By using bottom section of tower as Template

If the bottom section of tower (for broad based towers of special extensions) is

available before commencement of foundations, it can be used for setting the

stubs. Two sides of the section are assembled on opposite faces along with

stubs horizontally on the ground adjacent to the foundation pits. The sides are

lifted and stubs are lowered into the pits and both sections are joined together

with bracings. The assembly is aligned and the stubs are levelled by holding

the frame with cross bars under the bracing joints. Since alignment is difficult

by dropping plumb, it is done with theodolite placed at centre peg. All bolts &

nuts connecting the bottom section shall be fully tightened before concreting.

iii) By using a stub template common for all stubs

The Stubs are set with the help of the stub setting Templates which are

supplied loose, ready to be assembled at site. All four excavated pits are to be

lean concreted to correct level, sighted through and the stubs are to be placed

on the lean concrete pad. Correct alignment is carried out by 0.90 kg plumb

bob four in numbers hung from centre of horizontal bracings.

Following is the procedure for Stub-setting at site:

1. Assemble the Template as per the drawing sent alongwith the supply.

A sample drg. of template is enclosed herewith for reference only.

2. Set the Template 'as per the drawing at site.

3. Place the stub-setting Jacks below the Template.

4. Align Template, alongwith the line and centre it over the centre peg of

the location.

5. Fix up the stub to the Template and with the help of a dumpy level,

level the Template corners to the required level.

6. Ensure that all the four stubs are at the same level.

7. Check the alignment and centring of the Template again.

8. Check the diagonals distances of the stubs at least at two different

levels.

9. By placing on 8 to 12 screw jacks according to the length of Template,

with a levelling instrument fine adjustment can be made by lifting/

lowering the screw jacks and the stubs can be perfectly levelled. This

ensures accurate verticality of the tower. For ensuring all towers in one

line and cross-armd at right angle to it, four plumb bobs should

dropped from the center of the horizontal members of the Template to

correspond to the cross pegs and alignment pegs given during the line

alignment survey for the tower location.

CHAPTER-4

Foundation Construction

___________________________________________________________________________

CHAPTERFOUR

___________________________________________________________________________

FOUNDATION CONSTRUCTION


4.0 Concrete Type


For reasons of economy and progress it is normal practice to use coarse and

fine aggregates available along with line route and/or nearest locations of the

route. As such, it is not practicable to design the concrete mix and use

controlled concrete. Moreover, since the quantity of concrete involved is rather

small, ordinary plain or reinforced cement concrete given in IS 456:1978 shall

be used in overhead line foundations.

4.1 Mixes


For main foundation, M 150 or 1:2:4 (Volume) mix cement concrete generally

used. For lean concrete sub-bases or pads, M 100 or 1:3:6 mix cement

concrete may be used. The properties of concrete and mix proportions shall be

'in conformation to IS 456:1978.

It shall be permissible to proportionate the concrete as follows:

a) Prepare a wooden measuring box of 35 liters capacity (that is. equal to

1 bag or 50 kg of cement with inside dimensions of not exceeding

30 x 30 x 30 cm or alternatively 34 cm diameter and 39 cm height.

The mix quantities according to the measuring box shall be as follows:

S. No. Item M 150 M 100

1. Cement 1 bag 1 bag

2. Sand 2 boxes 3 boxes

3. Stone 4 boxes 6 boxes

4. Water 1 box less 1 boxes less

3 liters 1 liters

b) Measurement of water may be made with separate water-tight drums of

the above size or with 1-or 2-litre mugs.

Note: For concreting the bored foundations by displac-ing the drilling muds,

10 percent extra cement in the mix is required.

One bag of cement is taken to contain 50 kg or 35 liters of ordinary portland

cement.

4.2 Sizes of Aggregates


The coarse aggregates (stone) to be used shall be single size aggregates of 40

mm nominal size for slab/pyamid concrete and 20 mm nominal size for

chimney concrete conforming to IS 383 : 1970. These sizes are applicable to

ordinary plain cement concrete for RCC, the aggregates shall preferably be of

20 mm nominal size. The fine aggregate (sand) shall be of Zone I Grade

conforming to IS:383 : 1970 which is the coarse variety with maximum

particle size of 4.75 mm. Zone II Grade of fine aggregates may also be used.

4.3 Gravel Sub-base


In case the foundation happens to be over fine sand, 80 mm chick gravel sub-

base may be provided, if considered necessary, under the' foundation. The

maximum size of gravel or stone to be used shall be 80 mm.

4.4 Reinforcement


All reinforcement shall be properly placed according to design drawing with a

minimum concrete cover of 50 mm. The bars shall, however, be placed clear

of stubs and cleats where interfering. For binding iron wire of not less than 0.9

mm shall be employed and the bars may be bound at alternate crossing points.

The work shall conform to IS 2502 : 1963 wherever applicable. For bored

footings, stub angle shall be used as reinforcement.

In case the foundation having steel reinforcement in pyramid on base slab, at

least 50 mm Chick pad of lean concrete of 1: 3:6 nominal mix shall be

provided to avoid the possibility of reinforcement rod being exposed due to

unevenness of the bottom of the excavated pit.

4.5 Form Work


4.5.1 General

The form work shall conform to the shape, lines and dimensions as shown on

the design drawings, and be so constructed as to be regid during the placing &

the compacting of concrete, and shall be sufficiently tight to prevent loss of

liquid from concrete. It shall be of light design & easily removable without

distortions and shall be of steel, hardwood or framed plywood. The inner

surface coming in contact with concrete shall be smooth and free form

projections. Window on one face shall be provided for pyramid forms to

facilitate concreting in the lower parts which shall be fixed after concrete in

the bottom part is placed. In bored footings form work may be needed only

towards the top for the portion above ground level.

The form work for slabs and pyramids shall be made symmetrical about the

base of the chimney to ensure interchangeable faces as illustrated in Fig. 12.

4.5.2 Clearing and Treatment of Forms

All rubbish, particularly chippings, shavings and sawdust and traces of

concrete, if any, shall be removed form the interior of the forms before the

concrete is placed. The surface in contact with the concrete shall be wetted and

sprayed with fine sand, or treated with an approved composition before use,

every time. Concreting to be done for cold weather shall be as per IS 7861(Part

2) : 1981

4.5.3 Stripping Time under fair weather conditions (generally where average daily

temperature is 20"C or above) , and where ordinary cement is used, forms may

be removed after 24 to 48 hours of the placing of concrete. In dull weather

such as in rainy periods or in very cold temperature, the forms shall be

removed after 48 hours of the placing of concrete.

4.6 'Mixing, Placing and Compacting of Concrete


4.6.1 Mixing

Concrete shall preferably be mixed in a mechanical mixer, but hand mixing

shall be permissible. In case of emergency (when mechanical mixers are in

use) such as failure of the mixers, or where it is not practicable to haul the

mixers up to the location, and also for lean concrete sub-base, hand mixing

may be resorted to.

When hand mixing is adopted, it shall be carried out on water-tight platforms,

such as 1.8 mm galvanized iron plain sheets properly overlapped and placed

upon level ground. The coarse aggregates shall first be evenly spread out in

required quantity over the sheets. The fine aggregates shall be evenly spread

out over coarse aggregates. The aggregates shall then be thoroughly mixed

together and levelled. The required amount of cement shall be spread evenly

over the mixed aggregates and wet mixing shall start from one end with

required amount of water suing showels. The whole lot shall not be wetted,

instead mixing shall proceed progressively. If the aggregates are wet or

washed, cement shall not be spread out, but shall be put in progressively.

For mixing in the mechanical mixers, the same order of placing ingredients in

the drum shall be adopted, that is, coarse aggregates shall be put in first

followed by sand, cement and water.

Mixing shall be continued until there is a uniform distribution of material and

the mass is unform in colour and consistency but in no case shall mixing be

done for less than 2 minutes.

If the aggregates are wet, the amount of water shall be reduced suitably.

4.6.2 Transporting

Normally mixing shall be done right at the foundation. In places where it is not

possible, concrete may be mixed at the nearest convenient place. The concrete

shall be handled from the place of mixing to the place of final desposit as

rapidly as practicable by methods which shall prevent the segregation or loss

of any of the ingredients. If segregation does occur during transport the

concrete shall be remixed before being placed.

During hot or cold weather, concrete shall be transported in deep containers;

the deep containers, on account of their lower ratio of surface area to mass,

reduce the rate of loss of water by evaporation during hot weather and loss o'f

heat during cold weather.

4.6.3 Placing and Compacting

The concrete shall be placed and compacted before settling commences and

should not be subsequently disturbed. The placing should be such that no

segregation takes place.

Concrete shall be thoroughly compacted during the placing operation, and

thoroughly worked around reinforcement, around embedded fixtures and into

corners of form work by means of 16 mm diameter poking bars pointed at the

ends. The poking bars be worked 100 times in an area of 200 mm square for

300 mm depth. Over compaction causes the liquid to flow out upward causing

segregation and should be avoided.

If, after the form work has been struck, the concrete surface is found to have

defects, all the damaged surfaces shall be repaired with mortar application

composed of cement and sand in the same proportion as the cement and sand

in the concrete mix. Such repairs shall be carried out well before the

foundation pits are back filled.

Precautions to be taken on concrete work in extreme weather and under water,

as per the provisions of IS 4565:1978.

Field tests on workability of concrete and consistency may be carried out in the

form of slump test in accordance with IS 1199:1959.

4.7 Back Filling


Following opening of form work and removal of shoring and strutting, if any,

back filling shall be started after repair, if any, to the foundation concrete.

Back filling shall normally be done -with the excavated soil, unless it consists

of large boulders / stones, in which case the boulders shall be broken to a

maximum size of 80 mm. The back filling materials should be clean and free

from organic or other foreign materials. The earth shall be deposited in

maximum 200 mm layers, levelled and wetted and tamped properly before

another layer is deposited. Care shall be taken that the back filling is started

from the foundation ends of the pits, towards the outer ends. After pits have

been back filled to full depth, the stub template may be removed.

The back filling and grading shall be carried to an elevation of about 75 mm

above the finished ground level to drain out water. After back filling 50mm

high earthen embankment (bandh) will be made along the sides of excavated

pits and sufficient water will be poured in the back filled earth for at least 24

hours.

4.8 Curing


The concrete after setting for 24 hours old shall be cured by keeping the

concrete wet continuously for a period of 10 days after laying. The pit may be

back filled with selected earth sprinkled with necessary amount of water and

well consolidated in layers not exceeding 200 mm of consolidated thickness

after a minimum period of 24 hours and thereafter both the back filled earth

and exposed chimney top shall be kept wet for the remainder of the prescribed

time of 10 days. The uncovered concrete chimney above the back filled earth

shall be kept wet by providing empty cement bags dipped in water fully

wrapped around concrete chimney for curing and ensuring that the bags are

kept wet by the frequent pouring of water on them.

CHAPTER-5

Protection of Foundation

___________________________________________________________________________

CHAPTERFIVE

___________________________________________________________________________

PROTECTION OF FOUNDATIONS


5.0 Concrete Type


5.1 Uplift Resistance


The transmission line foundations are designed to withstand both down thrust

and uplift forces. The resistance of the soil in compression in reasonably well.

However, the resistance to uplift is uncertain and there are many theories

reported for uplift resistance in literature. These theories are generally based

on a slip surface rising vertically from the edge of the footing or a surface

rising at an angle of friction from the vertical, thus forming a frustum (Fig.13).

Under the vertical surface theory the shear resistance along the sides of the

plane or cylinder is calculated and added to the dead weight of the soil and

footing. Under the angle of friction theory, the dead weight within the frustum

is considered to provide resistance against uplift. Test results have shown that

neither of these methods provide reliable results. The cone method is usually

conservative at a shallow depth. This problem is solved by constructing

revetment or benching around the complete tower foundation or individual

tower leg.

The foundations are also required to be protected from landslide, earth slip.,

erosions of the hills due to flood etc. The Revetment or Benching also protects

the foundation from the above.

5.2 Revetment


Revetment is generally constructed at those locations where the angle of

repose intersects the ground at a difference of about 1.0m below the centre peg

level. Generally a wall is constructed around the individual tower leg or

around the complete foundation enclosing all the four tower legs. Revetment is

made around the complete foundation in case the tower base dimensions are

smaller i.e. within 10.0m. However, in case the tower base dimensions are

very very large, construction of Revetment around the individual Cower leg

may be economical. The site engineer is required to make a cost comparison

considering the revetment around the individual leg or all the four legs.

The Revetment wall can be constructed by random rubble masonry wall with

rectangular cross section having a width of 450mm and a staggered depth of

1 1/2 times the exposed portion of wall above ground level. A Random Rubble

masonry, wall of Trapezoidal cross section (Fig. 14) may be constructed for

the difference of elevation above 1m.

In case tower is located in hill slope i.e. where the difference in elevations is

very large. Revetments may not be economical. In such cases leg extensions of

structural steel can be designed for the standard length. No Revetment is to

made for the purpose of stub setting. Revetments should not be done for

levelling the-area under the tower base for the purpose of stub setting. The

payment for the levelling the area and Trench excavations along the sides as

well as diagonals of the tower legs is included in the unit rate of stub setting.

5.3 Benching


When the line passes -through .the hilly/undulated terrain, levelling of the

ground may be required for casting of the tower foundation as to protect the

stub from corrosion. All such activities shall be termed as benching and shall

include the cutting of excess earth above the centre peg level and filling the

same in the area below the centre peg level.

It is preferable to do the benching work after construction of the Revetment

wall since the excavation will infringe with the filled soil of the benching work

and cause inconvenience for excavation.

5.4 Protection of Foundation against Chemical Water


Whenever the chemicals are present in water in contact with steel or R.C.C.

member it will have a deteriorating effect on concrete as well as steel. To

prevent this, concrete incashing on the steel members to be done and

Bituminious paint to be provided over the concrete surface. The concrete

incasing to be done upto 200mm above the chemical water level. The bracing

members are to be enclosed accordingly. Minimum 50 mm clear cover to be

provided over the steel member.

5.5 Measurement of Volume for rivetment and benching


5.5.1 General

There are three methods generally adopted for measuring the volume. They are

:

(i) From cross-sections

(ii) From spot levels

(iii) From contours

The first two methods are commonly used for the calculation of each work

while the third method is generally adopted for the calculation of of depressed

area.

5.5.2 Measurement from Cross-Sections

This is the most widely used method. The total volume is divided into a series

of solids by the planes of cross-sections. The fundamental solids on which

measurement is based are the prism, wedge and prismoid. The spacing of the

sections depends upon the character of the ground and the accuracy required in

the measurement. The area of the cross-section taken along the line are first

calculated by standard formulae developed below, and the volumes of the

prismoids between successive cross-sections are then calculated by either

trapezoidal formula or by prismodial formula.

The various cross-sections may be classified as

(i) Level section, (Figs. 15 and 16)

(ii) Two-level section, (Fig. 17)

(iii) Side hill two-level section, (Fig. 18)

(iv) Three-level section (Fig. 19) and

(v) Multi-level section (Fig. 20).

General notations : Let

b = the constant formation (or sub-grade) width

h = the depth of cutting on centre line

w1 and w2 = the side widths, or half breadths, i.e., the horizontal distances

from the centre to the intersection of the side slopes with original ground level.

h1 and h2 = the side heights, i.e., the vertical distances from formation level to

the intersections of the slope with the original surface.

n horizontal to 1 vertical = inclination of the side slopes.

m horizontal to 1 vertical = the transverse slope of the original ground.

A = the area of the cross-section.

(a) Level Section (Fig. 16)

In this case the ground is level transversely.

h1 = h2 = h

w1 = w2 = w = b/2 + nh

A = {b/2 + (b/2+nh)} h

= (b+n) h

(b) Two-Level Section (Fig. 17)

Let O be the point on the centre line at which the two sides slopes intersect.

Hence BH : HO : : N : 1

OR ho = b/2n

The Area DCEBA = DCO + ECO- ABO

= ½ { (h+b/2n) w1 + (h+b/2n) w2 – b2/2n)

= ½ {w2+w2) (h+b/2n)-b2/2n) ……………………………………… (5.2)

The above formula has been derived in terms of w1 and w2 and does not

contain the term m. The formula is, therefore, equally applicable even if DC

and CE have different slopes, provided w1 and w2 are known. The formula can

also be expressed in terms of h1 and h2.

Thus Area DCEBA = DAH+ EBH+DCH+ECH

= ½ { (b/2) h2 + (b/2) h1 + hw2+hw1)}

= ½ {b/2 (h1+h2) + h (w1+w2)………………………………………… (5.3)

The above expression is independent of m and n. Let us now find the

expression for w1, w2, h1 and h2 in terms of b, h, m and n.

BJ = nh1 ……………………………………………………………… (1)

Also BJ = HJ-HB=w1 – b/2 …………………………………………. (2)

Nh1 = w1 – b/2 ……………………………………………………….. (i)

Also, w1 = (h1 – h) m

Substituting the value of w1 in (i), we get

Nh1 = (h1-h) m – b/2

Or h1 (m-n) = mh+b/2

Or h1 = (m/m-n) (h+b/2m)

Substituting the value of h1 in (i), wet get

W1 = b/2+nh1=b/2+mn/m-n (h+b/2m) ………………………………….. (5.4)

Proceeding in similar manner, it can be shown that

h2 = (m/m+n) (h-b/2m) …………………………………………….……. (5.5)

and w2 = b/2+mn/m+n) (h-b/2m) ……………………………………… (5.6)

Substituting the values of w1 and w2 in equation (5.2) and simplifying, we get

Area = (m2n/m2-n2) (h+b/2n)2-b2/4n ………………………………… (5.7)

Similarly, substituting the values of w1, w2, h1 and h2 in the equation (5.3),

we get

Area = {n (b/2)2 + m2 (bh+nh2)}/(m2-n2) ……………………………… (5.8)

(c) Side Hill Two-Level Section (Fig. 18)

In this case, the ground slope crosses the formation level so that one portion of

the area is in cutting and the other in filling.

Now BJ = nh1

Also, BJ = HJ – HB = w1-b/2

& nh1=w1-b/2 …………………………………………………………..... (i)

But w1 = (h1-h) m ……………………………………………………….. (ii)

Solving (i) and (ii) as before, we get

h1 = (mn/m-n) (b/2m+h) ………………………………………………. (5.9)

and w1 = b/2 + (mn/m-n) (b/2m+h) ……………………………..……. (5.10)

Let us now derive expression for w2 and h2 :

IA = nh2

Also IA = IH – AH=w2-b/2

nh2 = w2-b/2 …………………………………………………………… (iii)

Also w2 = (h+h2) m

nh2 = (h+h2) m – b/2 …………………………………………………. (iv)

and h2 (m-n) = b/2 – mh

or h1 = (mn/m-n) (b/2m-h) …………………………………………… (5.11)

Hence w2 = b/2+nh2=b/2+(mn/m-n) {(b/2m)-h} …………………… (5.12)

By inspection, it is clear that the expressions for w1 and w2 are similar; also

expression of h1 and h2 are similar, except for –h in place of +h.

Now area of filling = PBE=A1 (say),

And, area of cutting = PAD = A2 (say),

A1 = ½ (PB) (EJ) = ½ (b/2+mh) {(m/m-n) (b/2m+h)}

= (b/2+mh)2/2 (m-n) ………………………………………………….. (5.13)

and A2 = ½ (AP) (ID) = ½ {(b/2) – mh} [m/(m-n) {(b/2m) – h}]

= { (b/2) – mh}2 /2 (m-n) …………………………………………… (5.14)

(d) Three –Level Section (Fig. 19)

Let 1 in m1 be the transverse slope of the ground to one side and 1 in m2 be the

slope to the other side of the centre line of the cross section (Fig. 19).

The expressions for w1, w2, h1 and h2 can be derived in the similar way as for

case (b)

Thus, w1 = (m1n/m1-n) (h+b/2n) …………………………………….. (5.15)

w2 = (m2n/m2-n) (h+b/2n) ………………………………………….. (5.16)

h1 = (h+w1/m1) = (m1/m1-n) (h+b/2m1) ………………………….. (5.17)

h2 = (h-w2/m2) = (m2/m2+n) (h-b/2m2) …………………………… (5.18)

The area ABECD = AHD+BHE+CDH+CEH

= ½ [ (h2xb/2) + (h1xb/2) + hw2 + hw1]

= [b/4 (h1+h2) + h/2 (w1+w2)] ……………………………………… (5.19)

(e) Multi-Level Section (Fig. 20)

In the multi-level sections the co-ordinate system provides the most general

method of calculating the area. The cross-section does provide with x and y

co-ordinates for each vertex of the section, the origin being at the central point

(H). The x co-ordinates are measured positive to the right and negatives to the

left of H. Similarly, the y co-ordinates (i.e. the heights) are measured positive

for cuts and negative for fills. In usual form, the notes are recorded as below :

(h2/w2) (h1/w1) (h/o) (H1/W1) (H2/W2)

If the co-ordinates are given proper sign and if the co-ordinates of formation

points A and B are also included (one at extreme left and other at extreme

right) they appear as follows :

O/(-b/2) h/(-w2) h1/(-w1) h/o) H1/)+w1) H2/(+w2) o/+ (b/2)

There are several methods to calculate the area. In one of the methods, the

opposite algebric sign is placed on the opposite side of each lower term. The

co-ordinates then appear as :

O/(-b/2+) h2/ (-w2+) h1/(-w1+) h/(o) H1 / (+W1-) H2/(+W2-) o/(+b/2-)

The area can now be computed by multiplying each upper term by the

algebraic sum of the two adjacent lower terms, using the signs facing the upper

term. The algebraic sum of these products will be double the area of the cross-

section.

Thus, we get

H = ½ [h2 ( +b/2-w1) + h1 (+w2+o) + h (+w1+W1) +

H1 (o+W2)+H2 (-W1+b/2)] ………………………………………… (5.20)

5.5.3 The Prismoidal Formula

The volumes of the prismoids between successive cross-section are obtained

either by trapezoidal formula or by prismoidal formula. We shall first derive

an expression for prismodal formula.

A prismoid is defined as a solid whose end faces lie in parallel planes an

consist of any two polygons, not necessarily of the same number of sides, the

longitudinal faces being surfaces extended between the end planes.

The longitudinal faces take the form of triangles, parallelograms, or trapezium.

Let d = length of the prismoid measured perpendicular to the two end parallel

planes.

A1= area of cross-section of one end plane.

A2 = area of cross-section of the other end plane.

M = the mid-area = the area of the plane midway between the end planes and

parallel to them.

In fig. 21, let A1B1C1D1 be one end plane and A2B2C2D2 be another end

plane parallel to the previous one. Let PQRST represent a plane midway

between the end faces and parallel to them. Let Am be the area of mid-section.

Select any point O in the plane of mid-section and joint it to the vertices of

both the end planes. The prismoid is thus divided into a number of pyramids,

having the apex at A and bases on end and side faces. The total volume of the

prismoid will therefore be equal to the sum of the volume of the pyramids.

Volume of pyramid OA1B1C1D1 = 1/3 (d/2) A1 = (1/6) (A1d)

Volume of pyramid OA2B2C2D2 = (1/6) (A2d)

To find the volumes of pyramids on side faces, consider any pyramid such as

OA1B1B2A2.

Its volume = 1/3 (A1B1A2B2) x h, where h = perpendicular distance of PT

from O

= 1/3 (d x PT) h

= (1/3) d (2 OPT) = (2/3) d (OPT)

Similarly, volume of another pyramid OC1D1D2 on the side

face = (2/3) d (OSR) = (2/3) d (OSR)

Total volume of lateral (side) pyramids

= (2/3) d (PQRST) = (2/3) Am

Hence, total volume of the pyramid

= (1/6)A1d+(1/6)A2d + (2/3) d. Am

V = d/6 (A1+A2+4Am) …………………………………………..……. (5.21)

Let us now calculate the volume of earth work between a number of sections

having area A1, A2, A3 ………, An spaced at constant distance d apart.

Considering the prismoid between first three sections, its volume will be, from

equation (5.21).

= (2d/6) (A1+4A2+A3), 2d being the length of the prismoid.

Similarly, volume of the second prismoid of length 2d will be

= (2d/6) (A2+4A4+A5),

and volume of last prismoid of length 2d will be

= 2d/6 (An-2+4An-1+An)

Summing up, we get the total volume,

V= (d/3) [A1+4A2+2A3+4A4+ … + 2An-2+4An-1+An] …………… (5.22)

or V = (d/3) [(A1+An) + 4 (A2+A4+An-1)+2 (A3+A5+An-2)]

This is also known as Simpson’s rule for volumes. Here also, it is necessary to

have an odd number of cross-sections. If there are even number of sections, the

end strip must be treated separately, and the volume between the remaining

sections may be calculated by prismodial formula.

5.5.4 The Trapezoidal Formula (Average end area method)

This method is based on the assumption that the mid area is the mean of the

end areas. In that case, the volume of the prismoid of Fig. 21 is given by

V = (d/2) (A1+A2)

This is true only if the prismoid is composed of prisms and wedges only and

not of pyramids. The mid area of pyramid is half the average area of the ends;

hence the volume of the prismoid (having pyramids also) is over estimated.

However, the method of end area may not be accepted with sufficient accuracy

since the actual earth solid may not be exactly a prismoid. In some cases, the

volume is calculated and then a correction is applied, the correction being

equal to the difference between the volume as calculated and that which could

be obtained by the use of the prismoid formula. The correction is known as the

prismoidal correction.

Let us now calculate the volume of earth work between a number of sections

having areas A1, A2, ……… An spaced at a constant distance d.

Volume between first two sections = (d/2) (A1+A2)

Volume between next two sections = (d/2) (A3+A4)

Volume between last two sections = (d/2) (An-1+An)

Total Volume = V=d {(A1+A2)/2+A2+A3+An-1} …………………… (5.23)

5.5.5 The Prismoidal Correction (Cp)

As stated earlier, the prismoidal correction is equal to the difference between

the volumes as calculated by the end-area formula and the prismoidal formula.

The correction is always substractive, i.e. it should be substracted from the

volume calculated by the end area formula.

Let us calculate the prismoidal correction for the case when the end sections

are level sections. Let A, w1, w2, h1, h2 etc., refer to the cross-sections at one

end and A, w1, w2, h1, h2, etc., to the cross section at the other end.

Now A=h (b+nh)

And A = h (b+nh)

Volume by end area rule is given by

V = (d/2) [h (b+nh) + h (b+nh)]

= d [bh/2+bh/2+nh2/2+nh2/2] ……………………………………………. (i)

Again, the mid-area centre height = (h+h’)/2

Mid-area = {(h+h’)/2} [{b+n(h+h’)/2}]

Volume by prismoidal formula given by

V = d/6 [h(b+nh)+h’ (b+nh’)+4 {(h+h’)/2} x {(b+n(h+h’)/2}]

V=d/6 [3bh+3bh’+2+nh2+2nh’2+2nhh’]

=[bh/2+bh’/2+bh’/2+nh2/3+nh’2/3+nhh’/3] …………………………… (ii)

Substracting (ii) from (i), we get the prismoidal correction,

Cp = (dn/6) (h-h’)2 ………………………………………………… (5.24)

Similarly, the prismoidal correction for other sections can also be drived. The

standard expression for C2 are given below.

For two level section :

C2 = d/6n (w1-w’1) (w2-w’2) …………………………………….. (5.25)

For side hill two-level section ;

Cp (cutting) = (d/12n) (w1-w’1) {(b/2+mh)-(b/2+m’h’)} ……….. (5.26)

Cp (filling) = (d/12n) (w2-w’2) {(d/2-mh) – (d/2-m’h’) …………. (5.27)

For three-level section :

Cp = (d/12) (h-h’) {(w1+w2) – (w1’+w2’) …………………….. (5.28)

5.5.6 The Curvature Correction

The prismoidal and the trapezoidal formulae were derived on the assumption

that the end sections are in parallel planes. When the centre line of cutting or

an embankment is curved in plane, it is common practice to calculate the

volume as if the end sections were in parallel planes, and then apply the

correction for curvature. The standard expression for various sections are

given below. In some cases, the correction for curvature is applied to the areas

of cross-sections thus getting equivalent areas and then to use the prismoidal

formula.

(i) Level section : No correction is necessary since the area is symmetrical

about the centre line.

(ii) Two-level section and three-level section ;

Cc = (d/6R) (w12-W22) (h+b/2n) ………………………..…… (5.29)

Where R is the radius of the curve.

(iii) For a two-level section, the curvature correction to the area

Ae/A per unit length ………………………………………… (5.30)

Where e= the eccentricity, i.e., horizontal distance from the centre line to the

centroid of the area = w1w2 (w1+w2)/3An …………………………. (5.31)

The correction is positive if the centroid and the centre of the curvature are to

the opposite side of the centre line while it is negative if the centroid and the

centre of the curvature are to the same side of the centre line.

(iv) For side hill two-level section :

Correction to area = Ae/R per unit length ……………………. (5.32)

Where e = (1/3) (w1+b/2-nh) for the larger area …………….. (5.33)

And e = (1/3) (w2+b/2nh) for the smaller area ……………… (5.34)

5.5.7 Volume from Spot Levels

In this method, the field work consists in dividing the area into a number of

squares, rectangles or triangles and measuring the levels of their corners before

and after the construction. Thus, the depth of excavation or height of filling at

every corner is known. Let us assume that the four corners of any one square

of rectangle are at different elevations but lie in the same inclined plane.

Assume that it is desired to grade down to a level surface a certain distance

below the lowest corner. The earth to be moved will be a right truncated prism,

with vertical edges at a, b, c and d [Fig. 22]. If ha, hb, hc and hd represent the

depth of excavation of the four corners, the volume of the right truncated

prism will be given by

V = {(ha+hb+hc+hd)/4} x A ………………………………………. (5.35)

= average height x the horizontal area of the rectangle.

Similarly, let us consider the triangle abc of Fig. 22. If ha, hb and hc are the

depths of excavation of the three corners, the volume of the truncated

triangular prism is given by

V = {(ha+hb+hc) / 3} x A …………………………………………. (5.36)

= (average depth) x horizontal area of the triangle.

Volume of a group of rectangles or squares having the same area.

Let us now consider a group of rectangles of the same area arranged as shown

in Fig. 22. It will be seen by inspection that some of the heights are used once

only, some heights are common to two rectangles (such as at b), some heights

are common to three rectangles (such as at e), and some heights are common

to four rectangles (such as at f). Thus, in Fig. 22, each corner height will be

used as many times as there are rectangles joining at the corner (indicated on

the figure by numbers).

Let h1 = the sum of the heights used once.

h2 = the sum of the heights used twince.

h3 = the sum of the heights used thrice.

h4 = the sum of the heights used four times.

A = horizontal area of the cross-section of one prism.

Then, the total volume is given by

V = A (1h1+2h2+3h3+4h4)/4 …………………………………… (5.37)

Volume of a group of triangles having equal area [Fig. 22]

If the ground is very much undulating, the area may be divided into a number

of triangles having equal area. In this case, some corner heights will be used

once [such as point a of Fig. 22], some twice (such as at d), six times (such as

at f), and seven times (such as at j). The maximum number of times a corner

height will be used as many times as there are triangles joining at the corner

(indicated in the figure by numbers).

Let h1 = the sum of the heights used once.

h2 = the sum of the heights used twice.

h3 = the sum of the heights used thrice.

…………………………………………

…………………………………………

h8 = the sum of height used eight times.

A = area of each triangle.

The total volume of the group is given by

V = A/3 (1h1+2h2+3h3+4h4+5h5+6h6+7h7+8h8) ……….. (5.38)

5.5.8 Volume from Contour Plan

The amount of earth work or volume can be calculated by the contour plan

area. There are four distinct methods, depending upon the type of the work.

a) By Cross-Sections

It was indicated, that with the help of the contour plan, cross-section of

the existing ground surface can be drawn. On the same cross-section,

the grade line of the proposed work can be drawn and the area of the

section can be estimated either by oridinary methods or with the hel of

a planimeter.

Thus, in Fig. 23, the irregular line represents the origin ground while

the straight line ab is obtained after grading. The area of cut and of fill

can be found from the cross-section. The volumes of earth work

between adjacent cross-sections may be calculated by the use of

average and areas.

(b) By Equal Depth Contours

In this method, the contours of the finished or graded surface are drawn

on the contour map, at the same interval as that of the contours. At

every point, where the contours of the finished surface intersect a

contour of the existing surface the cut or fill can be found by simply

subtracting the difference in elevation between the two contours. By

joining the points of equal cut or fill, a set of lines is obtained

(represented by thick lines in Fig. 24). These lines are the horizontal

projections of lines cut from the existing surface by planes parallel to

the finished surface. The irregular area bounded by each of these lines

can be determined by the use of the planimeter. The volume between

any two successive area is determined by multiplying the average of

the two areas by the depth between them, or by prismoidal formula.

The sum of the volume of all the layers is the total volume required.

Thus, in Fig. 24, the ground contours (shown by this continuous lines)

are at the interval of 1.0 meter. On this a series of straight, parallel and

equidistant lines (shown by broken lines) representing a finished plane

surface are drawn at the interval of 1.0 meter. At each point in which

these two sets of lines meet, the amount of cutting is written. The thick

continuous lines are then drawn through the points of equal cut thus

getting the lines of 1, 2, 3 and 4 metres cutting. The same procedure

may be adopted if the contours of the proposed finished surface are

curved in plan.

Let A1, A2, A3 …………. Etc. be the areas enclosed in each of the

thick lines (known as the equal depth contours). This will be the whole

area lying within an equal depth contour line and not that of the strip

between the adjacent contour lines.

h = contour interval

V = Total volume

Then V = h/2 (A1/A2) by trapezoidal formula

Or h/3 (A1/4A2/A3) by prismoidal formula.

(c) By Horizontal Planes

The method consists in determining the volumes of earth to be moved

between the horizontal planes marked by successive contours.

Thus, in fig. 25, the thin continuous lines represent the ground contours

at 1m interval. The straight, parallel and equidistant lines (shown by

broken lines) are drawn to represent the finished plane surface at the

same interval. The point ‘P’ represent the points in which the ground

contours and the grade contours of equal value intersect. By joining the

p-points the line in which the proposed surface cuts the ground is

obtained. These lines have been shown by thick lines. Along thin line

no excavation or fill is necessary but within this line, excavation is

necessary and outside this line filling is necessary. Thus, the extent of

cutting between 17m ground contour and the corresponding 17m grade

contour is shown by hatched lines. Similarly, the extent of cutting

between the 16m ground contour and the corresponding 16m grade

contour is also shown by hatched lines. Proceeding like this, we can

mark the extent of earthwork between any two corresponding ground

and grade contours and the areas enclosed in these extents can be

measured by planimeter. The volume can then be calculated by using

end area rule.

CHAPTER-6

Concrete Technology

___________________________________________________________________________

CHAPTERSIX

___________________________________________________________________________

CONCRETE TECHNOLOGY


6.1 Introduction


Cement concrete is the most widely used structural material in the world for

civil engineering projects. Its versatility, economy, adaptability, and

worldwide availability, and especially its low maintenance requirements, make

it very useful. It consists of cement, water, and aggregate which have been

mixed together, placed, consolidated, and allowed to solidify and harden. The

cement and water form a paste, which acts as the glue, or binder. When fine

aggregate is added the resulting mixture is termed mortar. Then when coarse

aggregate is included concrete is produced. Normal concrete consists of about

three-fourths aggregate and one-fourth paste, by volume. The paste usually

consists of water-cement ratios between 0.4 and 0.7 by weight. Admixtures are

sometimes added for specific purposes, such as to entrain numerous

microscopic air bubbles, impart colour, retard the initial set of the concrete,

waterproof the concrete, etc. The operations involved in the production of

concrete will vary with the type of end use for the concrete, but, in general, the

operations,include the following (Fig.26) :

a) Batching the materials

b) Mixing

c) Transporting

d) Placing

e) Consolidating

f) Finishing

g) Curing

6.2 Proportioning Concrete Mixtures


For successful concrete utilization, the mixture must be properly proportioned.

First, although it takes water to initiate the hydraulic reaction, the higher the

water-cement ratio, the lower the resulting strength and durabilicy. Second,

the more water that is used the higher will be the slump. Third, the more

aggregate that is used, the lower the cost of the concrete. Fourth, the larger the

maximum size of coarse aggregate, the less the amount of cement paste that

will be needed to coat all the particles and provide necessary workability.

Fifth, the more that concrete is consolidated, the better it becomes. Sixth, The

use of properly entrained air enhances almost all concrete properties with little,

or no, decrease in strength if the mix proportions are adjusted for the air. And

seventh, the surface abrasion resistance of the concrete is almost entirely a

function of the properties of the fine aggregate.

6.3 Fresh Concrete


To the designer, fresh' concrete is of little importance. To the constructor,

fresh concrete is all-important, because it is the fresh concrete that must be

mixed, transported, placed, consolidated, finished, and cured. To satisfy both

the designer and the constructor, the concrete should:

a) Be easily mixed and transported.

b) Be uniform throughout, both within a given batch and between batches.

c) Be of proper workability so that it can be consolidated, will completely

fill the forms, will not segregate, and will finish properly.

The major property of importance to the constructor is the workability, which

is difficult to define in precise terms. Like the terms warm and cold,

workability depends upon the situation. One measure of workability is slump

Table (1) below gives the recommended slump for various types of Concrete

Construction.

Table (1) Recommended slumps for various types of Construction

Types of Construction Slump (inch)Maximum Minimum

Reinforced foundation walls

and footings

1 1

Plain footings, caissons, and

substructure walls

1 1

Beams and reinforced walls 4 1Building columns 4 1Pavements and slabs 3 1Mass concrete 2 1

6.4 Handling and Batching Concrete Materials


Most concrete batches, although designed on the basis of absolute volumes of

the ingredients, are ultimately controlled in the batching process on the basis

of weight.

Therefore it is necessary to know the weight volume relationships of all the

ingredients. Then each ingredient must be accurately weighed if the resulting

mixture is to have the desired properties. It is the function of the batching

equipment to perform this weighing measurement.

(i) Handling cement : Cement may be supplied to the project in paper

bags, each containing 1 Cu ft. loose measure and weighing 94 lb net.

However, for most large projects, the cement is supplied in bulk

quantities from cement is supplied in bulk quantities from cement

transport trucks, each holding 25 tons or more, or from railroad cars.

Bag cement must be stored in a dry place on pallets and should be left

in the original bags until used for concrete. If the batching of concrete

requires one or more whole bags of cement, the use of bag cement

simplifies the batching operation.

(ii) Batching and concrete : Usually, concrete specifications require the

concrete to be batched with aggregate having at least two size ranges

(coarse and fine) and up to six ranges. (Fig. 27) illustrates the proper

and improper methods of batching. Aggregate from each size range

must be accurately measured. The aggregate, water, cement, and

admixtures (if used) are introduced into a concrete mixer and mixed for

a suitable period of time until all the ingredients are adequately

blended together.

6.5 Batch plants and mixers


There are two types of concrete-mixing operations in use, job-batched concrete

and central-batched concrete. Today, unless/the project is in a remote location

or is relatively large, more and more of the concrete is batched in a central

batch plant and transported to the job site in ready-mixed concrete trucks. Fig.

28 shows a portable concrete batch plant, and Fig. 29 shows, a large central

batch plant of the type in general use. A concrete batch required four different

sizes of coarse aggregate, plus sand, two types of cement and water. The water

and liquid admixtures are normally measured by volume, while the cement and

aggregates are measured by weight. To control the batching, close tolerances

are maintained. Table (2) gives the permissible tolerances. Batch plants

are available in three categories, manual, semiautomatic, and fully

automatic. Manual batching is generally used for small jobs or low output

values (less than about 500 cu. yd total or around

20 cu. yd per hr). In semiautomatic plants the charging and discharging of the

batches are activated manually but are automatically terminated. In a fully

automatic batch plant, a single starter switch activates the batching sequence,

the weights and volumes of which have been previously programmed into the

system.

Present-day plants usually have mixers capable of mixing up to 8 cu yd of

concrete in each batch (although plants have been built with mixers capable of

mixing 12 cu yd of concrete in each batch), and can produce up to about 200

cu yd of concrete per hour. The mixer either tilts to discharge the concrete into

a truck or a chute is inserted into the mixer to catch and discharge the concrete.

To increase efficiency, many large plants contain two mixers connected in

series. The back mixer premixes the aggregates and cement, which reduces the

time necessary for the front mixer to completely mix the batch.

Although the figures and discussion herein cover drum mixing of concrete, there are two

other types of mixers in use-the pan mixer and the continuous mixer.

In determining the quantities needed and the output for a given plant, any

delays in productivity resulting from reduced operating factors should be

included.

Table (2) Recommended tolerances for batching concrete materials

Batch weights greater than

30% of scale capacity

Batch weights less than

30% of scale capacityIndividual Ingredient batching Cumulative batching Individual

batching

Cumulative

batchingCement and other

cementitious materials

1% or 0.3% of scale

capacity, whichever is greater

Not less than required weight or

4% more than required weightWater (by volume or

weight), %

1 Not recommended 1 Not recommended

Aggregates, % 2 1 2 0.3% of scale

capacity or 3% of

required cumulative

weight, whichever is

lessAdmixtures (by volume

or weight), %

3 Not recommended 3 Not recommended

6.6 Ready Mixed Concrete


Concrete is mixed in a central location and transported to the purchaser in a

fresh state, mixed at the plant or enroute. This type of concrete is termed ready

mixed concrete, concrete purchased in this manner enjoys wide acceptance.

Obviously, to be useful, readymixed concrete must be available within a

reasonable distance from the project. On remote sites and sites requiring large

quantities of concrete, generally field concrete batch plants are used.

Concrete purchased from a ready-mixed concrete plant can be provided in

several ways. These include :

a) Central mixed concrete

This is concrete which is completely in a stationary mixer and

transported to the project either in a truck agitator, a truck mixer

operating at agitating speed, or in a non agitating truck.

b) Shrink-mixer concrete

This is concrete which is partially mixed in a stationary mixer and then

mixed completely in a truck mixer (usually en route to the project).

c) Truck-mixer concrete

This is concrete that is completely mixed in a truck mixer, with 70 to

100 revolutions to be at a speed sufficient to completely mix the

concrete. This type of concrete is usually termed transit-mixed concrete

because it is generally mixed en route.

Transit mixers are available in several sizes up to about 14 cu yd, but

the most popular size is 8 cu yd (fig.30). They are capable of

thoroughly mixing the concrete within about 100 revolutions of the

mixing drum at mixing speed (generally 8 to 12 rpm). This mixing

during transit usually results a stiffening the mixture, and the addition

of water is done at the job site to restore the slump, followed by

remixing. This has caused problem and raised questions concerning the

uniformity of ready-mixed concrete. Some of the water be withheld

until the mixer arrived at the project site (especially in hot weather),

then the remaining water be added and an additional 30 revolutions of

mixing be required. To offset any stiffening, small amounts of

additional water are permitted, provided the design water-cement ratio

is not exceeded. The uniformity requirements of ready mixed concrete

are given in Table 3.

Table (3) Uniformity Requirements for Readymixed Concrete to be given

Tests Requirement, expressed as maximum

permissible difference in results of tests of

samples taken from two locations in the

concrete batch

Weight per cu ft calculated to an air-free

basis

1.0 lb/cu. Ft.

Air content, volume percent of concrete 1.0%

Slump :If average slump is 4 in. or less 1.0 in.

If average slump is 4 to 6 in. 1.5 in.

Coarse aggregate content, portion by weight

retained on No. 4 sieve

6.0%

Unit weight of air-free mortar based on

average for all comparative samples tested

1.6%

Average compressive strength at 7 days for

each sample, based on average strength of all

comparative test specimens

7.5%

Concrete may be ordered in several ways. They are :

a) Recipe batch

The purchaser assumes responsibility for proportioning the concrete mixture,

to include specifying the cement content, the maximum allowable water

content, and the admixtures required. The purchaser may also specify the

amounts and type of coarse and fine aggregate.

Under this approach, the purchaser assumes full responsibility for the resulting

strength and durability of the mixture, providing the stipulated amounts are

furnished as specified.

b) Performance batch

The purchaser specifies the requirements for the strength of the concrete, and

the manufacturer assumes full responsibility for the proportions of the various

ingredients that go into the batch.

c) Part performance and part recipe

The purchaser generally specifies a minimum cement content, the required

admixtures, and the strength requirements, allowing the manufacturer to

proportion the concrete mixture within the constraints imposed.

Today, most purchasers of concrete use the third approach, part performance

and part recipe, as it ensures a minimum durability while still allowing the

ready-mixed concrete supplier some flexibility to supply the most economical

mixture.

6.7 Moving and Placing Concrete


Once the concrete arrives at the project site, it must be moved to its final

position without segregation and before it has achieved an initial set. This

movement may be accomplished in several ways, depending upon the distance,

elevation, and other constraints imposed. These methods include buckets or

hoppers, chutes and drop pipes, belt conveyors and concrete pumps.

a) Buckets or hoppers

Normally designed bottom dump buckets permit concrete placement at the

lowest practical slump (Fig.31). Care should be exercised to prevent the

concrete from segregating as a result of discharging from too high above the

surface or allowing the fresh concrete to fall past obstructions. Gates should be

designed so that they can be opened and closed at any time discharge of the

concrete.

b) Manual or motor propelled buggies

Hand buggies and wheelbarrows are usually capable of carrying from 4 to 9 cu

ft of concrete, and thus are suitable on many projects, provided there are

smooth and rigid runways upon, which to operate. Hand buggies are safer than

wheelbarrows because they have two wheels rather than one. Hand buggers

and wheelbarrows are recommended for distances less than 200 ft. while

power-driven or motor driven buggies-with capacities up to around 14 cu ft.,

can traverse up to 1,000 ft economically (see Fig.32).

c) Chutes and drop pipes

Chutes are often used to transfer concrete from a higher elevation to a lower

elevation. They should have a round bottom, and the slope should be steep

enough for the concrete to -flow continuously without segregation. Drop

pipes are circular pipes used to transfer the concrete vertically. The pipe

should have a diameter at least eight times the maximum aggregate size at the

top 6 to 8 ft, and may be tapered to approximately six times the maximum

aggregate size. Drop pipes are usually used when concrete is placed in a wall

or column to avoid segregation from allowing the concrete to free-fall through

the reinforcement. In such areas, pipes should always be used.

d) Belt conveyors

Conveyors are classified into three types: (i) portable or self-contained

conveyors; (ii) feeders or series conveyors; and (iii) side-discharge or spreader

conveyors. All types must have the proper belt size and speed to achieve the

desired rate of placement. Fig.33 shows the use of several portable conveyors

to place concrete for a floor slab. This type of conveyor is capable of moving

large quantities of concrete rapidly. Particular attention must be given to points

where the concrete leaves one conveyor and either continues on another

conveyor or is discharged, as segregation can easily occur. Conveyors lend

themselves to moving concrete over long distances (Fig. 34) or up slopes

(Fig.35). The major disadvantage is the time necessary to set them up and to

change them. The optimum concrete slump for conveyors is from 2.5 to 3

inches.

e) Concrete pumps

The placement of concrete through rigid or flexible lines is not new. The pump

is an extremely simple machine. By applying pressure to a column of fresh

concrete in a pipe, it can be moved through the pipe if a lubricating outer layer

is provided and if the mixture is properly proportioned for pumping. In order

to work properly, the pump must be fed with concrete of uniform workability

and consistency. Today, concrete pumping is one of the fastest growing

specialty contracting fields. Pumps are available in a variety of sizes, capable

of delivering concrete at sustained rates of 10 to 150 cu yd per hr. Effective

pumping range varies from 300 to 1,000 ft horizontally, or 100 to 300 ft

vertically, although occasionally pumps have moved concrete more than 5,000

ft horizontally and 1,000 ft vertically.

Pumps require a steady supply of pumpable concrete to be effective. Today

there are three types of pumps being manufactured: piston pumps, pneumatic

pumps, and squeeze pressure pumps. They are shown diagrammatically in Fig.

36 (a), (b) and (c) , respectively. Most piston pumps today contain two pistons,

with one retracting during the forward stroke of the other to give a more

continuous flow of concrete. The pneumatic pumps normally use a reblending

discharge box at the discharge end to bleed off the air and to prevent

segregation and spraying. In squeeze pressure pumps, hydraulically powered

rollers rotate on the flexible hose within the drum and squeeze the concrete out

at the top. The vacuum keeps a steady supply of concrete in the tube from the

receiving hopper.

Pumps may be mounted on trucks, trailers, or skids. The truck-mounted pump

and boom combination is particularly efficient and cost-effective in saving

labour and eliminating the need for pipelines to carry the concrete.

Hydraulically operated and articulated. booms come in lengths up to 100 ft and

more (Fig.36).

Successful pumping of concrete is no accident. A common fallacy is to assume

that any good placeable concrete will pump successfully. The basic principle

of pumping is that the concrete moves as a cylinder through a lubricated line,

with the lubrication continually being replenished by the cylinder of concrete.

To pump concrete successfully, a number of rules should be carefully

followed. They are :

i) Use a minimum cement factor of 517 Ib of cement per cubic yard of

concrete (5.5 sacks per cu yd) .

ii) Use a combined gradation of coarse and fine aggregate that ensures no

gaps in sizes that will allow paste to be squeezed through the coarser

particles under the pressures induced in. the line. In particular, it is

important for the fine aggregate to have at lease 5 percent passing the

No.100 sieve and about 3 percent passing the No. 200 sieve. Line

pressures of 300 psi are common, and they can reach as high as 1,000

psi. This is the most often overlooked aspect of good pumping:

iii) Use a minimum pipe diameter of 5 in.

iv) Always lubricate the line with cement paste or mortar before beginning

the pumping operation.

v) Ensure a steady, uniform supply of concrete, with a slump of between

2 and 5 as and it enters the pump.

vi) Always presoak the aggregates before mixing them in the concrete to

prevent their soaking up mix water under the imposed pressure. This is

especially important when aggregates are used which have a high

absorption (such as structural lightweight aggregate).

vii) Avoid the use of reducers in the conduit line. One common problem is

the use of a 5-in to 4-in reducer at the discharge end so that workers

will have only a 4 in, flexible hose to move around. This creates a

obstruction and significantly raises the pressure necessary to pump the

concrete.

viii) Never use aluminum lines. Aluminium particles will be scraped from

the inside of the pipe as the concrete moves through and will become

part of the concrete. Aluminum and portland cement react, liberating

hydrogen gas, which can rupture the concrete - with disastrous results.

6.8 Consolidating Concrete


Concrete, being a heterogeneous mixture of water and solid particles in a stiff

condition, will normally contain a large quantity, of voids when placed into the

forms. It is the purpose of consolidation to remove these entrapped air voids.

The importance of proper consolidation cannot be overemphasized, as

entrapped air can render the concrete totally unstable. Entrapped air, can be

reduced two ways - use more water or consolidate the concrete. Fig. 37 shows

qualitatively the benefits of consolidation, especially on low-water -content

concrete.

Consolidation is normally achieved through the use of mechanical vibrators.

There are three general types : internal, surface and form vibrators. Internal or

spud vibrators as they are often called, have a vibrating casing or head which

is immersed into the concrete and vibrates at a high frequency (often as high as

10,000 to 15,000 vibrations per min) against the concrete. Currently these

vibrators are the rotary type and come in sizes from 3/4 in. to 7 in. (Fig. 38).

They are powered by electric motors or compressed air. Manufacturers have

extensive data on their vibrators.

Surface vibrators exert their effects at the top surface of the concrete and

consolidate the concrete from the top down. They are used mainly in slab

construction, and there are four general types: the vibrating screed, the pan-

type vibrator, the plate or grid vibratory tamper, and the vibratory rolling

screed. These surface vibrators operate in the range of 3,000 to 6,000

vibrations per min.

Form vibrators are external vibrators attached to the outside of the form or

mold. They vibrate the form, which in turn vibrates the concrete. These types

of vibrators are generally used in large precast concrete plants.

6.9 Recommended vibration practices


Internal vibration is generally best suited for ordinary construction provided

the section is large enough for the vibrator to be manipulated. As each vibrator

has an effective radius of action, vibrator insertions should be vertical at about

1.5 times the radius of action. The vibrator should never be used to move

concrete laterally, as segregation can easily occur. The vibrator should be

rapidly inserted to the bottom of the layer (usually 12 to 18 in. maximum lift

thickness) and at least 6 in. into the previous layer. It should then be held

stationary for about 5 to 15 sec until the consolidation is considered adequate.

The vibrator should then be withdrawn slowly. Where several layers are being

placed, each layer should be placed while the preceding layer is still plastic.

Vibration accomplishes two actions. First, it "slumps" the concrete, removing

a large portion of air that is entrapped when the concrete is deposited. Then,

continued vibration consolidates the concrete, removing most of the remaining

entrapped air. Generally, it will not remove entrained air. The question

concerning over vibration is often raised: When does it occur and how harmful

is it? The fact is that on low-slump concrete (concrete with less than 3 in

slump) it is almost impossible to overvibrate it with internal vibrators: When

in doubt as to how much vibration to impart to low-slump concrete, vibrate it

some more. The same cannot be said of concrete whose slump is 3 in. or more.

This concrete can be overvibrated, which results in segregation as a result of

coarse aggregate moving away from the vibrating head. Here the operator

should note the pressure of air bubbles escaping to the concrete surface as the

vibrator is inserted. When these bubbles cease, vibration is generally complete

and the vibrator should be withdrawn. Another point of caution concerns

surface vibrators. They too can overvibrate the concrete at the surface,

significantly weakening it if they remain in one place too long.

Another concern is the vibration of reinforcing steel. Such vibration improves the bond

between the reinforcing steel and the concrete/and thus is desirable. The

undesirable side effects 'include damage to the vibrator and possible

movement of the steel from its intended position.

Finally, revibration is the process whereby the concrete is vibrated again after

it has been allowed to remain undisturbed for some time. Such revibration can

be accomplished at any time. The running vibrator will sink of its own weight

into the concrete and liquefy it momentarily. Such revibration will i.-nprove

the concrete through increased consolidation.

6.10 Finishing and Curing Concrete


It cannot be stated too strongly that any work you do to a concrete surface after

it has been consolidated will weaken the surface. All too often, concrete

technicians overlook this fact and manipulate the surface of the concrete to

produce a smooth, attractive surface. On walls and columns, an attractive

surface may be desirable and the surface strength may not be too important,

but on a floor slab, sidewalk, or pavement, the surface strength is very

important. On the latter types of'surfaces only the absolute minimum finishing

necessary to impart the desired texture should be permitted, and the use of

"jitterbugging" (the forcing of coarse aggregate down into the concrete with a

steel grate tool) should not be permitted, as the surface can be weakened

significantly. Furthermore, each step in the finishing operation, from first

floating to the final floating or troweling, should be delayed as long as possible

and still permit the desired grade and surface smoothness to be obtained. In no

case should neat cement or mixtures of sand and cement be worked into such

surfaces to dry them up.

Along with placement and consolidation, proper curing of the concrete is

extremely important. Curing may be considered as the method whereby the

concrete is assured of adequate time, temperature, and supply of water for the

cement to continue to hydrate. The time normally required is 3 days, and

optimum temperatures are between 40 and 800F. As most concrete is batched

with sufficient water for hydration, the only problem is to ensure that the

concrete does not become dried out. This may be accomplished by ponding

with water (for slabs), covering with burlap or polyethylene sheets or spraying

with an approved curing compound. Curing is one of the least costly

operations in the production of quality concrete, and one that is all too

frequently overlooked. Concrete, if allowed to dry out during the curing stage,

will attempt to shrink. The developing bonds from the cementitious reaction

will attempt to restrain the shrinkage from taking place. But the end result is

always the same: the shrinkage wins out and a crack forms as the shrinkage

stress are always higher than the tensile strength of the concrete. Proper curing

does reduce the detrimental effects of cracking and develops the intended

strength of the concrete.

6.11 Placing Concrete in Cold Weather


When concrete is placed in cold weather, some provision must be made to

keep the concrete above freezing during the first few days after it has been

placed. Specifications generally require that the concrete be kept at not less

than 700F for 3 days or not less than 500F for 5 days after placement.

Preheating the water is generally the most effective method of providing the

necessary temperature for placement.

When the temperatures of the ingredients are known, the chart in Fig. 3 9 may be used to

determine the temperature of concrete. A straight line across all three scales,

passing through any two known tempera-tures, will permit the determination

of the third temperature. If the sand is surface-dry, the solid lines of the scales

giving the temperature of concrete should be used. However, if the sand

contains about 3 percent moisture, the dotted lines should be used.

6.12 Placing Concrete in Hot Weather


When the temperature of, fresh concrete exceeds" around 85 to 900F, the

resulting strength and durability of the concrete can be reduced. Therefore

most specifications require the concrete to be placed at a temperature less than

900F. When concrete is placed in hot weather, the ingredients should be cooled

before mixing. Methods of cooling include using ice instead of water in the

mix and cooling the aggregate with liquid nitrogen.

CHAPTER-7

Mechanised Construction

___________________________________________________________________________

CHAPTERSEVEN

___________________________________________________________________________

MECHANISED CONSTRUCTION


7.0 Introduction


Mechanised construction involves the followings

A. Mechanised Construction Equipment and their applications.

B. Work Study on Construction Equipment

C. Plant Purchase Vs. Plant Hire

a) Investment Subsidy

b) Establishment of Plant Hire Companies

D. Safety Programme.

7.1 Mechanical construction equipment & their applications


Table (1) Application of Machinery & Equipment

Sl. No. Construction Equipment Application1. Air Compressors Equipped with pavement breakers rock, steel and

wood, circular and chain concrete vibrators etc.

2. Cement Batching Plant Batching Plant delivers properly proportioned

batches of aggregate to dump trucks for delivery

to construction sites.

3. Crane Lifting in field or shop

4. Tractor Dozer Bulldozer is the best equipment for excavation

and construction of embankment where the lead

is not more than 300 ft.

Angle dozer should be used for side hill cuts for

road in consolidated soil and rock rooters should

be used to loosen material. Tractor dozer when

used for jungle clearance will give better

performance with tree felling attachment.

5. Power showel, dragline back

hoe, clamshell truck or

crawler mounted

Shovels used where excavation is above working

grade. Draglines and clamshells used where

excavations are below working grade. Power

shovel is most useful in two types deep face

excavation.

i) Excavation in which material is cast

directly from cut to fill. Examples are side hill

cuts for road and stripping thick over burden.

ii) Excavation involving long hauls by dump

trucks. Dragline can work below the work level

or under water and is particularly suited for

digging borrow pits excavating the mud and other

saturated material.

6. Rock drill, Pneumatic Used to bore holes for explosives and to shatter

and scale soft fractured rock.

7. Towed scrapers This equipment is economical where the haulage

distance is from 300 ft. to 1500 ft. but haulage

beyond 1500 ft. is not economical. As an

expedient it can also be used to haul and spread

aggregate.

8. Concrete spreader Spreads concrete into a continuous slab of

concrete, leaving a uniformly level surface for the

finisher.

9. Concrete finisher Follows spreader, consolidated and striking off

final finished surface.

10. Trucks For transportation of various construction

material to job site.

11. Trucks dump Used for haulage of earth aggregates and other

construction material.

12. Tower cranes Very versatile for high rise construction

particularly indispensable for mechanized

multistoreyed building construction.

a) Luffing jib

b) Trolley jib

13. Truck mixers Used for transportation of concrete from mixing

plant to the laying site. Concrete transported can

either be dry or wet.

14. Hoists For vertical transportation of building materials.

15. Concrete vibrators Used for compaction of concrete to prevent

honey combing. These can either be –

a) Air driven

b) Petrol engine driven

c) Electric driven

16. Bar benders and croppers Used for bending of various steel sections into

required shape for R.C.C. construction.

17. Pumps For pumping of water, sewage etc.

7.2 Work Study on construction equipment


7.2.1 The work study on construction equipment is very important so as to

economise in “STEMP”.

S = Space

T = Time

E = Effort

M = Materials

P = Power

7.2.2 Time and motion study on the use of construction equipment at each

construction site is to be carried out so as to reduce the cycle time of operation

to the barest minimum and result in increased productivity.

7.2.3 In due course, a library of production outputs with various types of plant and

machineries for different applications can be worked cut, which can then be

used for tendering purposes.

7.3 Plant Purchase versus Plant Hire


Since the purchase of construction plant and equipment involves considerable

capital outlay, judicious decision is to be taken on purchase of construction

plant versus plant hire at various sites of work. Needless to mention, for large

jobs involving spread over number of years, it may be ultimately economical

to buy the equipment but for jobs involving short term use, plant hire is more

economical. There are two issues which must be highlighted in this

connection.

7.3.1 Investment subsidy

Unfortunately, in our country, no investment subsidy is given by the

Government to contractors or plant owners. Even in an advanced country like

U.K., the Government gives subsidy to extent of 45% of the cost of the plant

in underdeveloped areas and 25% of the cost of the plant elsewhere as out

right grant. There is, therefore, considerable incentive to the builders to go in

for mechanization which results in up-gradation of technology and better

quality of work.

7.3.2 Establishment of Plant Hire companies

The concept of plant hire companies on a large scale has still not caught up in

our country. Abroad, it is very common for individual entrepreneurs to own a

few contracts’ Plant and Machinery and give them on hire to prospective

builders. In fact, young engineering graduates and private entrepreneurs should

be encouraged to come out in this profession of owing contractors’ plant and

machinery and rent them out to contracting Companies and Builders. In a

small country like Cyprus, there are three private parties owning and running

ready mix concrete plants and they are in business of selling RMC to

contracting companies/builders. There is tremendous scope for plant hire

companies to be established in the country. Infact large contracting companies

like NBCC, NPCC etc. owing their own construction plant and equipment can

open a plant hire cell so as to rent out the equipment during lean period and

run it as a profit centre.

7.4 Safety Programme


7.4.1 Accidents just do not happen. There are caused. One must remender that

“danger begins where safety ends”.

7.4.2 In case of mechanized construction, there is all the more need for following

added safety measures. Some of these are given below :

a) When heavy equipment like tractor, bulldozers and motorized scapers

are in operation, only one person, the operator should be permitted to

ride – accidental fall of any other person can be fatal.

b) When tractor dozer is parked, the blade should not be left in raised

position – accidental fall can crush people underneath.

c) During movement of dozers, the blade should be carried low for better

visibility.

d) People should not be allowed to travel in a tipper truck body. In case of

accidental operation of tipping lever, people can, be ejected out of a

moving tipper resulting in serious accidents.

e) All equipment to be driven by authorized operators only.

f) During maintenance, always support raised piece of equipment on

wooden sleepers etc. by solid support, rather than depending on

hydraulic jacks only.

g) Ensure use of protective clothings and accessories.

7.5 Why mechanical construction equipment?


a) To cut down cost of construction.

b) To accelerate the speed of work.

c) To ensure quality control.

d) To eliminate human elements involved.

Following essential requirements should be met :

a) Proper selection of equipments.

b) The work is planned for use of machinery and equipment.

c) The plant is correctly maintained and preventive maintenance carried

out deligently.

d) The plant engineer knows his job.

e) The plant operator does his job well.

7.6 Production Out Puts


Table (2) Production Out Puts

Sl. No. Equipment Lead Production Out Put

1. D-8-H Bulldozer 50 Meter 700 Cubic meters per day

2. D-8-H Bulldozer 100 Meter 400 cubic Meters per day

3. Towed Scraper 500 Meter 250 Cubic Meter per day

4. Scoop loader and

10 tippers

10 Kilo Meters 34 cubic meter per day

7.7 Production Trial


Table (2) Production Trial on 16”x9” Jaw Crushers

Sl. No. Item Description Production Capacity1. Dust 2.20 Cubic meter per crusher per day.

2. 6 mm Chips 2.02 Cubic Meter per crusher per day.

3. 10 mm Chips 4.06 cubic meter per crusher per day

4. Over sized up to 40 mm 8.27 cubic meter per crusher per day

Total = 16.55 cubic meter per day

7.8 Economic Life


Table (4) Economic Life Machines

Sl. No. Name of Machine Years Kms/Hours

1. Road rollers 15 12,000 hrs.

2. Truck tipper 12 2,40,000 kas

3. Dumper 12 10,000 hrs.

4. Stone crusher (electrical) 15 12,000 hrs.

5. Stone crusher (diesel) 12 10,000 hrs.

6. Hot mix plant 12 9,000 hrs.

7. Paver finisher 15 9,000 hrs.

8. Scoop loader 15 9,000 hrs.

9. Wheeled dozer 15 9,000 hrs.

10. Crawler dozer 15 9,000 hrs.

11. Motorised/Tower scrapper 15 9,000 hrs.12. Motor Grader 15 9,000 hrs.

13. Portable Generator 12 10,000 hrs.

14. Diesel welding set 15 10,000 hrs.

15. Pumping set Diesel 8 -

16. Jeep/Car/Mini Bus 10 2,00,000 kas

17. Mobile Crane 15 8,000 hrs

18. Vibrators 5 -

19. Concrete mixers 6 -

20. Air Compressor 12 9,000 hrs.

CHAPTER-8

Standard Field Quality Plan

___________________________________________________________________________

CHAPTEREIGHT

STANDARD FIELD QUALITY PLAN

8.0 STANDARD FIELD QUALITY PLANFOR TRANSMISSION LINE PACKAGES

Section : SURVEY & SOIL INVESTIGATION

Sl. No. Component/Operation &Description of Test

SamplingPlan with

basis

Ref. Document &acceptance norm

TestingAgency

Remarks Check

1. DETAILED SURVEY &ALIGNMENT

a) Field Survey 100% Route map & measurementschedules

Contractor Approval byPOWERGRID

B

b) Plotting of Route 100% Field book, POWERGRIDTechnical Specification &Geographical maps.


B

c) Profile Plotting 100% Approved Sag template &approved profile drawings.


B

d) Tower Spotting 100% Tower Spotting Data &POWERGRID technicalspecification


B

e) Tower Schedule 100% Approved profile drawings &route alignment


B

2. CHECK SURVEY

a) Bisection of Angle/Accuracyof alignment

100% Approved profile drawings &route alignment


B

b) Check for profile levels andelectrical & other clearances

100% Approved profile drawings Contractor Approval byPOWERGRID

B

c) Check for span marking andlengths

100% Approved profile drawings &POWERGRID technicalspecification


B

d) Check for tower type andposition as per siteconditions



B

e) Estimation of benching &Revetment volumes (As persite conditions)



B

f) Final profile & TowerSchedule



B

3. SOIL INVESTIGATION

A) AT NORMAL LOCATIONS

i) Borelog/Trial pit All other thanangle, rivercrossing &speciallocations

POWERGRID technicalspecification & relevant IS

Contractor/POWERGRIDapproved lab.

Approval byPOWERGRID.POWERGRID to witnessfor a min.25% oflocations

B

STANDARD FIELD QUALITY PLANFOR TRANSMISSION LINE PACKAGES


Sl.No.

Component/Operation &Description of Test

SamplingPlan with

basis


TestingAgency

Remarks Check

ii) Ground Water level All other thanangle, rivercrossing &speciallocations

POWERGRID technicalspecificatin & relevant IS

Contractor Approval byPOWERGRID.POWERGRID towitness for amin. 25% oflocations.

B

iii) Classification of foundations(based on soil classification,liquid limit, swell index &ground water level)

All other thanangle, rivercrossing &speciallocations

POWERGRID technicalspecification & relevantIS


B

B) AT ANGLE TOWERLOCATIONS (Min. one location in 4 kms.Stretch)

i) Borelog All angletowerlocations


Contractor/POWERGRIDapproved lab

Approval byPOWERGRID

B

ii) Standard Penetration Test All angletowerlocations



B

iii) Gradation All angletowerlocations


Contractor/POWERGRID approvedlab.


B

iv) Rock drilling whereverapplicable

All angletowerlocations


Contractor/POWERGRID approvedlab


B

v) Chemical Analysis of sub-soil

All angletowerlocations




B

vi) Bearing Capacity All angletowerlocations



B

vii) Classification of foundation All angletowerlocations



B

C) AT RIVER CROSSING ANDSPECIAL LOCATIONS

i) Borelog At RiverCrossing &SpecialLocations




B



Sl.No.

Component/Operation & Description of

Test

Sampling Planwith basis


TestingAgency

Remarks Check

ii) Standard PenetrationTest

At River Crossing& SpecialLocations




B

iii) Gradation At River Crossing& SpecialLocations




B

iv) Rock drilling whereverapplicable





B

v) Ground Water Level At River Crossing& SpecialLocations




B

vi) Chemical Analysis ofsub-soil





B

vii) Dynamic ConePenetration Test





B

viii) Vane Shear Test(Where UDS is notpossible)





B

ix) Bearing Capacity At River Crossing& SpecialLocations




B

x) Souring depth &velocity of river

At mid streamlocations



B

xi) Highest flood level At mid streamlocations



B

xii) Classification offoundations





B

D. SOIL RESISTIVITY All locations IS : 2131, IS : 2720 andPOWERGRIDspecifications



B



Sl.No.


Sampling Plan withbasis

Ref. Document& acceptance

norm

Testing Agency Remarks Check

E. TEST ON SOIL ANDROCK SAMPLES

a) Tests on undisturbed anddisturbed samples

All angle towerlocations, river crossingand special locations

IS : 2131, IS :2720 &POWERGRIDspecifications



B

i) Visual and EngineeringClassifications

ii) Sieve Analysis andHydrometer Analysis

iii) Liquid, Plastic andShrinkage limits

iv) Specific gravity

v) Chemical analysis

vi) Swell pressure and freeswell Index Determination

vii) Proctor compaction test

b) Tests on undisturbed anddisturbed samples

All angle towerlocations, river crossingand special locations

IS : 2131, IS :2720 &POWERGRIDSpecifications


Approval by POWERGRID

B

i) Bulk density & moisturecontent

ii) Relative density (for sand)

iii) Unconfined compressionTest

iv) Box shear test (in case ofsand)

v) Triaxial shear Test

a) Unconsolidatedundrained

b) Consolidated drainedtest

c) Consolidation



Sl.No.





c) Tests on Rock All angle towerlocations, rivercrossing andspecial locations

IS : 2131, IS : 2720 &POWERGRIDspecifications

Contractor/POWERGRIDapproved lab.


B

i) Visual Classification

ii) Moisture Content,Porosity and density

iii) Specific Gravity

iv) Hardness

v) Slake durability

vi) Unconfined compressiontest

vii) Point Load strength index

viii) Deformability test

d) Chemical analysis of sub-soil water

All angle towerlocations, rivercrossing andspecial Locations

IS : 2131, IS : 2720 & POWERGRIDSpecifications



B


Section : FOUNDATION MATERIALS

Sl. No. Component/Operation& Description of Test



TestingAgency

Remarks Check

4. CHECKING OFFOUNDATIONMATERIALS

A) CEMENT

i)

ii)

iii)

iv)

v)

Fineness

Compressive Strength

Initial & final setting time

Soundness

Heat of Hydration forlow heat cement (NotApplicable for OPC &PPC)

One sample per lotof 100 MT or partthereof from eachsource for MTCsand one sampleper lot of 200 MT orpart thereof fromeach source forsite testing

IS : 456, IS : 4031,IS : 269, IS : 8112,IS : 12269, IS : 1489& POWERGRIDSpecification.

Manufacturer/POWERGRIDapproved lab

Review ofmanufactu-rerstest certificates(MTCs) andlaboratory testresults byPOWERGRID

B

vi) Chemical Compositionof Cement

One sample per lotof 100 MT or partthereof from eachsource for MTCs.

IS : 456, IS : 4031,IS : 269, IS : 8112,IS : 12269, IS : 1489& POWERGRIDspecification

Manufacturer Review ofmanufactu-rerstest certificatesbyPOWERGRID

B

B) COARSEAGGREGATES

i)

ii)

iii)

iv)

v)

vi)

vii)

viii)

ix)

Determination ofParticle size (SieveAnalysis)

Flakiness Index

Crushing Value

Specific Gravity*

Bulk Density*

Absorption Value*

Moisture Content*

Soundness ofAggregate**

Presence of deteriousmaterials

One sample per lotof 200 cubic meteror part thereof fromeach source foreach size

IS : 383, IS : 2386and POWERGRIDspecification

POWERGRIDapproved lab

Each source tobe approved byPOWERGRID.Review andacceptance oftest result byPOWERGRID.

B

* Applicable to design mix concretes only. ** Applicable to concrete work subject to frost action.



Sl. No. Component/Operation & Description of

Test



TestingAgency

Remarks Check

C) FINE AGGREGATE

i)

ii)

iii)

iv)

v)

vi)

vi)

Gradation/Determination of Particle size(Sieve Analysis)

Specific Gravity anddensity*

Moisture Content*

Absorption Value*

Builking*

Silt Content Test

Presence ofdeleterious materials

One sample perlot of 200 cubicmeter or partthereof fromeach source

IS : 383, IS : 2386, IS :4031, IS : 236, IS : 456and POWERGRIDSpecification

POWERGRID approvedlab

Each source tobe approved byPOWERGRID.Review andacceptance oftest result byPOWERGRID

B

D) WATER

i) Cleanliness (VisualCheck)

100% IS : 456, IS : 3205 andPOWERGRIDspecification. The waterused for mixing concreteshall be fresh, clean andfree from oil, acids andalkalies, organicmaterials, or otherdeleterious materials

Contractor Each source tobe approved byPOWERGRID

C

ii) Suitability of water forRCC work

One sample persource

POWERGRIDspecification. Potablewater is generallysuitable for concreting.

Contractor Certificationregardingpotability ofwater bycontractor andapproval byPOWERGRID

B

iii) P.H. Value One sample persource

IS : 456, IS : 3025 andPOWERGRIDspecification.Min. 6.Max. 8.

POWERGRID approvedlab/Contractor


E) REINFORCEMENTSTEEL

i) Identification & size Random IS : 432, IS : 1139, IS :1786 & POWERGRIDspecification


B

* Applicable to design mix concretes only. ** Applicable to concrete work subject to frost action.



Sl. No. Component/Operation & Description

of Test

Sampling Plan with basis Ref. Document &acceptance norm


ii) Chemical AnalysisTest

One sample per heat IS : 432, IS :1139, IS : 1786 &POWERGRIDspecification

Manufacturer Review ofManufacturerstest certificatesbyPOWERGRID

B

iii)

iv)

v)

Tensile Test

Yield Stress/proofstress

PercentageElongation

One sample per lot of 40 MTor part thereof for each sizeof steel conforming to IS :1139 and 5 MT or partthereof for HDS wire foreach size of steel as per IS :432. For steel as per IS :1786 under 10 mm 1sample for each 25 MT orpart thereof. 10 mm – 16mm 1 sample for each 35MT or part thereof. Over 16mm 1 sample for each 45MT or part thereof.

IS : 432, IS :1139, IS : 1786 &POWERGRIDspecification

Manufacturers/POWERGRIDapproved lab

Review ofmanufacturerstest certificatesas well as labtest result byPOWERGRID

B

vii) Reverse Bend Testfor HDS wire

One sample per lot of 5 MTor part thereof for each size

IS : 432POWERGRIDspecification

Manufactu-rer/POWER-GRID appro-vedlab

Review ofmanufactu-rerstest certificatesas well as labtest result byPOWERGRID

B

F) EARTHINGMATERIALS

i) Identification,cleanliness &Galvanising defects

100% POWERGRIDapproved drawing& specification


C


Section : FOUNDATION

Sl.No.




TestingAgency

Remarks Check

5. TOWER FOUNDATION

A) BEFORE EXCAVATION

i) Checking of pegs conditionas per line and alignment

100% on eachlocation

IS : 4019, IS : 5613 &POWERGRID approveddrawings/specification.


C

ii) Checking of pit making asper drawings & RL


IS : 4019, IS : 5613 &POWERGRID approveddrawings/specification.


C

B) EXCAVATION

i) Dimensional conformity Each location IS : 4019, IS : 5613 &POWERGRID approveddrawings/specification.


B

ii) Verticality & Squareness ofeach pit

Each location IS : 4019, IS : 5613 &POWERGRID approveddrawings/specification.

JointInspection byPOWERGRIDand contractor


B

iii) Verification of classificationof foundation

Each location IS : 4019, IS : 5613 &POWERGRID approveddrawings/specification.



B

C) STUB & TEMPLATE

i) Identification & Assembly 100% on eachlocation

POWERGRID approveddrawings/specification.


Approval/clearance byPOWERGRID

C

ii) Template level, width &diagonal


POWERGRID approveddrawings/specifications



B

iii) Tightening of all bolts &nuts of template, stubs &cleats


POWERGRID approveddrawings/specification.



C

iv) Stub setting 100% on eachlocation

POWERGRID approveddrawings/specification



B




Test

SamplingPlan with

basis



D) P.C.C. Padding For alllocations

IS : 456 andPOWERGRIDapprovedfoundationdrawings &specification

Joint Inspection byPOWERGRID andcontractor


B

E) STAGING FORRAISED CHIMNEY

i) Check durability,strength & soundnessof staging, jointsadequacy of its joints &specific levels

100% POWERGRIDSpecification



B

F) SHUTTERING(Formwork)

i) Check for materials,breakage or damage

100% POWERGRIDSpecification/approved drawings



C

ii) Check for plumbalignment, parallelism,squareness andequidistance fromstub.

100% beforecasting

POWERGRIDSpecification/approved drawings



B

iii) Dimensional check 100% beforecasting




B

iv) Check for level &height

100% beforecasting




B

v) Check for rigidity offrame/tightness




C

vi) Cleaning and oiling 100% POWERGRIDSpecification/approved drawings



C




SamplingPlan with

basis



vii) Diagonal bracing if requiredas per drawings/siteconditions




C

viii) Checking of joints to avoidundue loss of cement slurry




C

G) PLACEMENT OFREINFORCEMENT STEEL

i) Check the steel bars for rust,cracks, surface flaws,laminate etc. (Visual check)

100% IS : 456 andPOWERGRIDSpecification/approved drawings



C

ii) Check as per the bar bendingschedule before placement ofconcrete

For alllocations

IS : 456 andPOWERGRIDSpecification/approved drawings



B

iii) Check cutting tolerance forbars as per checklist/drawings.

Check whether all the bentbars and lap lengths are asper approved bar bendingschedule

For alllocations

IS : 456 andPOWERGRIDSpecification/approved drawings



B

iv) Check whether all joints &crossing of bars are tiedproperly with right guage &annealed wire as perspecification




C

v) Check for proper coverdistance, spacing of bars,spacers & chairs after thereinforcement cage has beenput inside the formwork




C

vi) Check whether lapping ofbars are tied properly withright guage and annealedwire as per specification




B



Sl.No.


SamplingPlan with

basis



H. PILE FOUNDATION (additional Tests)(For normal tower foundations)

i) Checking of centre line of pilegroup

Each pilegroup

IS : 2911 &POWERGRIDapproved pilefoundationdrawings/specification.

Joint Inspectionby POWERGRIDand contractor

Checklist to beprepared andsigned jointly

B

ii) Check pile location Each pile IS : 2911 &POWERGRIDapproved pilefoundationdrawings/specification.



B

iii) Temporary casing tube &permanent liner also checkthickness of liner material (if applicable)

Each pile IS : 2911 &POWERGRIDapproved pilefoundationdrawings/specification.


Verticality of thetube to bechecked

B

iv) Bentonite slurry (if applicable) Each pile IS : 2911 &POWERGRIDapproved pilefoundationdrawings/specification.


Records to bekept byPOWERGRIDfor specificgravity of slurry

B

v) Pile depth, level, size andalignment

Each pile IS : 2911 &POWERGRIDapproved pilefoundationdrawings/specification.



A

vi) Chipping of pile head Each pile IS : 2911 &POWERGRIDapproved pilefoundationdrawings/specification.


Beforeconcreting pilecap, pile headto be chippedoff forconcreting

B

Vii) Standard Penetration Test As perPOWERGRID BOQ/Specification



Records to bekept byPOWERGRID.Approval byPOWERGRID.

B




SamplingPlan with

basis



Viii) Pile load testing As perPOWERGRIDBOQ/Specifi-cation



Records to bekept byPOWER-GRID.Approval byPOWER-GRID.

B

ix) Anchor bolts if applicable

a) Level, centre to centredistance of bolts

100% oneach location

POWERGRIDapproved pilefoundationdrawings/specification



B

b) Visual check for galvanising 100% oneach location

POWERGRIDapproved pilefoundationdrawings/specification



B

6. CONCRETINGA) BATCHING, MIXING

& PLACING OFCONCRETE ANDCOMPACTING

100% IS : 456 andPOWERGRIDapproved drawingsand specifications.



B

B) FIXING OFCHIMNEY COLUMNCheck forWidth/length,squareness, parallelism& equidistance fromstub




C

C) PLACINGCONCRETE, POKINGAND COMPACTING



Min. gapbetween boxesandreinforcementbars should bemaintained.Approval byPOWERGRID

C

D) CONCRETE TESTINGi) Slump Test One sample

per locationIS : 456, IS : 516, IS : 1199 andPOWERGRIDspecifications.


B



Sl.No.


SamplingPlan with

basis


TestingAgency

Remarks Check

ii) Check for quantitiesfor cement, fineaggregate, coarseaggregate and waterwhile batching

100% on alllocations

IS : 456, IS : 516, IS : 1199 andPOWERGRIDspecifications.

Contractor Checklist to beprepared andsigned jointly

B

E) CHECK FINISHING,DIMENSIONALCONFORMITY ANDWORKMANSHIPBEFORE & AFTERBOX REMOVAL

100% IS : 456, IS : 516, IS : 1199 andPOWERGRIDspecifications.

Contractor Checklist to beprepared andsigned jointly

B

F) BACKFILLING 100% POWERGRIDSpecification


C

i) Check for thickness oflayer & watering

100% POWERGRIDSpecification


C

ii) Check forcompaction/ramming

G) REVETMENTi) Size of stone for

Revetment (Stoneswith round surfaceshall not be used)

100% POWERGRIDspecification & approveddrawings.


C

ii) Moisture content forRevetment stone

One sampleper source

IS : 1124 Max. 5% POWERGRID approvedlab


B

iii) Check for Weep holesand Bond stones inRevetment

100% POWERGRIDSpecification/approveddrawings/IS : 1597


C

H) COPING 100% on alllocation

POWERGRIDSpecification


B

I) CURING 100% on alllocation

POWERGRIDSpecification


C

J) EARTHING (Pipe orcounter poise type)

100% IS : 5613 andPOWERGRIDSpecification


B




Test

Sampling Plan withbasis


TestingAgency

Remarks Check

K) CONCRETECUBE TESTING

i) CompressiveStrength

a) One samplelocations (Onesample consists ofmin. 3 test cubes for28 days strength)

b) For pilefoundation onesample for each pile

IS : 1199, IS : 456, IS : 516 andPOWERGRIDSpecification


Approval byPOWERGRIDCubes must betested within aweek after 28days curingperiod and testresults shouldbe approvedbefore towererection

A

ii) CompressiveStrength forconcrete of pilecap, beams,chimney etc.

One sample forevery 20 Cum ofconcrete or partthereof for eachdays of concreting

IS : 1199, IS : 456, IS : 516 andPOWERGRIDSpecification


-do- A


Section : ERECTION


SamplingPlan with

basis



7. TOWER ERECTIONA) MATERIAL CHECKINGi) Visual checking of tower

members for damage,cleanliness, galvanising andstacking

100% IS : 5613 andPOWERGRIDapproveddrawings/specification


Check list to beprepared andsigned jointly

C

ii) Visual checking ofgalvanised bolts and nuts,step bolts, D-shackles, U-bolts, spring washers &enamelled plates

100% IS : 5613 andPOWERGRIDapproveddrawings/specification



C

B) ERECTION OF SUPERSTRUCTURE

i) Tightness of bolts,identification, cleanliness &galvanising


POWERGRIDapproveddrawings/specification



C

ii) Punching of tightned bolts 100% oneach location




C

iii) Checking of assembly andverticality





B

iv) Tack welding 100% oneach location




B

v) Tower footing resistance 100% oneach location



Record to bekept for towerfootingresistancebefore and afterearthing

B


Section : ERECTION

Sl.No.


SamplingPlan with

basis



vi) Fixing of danger plate,number plate, phase plates& circuit plate as applicable

100% oneachlocation




C

8. LINE STRINGINGA) Insulator Checkingi) Visual checking of

Insulators (Indentification,cleanliness, glazing, cracks& white spots)

100% IS : 5613 &POWERGRIDapproveddrawings/specifications



C

ii) IR Measurement 100% POWERGRIDspecification

-do- -do- B

B) Visual Checking ofConductor and Earthwire




C

C) Visual checking ofhardware fittings(identification, cleanliness,galvanising and mechanicaldamages)




C

i) Identification, cleanliness &packing

ii) Damage of Conductor &Earthwire

iii) Drum rubbing againstground or any metal part

D) Conductor & EarthwireStringing

i) Initial conductor position Entireroute

IS : 5613 &POWERGRIDapproved SAG &Tension Charts andSpecifications



B

ii) Check for temperature Entireroute

IS : 5613 &POWERGRIDapproved SAG &Tension Charts andSpecifications



B


Section : ERECTION

Sl.No.


SamplingPlan with

basis



iii) Final Conductor &Earthwire Position

Entire route IS : 5613 & POWERGRIDapproved SAG & TensionCharts and Specifications


Records to bekept duly signedby POWERGRIDand contractor

B

a) Electrical Clearancesb) Sag/Tension for

conductor & earthwirec) Joints in conductor and

earthwireiv) Jumpering Entire route IS : 5613 & POWERGRID

approved SAG & TensionCharts and Specifications



B

v) Fixing of pilot insulatorstring (if any)

Entire route IS : 5613 & POWERGRIDapproved SAG & TensionCharts and Specifications



B

9. FINAL CHECKINGa) Check for the

completion of back-filling & leftovermaterials

100% IS : 5613 & POWERGRIDapproveddrawings/specifications



B

b) Fixing of ACD & alltower accessories

Entire route IS : 5613 & POWERGRIDapproveddrawings/Specifications



B

c) Tightening, punchingand tack welding ofbolts

d) Final ground andelectrical clearances

e) Earthing


Section : FINAL TESTING & PRE-COMMISSIONING


SamplingPlan with

basis



10. MEGGAR TEST 100% POWERGRID latest Pre-Commissioning procedures(Doc. No. D-2-01-70-01-00)



A

11. FINALTESTING &PRE-COMMISSIONING ON LINE

100% POWERGRID latest Pre-CommissioningProcedures (Doc. No. D-2-01-70-0-00)



A

Section : GENERAL GUIDELINES FOR IMPLEMENTATION

1. Details of categories of check codes A, B & C including accepting anddeviation dispositioning authorities are indicated at Annexure-I.

2. POWERGRID specification shall mean POWERGRID technicalspecification, approved drawings/data sheets and LOA provisionsapplicable for the specific contract.

3. Acceptance criteria and permissible limits for certain tests areindicated at Annexure-II. For balance tests, site to verify the samewith respect to POWERGRID specification, relevant Indian Standardsand/or prevalent code of practice.

4. It is clarified that the tests indicated at column 2 of this FQP i.e.against column "Component operation & Description of Test," areonly generally required to be conducted. However, POWERGRIDreserves the right to carry-out any additional tests at any stage if thesituation so warrants.

5. POWERGRID site representative shall witness all the tests conductedby the contractor as mentioned in this FQP. However, in case oftests conducted in the POWERGRID approved lab, it is preferred towitness the tests in the lab itself, if possible.

6. Head of GHQ shall approve testing laboratory before accepting thetest results from the lab.

7. Head of GHQ shall approve the sources for cement, coarseaggregate, fine aggregate & water before actual utilisation.

8. All the testing & measuring equipments used by the contractor fortesting are required to be calibrated. A copy of valid calibration reportshall be retained by POWERGRID as records.

9. Classification of foundations shall be approved by POWERGRIDbased on the Joint Inspection Report & soil investigation reports.

10. Curing of concrete work should be continued for a minimum period of10 days.

11. Zone-IV fine aggregate shall not be used for concreting work.

Section : GENERAL GUIDELINES FOR IMPLEMENTATION

12. Identification and traceability records in the standard formats forvarious materials in line with QA&I circular dated 7-5-96 shall bemaintained and retained in POWERGRID.

13. CEMENT

13.1 In case supply of cement is in the scope of the contractor, the sameshall be procured from sources approved by POWERGRID site andgot tested at site on sample basis for specified acceptance tests asspecified in this FQP at a reputed Third Party Lab approved byPOWERGRID site.

13.2 The samples of cement for site testing shall be taken within threeweeks of the delivery and all the tests shall be commenced within oneweek of sampling.

14. REINFORCEMENT STEEL

14.1 In case supply of reinforcement steel is in the scope of the contractor,the same shall be procured from the main producers i.e. SAIL,TISCO, IISCO or Rashtriya Ispat Nigam or the rerollers approved bymain producers. The reinforcement steel shall be got tested at siteon sample basis for specified acceptance tests as specified in thisFQP at a reputed Third Party Lab approved by POWERGRID site.

14.2 The results of the testing of cement and reinforcement steel referred to in13.1 and 14.1 above shall be got approved from POWERGRID site beforecement and reinforcement steel are put to use. However, in exceptionalcases due to exigencies of work., POWERGRID site may authorise thecontractor to use Cement and Reinforcement Steel even before the testresults are received. However, in all such cases, if the test resultssubsequently received are found to be not complying with the specifiedacceptance criteria, the contractor shall have to dismantle and recast all suchfoundations cast with such non-conforming materials at his own cost.Confirmation to this effect shall be obtained from the contractor by the Projectauthorities beforehand in all such cases.

ANNEXURE-IPAGE 1 OF 1

ACCEPTING AND DEVIATION DISPOSITIONING AUTHORITIES FORDIFFERENT CATEGORIES

OF CHECKS AS ENVISAGED IN FIELD QUALITY PLAN

CATEGORY TYPE OFCHECK

100% CHECKING/WITNESSING BY

COUNTERCHECK/SURVEILLANCE

CHECK BY

ACCEPTINGAUTHORITY, IF TEST

RESULTS ARE WITHINPERMISSIBLE LIMITS

DEVIATIONDISPOSITIONING

AUTHORITY

A CRITICAL EXECUTING DEPTT.PLUS FQA

REPRESENTATIVEGHQ

FQA REPRESENTATIVEAND RHQ/DHQ

REPRESENTATIVE

HEAD OF DHQ HEAD OF RHQ INCONSULTATION

WITH CQA, IFREQUIRED

B MAJOR EXECUTING DEPTT. DHQ REPRESENTATIVE HEAD OF GHQ HEAD OF DHQC MINOR CONTRACTORS

REPRESENTATIVEEXECUTING DEPTT. MINIMUM E4 LEVEL

EXCUTIVE OF SUB-STATION/TL

HEAD OF GHQ

ANNEXURE-IIPAGE 1 OF 3

ACCEPTANCE CRITERIA AND PERMISSIBLE LIMITS FOR FOUNDATION MATERIALS & CONCRETE

A) CEMENT

Description of thetests

33 Grade OPCas per IS : 269

43 Gradecement asper IS : 8112

PPC as per

IS : 1489

Low Heat Cement

(i) Fineness (min.) 225 m2/kg 225 m2/kg 300 m2/kg 225 m2/kg(ii) Compressive

Strength (min.)

721 hours 160 kgf/cm2 23 MPa 16 MPa 100 kgf/cm21682 hours 220 kgf/cm2 33 MPa 22 MPa 160 kgf/cm26724 hours - 43 MPa 33 MPa 350 kgf/cm2

(iii) Initial Setting Time(Minimum)

30 Minutes 30 Minutes 30 Minutes 30 Minutes

(iv) Final Setting Time(Maximum)

600 Minutes 600 Minutes 600 Minutes 600 Minutes

(v) Soundness(Le chatelier Method)

Maximum 10mm expansion

Maximum 10mm expansion

Maximum 10 mmexpansion

Maximum 10 mm expansion

(vi) Heat of hydration (Max.)

- - - Max. 65 cal/gm for

7 days & max. 75cal/gm for 28 days

(vii) Chemical Composition As per IS As per IS As per IS As per IS

B) COARSE AGGREGATE :

(i) Sieve Analysis

IS SIEVE DESIGNATION PERCENTAGE PASSING FOR GRADEDAGGREGATE OF NOMINAL SIZE

40 mm 20 mm

40 mm 95 to 100 100

20 mm 30 to 70 95 to 100

10 mm 10 to 35 25 to 55

4.75 mm 0 to 5 0 to 10ANNEXURE-IIPAGE 2 OF 3

(ii) Flakiness Index - Not to exceed 25%.

(iii) Crushing Value - Not to exceed 45%.

(iv) Soundness of aggregate - Loss of weight after 5cycle not to exceed

applicable for concrete works 12% when testedwith Sodium sulphate and

subject to froast action 18% when tested withmagnesium sulphate.

(v) Deleterious material - Not to exceed 5% of theweight of aggregate.

C) FINE AGGREGATE

(i) Sieve Analysis - Shall confirm to Zone I, Zone IIor Zone III.

IS Sievedesignation

Percentage Passing forGradingZone-I

GradingZone-II

GradingZone-III

GradingZone-IV

10 mm 100 100 100 100

4.75 mm 90-100 90-100 90-100 90-100

2.36 mm 60-95 75-100 85-100 95-100

1.18 mm 30-70 55-90 75-100 90-100

600 Micron 15-34 35-59 60-79 80-100

300 Micron 5-20 8-30 12-40 15-50

150 Micron 0-10 0-10 0-10 0-15

(ii) For guidance of adjusting the quantity in mix of concrete, the following table may beused.

Moisture Content % Bulking % by volume2 153 204 255 30

(iii) Silt content Test : Shall not exceed 8%.

(iv) Deleterious Materials : Total deleterious material shall not be more than 5% byweight.

(D) REINFORCEMENT STEEL : As per relevant IndianStandards.

ANNEXURE-IIPAGE 3 OF 3

(E) CONCRETE CUBE TEST

For nominal (volumetric) concrete mixes, compressive strength for 1:1½:3 (cement :sand : Coarse aggregate) concrete shall be 265 kg/cm2 for 28 days and for 1:2:4nominal mix, it shall be 210kg/cm2.

(F) ACCEPTANCE CRITERIA BASED ON 28 DAYS COMPRESSIVE STRENGTH FORNOMINAL MIX CONCRETE

a) The average of the strength of three specimen be accepted as thecompressive strength of the concrete, provided the strength of any individualcube shall neither be less than 70% nor higher than 130% of the specifiedstrength.

b) If the actual average strength of accepted sample exceeds specified strengthby more than 30%, the Engineer-in-charge, if he so desires, may furtherinvestigate the matter. However, if the strength of any individual cubeexceeds more than 30% of specified strength, it will be restricted to 30% onlyfor computation of strength.

c) If the actual average strength of accepted sample is equal to or higher thanspecified strength upto 30%, then strength of the concrete shall beconsidered in order and the concrete shall be accepted at full rates.

d) If the actual average strength of accepted sample is less than specifiedstrength but not less than 70% of the specified strength, the concrete may beaccepted at reduced rate at the discretion of Engineer-in-Charge.

e) If the actual average strength of accepted sample is less than 70% ofspecified strength, the Engineer-in-Charge shall reject the defective portionof work represented by sample and nothing shall be paid for the rejectedwork. Remedial measures necessary to retain the structure shall be taken atthe risk and cost of contractor. If, however, the Engineer-in-Charge sodesires, he may order additional tests to be carried out to ascertain if thestructure can be retained. All the charges in connection with these additionaltests shall be borne by the Contractor.

(G) ACCEPTANCE CRITERIA FOR DESIGN MIX CONCRETE SHALL BE ASPER IS:456

CHAPTER-9

Guidelines

___________________________________________________________________________

CHAPTERNINE

___________________________________________________________________________

GUIDELINES


9.0 Pit Marking


Name of the Line :- Location No. :-

Name of Contractor:- Type of Tower :-

(i) It should be ensured that approved drawings are available for execution of the

work.

(ii) It shall be checked that reference level has been measured correctly and recorded.

(iii) Alignment of location shall be checked with respect to previous and next location.

(iv) Location of centre peg / position of various land marks shall be matched as per

profile.

(v) The possibility of realignment / shifting of location shall be checked due to any

new feature on the ground with respect to profile.

(vi) The proceeding span as well as succeeding span shall be measured and compared

as per the profile.

(vii) The actual angle of deviation and bisection of the angle tower shall be measured

and compared as per profile.

(viii) The position of cross pegs in tranverse direction shall be checked.

(ix) The safety of all the four pits should checked.

(x) Dimensions of pits should be checked as per the drgs.

(xi) The requirement of Benching / Revetment shall be examined and contour maps /

Revetment drgs. shall prepared wherever necessary.

(xii) In case of benching, the volume of cutting and filling shall be calculated and

recorded in cu.m. as per the benching drg.

(xiii) In case of Revetment, the volume of Revetment quantity shall be calculated

and recorded as per the Revetment drg.

9 .1 Stub Setting



(i) It should be ensured that the drgs. are approved for the stub setting.

(ii)

a) The depths of all four pits (A, B, C, D) shall be measured and tabulated from Ground

level as well as Reference level.

b) Pit dimensions shall be checked as per approved found, classifn. drg.

c) Excavated soil should be stacked at least 2m away from pit edge to avoid collapse of the

foundation pit.

d) Undercutting of foundation shall be checked as per the drg. in case of fissured rocks.

(iii)

a) Tangent Tower

The alignment of the template in the direction of the line shall be checked in case of

tangent Tower.

b) Angle Tower

(b.a) The Angle of deviation shall be checked as per the drg.

(b.b) The alignment of template on bisection shall be checked.

(iv) Diagonals of template shall be measured with respect to the approved drgs.

Stub Setting on Bisection

(v) The Level of template should be checked by dumpy level.

(vi) Ht. of template above ground level shall be checked.

(vii) The clearance (not less than 15 cm or as specified in the drg.) between lowest part

of all the four stubs and base of the pit shall be checked.

(viii) Positioning of the template support shall be checked with regard to any danger to

the collapse of pit.

(ix) Tightening and erection of the template should be checked as per drg.

(x) Checking of stubs.

(a) The dimensions of the stubs shall be checked as per type of tower.

(b) The proper erection of the plates / cleats with regd. nos of properly tightened bolts

shall be checked as per the drg.

9.2 Construction Materials




i) The availability of required quantity of approved quality sand should be checked as per

the approved drgs. and specifications.

ii) The availability of required quantity & approved quality of both 20nmi and 40mm metal

should be checked as per the approved drgs. and specifications.

iii) The dimensions of the measuring box (30cm x 30cm x 39cm height) shall be checked.

iv) The proportions of nominal mix should be checked as per the table given below:

Grade of

concrete

Qty. of Coarse

Aggregate

Qty. of fine

Aggregate

Qty. of

Cement

Qty. of Water

M-100 6 Boxes 3 Boxes 1 Bag 1 Box less 1 Litre

M-150 4 Boxes 2 Boxes 1 bag 1 Box less 3 Litres

(v) The required quantity and quality of water shall be checked as per specifications.

(vi) Reinforcement steel

(a) The diameter wise qty. & quality of the reinforcement steel shall be checked as per

apprd. drgs.

(vii) Form Boxes

(a) The dimensions of the form boxes should be checked as per apprd. drgs.

(b) Proper oiling of inner wall of form boxes shall be checked.

(viii) The availability of T&P and man power shall be checked as per annexure IA & IB.

(ix) Lean Concreting;-

(a) The cleanliness of the pits from all foreign materials shall be checked.

(b) Proper dewatering of the pits shall be checked.

(c) Mix ratio of 1:3:6 concrete with 40mm metal shall be checked.

(d.a) Concrete mixing by mixer as per specn. shall be checked.

(d.b) Mixure running Time (Mixing Time-2 Min. ) shall be checked.

(e) De-watering of the pit shall be checked.

(f) The specified area and level of lean concrete in all the four pits shall be checked.

(g) The actual consumption of the cement bag as per approved drawing shall be

checked.

(x.a) Filling of excess excavation by the lean concrete shall be checked.

(x.b) The volume of excess lean concrete shall be measured and recorded.

9.3 Installation of Reinforcement Steel & Form Boxes




i) It should be ensured that the approved drgs. are available for the execution of the work.

(ii) Reinforcement Steel

(a) The quality and quantity of the reinforcement steel shall be checked as per the

drawing and specification.

(b) Bending / Placing shall be checked as per apprd. drgs. and specification.

(c) The diameter (Min. Dia. - 12mm) and spacings (Max. Spacing - 500mm) of the

chairs shall be checked.

(d) The binding of the Reinforcement steel shall be checked.

(e) Any undue development of stress due to improper bending of steel bars shall be

checked.

(f) Cleanliness of the Reinforcement steel from any foreign materials or loose rust

shall be checked.

(g) Position of bars w.r.t. stub shall be checked as per drg.

(iii) Form Boxes :

(a) The dimensions shall be checked as per appd. drgs.

(b) Placing of the stub shall checked as per apprd. drg.

(c) Water tightness of Bolts and Nuts shall be checked.

(iv) Clear cover of 50 mm (or as per drg. / specn.) shall be checked.

(v) Fixing of the Earth strip shall be checked as per apprd. drg.

9.4 Mixing, Placing and Compacting of Concrete




(i) It should be ensured that the approved drgs. are available for the execution of the

work.

(ii) Mix Ratio

(a) Mix ratio of 1:2:4 Concrete for Pyramid / base with 20mm metal shall be checked.

(b) Mix ratio of 1:2:4 Concrete for chimney with 20mm metal shall be checked.

(c) Water to cement ratio shall be checked as per specification.

(iii) Mixing done by

(a) Running Time of mixer (Running time - 2 Min.) shall be checked.

(b) Hand mixing (with 10 extra cement or as specified in LOA) of concrete shall be

checked.

(c) It should be ensured that the hand mixing of concrete is done on GI sheet platform

to avoid mixing of concrete with undersirable material.

(iv) The proper compaction of concrete with the help of Vibrator should be ensured.

(v) In case of non availability of vibrator, compaction to be done by peeking rod.

(vi) The levels and diagonals of the template shall be checked at regular intervals.

(vii) The casting of legs in continuity shall be checked.

(viii) Actual consumption of the cement bags shall be checked as per the drg. and

specification.

(ix) Construction of the coping shall be checked as per the appd. drg.

(x) It should be ensured that the cubes have been collected and recorded as per the table

given below:

Twr. Leg. Pyramid (Date) Chimney (Date) No. of cubes

A

B

C

D

(xi) The curing of the foundation should be started after 24 hrs of construction and the

foundation should be kept continiously in wet conditions by putting wet gunny

bags.

(xii) The removal of form boxes after 24 hrs of casting shall be checked.

(xiii) Availability of sufficient qty. of water near the loc. for the backfilling shall be

checked.

(xiv) The soil for the backfilling of the foundation should be free from all foreign

materials and acceptable.

(xv) Proper compaction of the backfilling with adequate sprinkling of water shall be

checked.

(xvi) The level of backfilling upto 75 mm above ground level or as specified in specn.

Shall be checked.

(xvii) It should be ensured that the height of earth embankment of 50mm (or as per

specn.) has been made along the side of back filled earth.

(xviii) Proper curing of the chimney by wet gunny bags shall be checked.

(xix) Careful removal of template after complete back filling shall be checked.

(xx) Curing period of foundation and chimney checked as per specn. (Minimum period

of curing 14 days after concreting both in Morning & Evening).

(a) The date of start of curing and date of completion of curing shall be recorded.

(xxi) The arrangement for testing of the cubes as per approved FQP shall be checked.

(xxii) The removal of all the surplus materials from site shall be ensured.

Note : Foundn. Is cleared for tower erection subject to fulfillment of part (I) before tower

erection and part (II) in due course as per planning.

Part-II (i) Revetment Benching proposal status

(ii) Rivetment / Benching likely execution date

___________________________________________________________________________

CHAPTERTEN

___________________________________________________________________________

CHECK FORMAT


1.0 Check format for Pit Marking




(i)

App

Apprd. Drg. nos. ……………………………………

(ii) Reference level ……………………………………(iii) Alignment of loc. W.r.t. previous and next.

Loc.

O.K./NOT O.K.

(iv) Loc. Of center peg/position of various land

marks are matching as per profile

O.K./NOT O.K.

(v) Any new features on grnd. W.r.t. profile

necessitating realignment/shifting of loc. Or

due to any other reasons

Yes/No

(vi) Span on both sides of loc. A Per profile Actual

(Mtrs. (Mtrs.)

a) Preceding span (loc. No. )

b) Succeeding span (loc. No. )

(vii) Angle of deviation and bisection in case of

angle tower loc.

As per profile Actual

a) Angle of deviation O.K./NOT O.K.

CHAPTER-10

Check Format

b) Bisection found O.K./NOT O.K.

(viii) Position of cross pegs in transverse dirn. O.K./NOT O.K.

(ix) Position of all four pits are on leveled grnd.

And safe

Yes/No

(x) Dimensions of pits are as per drgs. O.K./NOT O.K.

(xi) Whether Benching/Revetment reqd. if yes,

then

Yes/No

a) If countour maps/revetment drgs. prepared Yes/No

b) Possibly calculate vol. ……….. cu.m.

FOR POWERGRIDSignature ………………………..

Name ……………………………

(Jr. Engr./E1/E2/E3)

Date ………………………..

2.0 Check format for Foundation Classification


NAME OF LINE : - LOCATION NO. :-

NAME OF CONTRACTOR :- TYPE OF TOWER :

(i) Strata wise pit details

STRATA DEPTH RECEIVING END

STRATA DEPTH

……………………………………………………….…………………

PIT C PIT B

STRATA DEPTH STRATA DEPTH

Trial pit details/

Bore log details

PIT D SENDING END

PIT A

NOTE : CLASSIFICATION MAY ALSO BE GIVEN ON TRIAL PIT OR ONE PIT

EXCAVATION BASIS.

(a) Predominant soil.

(ii) Sub soil water table details as on date.

PIT A PIT B PIT C PIT D

(iii) Water table in nearby well as on date …………

…… mtrs.

(iv) Maxm. Subsoil water table in monsoon

season after thorough local enquiry …………

…… mtrs.

(v) Surface water table on grnd. In monsoon

season and its duration. …… mtrs. For

….. days

(vi) Type of cultivation

Paddy fields/Cultivated

land/Barren land

(vii) Whether encasement of stubs

reqd. due to surface water? Yes/No

If yes, ht. Of encasement above grnd. Level …

…………. Mtrs.

(viii) Whether soil invest. Carried out at this loc.

or nearby loc. Loc. No. ………

……

(ix) If this loc. strata details are comparable with above

soil invest. Report or any other loc. of this line.

Loc. No. ………………

(x) Details of Soil Invest. Report Loc. No. ………

………

(a) STRATA DEPTH

…………….…………….……………..……………..

(b) Subsoil water table …………. Mtrs.

(c) Ultimate bearing capacity ……… Kg./m2

(d) Angle of repose. () ……….. degrees

(xi) Fndn. Classifn. Proposed by contractor

(xii) Fndn. Classifn. Recommended

As per soil Actual

Invest.

Remarks/Reasons :-

…………………………………………………………………………………………………

…………………………………………………………………………………………………

FOR

POWERGRID

Signature

………………..………

Name ……

……………………...

(E1/E2/E3)

Date ……

……………………….

Approval

Site visited on ………………… and details verified.

The classifn. of fndn. Is approved as …………………

FOR

POWERGRID

Signature

………………..………

Name ……

……………………...

(Line

Inch./Grp. Head)

Date ……

……………………….

3.0 Check format for Stub Setting




(i)

App

Apprd. Drg. nos. ……………………………………

(ii) Pit Dimensions ……………………………………

(a) Depth of pits From Ref. level Ground level

Pit A

Pit BPit C

Pit D

(b) Pit dimensions are as per apprd. Foundn. Classifn. Yes/No

(c) Excavated soil is kept 2m away from pit edge Yes/No

(d) Under cutting done in case of fissured rocks Yes/No

(iii) Alignment of template(a) Tangent Tower

(a.a) In the direction of line Yes/No

(b) Angle Tower

(b.a) Angle of deviation …………. Degrees

(iv) Diagonals of template

AC ……………….. m

BD ……………. M

= Angle of Deviation.

PQ = Line of Bisection.

(Lines AD and BC are

perpendicular to PQ)

Stub setting on bisection.

(v)

App

Level of template checked by dumpy level …………… YES/NO

(vi) Ht. Of template above grnd. Level O.K./Not O.K.

(vii) Clearance between lowest part of stub and

base of pit (Not less than 15 cm or as specified

in the drg.)Leg A ………………. Cm

Leg B ……………… Cm

Leg C ……………… Cm

Leg D …………….. Cm

(viii) Template support positioning is causing any

danger to collapse of pit

O.K./NOT O.K.

(ix) All members of template are fixed as per drg.

and fully tightened

YES/NO

(a) Stub dimensions are as per type of tower YES/NO

(b) All plates/cleats fixed with reqd. no. of

Nut/Bolts and are fully tightened

YES/NO

CERTIFICATE : - Stub Setting Approved.

FOR

POWERGRID

Signature

………………..………

Name ……

……………………...

(Line

Inch./Grp. Head)

Date ……

……………………….

4.0 Check format for Construction Materials




(i) Quality/Qty. of sand as per apprd. Drgs.

and specns.

Qty. Reqd. Qty. Avail. Apprd. Source Quality

(OK/NOT OK)

(ii) Quality/Qty. of metal as per apprd. Drgs. and specns.

Size Qty. Reqd. Qty. Avail. Apprd. Source Quality

(OK/NOT OK)

20 mm

40 mm

(iii) Dimensions of the measuring Box

(30 cm x 30 cm x 39 cm Height) OK/NOT OK

(iv) Proportions of nominal Mix.

Grade of

Concrete

Qty. of Coarse

Aggregate

Qty. of fine

Aggregate

Qty. of Cement Qty. of Water

M-100 6 Boxes 3 Boxes 1 Bag 1 Box less

1 Litre

M-150 4 Boxes 2 Boxes 1 Bag 1 Box less

3 Litres

(v) Quality & Qty. of water as per specns. O.K./NOT

O.K.

(v) Reinforcement steel

(a) Qty. & Qualify as per apprd. Drgs./specns.

Dia Qty. Reqd. (MT) Qty. Avail.(MT)

Apprd. Source Quality(OK/NOT OK)

6 mm

8 mm12 mm

16 mm

32 mm

.. mm

.. mm

(vii) Form Boxes

(a) Dimensions are as per apprd. Drgs. O.K./NOT

O.K.

(b) Oiling of inner wall of form boxes O.K./NOT O.K.

(viii) T&P and man power as per Annexure IA & IB

are available at site YES/NO

CERTIFICATE : Material & T&P Cleared for lean concreting.

(ix) Lean Concreting

(a) Pits are free from all Foreign Materials YES/NO

(b) Pits are free from standing water

(Dewatering continued in advance by

Pumps/Buckets) YES/NO

(c) Mix ratio 1:3:6 with 40 mm metal YES/NO

(d) Concrete mixing by mixer as per specn. YES/NO

(e) Mixture running Time (Mixing Time-2 Min.)

OK/NOT OK

(f) De-watering done YES/NO/NOT

REQUIRED

(g) Lean concreting done upto specified

level and area in all the four pits YES/NO

(h) No. of cement bags consumed AS

PER DESIGN ACTUAL

(x) In case of excess excavation filling

is done by lean concrete & no loose

soil is permitted for filling.

Vol. Of excess lean concrete ……………. Cu.m.

CERTIFICATE : Pits are cleared for installation of reinforcement and form boxes.

FOR

POWERGRID

Signature

………………..………

Name ……

……………………...

(E1/E2/E3)

Date ……

……………………….

5.0 Check format for Installation

of Reinforcement Steel & Form Boxes




(i) Apprd. Drg. Nos. …………

……………..

(ii) Reinforcement Steel …………

……………

(a) Quality/Qty./as per specn.

YES/NO

(b) Bending/Placing as per apprd.

Drgs. YES/NO

(c) Reqd. no. of chairs provided

(Min. Dia-12 mm, Max. Spacing-

500 mm) YES/NO

(d) Binding done as per specns.

YES/NO

(e) Any undue stress or bending of

steel bars YES/NO

(f) Steel is clean and free from loose

rust or

any other foreign matls.

YES/NO

(g) Position of bars w.r.t. stub as per

drg. OK/NOT OK

(iii) Form Boxes :-

(a) Dimensions as per appd. Drgs.

OK/NOT OK

(b) Placing w.r.t. stub as per apprd.

Drg. OK/NOT OK

(c) Bolts and Nuts are watertight

YES/NO

(iv) Clear cover of 50mm (or as per

specn.)

available YES/NO

(v) Earth strips fixed as per apprd.

Drg. YES/NO

CERTIFICATE : Cleared for foundation casting.

FOR

POWERGRID

Signature

………………..………

Name ……

……………………...

(E1/E2/E3)

Date ……

……………………….

6.0 Check format for Mixing,

Placing and Compacting of Concrete




(i) Apprd. Drg. Nos. …………

……………..

(ii) Mix Ratio …………

……………

(a) For Pyramid/base with 20 mm

metal

with ratio 1:2:4 YES/NO

(b) For chimney with 20 mm metal

with ratio 1:2:4 YES/NO

(c) Water to cement ratio as per

specification YES/NO

(iii) Mixing done by

(a) Mixer (Running time – 2 min.)

(b) Hand mixing (with 10% extra

cement

or as specified in LOA)

YES/NO

(c) Hand mixing done on GI Sheet

platform YES/NO

(iv) Use of poking rod for compacting

YES/NO

(v) Use of vibrator for compacting

YES/NO

(vi) Checking of template levels &

its diagonals at regular intervals.

OK/NOT OK

(vii) Casting of legs done in continuity

YES/NO

(viii) No. of cement bags consumed

AS PER DRG. ACTUAL

(ix) Coping is done as per appd. Drg.

YES/NO

(x) Details of cubes collection.

Twr. Leg Pyramid (Date) Chimney (Date) No. of cubes

A

B

C

D

(xi) Curing is started after

24 hrs. of foundn. Casting and

foundn. Kept

continuously in wet condn. By putting

wet gunny bags or

otherwise. YES / NO

(xii) Form Boxes are

removed after 24 hrs. of casting YES/NO

(xiii) Sufficient qty. of

water available at loc. Before

backfilling

YES/NO

(xiv) Back filling is done by

soil as per specn. and

free from foreign

material. YES/NO

(xv) Backfilling is done in

layers with proper

compacting and

adequate water sprinkling YES/NO

(xvi) Backfilling is done

upto 75 mm above ground

level or as specified in

specn. YES/NO

(xvii) Earth embankment of

ht. 50 mm or as per

specn. made along the

side of backfilled earth YES/NO

(xviii) Sufficient qty. of

water sprinkled over backfilled

earth and chimney

kept wet by gunny bags. YES/NO

(xix) Template is removed

after complete back filling YES/NO

(xx) Curing of backfilled

earth & chimney carried

out for period as per

specn. (Minimum period

of curing 14 days after

concreting both in Morning

& Evening)

YES/NO

(a) Date of start of curing

………………….

(b) Date of completion of

curing …………………

(xxi) Cubes sent for Testing

as per approved FQP YES/NO

(xxii) All the surplus

materials removed from site YES/NO

CERTIFICATE : Foundn. Is cleared for tower erection subject to fulfillment of part (I)

before tower erection and part (II) in due course as per planning.

Part-I Setting period (28 days) is allowed as per specn.

Part-II (i) Revetment Benching proposal status …………………….

(ii) Revetment/Benching likely execution date ………………………

FOR

POWERGRID

Signature

………………..………

Name ……

……………………...

(E1/E2/E3)

Date ……

……………………….

ANNEXURE-IA


TOOLS & PLANTS

FOR

Excavation, Stub Setting and Concreting

A. Tools & Plants reqd. : Tools & Plants reqd. for excavation, stub setting and

concreting gang shall be as follows :

(1) Stub setting templates - 2 Nos./as per reqt.

(2) Stub setting jacks - Min. 20 Nos./as per reqt.

(3) Form Boxes/chimneys - Min. 4 Nos./as per reqt.

(4) Mixer machine

Diesel Engine driven - 2 Nos.

Hand driven - 1 No.

(5) Needle vibrator for compacting - 2 Nos.

(6) De-watering pumps - 2 Nos.

(7) Air compressor for drilling holes in rock - As per reqt.

(8) High carbon drilling rods. For drilling

holes in rock - As per reqt.

(9) Exploder - As per reqt.

(10) Water tanker trailer - 2 Nos.

(11) Theodolite with stand - 1 No.

(12) Ranging rods with flag - 12 Nos.

(13) Dumpy level with stand - 1 No.

(14) Levelling staff - 1 No.

(15) Survey Umbrella - 1 No.

(16) Concrete cube moulds - 6 Nos.

(17) Wooden shuttering & Poles - As per reqt.

(18) Mixing sheets - 12 Nos.

(19) Measuring boxes - 6 Nos.

(20) Sand screen 4.75 mm - 2 Nos.

(21) Empty Barrel (200 L capacity) - 6 Nos.

(22) Ladder, 3.5 meter length - 5 Nos.

(23) Steel Tape (30 mts.) - 2 Nos.

(24) Engineer’s spirit level - 2 Nos.

(25) Steel Piano wire/Thread - 50 m

(26) Crow Bar - 12 nos.

(27) Pick Axe - 12 Nos.

(28) Spade - 15 Nos.

(29) Shovels - 8 Nos.

(30) Cane Basket - 20 Nos.

(31) Sledge Iron Hammer (0.9 kg) - 4 Nos.

Iron Hammer (4.5 kg) - 4 Nos.

(32) Manila Rope 12 mm dia - 30 m

38 mm dia - 150 m

(33) Pocking rod (16 mm dia)

3.5 m long - 2 Nos.

1.5 m long - 2 Nos.

(34) Blasting mats. - As per reqt.

(35) Tommy Bars, plumb BOB (0.45 kg)

Spanners (Both ring & flat) - As per reqt.

(36) Buckets - 12 Nos.

(37) Tents, water drums, camping, cots, tables,

chairs & petromax etc. - As per reqt.

B. Transport reqt. for stub setting/concreting gang

1. Truck - 1 No.

2. Tractor with trailer - 1 No.

3. Motor cycle - 2 Nos.

4. Jeep - 1 No.

C. Safety Equipments

1. Safety helmets - 16 Nos.

2. First Aid Box - 1 No.

3. Hand gloves - 16 Pairs

4. Shoes - 16 Pairs

5. Welding goggles - 4 Sets

ANNEXURE-IB


MANPOWER REQUIREMENT

FOR

EXCAVATION, STUBSETTING & CONCRETING GANG

(1) Engineer (Part time) 1 No.

(2) Jr. Engineer 4 Nos.

(3) Skilled Manpower :

(a) Fitter 8 Nos.

(b) Mixer m/c operator 2 nos.

(c) Water pump/vibrator operator 2 Nos.

(d) Carpenter As per

reqt.

(e) Skilled workers for

miscellaneous works 8 Nos.

(4) Unskilled workers

40 Nos.

(5) Mechanic As per

reqt.

Note : Manpower strength to

be increased from 65 to 85 depending upon Soil parameters and other site conditions. Also

for specified jobs like benching/Revetment, blasting etc., separate manpower is to be

engaged.

ANNEXURE-IC


REINFORCED CONCRETE RETAINING WALLS

1.0 Cantilever Retaining Walls : A cantilever retaining wall consists of a vertical

cantilevering slab called the stem and a base slab (fig. 40). This type of wall may

be used to retain earth up to 6 meters. For greater heights a counterfort retaining

wall should be used. The base slab consists of :

(i) The toe slab and (ii)

Heel slab. The heel slab is that part of the base slab, under the retained

earth. The toe slab is the projection of the base slab on the front side of the

retaining wall.

Top width of stem = 20 cms.

Bottom width of stem = To be computed

Width of base slab = B

b = 0.5 H to 0.6 H

for walls without surcharge

b = 0.7 H for surcharged walls

H bToe projection = _______ or ____

6 3

H = Overall height of wall.

The bottom width of the stem should be determined from bending moment

considerations. Usually the thickness of the base slab is made equal to the bottom

thickness of the stem.

Method of design. (a) A tentative cross-section should be first assumed.

(b) For one metre run of the wall the maximum bending moment at the bottom

of the stem is determined. By equating the bending moment to the moment of

resistance of Qbo the effective depth is determined. The cover the reinforcement

in the stem is usually 3 to 4 cm. Hence assuming the diameter of the reinforcement

the overall width of the stem at the bottom is determined. The base slab thickness

is made equal to the width of the stem at the bottom.

(c) The stability of the structure is studied. The maximum and minimum

pressures at the base are worked out. The maximum pressure at the base shall not

exceed the safe bearing capacity of the soil.

(d) The reinforcement required for the stem is computed. This is given by

Max. B.M. in Newton cm. Max. B.M. in kg. cm.At (sq. cm) = _____________________ or ____________________

14000 x 0.87 d 1400 x 0.87 d

(e) Calculate the maximum bending moment for the toe slab. The toe slab

is designed as a cantilever and acted upon by upward soil reaction. The

depth provided is checked for the bending moment. A cover of 5 cm.

To 6 cm. may be provided to reinforcement in the base slab.

(f) Calculate the maximum bending moment for the heel slab. The heel

slab is also designed as a cantilever subjected to downward loads

consisting of its own weight, the weight of the soil above it and super

load and any loading due to the surcharge, and upward soil reactions.

The reinforcement required is now determined.

(g) The tendency for the wall to slide forward due to the lateral earth

pressure should be investigated. A factor of safety of at least 1.5 shall

be provided against sliding. If the factor of safety is insufficient a key

(also called rib or cut off wall) would be designed to prevent the lateral

movement of the structure. (See Fig. 43).

Figs. 41 and 42 show how the various components of a cantilevering

wall can fail.

The above figures must obviously give an idea as to where the reinforcements

are required. Fro the stem, reinforcement is required near the earth side. For

the toe slab the reinforcement is required at the bottom of the slab. For the heel

slab the reinforcement is required at the top of the slab. For the key the

reinforcement is required on that side where convexity of bending will occur

(see Figs. 42 and 43). Fig. 43 shows a section of an R.C. retaining wall

showing places where the main reinforcements are required.

Usually the requirement of reinforcement for the key will be small and hence

alternate bars of toe slab may be continued and bent down to form the

reinforcement for the key. The key may alternatively be provided under the

stem so that alternate bars of the stem reinforcement may serve as

reinforcement for the key.

Shear reinforcement. Shear reinforcement is not normally used in retaining

walls. The resistance of the concrete itself must be sufficient to resist the

sharing forces imposed.

Distribution steel. Horizontal distribution steel should be provided in both the

stem and the base slab. This reinforcement shall not be less than 0.15% of the

gross area of concrete.

Expansion and contraction joints. Keyed expansion and contraction joints

should be provided at 30 m intervals.

2.0 Counterfort Retaining Walls

Retaining walls over 5.5 metres in height are usually made of the counterfort type. The

various components of such a wall are shown in Fig. 44.

(i) Upright slab. The upright slab will be designed as a continuous slab

spanning on the counterforts and subjected to lateral earth pressure. Let the

lateral, horizontal pressure intensity at the bottom of the upright slab be p

per sq. metre. Consider the bottom 1 metre deep strip of the upright slab. If

the spacing of counterforts be 1 metres centre to centre then the maximum

being moment for theupright slab = pI2/12. The thickness required to suit

this bending moment may now be computed. The slab is usually built of

the same thickness. The main reinforcement requirement may now be

calculated. This steel runs horizontally, its requirement being away from

the earth side at sections mid-way between the counterforts and near the

earth side at the sections on the counterforts.

The slab shall also be provided with distribution steel at not less

than 0.15% of the gross area of the section. The distribution steel is placed

vertically near both the faces, since the upright slab is considerably thick.

These bars should form a mesh with the horizontal bars. Hence these bars

will have to be supported by additional horizontal bars at certain places

where main horizontal bars are not forming a mesh with them.

(ii) The base slab. The width of the base slab may be made 0.6 H to

0.7 H where H is the overall height of the retaining wall. The base slab

consists of the toe slab and the heel slab. The toe projection is usually one-

fourth of the total width of the base slab.

Heel slab. The heel slab should be designed as a continuous

horizontal slab with the counterforts as the supports. The slab is designed

as a continuous slab consisting of continuous strips parallel to the wall.

Each stip is uniformly loaded; but the loading on the various strips

varies from a maximum at the heel edge to a minimum near the wall.

The loading on a strip of heel slab will consist of the following :

(a) Dead load of the strip

(b) Weight of earth above the strip

(c) Vertical component of lateral pressure in the case of earth

surcharged at an angle. If the surcharge angle is a, then the intensity

of vertical component of lateral pressure

= Cp wh’ sin tan

Cos – (cos2 – cos2)1/2

Where Cp = cos _______________________ Cos + (cos2 – cos2)1/2

h’ = height of earth above the strip

= angle of repose.

(d) Superload intensity acting on the retained soil if any

(e) Upward soil pressure.

It will be seen that the net load on the heel slab will be a downward

load. If the net load be Q per unit area near the heel end, then consider a

one metre wide strip near the heel end. The maximum bending moment for

the strip

= QI2/12. The moment will be a sagging moment at sections midway

between the counterforts and will be a hogging moment at the sections

over the supports.

Thickness of the base slab. The author suggests that this may be

taken not less than the following, in order it may not be found unsafe from

B.M. and S.F. considerations.

D = 4.17I (H)1/2

D = 2 IH

Where

D = Thickness of the base slab in cm.

I = Spacing of counterforts in metres.

H= overall height of wall in metres.

If the soil is surcharged at angle increase H by 0.7m.

Super load intensityIf the soil is superloaded increase H by------------------------------------------------ Wt. Per unit volume of thesoil

Spacing of counterforts. Counterforts are spaced from 3 metres to 3.50 metres.

This spacing may also be taken from one third the height of the wall to half the

height of the wall.

The spacing may also be computed as the spacing for which the maximum

bending moment for the upright slab requires an overall thickness of 30 cm.

Let the spacing be 1 metres. Let the height of upright slab be h metre.

In M.K.S. units, to satisfy the above condition,

454.8l = ---------- metr for M 150 concrete (wh)1/2

In S.I. units,

1438.25.8t = --------------- metr for M 150 concrete (wh)1/2

Toe slab. The design of the toe slab depends upon whether the toe slab is

allowed to remain a cantilever, or it is made to act as a continuous slab by

providing front counterforts. When the front counterforts are not provided the

toe slab should be designed as a cantilever slab subjected to upward soil

reaction. But if a front counterfort be provided then, the toe slab shall be

designed as a continuous slab with the front counterforts as the supports. In

such a case at section midway between the front counterforts the bending

moment for the toe slab will be of a hogging type, while at the section on the

supports, the bending moment for the toe slab will be of the sagging type.

(iii) Counterforts. As mentioned already the retaining wall may have main

counterforts or main counterforts and front counterforts.

Main counterforts. These are designed as vertical cantilevers held in position

by the base slab. The loading on these counterforts is due to the lateral earth

pressure acting on the upright slab.

Let h be the height of cantilever above the base.

L = spacing of counterforts

=surcharge angle

Total horizontal force transferred to one counterfort

wh2

Ph = Cp --------- I cos acting at a height of 2

h/3 above the base

Max. bending moment for the counterfort

= M = Ph (h/3)

M = Cp (wh3)/6 I cos

The reinforcement required to resist this bending moment can be easily

calculated.

At = (M/at) sec

Where = inclination of the reinforment with the normal to the horizontal section of

counterfort (i.e., inclination of the reinforcement with the vertical).

We know At (M/a) (M/d) (M/h) approximately

At (h3/h)

At h2

If At1 and At2 are the areas of steel required at depths h1 and h2

We have At1/At2 = h12/h2

2

But At is proportional to the number of bars.

Let n be the number of bars at the depth h

n1 be the number of bars at the depth h1



Then we have

n1/n = h12/h2 …………………………………….. (1)

n2/n = h22/h2 ……………………………………. (2)

n3/n = h32/h2 …………………………………… (3)

and so on.

Hence at what depth a certain number of bars can be curtailed, can be

determined.

Front counterforts. These are designed as horizontal cantilevers. The loading

on these will be due to the upward soil reaction on the toe slab. It is quite

likely that the front counterfort will be subjected to considerable shear force.

Hence shear stirrups of two or four legs must also be provided.

The main reinforcement of the main counterfort and also that of the front

counterfort should be embedded into the base slab for sufficient length to

develop the necessary bond strength. The bars of the main counterfort should

be securely anchored at the bottom by bending them back into the base slab.

In the case of a wall provided with main as front counterforts the critical

section for the max. bending moment for the main counterforts shall be taken

at a level corresponding to the top level of the front counterfort.

Horizontal ties connecting the main counterforts and upright slab.

Horizontal links of two legs are provided connecting the main counterfort and

the upright slab to tie the wall to the counterfort and also to resist diagonal

tension in the counterfort. These links must be looped around the main

reinforcement of the counterfort. Fig. 47 shows the horizontal links and Figs.

48 and 49 show two alternative ways in which the horizontal links may be

provided.

Vertical ties connecting the counterforts and the Heel slab. We know that the heel slab

will transfer its load to the counterforts which are supporting them. In order

that the heel slab may transfer its load to the counterfort, it is necessary to

provide vertical ties which are in the form of vertical links of two legs.

----------------------------------------------------------------------------------------------------------------

BIBLIOGRAPHY----------------------------------------------------------------------------------------------------------------

(1) “Transmission Line Structure” by S.S. Murthy and A.R. Santhakumar.

(2) “Manual on Transmission Line Towers” – CBI&P – Technical Report No. 9.

(3) “Workshop on Transmission Line” – CBI&P-Vadodara (29th Nov. –2nd Dec. 94).

(4) “Symposium on Design & Protection of 400 KV Transmission Lines” – CBI&P –

Publication No. 131.

(5) “Code of Practice for Design and Construction of Pile Foundation” – IS 2911 (Part-I

to Part-IV).

(6) “Pile Design and Construction Practice” – M.J. Tomlinson.

(7) “Manual on Transmission Line Towers” – Central Board of Irrigation and Power.

(8) “Handbook on under-reamed and Bored compaction Pile Foundation” – Central

Building research institute, Roorkee.

(9) “Construction Manual, Part-II, Transmission Line Construction” SRTS – Power Grid

Corporation of India Ltd.

(10) “Soil Mechanics and Foundation Engineering” by K.R. Arora.

(11) “Modern Geotechnical Engineering” by Alam Singh.

(12) “Foundation Design” by Wayne C. Teng.

(13) “Construction Planning equipment & Methods” by Robert L. Peurifoy and William B.

Ledbetter.

(14) “Foundation analysis and Design” by Joseph E Borles.

Foundation & Soil Investigation

Documents

Transcript of Foundation & Soil Investigation