MilQasim-1,Soil Investigation Report

5/26/2018 MilQasim-1,Soil Investigation Report

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College of Engineering

SOIL INVESTIGATION

For

Base Slab for Well Equipments

(MilQasim-1 Drillsite)

(Western ZAGROS)

April 2011


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CONTENTS

1- INTRODUCTION 2

1.1 Authorization and Scope 2

1.2 Site location 2

1.3 Report Layout 2

2 SEISMICITY OF THE AREA 3

3 FIELD WORKS 4

3.1 Boring 4

3.2 Recovery of Samples 4

3.3 In-situ Test 4

4- LABORATORY TESTING 7

5- SUB-SOIL CONDITION 7

5.1 Sub-soil profile 7

5.2 Groundwater Level 7

6- EVALUATION AND DISCUSSION OF RESULTS 8

6.1 Atterberg Limits 8

6.2 Unconfined Compression Test Results 8

6.3 Consolidation Properties 9

6.4 Texture of Soil 9

6.5 Chemical Properties 9

7 STRUCTURAL DESIGN INFORMATION 10

8 - RECOMMENDATIONS 10

8.1 Type of footings 10

8.2 Depth of Footing 10

8.3 Allowable bearing Capacity 10

8.4 Groundwater 10

8.5 Expansive soil 11

8.6 Type of Cement 11

9.0 MODULUS OF SUB-GRADE REACTION; 11


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Base Slab for Well Equipments (MilQasim-1 Drillsite)

1.1 Authorization and ScopeThe WesternZAGROS Company requested from Consulting Engineering Bureau \

College of Engineering \ University of Sulaimani to undertake the geotechnical

investigation for the new proposed location of the oil well equipments at Kifry District.

This report includes the results of soil investigation for the proposed project. Also it

incorporates the results of subsurface exploration, laboratory testing, discussion of test

results and recommendations about requirements for foundation designing.

1.2 Site Location

The site is located at Sulaimany Governorate, especially at Kifry District \ MilQasim

Area.

1.3 Report Layout

The soil investigation for the project includes simple investigation by digging two

bore-holes to a depth of 20.0 m. The boreholes were drilled from the ground surface, and

taking disturbed and undisturbed samples for laboratory testing.

This report presents and discusses the laboratory test results as well as

recommendations for the foundations of the base slab.

1.4 Report Layout

The soil investigation for the new proposed project includes simple investigation by

digging two bore-holes to a depth of 20.0 m. The boreholes were drilled from the ground

surface, and taking disturbed and undisturbed samples for laboratory testing.

This report presents and discusses the laboratory test results as well as

recommendations for the foundations of the base slab.


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2. SEISMICITY OF THE AREA

According to Iraqi seismic code (No. 2/1997), the ordinary structure may be designed

by the equivalent static method using conventional liner elastic analysis. The seismic

analysis of structures shall take the dynamic properties of the structure into consideration by

equivalent static analysis. In this analysis the seismic hazard and zoning coefficient (Z) are

required. The evaluation of seismic hazard in different seismic areas for the design of

buildings and structures shall be performed according to the seismic zoning map of Iraq,

(Fig. 1). The value of coefficient (Z) can be taken as follows;

Zone Z

I 0.05

Site of project

Z

0.05

0.07

0.09

0.000

I

IIII


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3. FIELD WORK

3.1 Boring

Two boreholes were drilled to a depth of 20.0 m from the present ground

level. Figure (2) shows a sketch showing locations of the bore-holes. The

boreholes were advanced by using power drilling machine. The applied

method for drilling was continuous flight auger method (Photo No. 1).

3.2 Recovery of Samples

Representative samples were generally taken at appropriate intervals

ranging from (1 to 2) meters depth or where the stratum was changed. The

disturbed samples (D) were collected from the cutting of the auger.

The undisturbed samples (U) were obtained from the boreholes by

installing 100 mm diameter, thin walled Shelby tubes into the stratum.

3.3 In-situ Tests

Bowels (1995) stated that, 90 percent of conventional foundation design in

America is made using the SPT. This test is also widely used in other parts of

the world.

During the sub-soil investigation, the only in-situ test conducted was the

Standard Penetration Test (SPT). The test consists of driving standard 50-

mm diameter split spoon sampler of 450-mm length into soil stratum by

means of a 63.6-kg weight hammer falling freely 760-mm height. The

number of blows for every 150-mm of penetration are recorded, the total

number of blows required to drive the second and third 150-mm of

penetration is called the standard penetration resistance N-value which

represents the number of blows per 300-mm of penetration.

The test is halted if more than 50 blows are required for 150-mm

increment. When the result is written as SS > 50.

The N-values obtained are shown in the Bore log sheet appended. Photo

(2) shows all parts of the standard split spoon used in this test.


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Fig (2) Sketch of the Site showing the location of the well and boreholes

BH 1BH 2Well

7.0 m7.0 m

SouthNorth


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Photo (1) power drilling machine using continuous flight auger method for drilling.


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Photo (2) Standard Split spoon used for testing SPT.

4-LABORATORY TESTING

4.1 Type of Tests

4.1.1 Tests on undisturbed & disturbed soil samplesi) Liquid & Plastic Limits.

ii) Sieve analysis.

iii) Chemical Tests.

4.1.2 Tests on undisturbed soil samplesiv) Natural dry density and moisture content.

v) Unconfined Compression Test.

vi) Consolidation Test.

4.2 Method of Testing

Undisturbed samples were used for strength and compressibility tests. Disturbed or

undisturbed samples available were used for classification and chemical tests. All the

tests were carried out according to the recommendations and procedures called for by

ASTM and B.S as appropriate or applicable for any given case.

4.3 Presentation of ResultsAll the test results are summarized in tables, as shown in the latter sections.

5- SUB-SOIL CONDITION:

5.1- Sub-soil Profile:

The sub-soil stratification is shown in the boreloge sheets, from which the sub-soil

condition can be summarized as follows:

(a) A layer of a backfill soil was found from the ground surface and covering the site.

Thickness of this layer is about 1.0 m.

(b) The upper layer is underlained by a cohesive layer of a hard light brown to green

Clay. This layer is continued to the end of boring.

5.2 Underground Water Condition

The groundwater table was not encountered after completion of excavation, within

the depth of the bore-holes (20.0 m) from the ground surface.


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6- EVALUATION AND DISCUSSION OF RESULTS:

6.1 Atterberg Limits:The values of Liquid Limit (LL), Plastic Limit (PL), and Plasticity Index (PI), for the

cohesive layer at different depths are shown in Table (1) below:

Table (1) Atterberg limits tests resultsBorehole

No.

Depth *

( m )

Liquid Limit

( LL ) %

Plastic Limit

( PL ) %

Plasticity

Index (PI) %

BH 1

3.0-3.5 55.0 32.41 22.6

3.5-5.5 66.5 35.77 30.7

6.0-8.0 57.5 28.88 28.6

8.0-8.5 49.2 28.63 20.6

8.5-10.5 61.9 29.7 32.2

10.5-11.5 55.2 32.84 22.411.0-14.0 54.1 31.71 22.4

14.5-17.0 57.1 32.86 24.2

17.0-17.5 50.4 29.19 21.2

17.5-19.5 57.4 33.86 23.5

19.5-20.0 53.2 29.63 23.6

BH 2

4.5-7.0 69.7 36.69 33.0

7.0-7.5 63.2 31.27 31.9

7.5-10.0 52.1 29.56 22.5

10.5-13.5 61.6 32.67 28.9

13.5-14.0 49.3 27.54 21.8

14.0-16.5 59.6 30.61 29.0

16.5-17.0 45.7 27.77 17.9

17.0-19.5 57.6 30.23 27.4

19.5-20.0 58.7 33.21 25.5

From this table it can be obtained that the cohesive soil can be classified as a medium

to high expansive soil.

6.2 - Unconfined compression test results:

Undisturbed soil samples are collected by small diameter of thin wall tubes

(38 mm), which are suitable for conducting unconfined compression tests.

Table (2) shows the result of (qu) values of unconfined compression test,

and also shows natural moisture content, bulk and dry unit weight.

Table (2) Unconfined compression test results

Bore-

hole No.

Depth*

( m )

Natural moisture

content (%)wet

(gm/cm3)

dry(gm/cm

3)

Unconfined

compression strength

( qu) ( kN/m2)

BH 1 5.50 6.0 21.15 2.0906 1.7257 278.20


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14.0 14.50 19.04 2.1122 1.7743 519.19

BH 24.0 4.50 21.27 2.0266 1.6711 288.76

10.0 10.50 21.55 2.1607 1.7777 475.19

6.3 Consolidation Properties

Consolidation tests are performed on undisturbed cohesive samples by using

consolidation ring 50-mm diameter by 19-mm thick. The applied pressure used is in

the range of 25 to 800 kN/m2.

The results of consolidation tests are shown in consolidation graphs appended on

the form of (e-log p) curve. Casagrandes method is used to determine

preconsolidation pressure (Pc).

The results of overburden, preconsolidation pressure and consolidation parameters

are shown in Table (3). This table indicates that the cohesive layer is overconsolidated

soil. These results indicate that the anticipated settlement for the suggested structures

will be tolerable.

Table (3) Overburden, preconsolidation pressure & consolidation parameters with depth

Borehole

No.

Depth

(m)

Overburden

pressure

(Po) (kN/m2)

Preconsolidation

pressure(Pc)

(kN/m2)

Initial

void ratio

(eo)

Compression

Index

(Cc)

Expansion

Index

(Ce)

BH 1 5.50-6.0 121 280 0.5262 0.0982 0.0210

BH 2 4.0-4.50 81 260 0.6498 0.1219 0.0260

6.4 Soil Texture:

The grain size analysis test was carried out for granular samples and the texture of

the tested samples are shown in Table (4) below:

Table (4) Soil Texture

orehole No.Depth

( m )

Gravel

%

Sand

%

Clay + Silt

%

BH 1 3.0 75.2 7.0 17.8

BH 2 1.50 77.8 8.4 13.8

6.5 Chemical PropertiesThe results of chemical tests for the soil samples are shown in Table (5).

Table (5) Chemical tests for soil samples

Bore-hole

No.

Depth

(m)pH SO3%

BH 1

2.0 7.8 0.30

3.50 7.9 0.26

7.0 7.7 0.32


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BH 21.50 7.8 0.35

5.0 7.9 0.28

7- STRUCTURAL DESIGN INFORMATION

The client has provided the following information to us; -

1. It is suggested to construct a concrete base slab.

2. The base slab will be used as a base for the oil well drilling machines.

8. RECOMMENDATIONS

8.1 Type of footings

According to the proposed structure type, which is the Concrete base slab, and

depending on the loading condition and recommended value of the allowable bearing

capacity, suitable types of foundations of rigid raft or mat foundation can be used.

8.2 Depth of footings

It is recommended to place the foundation at a depth of 1.0 m or more. But it should

be ensured that all backfill materials to be excavated and removed before placing the

foundation. Also it is recommended to place all parts of the base slab on the granular

layer of sandy gravel with clay.

8.3 Allowable Bearing Capacity

According to the laboratory test results and field test of (SPT) with a sub-

soil condition, the allowable bearing capacity of 150 kN/m2 (15.0 ton/m

2)

(3.13 ksf) can be considered in designing of the foundations at a depth of

1.0m or more.

8.4 Groundwater

No groundwater was encountered up to end of boring, so no construction problem due

to groundwater is anticipated.


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8.5 Expansive Soil

The cohesive soil in this site is classified as a medium to high expansive soils.Therefore, problem of swelling is anticipated. Expansive soils undergo volume changes

upon wetting and drying. Foundations constructed on these clays are subjected to large

uplifting force caused by the swelling. These forces will induce heaving, and cracking.

The following precautions are suitable for the situation of this site and needed to be taken

during construction of the foundations:

1- The foundation soil should be protected from wetting, especially if the construction is

done during the winter. In this case the foundation structure should be cast as soon as

possible after excavation of the soil, because increasing moisture content of the

foundation soil before casting the foundation will cause heave of the soil, which causesthe soil to be more compressible.

2- It is recommended to place the foundation on the granular layer at a depth of 1.0 m or

more.

3- During the construction, if filling process is required, sub-base materials or granular soil

should be used, and the available cohesive soil in the site should not be used as fill

materials.

8.6 Type of CementGenerally the concentration of Sulphates (SO3) of the soil is greater than 0.2 % but less

than 0.5 %. So one of the following recommendations can be used:

1- By using Ordinary Portland Cement (OPC) with a minimum cement content of

(330 kg/m3) and Maximum water / cement ratio of 0.50.

2- By using Sulphate Resisting Portland Cement (SRPC) with a minimum cent

content of (300 kg/m3) and Maximum water / cement ration of 0.55.

9.0 MODULUS OF SUB-GRADE REACTION;

Modulus of sub-grade reaction for the allowable bearing capacity of 150 kN/m2can

be considered as 18000 kN/m3.


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Dr. Kamal Ahmad Rashed

Geotechnical Consultant

References

1. American Society for Testing and Material Annual Book of ASTM Standard

2. Bowels, E. Joseph (1995) Foundation Analysis and Design Mc Graw-Hill

Companies

3. British Standards Code of Practice (BS)

4. Craig, R. F. (1997) Soil Mechanics E & FN Spon , London.

5. Das, B. M. (1983) Advanced Soil Mechanics Mc Graw-Hill Book Companies.

6. Das, B. M. (1990) Principles of Geotechnical Engineering Pws-kent Publishing

Company Boston.

7. Das, B. M. (1999) Principle of Foundation Engineering Pws-kent Publishing

Company Boston.

8. Day, R. W. (2001) Soil Testing Manual Mc Graw- Hill Inc.

9. Head, K. H. (1981) Manual of Soil Laboratory Testing Vol. 1, Vol. 2 & Vol. 3 ,

Pentch press , London

10. Mc Carthy, D. F. (1998) Essentials of Soil Mechanics and Foundations Prentice

Hall company.

11. Uni Budhui (2000) Soil Mechanics & Foundation John Wiley & Sons, Inc ,

Newyork.

12. Tomlinson, M. J. (1996) Foundation Design & Construction Longman Company.

MilQasim-1,Soil Investigation Report

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