Final Year Project Report.

5/21/2018 Final Year Project Report.

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KYAMBOGO UNIVERSITY

Faculty of Engineering

Department of Civil and Building Engineering

Final Year Project Report

Upgrading Nsambya-Kirombe

(Gogonya) Road to a Bituminous

Paved Surface

Projects coordinator: Eng Dr Isaac Mutenyo

Supervisor: Mr. Francis Eugene Okello

Student: Norman John Byamukama

RegNo: 06/U /190/ECD/GV

Project Report submitted as a partial fulfilment for the award of a bachelor of Engineering

in Civil and Building of Kyambogo University.

June 2010


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iAuthentication

.

This report is dedicated to my dear

Parents Mr & Mrs Kezire.


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iiAuthentication

Authentication

Declaration

I declare that all the work contained in this report is a true reflection of what transpired

during the project process and has not been presented to any institution for the award of a

Bachelors degree.

Signature Date.

Norman John Byamukama

Approval

This is to certify that Norman John Byamukama (RegNo. 06/U/190/ECD/GV) carried out this

project titled Upgrading Nsambya-Kirombe (Gogonya) road to a bituminous paved surface

under my supervision.

Signature..................................... Date.

Mr. Francis Eugene Okello


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iiiAbstract

Abstract

This report consists of a detailed proposed design for upgrading Nsambya-Kirombe

(Gogonya) road to a bituminous paved surface which stretches a distance of 1.135km. The

main objective was to a design flexible pavement with respect to the route, geometry,

drainage and pavement. This was done by assessing the current traffic using the road,

existing geometry, pavement structure and designing an appropriate drainage system. The

project road was characterised by a broken back curve, reverse curve and sharp curves,

which brought about so many delays. Lab and field tests, surveys, consultations, and

observations were some of the methods that were used to collect data.

From the results obtained, the Average Daily Traffic was 1116Vehicles/day, Motorcycles

taking up the greatest percentage of traffic (43%), the subgrade at section 0+500 was found

unsuitable having a CBR of 10%, and most of the curves were substandard having a radius

of less than 100m. A trapezoidal channel section, culverts were designed to cater for

drainage. A double surface dressing has been proposed with chippings being sprayed at

13.367kg/m2

and 9.548kg/m2

for the first and second layer and binder being sprayed at

1.229kg/m2

and 0.949kg/m2

for first and second layer.

The ADT showed that the road was due for upgrading considering the Ministry of Works

and transports criterion for upgrading a road in an urban setting with more than

300Vehicles/day.A realignment has been proposed with curves having a minimum radius of

100m, continuous maintainace of the drains is necessary so as to prevent silting. Quality

control should be ensured for materials in accordance with the specifications as stipulated.


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ivAcknowledgement

Acknowledgement

My sincere thanks go to all those that have enabled me reach to a successful completion of

my Bachelors degree especially My Supervisor Mr Francis Eugene Okello who has guided

me professionally and been a great inspiration. Resource persons Mr Mubangizi Jude and

Mr Busuulwa Patrick for their technical advice, my parents and family members for their

moral and financial support, lastly all my friends and coursemates.

May the Almighty God richly bless you.


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vTable of contents

Table of contents

Authentication......................................................................................................................ii

Abstract ............................................................................................................................. iii

Acknowledgement ..............................................................................................................iv

List of tables .....................................................................................................................viii

List of figures......................................................................................................................ix

Acronyms and abbreviations ................................................................................................x

List of symbols ...................................................................................................................xi

Chapter one...................................................................................................................1

1.0 Introduction.............................................................................................................1

1.1 Background.............................................................................................................1

1.2 Problem statement...................................................................................................2

1.3 Main Objective........................................................................................................2

1.4 Specific Objectives..................................................................................................3

1.4.1 Geometric Design....................................................................................................3

1.4.2 Drainage..................................................................................................................3

1.4.3 Pavement Design.....................................................................................................3

1.4.4 Environmental, Impact Assessment .........................................................................3

1.5 Project Scope...........................................................................................................4

1.6 Outline Methodology...............................................................................................4

1.6.1 Data Collection and Classification...........................................................................4

1.6.2 Modeling and Analysis............................................................................................4

1.6.3 Design and Simulation.............................................................................................4

1.6.4 Storage and Retrieval ..............................................................................................5

1.6.5 Publication and Dissemination.................................................................................5

1.7 Justification .............................................................................................................5

1.8 Significance.............................................................................................................5


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viTable of contents

Chapter Two................................................................................................................6

2.0 Literature review.....................................................................................................6

2.1 Introduction.............................................................................................................6

2.1.1 Project Description..................................................................................................6

2.1.2 Project Location ......................................................................................................6

2.1.3 Demography............................................................................................................6

2.1.4 Land use..................................................................................................................6

2.1.5 Climate....................................................................................................................7

2.2 Route Selection Process...........................................................................................7

2.3 Geometric Design....................................................................................................8

2.3.1 Geometric design standards.....................................................................................8

2.3.2 Design criteria and control.......................................................................................8

2.4 Pavement Design...................................................................................................29

2.4.1 Introduction...........................................................................................................29

2.5 Drainage design.....................................................................................................47

2.5.1 Introduction...........................................................................................................47

2.5.2 Types of drainage ..................................................................................................47

Chapter Three......................................................................................................55

3.0 Methodology.........................................................................................................55

3.1 General..................................................................................................................55

3.1.1 Data collection and classification...........................................................................55

3.1.2 Modeling and analysis ...........................................................................................57

3.1.3 Simulation and design ...........................................................................................57

3.1.4 Publication and dissemination ...............................................................................58

Chapter Four ........................................................................................................59

4.0 Results and discussion...........................................................................................59

4.1 Traffic ...................................................................................................................59

4.1.1 Horizontal alignment Data.....................................................................................60

4.1.2 Vertial alignment Data...........................................................................................61


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vii

4.2 Drainage Design....................................................................................................62

4.3 Pav ement Design..................................................................................................63

Chapter Five..........................................................................................................66

5.0 Reflections ............................................................................................................66

Chapter Six..................................................................................................................67

6.0 Conclusions and Reccomendations........................................................................67

Bibliography......................................................................................................................69

Appendices ........................................................................................................................70

Appendix A, Analysis and Design......................................................................................71

Appendix B:Tables ............................................................................................................83

Appendix C: Geometric Design tables................................................................................85

Appendix D:Pavement design ............................................................................................95

Appendix E: Drainage Design............................................................................................96

Appendix E: Financial Documentation.................................................................................100

Appendix E: Appraisals.........................................................................................................107


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viiiList of tables

List of tables

Table1.1: Highway Length Statistics ...................................................................................83

Table1.2: On going Projects....................................................................................................84

Table 2.1: Division into road category.................................................................................85

Table 2.2: Division into road class.......................................................................................85

Table 2.3: Design Vehicle Characteristics ...........................................................................85

Table 2.4: Terrain Classification..........................................................................................85

Table 2.5: Design parameters...............................................................................................86

Table 2.6: 30th

HV as a fraction of ADT..............................................................................10

Table 2.7: Conversion into PCUs.........................................................................................11

Table 2.8: Vehicle category description...............................................................................11

Table 2.9: Minimum radius as recommended by MoW&T..21

Table 2.10: Maximum grades................................................................................................24

Table 2.11: Pavement deign life selection............................................................................36

Table 2.12: surface category................................................................................................38

Table 2.13: Traffic Categories .............................................................................................38

Table 2.14:Nominal size of Chippings.................................................................................39

Table 2.15: Conditions for determining rate of spread of binder...........................................39

Table 2.16 Properties of unbound materials .........................................................................38

Table 2.17 Grading..............................................................................................................38

Table 2.18 Reccomended Plasticty Charactreristics of Granular subbase .............................39

Table 2.19 Typical PSD for sub base ...................................................................................39

Table 4.1: Circular curve data ................................................................................................60

Table 4.2: Transition curve data...........................................................................................60

Table 4.3: Grade.................................................................................................................61

Table 4.4: Vertical alignment data .......................................................................................61

Table 4.5: Crossectional data...............................................................................................61


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ixList of figures

List of figures

Figure 1.1: Highway location process ..................................................................................85

Figure 2.1: Typical vertical curves.......................................................................................22

Figure 2.3: Sight distance over crest curves ......................................................................... 25

Figure 2.4: Climbing lane outside ordinary lane...................................................................25

Figure 2.5: Crossectional elements ......................................................................................25

Figure 2.6: Pavement layers.....................................................................................................29


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xAcronyms and abbreviations

Acronyms and abbreviations

AADT Average Annual Daily Traffic

ADT Average daily Traffic

BS British Standard

CBR California Bearing Ratio

MDD Maximum Dry Density

TRRL Transport and Road Research Laboratory

TRL Transport Research Laboratory (UK)

SANRA South African National Roads Agency

SATCC Southern Africa Transport and Communications Commission

AADT Annual Average Daily Traffic

AASHTO American Association of State Highways and Transportation Officials

ALD Average Least Dimension

E.S.A Equivalent Standard Axle

GB3 Granular Base-material type 3

HW Allowable Headwater depth

LL Liquid Limit

LS Linear Shrinkage

M.S.A Millions of equivalent standard axle

MC Moisture Content

MDD Maximum Dry Density

OMC Optimum Moisture Content

ORN Overseas Road Note

PI Plasticity Index

PL Plastic Limit

GB3 Granular Base-material type 3

UBOS Uganda Beaura of Statistics

UNRA Uganda National Roads Authority

NTMP National Transport Master Plan


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xiList of symbols

List of symbols

m Meters

mm Millimetres

v velocity

w weight

Kg Kilograms

L Litres

E Easting

N Northing

Z Elevation

Ft Feet

P Force

% Percent


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1Introduction

1.0 Introduction

Transport is very vital for the social, economic and political well being of any country;

hence it is of paramount importance. Highway transportation overwhelmingly

dominates the transportation of people, accounting for 91% of all personal trips (Wright

& Paquette 1979). Planning, design, construction and maintainace of highways depend

on highway engineers who must translate the desires of the people.

From the recent statistics, the total highway length in the world is14, 662, 278.5 km,

United States of America having the largest highway length of 6,406,296 km. Of these,

4,148,395km are paved and 2,257,902km unpaved .India has a total highway length of

3,319,644km, of which 1,517,077km are paved and 1,802,567km unpaved. Ugandaamong the developing countries has 27,000km of highway length of which 1809km are

paved and 25,191km are not paved (CIA, 2008). Details of other countries are shown in

Table 1.1, Appendix B. From the statistics the following can be inferred, United States

of America, one of the most developed nations has most of its highways are paved

compared to others. This indicates that development is directly proportional to paved

highway length.

1.1 Background

In Uganda, the road network length was approximately 78,100km in 2008, made up of

10,800km of national roads, 27,500km of district roads, 4,800km of urban roads and

35,000km of community roads (NTMP, 2009).with UNRA now established to maintain

and improve national roads, a length of 8-10,000km of district roads is to be defined and

transferred to the national network giving a new total length of 20,000km each for

national and district networks. Presently, Uganda is investing most of its resources in

road construction and maintainace. There are many ongoing projects aimed at up

grading gravel roads to bitumen standards these include; Kampala Mityana road

Masaka-Mbarara road and Matugga-Semuto-Kapeeka road. These are funded by

European Union (UNRA, 2010).See details of ongoing and intended projects by 2013 in

Table 1.2 AppendixB. Nsambya-kirombe road is Located in Makidye division, Kampala

district. The road stretches a distance of 1.13 km; its a district feeder road that falls

under Kampala City Council (KCC).



2Problem statement

This road was mainly established so as to transport local bricks from Kirombe since it

was a place where they were manufactured (MOLG, 2009). Presently the manufacture

of bricks has seized and many developments are taking place around the project area.

This road connects to the National Medical Stores and other supermarkets in the area.

This has increased the level of service on this road that it accommodates an Average

Daily Traffic is more than 300vehicles per day. Since the road way was not originally

designed, it has a narrow width that cannot offer an adequate two way movement of

vehicles bringing about delays, its also dusty, with a poor alignment, drainage system is

absent along some sections, riding surface is rough, bringing about discomfort during

travel. Funds are being sought to have this road upgraded (MOLG, 2009).see Google

earth image in, Figure 1.2 in appendix H.

1.2 Problem statement

Roads deteriorate gradually, they under go either functional deterioration or structural

deterioration ,functional deterioration refers to the reduction in riding quality while

structural deterioration indicates that the pavement layers lose their bearing capacity

(Thagesen, 1996) .Failures on roads occur on the pavement layers and drainage system.

In this respect, the project road has no drainage system, has a narrow carriage way

width of approximately 4.6m, according to the geometric design manual of Uganda, the

minimum carriage width for a Gravel C road like the project road is 5.6 m, Poor

alignment such as a sharp curve on section 0+243-0+336 of 50m, the minimum radius

for the project road should be 100m.A Steep grade of 10% at section 0+580, maximum

grade for the project road should be 9% according to the Uganda road design manual.

Undulating surface that causes delays, discomfort and dust pollution amounting to

approximately 1.5 kg/m2/yr.The international roughness index ((IRI) for the road is 16-

17.5m/km. The road is therefore due for upgrading.

1.3 Main Objective

To design a structurally stable flexible pavement with respect to the route, geometry,

drainage and pavement with an environment impact assessment report so as to promote

adequate, safe, well maintained works, transport infrastructure and service for social-

economic development of Uganda.


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3

1.4 Specific Objectives

Based on the recommendations of (TRL, ORN6, 1998) the following specific objectives

were arrived at;

1.4.1 Geometric Design

a) Definition of the basic parameters of road function, traffic flow and terrain type;

b) On the basis of the above estimates, a design class is selected;

c) Determination of trial alignment;

d) Selection of design class standards;

e) Approach speed estimation;

f) Economic consequences;

g) Economic return;

h) Environmental impacts will be considered.

1.4.2 Drainage

In designing drainage the following will be considered;

a) Hydrology;

b) Hydraulics;

c) Hydraulic structures;

d) Environmental, impacts

1.4.3 Pavement Design

Basing on the recommendations of (TRL ORN 31), the following specific objectives

were arrived at;

a) Assess traffic so as to assign a traffic class;

b) Asses the subgrade strength so as to determine the subgrade class;

c) Selection of appropriate materials and layer thickness with an economic

consideration;

d) Selection of the pavement structure from the traffic class an subgrade class that

will be attained above ;

1.4.4 Environmental impacts will be taken into consideration

Basing on the recommendations of Kiely, 1997, the following components of EIA of a

road will be considered.



4Project Scope

a) A summary of the proposed road developments and of the principal

environmental impacts;

b) General project description and alternatives considered;

c) A baseline survey of the existing environment;

d) Assessment of the environmental impacts;

e) The implications for the land use and development plans for the affected area;

f) The financial implications;

g) Mitigation measures proposed to reduce negative impacts;

h) A synoptic table summarising the individual impacts and costs of alternative

considered;

i) Conclusions

1.5 Project Scope

The project will be limited to the following; geometry, drainage and pavement design

accompanied with an environmental impact assessment report and a cost estimate of the

project.

1.6 Outline Methodology

This has been broken down into the following main headings;

1.6.1 Data Collection and Classification

Data will be collected as follows;

Laboratory and field tests, observations, use of questionnaires, documentated literature

and consultations. It will be classified by using qualitative and quantitative methods.

1.6.2 Modeling and Analysis

Modelling will be done by Civil Cad, AutoCAD Land development .Analysis will be

done by using programmed excel spread sheets and UK DCP soft ware.

1.6.3 Design and Simulation

Designing will be done using the following standards, Transport Research Laboratory,

(TRL), Association of American State Highway and Transportation Officials

(AASHTO), South.African.National.Roads.Agency, (SANRA) South. African and



5Storage and Retrieval

Communications Commission (SATCC) and the Uganda Design Manual. While

Simulation will be done by Civil Simulate.

1.6.4 Storage and Retrieval

A data base for all information will be created using Microsoft access, folders will be

created for all the project work on the computer. A backup of all the information will be

created on an external hard disk, Compact Discs, Flash disks and E-mail address.

Information will retrieved by printing and keeping hard copies.

1.6.5 Publication and Dissemination

The project report will be published by the Author and then a copy will be forwarded to

Kyambogo University, others copies shall be given to Kampala city council and other

Public libraries. Soft copies will be converted to PDF, to prevent any distortion of the

document.

1.7 Justification

The project road has an average daily traffic (ADT) of more than 300 vehicles per day.

The Ministry of Works and Housing criterion for upgrading a road with in an urban

setting is when ADT is greater than 300 vehicles/day. Vehicle operating costs will be

saved since a smooth riding surface will be realised. Upgrading from a gravel surface to

a paved road will be justified principally by savings in vehicle operating costs arising

from the smoother running surface, but time savings may also be important (TRL 2005).

1.8 Significance

a) The roadway will be widened to 8.6m hence easy manoeuvring of the vehicles.

b) Dust pollution will be cease.

c) Employment opportunities will be created for people hence economic development.

A bout 50 people will be employed during the construction of the road.

d) More traffic will be accommodated because diverted traffic and generated will now

use this road because of the improvement of the road.

e) Comfort due to a good alignment since gentle curves will be introduced.

f) Flooding will be controlled since a drainage system will be put in place.

g) Reduced highway user costs through increased speed, lesser delays. Since traffic has

been flowing at an average speed of 30km/hr, it will now flow at 50km/hr.this will

result into a saving of 0.78 minutes per kilometre.



6Literature review

2.0 Literature review

2.1 Introduction

2.1.1 Project Description

Upgrading is improving the quality of something (Microsoft Corporation, 2008).

Upgrading projects aim specifically at providing additional capacity when a road is

nearing the end of its design life or because there has been an unforeseen change in use

of the road. Typical examples of upgrading projects are the paving of gravel roads, the

provision of strengthening overlays for paved roads and the widening of roads (TRL

2005).Factors that influence pavement performance include, initial structural capacity,

quality of construction, load magnitude and repetitions, drainage conditions, climate and

maintainace policies and practices (OFlaherty 2002).The appraisal of upgrading

projects is similar to that of new projects. In fact most new projects are essentially

upgrading projects (TRL 2005).

This project looks at upgrading the existing gravel road by locating an appropriate

alignment, recommending an appropriate drainage system, selecting appropriate

materials, recommending appropriate layer thicknesses for structural stability with the

necessary geometric and structural design.

2.1.2 Project Location

This project road is located in Greater Kampala Metropolitan Area (GKMA), Kampala

district, Makidye division, Nsambya, which is approximately 4.8km south southwest

of the Central business district of Kampala along Ggaba road at coordinates of

00O1757N and 32

o3517 E at an elevation of 4003ft (Wikipedia,2009). It connects

Kabega road to Lukuli road.

2.1.3 DemographyUganda has a population of about 29.6 million (UBOS, 2008). The population is

projected to be 49.3million people by 2023. Kampala has population of about 1,420,200

(UBOS, 2008) .The project road serves about 1500 people.

2.1.4 Land use

The main activity in this area is farming especially poultry.



7Climate

2.1.5 Climate

Kampala is Characterized by Tropical wet and dry seasons because of its altitude having

heavy rains from August to December and shorter rains from February to June. April

has the heaviest amounts of precipitation of about 175mm /hr, January being the

warmest (Wikipedia, 2009).

2.2 Route Selection Process

In the relocation or construction of existing highways and the establishment of new

ones, surveys are required for the development of project plans and the estimation of

costs. The performance of good surveys requires well trained engineers who have an

understanding of design, planning and economic aspects of highway location and who

are sensitive to the social and economic impacts of highway development. The work of

a highway location may include desk study, reconnaissance survey, preliminary surveyand a final location survey. See figure 2.1 in Appendix B. Road location is most easily

determined through low cost relatively underdeveloped lands, in such locales basic

engineering and construction cost considerations normally dominate analyses once the

traffic planning need has been established and accepted also provided that

environmental issues are not of major concern. The problems become more complex

and non engineering issues become more prominent as a route is sought through well

developed lands, and when interactions with existing roads and built up areas have to be

taken into account. the problems are normally in and about major urban areas where

community aspirations, interactions with existing roads, streets and economic,

environmental and planning issues become critical. Thus, whilst ideally a new major

road needs to be located where it can best serve the traffic desire lines, be as direct as

possible, and maximise its function of allowing convenient free flowing traffic

operation at minimum construction, environmental, land, traffic operations and

maintainace costs. The project road is already in existence; only the alignment will be

studied to see if its adequate.



8Geometric Design

2.3 Geometric Design

Geometric design is the process whereby the layout of the road in the terrain is designed

to meet the needs of the road users. The principal geometric features are the road cross-

section, horizontal and vertical alignment. Good geometric design ensures that adequate

levels of safety and comfort are provided for drivers for vehicle manoeuvres at the

design speed, and that the road is designed uniformly and economically, blending

harmoniously with the land escape (OFlaherty, 2002).

The use of geometric design standards fulfils three inter related objectives. Firstly,

standards are intended to provide minimum levels of safety and comfort for drivers by

the provision of adequate sight distances, coefficients of friction and road space for

vehicle manoeuvres; secondly, they provide the framework for economic design; and,

thirdly, they ensure a consistency of alignment. The design standards adopted must take

into account the environmental road conditions, traffic characteristics, and driver

behaviour.

2.3.1 Geometric design standards

The design standards adopted for this project will be the Ministry of Works, Housing

and Communication design manual of 2005, TRL Over Seas Road Notes, SATCC and

SANRA.The design will be based on the road category, expected volume and

compositions. The restrictions are mainly by the terrain classification and roadenvironment.

2.3.2 Design criteria and control

Highway geometrics are generally affected by so many factors some of which include

the following, Design speed and limit, Road function, topography, traffic, capacity,

design vehicle, control of access and level of service.

a) Design Speed

The assumed design speed for a highway may be considered as the maximum safe

speed that can be maintained over a specified section of highway when conditions are so

favourable that the design features govern. The choice of design speed will depend

primarily on the terrain and functional class of the highway. Other factors determining

the selection of design speed include traffic volume and composition, costs of right of

way and construction, and aesthetic considerations (Wright &Paquatte, 1979).



9Road function Design

Design speed is used as an index which links road function, traffic flow and terrain to

the design parameters of sight distance and curvature to ensure that a driver is presented

with a reasonably consistent speed environment. In practice, most roads will only be

constrained to minimum parameter values over short sections or on specific geometric

elements (TRL, ORN6).For this project a design speed of 50km/hr will adopted as per

Table 2.5: Appendix C.

b) Road function Design

h) Division into road category

The roads in Uganda are divided into the following categories according to their major

function within the network; see Appendix C, Table 2.1 .Basing on its function, the

project road falls under category C since service is provided to smaller communities.

ii) Division into road class

The division is governed by the design speed and design traffic (MoWH&C, 1994) See

Table 2.2: Appendix C. from the above table, the project road falls under class C Gravel

from the existing characteristics of capacity, carriage width and capacity.

c) Topography

The Uganda Road Design Manual (2004) defines the following types of terrain as

shown in Table 2.4, Terrain Classification See appendix C, from the description, the

project road fall under rolling terrain since it has a traverse slope of approximately 10%

which lies between 20% and 5%

d) Capacity

Capacity can be defined as the maximum number of vehicles per unit time that

can be handled by a particular roadway component or section under the prevailing

conditions. Road capacity information is useful for

(i) Transportation planning studies to assess the adequacy or sufficiency of

existing road network to service current traffic and to estimate the time in the

future when traffic growth may overtake capacity.

(ii) It is important in design of road dimensions, number of lanes and minimum

length of weaving length;

(iii) In traffic operation analysis in improvement of traffic operation (Uganda

geometric design manual, 2004)



10Traffic

a) Level of service

Level of Service expresses the effectiveness of the road in terms of operating

conditions. It is a qualitative measure of the effect of traffic flow factors, such as

speed and travel time, interruptions, freedom of maneuver, driver comfort and

convenience, and indirectly safety and operation costs( (MoW&T, 1994).

b) Traffic

Traffic volume indicates the level of service for which the highway is being planned and

directly affects the geometric features such as width, alignment and grades (Kadiyali,

2008).

i) Design hour volume

The unit for measuring traffic on a highway is the Annual Average Daily Traffic

volume, abbreviated as (AADT). It is equal to the total annual volume of traffic divided

by the number of days in the year. This is not commonly used in geometric design,

since it does not represent the variations in traffic during various months of the year,

days of the week and hours of the day. It is not economically sound to design a facility

to be congest free every hour through the year, however it has been established that each

year the traffic volume often reaches that of the 30th

heaviest hour, which is the hourly

volume exceeded only 29 hours a year. ( (Thagesen, 1996) hence a unit for geometric

design is the 30th highest hourly volume abbreviated as 30 HV which is defined as the

30th

highest hourly volume during the year (Kadiyali, 2008). DHV = AADT x K Where

K is estimated from the ratio of the 30th HV to the AADT from a similar site and is

expressed as a fraction of ADT can vary as indicated in the following table.

Table 2.6: 30th HV as a fraction of ADT for different traffic Conditions

Traffic Condition 30th HV as a fraction of ADT

Rural Arterial (average value) 0.15

Rural Arterial (maximum 0.25

Heavily trafficked road under

Congested urban conditions0.08 0.12

Normal urban conditions 0.10 0.15

Road catering for recreational

Other traffic of seasonal0.20 0.30

Source: Uganda Road Design Manual (2005)

The project road falls under Normal Urban Conditions, thus it has a K value 0.15 which

is taken as the average of (0.10 0.15) for design purposes.



11Traffic composition

ii) Directional distribution of traffic

Traffic flow figures available are for two way flow, and the directional split ratio is 1:2

and this will be adopted for the project (Kadiyali, 2008).

a) Traffic composition

Traffic composition has a vital effect on capacity and other design considerations. It is

customary in this country to express the traffic volume in terms of passenger car units

(PCUs), also representative for combined group of medium and heavy goods vehicles

and buses.

Table 2.7: Conversion into PCU

Level Rolling Mountainous

Passenger cars 1 1 1.5

Light goods vehicle 1 1.5 3

Medium goods vehicle* 2.5 5 10

Heavy goods vehicle 3.5 8 20

Buses 2 4 6

Motor cycles, Scooters 1 1 1.5

Pedal cycles 0.5 0.5 NA

Vehicle Type

Terrain

PCU

Source: Uganda Road Design Manual, 2005

The following definitions apply to the different vehicle types mentioned in the table.

Table 2.8: Vehicle category Descriptions

Vehicle Category Description

Passenger cars Passenger vehicles with less than nine seats.

Light goods vehicle Land rovers

Minibuses and goods vehicles of less than1500kg un-laden weight with payload capacities less than 760 kg.

Medium goods vehicle Maximum gross vehicle weight 8500 kg.

Heavy goods vehicle Gross vehicle weight greater than 8500 kg.

Buses All passenger vehicles larger than minibus

` Source: Uganda Road Design Manual, 2005

iii) Estimation of traffic flows

a) Baseline traffic flows (FO)

This is the Average Daily Traffic (ADT) which is defined as the total annual traffic

summed for both directions and divided by 365. For this project, the traffic currently

using the route was classified into the vehicle categories of cars, light goods vehicles,

trucks (heavy goods vehicles) and buses



12Projected traffic (Fp)

b) Projected traffic (Fp)

For this project, time series was used to project traffic growth rates.

n

P OF =F (1+r) 2.1

Where,

PF = Cumulative number of commercial vehicles after n years;

OF = Present number of vehicles after the traffic survey;

r = Growth rate of commercial vehicles;

n = Number of years of projection

iv) Design vehicle

The dimensions of the motor vehicle also influence design practice. The physical

characteristics of vehicles and the proportions of the various sizes of vehicles using a

road are positive controls in design and define several geometric design elements,

including intersections, on and off-street parking, site access configurations and

specialized applications such as trucking facilities. Therefore, it is necessary to examine

all vehicle types, select general class groupings, and establish representatively sized

vehicles within each class for design use. Vehicle characteristics affecting design

include power to weight ratio, minimum turning radius, and travel path during a turn,

vehicle height and width. The main road elements affected are gradient, road widening

in horizontal curves and junction design. In the design of road facility the largest design

vehicle likely to use that facility with considerable frequency or a design vehicle with

special characteristics that must be taken into account in dimensioning the facility is

used to determine the design of such critical features as radii at intersections and radii of

horizontal curves of roads. For this project the design vehicles DV 5 will be used to

control the geometric design. See appendix C,Table: 2.3 for the design vehicles.

2.3.3 Alignment

An ideal and most interesting roadway is the one that generally follows the existing

natural topography of a country. This is the most economical to construct, but there are

certain aspects of design that must be adhered to which may prevent the designer from

following this undulating surface without making certain adjustments to the in the

vertical and horizontal directions. The designer must produce an alignment in which

conditions are consistent. Sudden changes in the alignment should be avoided as much

as possible, for example, long tangents should be connected with long sweeping curves,

and short curves should not be interspersed with long curves of small curvature. The



13Horizontal alignment

ideal locations are one with consistent alignment where both grade and curvature

receive consideration and satisfy limiting criteria. The final alignment will be that in

which the best balance between grade and curvature is achieved (Wright & paquatte,

1979).

Horizontal and vertical alignment should not be designed independently, they

compliment each Other and proper combination of horizontal and vertical alignment,

increases road utility and safety, encourages uniform speed, and improves appearance,

can almost always be obtained without additional costs. it is further more important that

the choice of the standard for the above geometric design elements is balanced to avoid

the application of minimum values for one or a few of the elements at a particular

location when other elements are considerably above minimum requirements.

(Thagesen, 1996) the author intends to assess the existing alignment and up grade

where necessary.

a) Horizontal alignment

Horizontal alignment of a highway defines its location and orientation in plan

view. It consists of a series of intersecting tangents and circular curves, with or

without transition curves. (Thagesen, 1996) The design elements of a horizontal

alignment are the tangent (straight section), the circular curve, the transition curve

(spiral curve) and the super elevation sections.

The horizontal alignment should always be designed to the highest standard consistent

with the topography and chosen carefully to minimize earthworks. The alignment

design should also be aimed at achieving a uniform operating speed.

Near minimum curves shouldnt be used at the following locations;

On high fill or elevated structures, as the lack of surrounding objects reduces the

drivers perception of the road alignment.

At or near a vertical curve, especially crest curves, as it would be extremelydangerous, in particular at night time.

At the end of long tangents or a series of gentle curves; also compound curves,

where a sharp curve follows a long flat curve, should be avoided in order not to

mislead the driver.

At or near intersections and approaches to bridges, in particular approaches to

single lane bridges (Thagesen,1996).



14Horizontal alignment

Long straights should be avoided as they are monotonous for drivers and cause

headlight dazzle on straight grades.

i) General controls for horizontal alignment

The following general controls for horizontal alignment should be kept in view in a

sound design practice:

The alignment should be as directional as possible;

The alignment should be consistent with topography and should generally

conform to the natural contours. A line cutting across the contours involves high fills

and deep cuts, mars the landscape and is difficult for maintenance;

The number of curves should, in general, be kept to a minimum;

The alignment should avoid abrupt turns. Winding alignment consisting of short curves

should be avoided, since it is the cause of erratic vehicle operation; A sharp curve at the end of along tangent is extremely hazardous and should be

avoided. If sharp curvature is unavoidable over a portion of the route selected, it is

preferable that this portion of the road be preceded by successive sharper curves.

Proper signage, well in advance of a sharp horizontal curve is essential;

Short curves giving the appearance of kinks should be avoided, especially for small

deflection angles. The curves should be sufficiently long to provide a pleasing

appearance and smooth driving on important highways. They should be at least 150m

long for a deflection angle of 5 degrees, and the minimum length should be increased by

30m for each 1 degree decrease in the deflection angle;

For a particular design speed, as large a radius as possible should be adopted. The

minimum radii should be reserved only for the critical locations;

The use of sharp curves should be avoided on high fills. In the absence of cut

slopes, shrubs, trees, etc., above the roadway, the drivers may have difficulty in

estimating the extent of curvature and fail to adjust to the conditions;

While abrupt reversals in curvature are to be avoided, the use of reverse curves

becomes unavoidable in hilly terrain. When they are provided, adequately long

transitional curves should be inserted for super-elevation run-off;

Curves in the same direction separated by short tangents, say 300m -500m long,

and are called broken-back curves. They should be avoided as they are not pleasing in

appearance and are hazardous;

Compound curves may be used in difficult topography in preference to a broken-

back arrangement, but they should be used only if it is impossible to fit in a single



15Types of curves

circular curve. To ensure safe and smooth transition from curve to curve, the radius of

the flatter curve should not be disproportional to the radius of the sharper curve. A ratio

of 2:1 or preferably 1.5:1 should be adopted; The horizontal alignment should blend

with the vertical harmoniously. General controls for the combination of horizontal and

vertical alignments should be followed (Kadiyali, 2008).

ii) Super elevation

When a fast moving vehicle negotiates a horizontal curve, an outward centrifugal force

acts on the vehicle and its lateral stability gets affected. The value of this centrifugal

force P in kgs is given as

2wvP=

gR 2.2

Where w the weight of the vehicle and v is the speed in /m s , 29.8 /g m s= and R is

the radius of the horizontal curve in metres. The centrifugal force acts in the horizontal

direction and the mass passes through the centre of gravity of the vehicle. If the value of

the centrifugal force is greater than the lateral frictional resistance between wheels and

the road surface, skidding of the vehicle may occur and if the vehicle speed is still not

reduced the vehicle may topple over. To reduce this tendency of the vehicle skidding,

the outer edge of the road pavement is raised with respect to the inner edge, thus tilting

the road surface from the outer edge towards the inner edge. This lateral inclination to

the road surface is known as super elevation (Singh, 2004).

It is common practice to utilize a low maximum rate of super elevation, usually 4

percent. Similarly, either a low maximum rate of super elevation or no super elevation

is employed within important intersection areas or where there is a tendency to drive

slowly because of turning and crossing movements, warning devices, and signals.

Super elevation is a requirement for all standards of roads. (Uganda Road design

Manual, 2004) A maximum super elevation of 4% will be employed for the project

road.

Types of curves

i) Circular curves

Circular curves may be described by giving either the radius or degree of a curve.

As a vehicle traverses a circular curve, it is subject to inertial forces which must be

balanced by centripetal forces associated with the circular path. For a given radius and



16Circular curves

speed a set of forces is required to keep the vehicle in its path. The radius can be

expressed by the formula

2.3

Where

R= Radius of the curve (metres)

e=Crossfall of the road (%) (Is negative for adverse crossfall)

f =Coefficient of side (radial) friction force developed between the tyres and road

pavement (Uganda road design manual)

According to Kadiyali, (2008), radius is given as

2VR =

225e2.4

v= is the design speed

e= Super elevation rate

ii) Transition curves

The characteristic of transition (spiral or clothoid) curve is that it has a constantly

changing radius. Transition curves may be inserted between tangents and circular

curves to reduce the abrupt introduction of the lateral acceleration. They may also be

used to link straights or two circular curves.

In practice, drivers employ their own transition on entry to a circular curve and

transition curves contribute to the comfort of the driver in only a limited number of

situations. However, they also provide convenient sections over which super elevation

or pavement widening may be applied, and can improve the appearance of the road by

avoiding sharp discontinuities in alignment at the beginning and end of circular curves.

For large radius curves the rate of change of lateral acceleration is small and transition

curves are not normally required.

The Euler spiral, which is also known as the clothoid, is preferred to be used. The

radius of clothoid varies from infinity at that tangent end of the spiral to the radius of

the circular arc at the circular curve end. By definition the radius at any point of the

spiral varies inversely with the distance measured along the spiral.

The following equation is used for computing the minimum length of spiral.

2VR=

127(100e+f)



17Re quirements of Transition curves

30.0702VL=

RC ..2.5

Where:

L = minimum length of spiral, (m);

V = speed, km/h;

R = curve radius, (m); and,

C = rate of increase of centripetal acceleration, m/s3

MoWT, 2004) .The factor C is an

empirical value indicating the comfort and safety involved. The value C=1 is

acceptable for railroad operation, but values ranging from 1 to 3 have been used for

roads. A more practical control for the length of spiral is that in which it equals the

length required for super elevation runoff.

Re quirements of Transition curves

Transition curves are required if the following relationship is fulfilled:

3V

R 12

Surfaces, usually a surface dressing which is very rich in binder and has virtually nosurface

texture. Even large chippings will be submerged under heavy traffic.

Source, TRL, 1993

Traffic categories

The number of traffic is considered in terms of the number of commercial vehicles perday in the lane under consideration. The traffic categories are defined in table below. It

should be noted that, this differs from the traffic class used in the selection of the

pavement structure

Table 2.13: Traffic categories

Category

Approximate Nunber of Vehicles

with unladen weights greater than

1.5tonnes(per day)

1 over 2002

2 1000-2002

3 200-1000

4 40-200

5 Less than 20

Source: TRL (1993)

iii) Chippings

The nominal size of chippings is chosen to suit the level of traffic and hardness of the

underlying surfaces shown in table. In selecting the nominal size of chippings from



36Binder

double surface dressing, the size of chipping of the first layer should be selected on the

basis of the hardness of the existing surface and the traffic category as indicated in table

(TRL, 1993).

Table 2.14: Nominal size of chippingsSurface Category Traffic ctegory

1 2 3 4 5

Very hard 10 10 6 6 6

Hard 14 14 10 6 6

Normal 20 14 14 10 6

Soft * 20 14 14 10

Source: TRL, 1993

The nominal size of chipping selected for the second layer should be about half the

nominal size of the first layer to promote good interlock between the layers. The least

dimension of at least 200 chippings should be measured and the average Least

Dimension (ALD) determined. This is then used in the figure (see appendix) together

with the line labelled AB and the approximate rate of chippings read from the upper

scale (TRL, 1993).

iv) Binder

The rate of application of binder is determined using appropriate factor from table 2.4

below for each of the four sets of conditions listed. The four factors are then added

together to give the total weighting factor. The Least Dimension of the chippings and

the total weighting factor obtained from the condition constants are then used to obtain

the rate of application to binder (TRL, 1993,).

Table 2.15: Condition for determining the rate of application of the binder

Traffic Vehicle/day Constant Type of Chipping Constant

Very light 0-50 +3 +2

light 50-250 +1 Cubical 0

Medium 250-500 0 Flaky -2

Medium -Heavy 500-1500 -1 Precoated -2

Heavy 1500-3000 -3Very Heavy 3000+ -5

Existing Surface ClimateCondition

Untreated/Primed road base +6 Wet and cold +2

Very lean bituminous +4 Tropical(Wet and hot) +1

Lean bituminous 0 Temperate 0

Average bituminous -1 Semi arid(Dry and hot) -1

Very rich bituminous -3 Arid(Very dry and very hot) -2

Round/dusty

Source: TRL, 1993



37Unbound pavement materials

The ESA of design traffic volume is computed basing on the AASHTO method in TRL

and shown in. Only commercial and heavy goods vehicles with axle weights greater

than,1,500kg are considered.

The pavement thickness is determined from the structure catalogue using the traffic

class together with the CBR value of the sub grade (sub grade strength). Where the

CBR of sub grade exceeds 30%, then there is no need for the sub -base layer.

Thickness of surfacing of a pavement largely depends on the traffic anticipated to use

that pavement. The loads imposed by private cares with unladen weight less than

1500kg and motorcycles do not contribute significantly to the structural design cars

caused to road pavements traffic. Therefore for the purpose of structural design cars

and motorcycles can be ignored and only a total number and axle loading of

commercial vehicles that will use the road during its design life need to be

considered. Commercial vehicles can be defined as goods or public service vehicles that

have un-laden weight of 1500kg or more. However during traffic census a count of

all types of vehicles is carried out and these counts are expressed in design value

called passenger car unit (P.C.U) this data is used in high way planning and hence

the design of road pavements, control measures, cost benefit analysis, accidents etc.

Estimating the number of vehicles Traffic census is normally carried out mainly:-

To know the number of commercial vehicles that will use the road when it is first

opened to traffic. To forecast the annual growth of traffic

The most probable information of the initial traffic flow can be obtained from the

results of the traffic counts taken along the existing road. This gives the number of

vehicles that flow on the road per day and hence average daily traffic (A.D.T).

d) Unbound pavement materials

Selection of unbound materials for use as road base, sub base, capping and selected sub

grade layer normally depends on the properties of unbound materials (TRL1993).



38Natural Occurring granular materials (Road Base)

The main categories with a brief summary of their characteristics are shown in table

Table 2.16: Properties of unbound materials

Code Description Summary of Specification

GBI.A Fresh, crushed rocks Dense graded, un- weathered

crushed stones, .Non -plastic

parent fines

GBI.B Crushed rocks, Dense grading, P1



39Natural Occurring granular materials (Road Base)

ii) SubBase materials (GS)

The selection of sub-base materials depends on the design function of the layer and the

anticipated moisture regime both in service and at construction. Since sub- bases act as

a working platform for the construction of the upper pavement layers and as a

separating layer between sub grade and road base (TRL, 1993) a minimum CBR of

30% is required at the highest anticipated moisture content when compacted to the

specified field density, usually a minimum of 95% of MDD. To achieve the required

bearing capacity, and for uniform support to be provided to the upper pavement,

limits on soil plasticity and particle size distribution may be required. Materials that

meet the recommendations of table 2.18and 2.19 below will usually be found to have

adequate bearing capacity.

Table 2.18: Recommended plasticity characteristics for granular sub base (GS).,

Climate Liguid Limit Plasticity Index Linear Shrinkage

Moist tropical and wet tropica



40Aggregates

These criteria may be applied to the materials at both the road base/ sub base and

the sub base base-grade interface (TRL, 1993)

iii) Aggregates

For road construction, aggregates play a role in bearing the main stresses occurring

in the road pavement as a result of application of static , traffic or dynamic loads, the

necessity of the geological production and testing of aggregate properties and

characteristics must be carefully assessed if the aggregates are to meet the required

purpose. Aggregates are obtained from natural rocks that occur as rock outcrops, gravel

or sand. The physical properties governing the suitability of aggregates for use differs

not only widely in each group but also often show considerable variation in

samples taken at different times from the same parent .

Aggregate properties and their significance

Road aggregates should be strong enough to withstand stresses caused by traffic

loads

Offers resistance to abrasive action of traffic, normally in the wearing coarse

They take up subjected wheel impact loading

Aggregates should be capable of standing test of time by resisting weathering

agents e.g. Rain during the design life of the road.

Cubicalangular aggregates are normally preferred because of their high affinityfor bitumen and water.

Some of the tests carried on aggregates include the Following

a) Flakiness index (FI) test

Flakiness index is an empirical factor expressing the total material passing through the

slots of the thickness gauge as the percentage of the mass of the sample taken for

testing. The test is not applicable to aggregate sizes less than 6.3mm. Aggregates are

classified as flaky when they have a thickness of less than 60% of their mean sieve size.

This is a test carried out to determine the shape and angularity of the aggregate particles,

in order to analyze its suitability for use as a stone base or a surfacing material or

bituminous base course. The test is carried out as per BS812: section 105.1:1989

Its one of the tests used in the classification of stones and aggregates. In pavement

design there are specific requirements regarding the flakiness index of materials. For



41Aggregate least dimension (ALD)

base course and wearing course aggregates, the presence of flaky particles are

considered undesirable as they may cause inherent weakness with a possibility of

breaking down under traffic loading.

The lower the flakiness index, the more cubicles the chippings are and this guarantee a

better particle interlock and a stable mosaic. When the material is used as stone base or

a surfacing material, the end result is a stable and strong pavement structure.

The specifications for the different area of use are;

For stone base 30% maximum.

For surface dressing and thin premix surface a maximum of 30%

For bituminous macadam base course a maximum of 35%.

b) Aggregate least dimension (ALD)

This is the minimum dimension of the aggregate required for surface dressing,

determined from the results of; Flakiness index and the average value of the sieve size

through which 50% of the aggregate sample pass, when the two values are plotted on a

monogram TRL (1993). The maximum aggregate size required for surface dressing is a

function of the road surface hardness and the traffic category. The next lower size

required is the Average Least Dimension TRL (1993).

The Average Least Dimension (ALD) should not be less than half the maximum sieve

size, derived from the traffic category and the road surface hardness i.e. 20/14, 14/10,

and 10/6.

c) Aggregate crushing value (ACV) test

This test is carried out to examine the crushing strength of the aggregates to be used in

road base or surfacing. The crushing strength is reported in terms of Aggregate

Crushing Value or ACV. The test is carried out as per BS 812:Part110:1990.

A load of up to 400KN is gradually applied on the test sample of aggregates passing

14mm sieve and retained on 10mm sieve placed in a cylinder.

The test result gives an indication of the strength characteristics of the aggregate in

resisting crushing due to compressive force of the rollers and wheel loads during the

design life of the road pavement. Pavement failure can result from crushing of the

aggregates. The higher the ACV percentage the more susceptible are the aggregates to

crushing and the lower the ACV percentage the better is the aggregate resistance to



42Aggregate impact value (AIV) test

crushing and thus better performance during wheel loading. The strength is categorized

as;

Exceptionally strong for ACV < 10%

Very weak for ACV > 35 %

An aggregate with a maximum ACV 30% is recommended for use on road base and

surfacing (Kadiyali. 2006).

d) Aggregate impact value (AIV) test

This is the test designed to evaluate the resistances of an aggregate to sudden impact.

The measure of this resistance is reported quantitatively in terms of Aggregate Impact

Value or AIV. The test is carried out as per BS 812:Part112: 1990.

An aggregate sample passing a BS 14mm sieve and retained on 10mm sieve is placed in

layers in a test cylinder to full capacity, each layer receiving 25 blows from a tamping

rod, and then subjected to an impact from a free falling harmer. The weight of the

crushed sample passing through BS 2.36mm sieve is expressed as a percentage of the

total mass of the sample as a measure of the Aggregate Impact Value.

The test gives an indication of the relative resistance of the aggregate to sudden shock

or impact loading during compaction and also due to wheel loading on a road pavement.

If the AIV is too high, it means that the aggregate is susceptible to crushing during the

design life of the pavement and this significantly affects the durability of the road.

Depending on pavement layer on which the aggregate will be used, there is a maximum

value of AIV above which a particular aggregate is regarded as unsuitable. The

following are recommended.

For surfacing course a maximum AIV of 30%

For a base course a maximum AIV of 40% For a sub base a maximum AIV of 50% Kadiyali(2006).

e) Ten percent fines value (TFV) test

This test is carried out to determine the force required to crush an aggregate sample

passing BS 14mm sieve and retained on 10mm sieve so that 10% of the crushed

material passes through the BS 2.36mm sieve after crushing. The test gives a relative

resistance of the aggregate to crushing due to a gradually applied load that will cause a



43Los Angeles Abrasion Value Test. (LAAV)

penetration of 20mm in ten (10) minutes. The test is carried out as per BS 812: Part

111:1990 The test gives an indication of the strength of the aggregates that is reported

quantitatively as a force. The higher the force, the stronger is the aggregate and the

lower the force, the weaker is the aggregate. Weaker aggregate are undesirable in

pavement construction or design.

Stronger aggregates have better performance in resisting the traffic loading. For an

aggregate to be guaranteed that it will not crush under traffic loading, it must have a

minimum Ten Percent Fines (TPF) value of 110KN.

The aggregate meeting this criterion qualifies to be used in surfacing and road base.

f) Los Angeles Abrasion Value Test. (LAAV)

The test is designed to evaluate the resistance of the mineral aggregate of standard

grading to degradation resulting from abrasion, impact and grinding. The test is carried

out as per ASTM 539-89.The measure of this resistance is reported quantitatively in

terms of Los Angeles Abrasion Value (LAAV).

For coarse aggregates used in pavement construction, or surfacing course, the

aggregates are subjected to constant wearing at the top and may get abraded due to the

movement of traffic. High abrasive value is an indication of very weak aggregates,

which leads to very low durability, whereas aggregate with low abrasion value will lead

to construction of a more durable road.

This is based on a standard maximum value of the abrasion test result that will lead to

better performance, offering a high durability during service. This value is usually set at

a maximum of 30% percent for road base and 25% for the surfacing course.

iv) Bitumen

Bitumen is a dark bituminous product which is a conglomeration of compels

hydrocarbons. The process of atmospheric distillation produces most bitumen. There are

two main properties used as basis for the grading of bitumen:

Viscosity (mostly used in U.S.A, European countries) .This refers to resistance to

flow within or without fluids;

Penetration (mostly used in Uganda.

Grading based on viscosity



44Bitumen

The standard bitumen grade is ASTMD 3381. There are various grades: AC-5, AC-10

AC-30, and C-40. Where AC refers to asphalt cement. The numbers, 5, 10, 30 and 40

designates the viscosity of the bitumen at standard temperature of 60oC.

a) Types of tar products

i) Coating tars. These are graded with a C. There are a number of grades namely

C-30, C-34, C-24, C-50, C-54 and C-58.The following tests are carried out on bitumen

The Penetration Test, The Viscosity Test, The Softening Point Test The Flash Point

Test, The Fire Point Test, The Marshall Test. Penetration of a bituminous material is the

distance in tenths of a mm, that a standard needle weighing 100g would penetrate

vertically into a sample of the material under standard conditions of temperature, and

time. The needle is allowed to penetrate into the sample for five (5) seconds at a

temperature of 250C.The penetration test is in no way indicative of the quality of the

bitumen but does allow the material to be classified. The softening point is the

temperature at which all refinery bitumen have the same viscosity (about 1200

Pa.s).This test is also referred to as the Ring and Ball Test. The softening point of

bitumen or tar is the temperature at which the substance attains a particular degree of

softening. It is the temperature at which a standard ball passes through a sample of

bitumen in a mould and falls through a height of 2.5 cm, when heated under water or

glycerine at specified conditions of the test.

The binder should have sufficient fluidity before its application in roads uses. The

determination of the softening point helps to know the temperature up to which a

bituminous binder should be heated for various road use applications.

This test is done to determine the flash point and the fire point of asphaltic bitumen and

fluxed native asphalt, cutback bitumen and blown type bitumen as per IS: 1209 1978.

The principle behind this test is given below:

Flash Point The flash point of a material is the lowest temperature at which the

application of test flame causes the vapors from the material to momentarily catch fire

in the form of a flash under specified conditions of the test.



45Bitumen

Fire Point The fire point is the lowest temperature at which the application of a test

flame causes the material to ignite and burn at least for 5 seconds under specified

conditions of the test.

At high temperature, bituminous materials emit hydrocarbon vapors which are

susceptible to catch fire. Therefore the heating temperature of bituminous material

should be restricted to avoid hazardous conditions.

The flash point is one measure of the tendency of the test specimen to form a flammable

mixture with air under controlled laboratory conditions. It is only one of a number of

properties that should be considered in assessing the overall flammability hazard of a

material. Flash point is used in shipping and safety regulations to define flammable and

combustible materials.

Flash point can indicate the possible presence of highly volatile and flammable

materials in a relatively nonvolatile or nonflammable material. For example, an

abnormally low flash point on a test specimen of engine oil can indicate gasoline

contamination.

This test method shall be used to measure and describe the properties of materials,

products, or assemblies in response to heat and a test flame under controlled laboratory

conditions and shall not be used to describe or appraise the fire hazard or fire risk of

materials, products, or assemblies under actual fire conditions.

Flash point and fire point tests are used to determine the temperature to which

bituminous material can safely be heated i.e. the safety of the working group on site and

care is necessary when handling with medium and rapid curing cutback bitumen whose

flash and fire points are low.

The fire point is one measure of the tendency of the test specimen to support

combustion

b) The Marshall MethodAsphalt concrete and sand asphalt is usually designed using the Marshall method by

choosing the optimum binder content for a particular mix. While rolled asphalt and

asphalt macadam are often made to recipe specification. The test procedure is used in

designing and evaluating bituminous paving mixes and is widely applied in routine test

programs for the paving roads. The major features of the test are to determine the two

important properties of strength and flexibility.



46Bitumen

Strength is measured in terms of the marshal stability of the mix defined as the

maximum load carried by a compacted specimen at a standard test temperature of

60oc.this temperature represents the weakest condition for a bituminous pavement in

use. The flexibility is measured in terms of the flow value which is measured by change

in diameter of the sample in the direction of load application between the start of the

loading and the time of maximum load. In this test an attempt is made to obtain

optimum binder content for the aggregate mix type and traffic intensity.

i) Viscosity

Is a property of a fluid that retards its flow .The viscosity of a fluid slows down its

ability to flow and is of particularly significance at high temperatures when the ability

of the bitumen to be sprayed on to or mixed with aggregate material is of great

significance .The main objective of carrying out this test is to determine the viscosity ofbituminous binder. Viscosity of a fluid is the property by virtue of which it offers

resistance to flow. The higher the viscosity, the slower will be the movement of the

liquid. The viscosity affects the ability of the binder to spread, move into full up the

voids between aggregates. It also plays an important role in coating of aggregates.

Highly viscous binder may not fill up the voids completely thereby resulting in poor

density of the mix. At lower viscosity, the binder does not hold the aggregates together

but just acts as a lubricant. Viscosity is also important in determining the workability of

the mix. The viscosity of bituminous binders falls rapidly as the temperatures rise. Since

binders exhibit viscosity over a wider range, it is necessary to use different methods for

the determination of viscosity.



47Drainage design

2.5 Drainage design

2.5.1 Introduction

Highway drainage may be defined as the process of interception and removal of water

from over, under, and the vicinity of the road surface (Singh, 2004).One of the most

important aspects of road design is the provision made for protecting the road from

surface and ground water on the pavement as it slows traffic and contributes to

accidents from hydroplaning and loss of visibility from splash and spray. If water is

allowed to enter the structure of the road, the pavement and the subgrade will be

weakened and it will be more susceptible to damage by traffic when roads fail its

usually due to inadequate drainage.

The drainage system has four main functions:

To convey storm water from the surface of the carriageway to outfalls;

To control the level of water table in the sub grade beneath the carriageway;

To intercept ground water and surface water flowing towards the road;

To convey water across the alignment of the road in a controlled fashion.

The first three functions are performed by longitudinal drainage components, in

particular side drains, while the fourth function requires cross-drainage structures such

as culverts, fords, drifts and bridges (Thagesen, 1996).

2.5.2 Types of drainage

There are basically three types of drainage systems, these include; Surface drainage,

Subsurface and cross drainage.

a) Longitudinal drainage

The road surface must be constructed with sufficient camber or cross fall to shed

rain water quickly ; and the formation of the road must be raised above the level of

the local ground water table. It is important to maintain a minimum longitudinal

gradient on curbed pavements than on uncurbed pavements in order to avoid undue

spread of storm water on the pavement. Vegetation along the pavement edge may

impede the runoff of water from uncurbed pavements if the gradient is flat. Where the

longitudinal gradient of the roadway has to be near zero, the depth of side drains may

have to be varied to obtain sufficient gradient of the ditch. The longitudinal gradient

should therefore preferably not be less than 0.3% for curbed pavements and not less

than 0.2% in very flat terrain. (Thagesen, 1996)



48Types of drainage

According to Thagesen, Longitudinal drainage can be classified into various forms of

open roadside drainage channels basing on the various functions they perform.

i) Ditches: These are channels provided to remove the runoff from the road

pavement, shoulders and cut and fill slopes. Its depth should be sufficient to remove the

water without risk of saturating the pavement sub grade. It may be lined to control

erosion. Unlined ditches should preferably have side slopes not steeper than 4

horizontal to 1 vertical).

ii) Gutters: They are the channels at the edges of the pavement or the shoulder

formed by a curb or by a shallow depression. They can paved with concrete, bricks

stone blocks or other structural materials.

iii) Turnouts; or Mitre drains. They are short, open, and skew ditches used to

remove water from the roadside ditches or gutters. They are used to reduce the sizes of

the side ditches and minimize the velocity of water and thereby the risk of erosion.

These must be provided at intervals depending on the runoff, permissible velocity of the

water and slope of the terrain.

iv) Chutes: they are also open, lined channels or closed pipes used to convey water

from gutters and sid

Final Year Project Report.

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