Final Year Project Report.
January 23, 2017 | Author: Kanabu Evans | Category: N/A
Short Description
Download Final Year Project Report....
Description
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
Authentication
i
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
i
.
This report is dedicated to my dear Parents Mr & Mrs Kezire.
Authentication
ii
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 Bachelor’s 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
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
ii
Abstract
iii
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.
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
iii
Acknowledgement
iv
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.
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
iv
Table of contents
v
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
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
v
Table of contents
vi
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
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
vi
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
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
vii
List of tables
viii
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
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
viii
List of figures
ix
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
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
ix
Acronyms and abbreviations
x
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
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
x
List of symbols
xi
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
xi
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
Introduction
1.0
1
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. Uganda among 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; it’s a district feeder road that falls under Kampala City Council (KCC).
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
1
Problem statement
2
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 1617.5m/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 socialeconomic development of Uganda.
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
2
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. ©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
3
Project Scope a)
4
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
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
4
Storage and Retrieval
5
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.
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
5
Literature review
6
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 (O’Flaherty 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 O
at coordinates of
o
00 17’57”N and 32 35’17” E at an elevation of 4003ft (Wikipedia,2009). It connects Kabega road to Lukuli road. 2.1.3
Demography
Uganda 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.
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
6
Climate 2.1.5
7
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 survey and 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 it’s adequate.
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
7
Geometric Design
2.3
8
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 crosssection, 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 (O’Flaherty, 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 road environment. 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).
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
8
Road function Design
9
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) ©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
9
Traffic a)
10
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 0.08 – 0.12 Congested urban conditions Normal urban conditions 0.10 – 0.15 Road catering for recreational 0.20 – 0.30 or Other traffic of seasonal 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.
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
10
Traffic composition
ii)
11
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 Vehicle Type Passenger cars Light goods vehicle
1
Terrain Rolling PCU 1
Level
Mountainous 1.5
1
1.5
3
Medium goods vehicle*
2.5
5
10
Heavy goods vehicle Buses Motor cycles, Scooters
3.5 2 1
8 4 1
20 6 1.5
Pedal cycles
0.5
0.5
NA
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 Medium goods vehicle Heavy goods vehicle Buses
of less than1500kg un-laden weight with payload capacities less than 760 kg. Maximum gross vehicle weight 8500 kg. Gross vehicle weight greater than 8500 kg. 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
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
11
Projected traffic (Fp) b)
12
Projected traffic (Fp)
For this project, time series was used to project traffic growth rates. FP = FO (1+ r)n
… 2.1
Where,
FP = Cumulative number of commercial vehicles after ‘n’ years; FO = 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 ©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
12
Horizontal alignment
13
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 shouldn’t 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 extremely dangerous, 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).
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
13
Horizontal alignment •
14
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 ©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
14
Types of curves
15
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
P=
wv 2 gR
…2.2
Where w the weight of the vehicle and v is the speed in m /s , g = 9.8m / s 2 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
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
15
Circular curves
16
speed a set of forces is required to keep the vehicle in its path. The radius can be expressed by the formula
R=
V2 127(100e+ f)
…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 R=
V2 225e
…2.4
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. ©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
16
Re quirements of Transition curves
L=
0.0702V 3 RC
17
…..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: R<
V
3
432
…2.6
Where: R = Radius of curve (m); and,
V = Design speed (km/hr) In all other cases where the above is not fulfilled, transition curve is not required. (MoWT, 2004) According to Kadiyali (2000), Length of the transition is given as Ls =
C=
0.0215V
3
c×R
…2.7
80 75 + V
Where V is the design speed in km/hr. The author intends to use this formula according to Kadiyali for designing transition curves.
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
17
Vertical alignment a)
18
Vertical alignment
The vertical alignment of a road has a strong influence upon the construction cost, the operating cost of vehicles using the road, and the number of accidents. The vertical alignment should provide adequate sight distances over crests and should not present any sudden hidden changes in alignment to the driver. Gradients need to be considered from the standpoint of both length and steepness, and the speed at which heavy vehicles enter the gradient. They should be Chosen such that any marginal increase in construction costs is more than offset by the savings in operating costs of the heavy vehicles ascending them over the project analysis period. Vertical Alignment of a highway deals with its shape in profile. For a roadway with contiguous travel lanes, alignment can be conveniently represented by the centerline of the roadway.The two major aspects of vertical alignment are vertical curvature, which is governed by sight distance and comfort criteria and gradient which is related to vehicle performance and level of service (MoWT, 2004). Vertical curves are required to provide smooth transitions between consecutive straight gradients. The simple parabola is recommended for these. The parabola provides a constant rate of change of curvature and hence acceleration and visibility, along its length and it has the form: g -g r= 2 1 L 2 rx y= + g1x + BVCelevation 2
…2.8
Where r=
Rate of change of grade per section (%)
g1 = Starting grade (%) g2 = Ending grade (%) L=
Length of curve (horizontal distance (m)
y=
Elevation of a point on the curve
x=
Distance in stations from the BVC (beginning of vertical curve) (meters/100)
BVCelevation = Elevation of beginning of the vertical curve EVC = End of the vertical curve ©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
18
Vertical alignment
19
A related formula is: y=
G * L x
2
200 L
… 2.9
Where y = vertical distance from the tangent to the curve (meters) x = horizontal distance from the start of the vertical curve (meters) G = algebraic difference in gradients (%) L=
length of vertical curve (meters)
The two main requirements in the design and construction of vertical curves are the provision of: adequate visibility, Passenger comfort and safety. In order to provide adequate visibility, oncoming vehicles or any obstructions in the road must be seen clearly and in good time to ensure that vehicles travelling at the design speed can stop or overtake safely. In order to provide passenger comfort, the effect of the radial force on the vehicle traversing a vertical curve must be minimized. In crest curve design, this effect could cause the vehicle to leave the road surface
while in the sag curve the
underside of the vehicle would come into contact with the surface, particularly where the gradients are steep. i)
General Controls for Vertical Curve Alignment
The following general controls for vertical alignment should be kept in view while designing the vertical profile of a highway: •
The grade line selected should be smooth with gradual changes, consistent with the class of highway and terrain. Numerous breaks and short lengths of grades should be avoided;
•
The ‘roller-coaster’ or ‘hidden type’ of profile should be avoided as it is hazardous and aesthetically unpleasant;
•
Undulating grade line, involving substantial lengths of momentum grades, should be appraised for their effect upon traffic operation. Such profiles permit heavy trucks to Operate at higher overall speeds than when an upgrade is not preceded by a down grade, but may encourage excessive speeds of trucks with consequent hazard to traffic;
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
19
Stopping sight distance
20
A broken-back grade line (two vertical curves in the same direction separated by short Section of tangent grade) should generally be avoided; •
On long continuous grades, it may be preferable to place the steepest grades at the bottom and flatten the grades near the top. Alternatively, long grades may be broken by short intervals of flatter grades;
•
Intersections on grades should be avoided as far as possible. Where unavoidable, the Approach gradients and the gradient through the intersections should be flattened to the Maximum possible extent.
ii)
Sight distance
Safe highways must be designed to give the driver a sufficient distance of clear vision ahead so that he/she can avoid hitting unexpected obstacles and can pass slower vehicles without danger. Sight distance is the length of highway visible ahead to the driver of a vehicle. When this distance is not long enough to permit passing an overtaken vehicle, it is termed stopping sight distance (Wright & paquatte, 1979). •
Stopping sight distance
Minimum distance required for stopping a vehicle travelling at or near the design speed before reaching an object in its path. Minimum stopping sight distance is based upon the sum of two distances (Wright& paquatte, 1979). The distance travelled from the time the object is sighted to the instant that the brakes are applied, and the distance require for stopping the vehicle after the brakes are applied. The first of these two distances is dependant upon the speed of the vehicle and brake reaction time of the operator. The second distance depends upon the speed of the vehicle, condition of brakes, tyres, roadway surface, alignment and grade of the highway. •
Passing sight distance
When the sight distance is long enough to enable a vehicle to overtake and pass another vehicle on a two lane highway without interference from an oncoming vehicle, it is termed passing sight distance (Wright& paquatte, 1979).
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
20
Crest curves
iii)
21
Vertical curves
A vertical curve provides smooth transition between successive tangent gradients in the road profile. When the algebraic difference of the two gradients is positive the curve is called a crest or summit. When the difference is negative, it’s called sag. As a motorist traverses a vertical curve, a radial force acts on the vehicle and tries to force it away from the centre of curvature and this may give discomfort to the driver. This discomfort may be minimised by restricting the gradients and by using a type and length of vertical curve which allows a radial force to be experienced gradually and uniformly. Sight distance requirements are also aided by use of vertical curves on both crest and sag (O'Flaherty, 2002). Figure 2.2: Typical Vertical curves
Source O’Flaherty, 2002 Table 2.9: Minimum radius as recommended by MoW&T Radius(m)R (R=K*100) Speed(Km/h)
Stopping desirable
minimum
desirale
50
1100
600
11000
5500
80
4500
3000
32000
15000
65000
24000
100 10000 7000 Source, Uganda road design manual, 2004
a)
Overtaking "No overtaking"centreline markings
Crest curves
The sight distance requirements for safety are critical to the design of a crest curve. Thus when calculating the minimum lengths of crest curves, there are two design conditions that have to be considered.
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
21
Crest curves
22
Sight distance over crest curves when a) S•L and S>L Figure 1.3: Sight Distance over crest curves
Source, O’Flaherty, 2002
For S•L Lmin =
AS 2 2 2h1 )1/2 + (2h2
…2.10
S>L
2[h1 + h2 ]
2
Lmin = 2S −
A
…2.11
Where h1= Drivers eye height (Usually 1.05m) h2= Object height (usually 0.26m) L = Minimum length of sag curve (m) A = algebraic difference in grades expressed as a decimal. D = vertical clearance (ideally taken as 5.7m) to the critical edge of the Bridge The critical edge is assumed to be directly over the point of intersection of tangents. In practice both equations can be considered valid provided that the critical edge is not more than 60m from the point of intersection [O’Flaherty, 2002]. If h1=1.05m and h2=0.26m then the above equations refer to the safe stopping sight distance (SSD) and become, for SSD•L
Lmin =
AS 2 471
…2.12
FOR SSD>L
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
22
Crest curves
Lmin = 2S −
471 A
23
…2.13
If h1=h2=1.05m then the equations refer to the full overtaking distance (FOSD), and then, for FOSD•L
Lmin =
AS 2 840
…2.14
For FOSD>L
Lmin = 2S −
840 A
Based on Motorist Comfort The minimum length of vertical sag curve is given by:
Lmin =
V 2A V 2A = 3α 390
…2.15
Where; V = design speed (km/hr), A is the algebraic difference in grade (%), and • = vertical radial acceleration (m/s2) usually taken as 0.3 m/s2 for comfortable design (O’Flaherty, 2002). Sag Curves When a road passes beneath an overpass, the driver’s line of sight may be obstructed by the edge of the bridge. Then the minimum length of a sag curve which meets minimum stopping sight distance requirements is given by Lmin =
S 2A 8D − 8(h1 + h2 When SSD•L 2
8D − 8( h1 + h2 ) 2 Lmin = 2S − When SSD•L A
…2.16
…2.17
if eye height h1=1.05m and object height h2 =0.26mm the above equations becomes
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
23
Climbing lanes Lmin =
S 2A [800D − 524]
Lmin = 2S −
When SSD•L
24
…2.18
[800D − 524] A
When SSD>L
…2.19
L= minimum length of the sag curve (m) S= minimum stopping sight distance (m) and A is algebraic difference in grades expressed in decimal form, and D=vertical clearance (ideally, taken as 5.7m to the critical length of the over bridge. (O'Flaherty, 2002) iv)
Gradients
The rate of rise or fall of road surface along its length with respect to the horizontal distance is termed as gradient. it may also be defined as a longitudinal slope of a road pavement a rising grate is denoted by + sign while a falling gradient is denoted –sign Grade of a road should not be very steep, steep grades are not only difficult to climb but also increase operational costs of vehicles. (Singh, 2004) In the establishment of a grade, an ideal situation is one in which the cut is balanced against the fill without a great deal of borrow or an excess cut to be wasted. (Wright & paquatte, 1979) A minimum gradient of 0.5 is needed for longitudinal drainage (O'Flaherty, 2002). Table 2.10: Maximum grades Maximum Grade (%) Speed (km/hr) Flat Rolling Mountainous 50 6-8 7-9 9-10 80 4-6 5-7 7-9 100 3-5 4-6 6-8 Source: Uganda Road Design Manual (2004)
For the project road a maximum grade of 9% will be considered since it is a rolling terrain. •
Climbing lanes
The maximum gradient is not in itself a complete design control, and an extra climbing lane is often provided on long uphill climbs. the addition of a climbing lane is normally considered when the combination of hill severity and traffic volumes and composition is such that the operational benefits achieved are greater than the additional cost of providing the extra lane (O'Flaherty, 2002) These improve overtaking opportunities,
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
24
Cross-sectional Elements
25
capacity and safety because of the presence of a steep uphill gradient. It is inserted into the carriageway by means of entry and exit tapers to the left of the continuous lane so that slow moving vehicles have to merge into the faster traffic at the termination point. An overtaking lane serves the same objectives without a steep gradient. Climbing lanes should be considered if the design truck speed decreases more than 20 km/h under the truck speed limit, normally 80 km/h in rural conditions (MoWH&C, 2004). Figure 2.4: Climbing lane outside the ordinary lane
Source, Uganda Road Design Manual, 2004
b)
Cross-sectional Elements
These are elements of a roadway which form its effective width. These include a carriage way, central reservation and the side slopes of cuttings and embankments. Figure 2.5: Cross sectional elements for a single carriage way
Carriage way Shoulder
Traffic lane Camber
Traffic lane
Shoulder
Camber
Embarkment
Foreslope cut
Backslpoe
Road reserve
Source, Uganda road design manual, 2004
i)
Road reserve
The road reserve or right-of-way width is the width of land secured and preserved in public interest for road development purposes. The road reserve should be adequate to accommodate all the elements that make up the cross-section of the highway and may reasonably provide for future development. Such as upgrading of the alignment. The right of way must include the acquisition of land for short cuts and path of pedestrians,(TRL,1993) ,for the project road, a road reserve of 7.5m will be considered due to a narrow existing carriage way, it would cost around 20 billion to compensate people e along the road. ii)
Carriage way width
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
25
Kerbs
26
The term “carriageway” is used here to cover the traffic lanes, any auxiliary lanes, and the shoulders (MoWH&C, 2004). The width of traffic lanes governs the safety and convenience of traffic and has a profound influence on the capacity of a road. Factors that influence the width of the carriage way is: design volume, vehicle dimensions, design speeds and road classification. Internationally, it is generally accepted that lane widths should normally be at least 3.5m, although narrower lanes are often used for economic or environmental reasons on both rural and urban roads. However, increasing the lane width up to 3.65m on two lane two way rural roads decreases accident rates (O’Flaherty, 2002). For the project road a lane width of 2.8m will be considered from classification of a gravel C, see Appendix C, Table 2.5. iii)
Central reservation strip
A central reservation strip is the longitudinal space separating dual carriageways. The functions of the median strip are: To separate high speed opposing traffic, there by lessening the chances of head-on collisions, Provides a safe waiting place for pedestrians crossing the high speed carriage way and provide space for road furniture and markings. For the project road, a central reservation will not be considered because of the existing carriageway width. iv)
Shoulders
A shoulder is that surfaced clear portion of the roadway cross-section immediately adjacent to the carriage edge. Shoulders have several numbers of purposes such s refuge for vehicles forced to make emergency stops, (O'Flaherty, 2002)
An area out of the
Lateral support of the roadway structure. In addition, shoulders support use of the road by other modes of transport, for example cyclists and pedestrians (SANRA,..) a slope of the shoulder should be greater than the that of the pavement for drainage purposes (Wright &Paquatte, 1979) for the project road a shoulder of 1.5m will be used as in table2….as stipulated in the Uganda road design manual v)
Kerbs
A kerb is a vertical or sloping member along the edge of a pavement or shoulder, forming part of gutter, strengthening or protecting the edge, and clearly defining the edge to vehicle operators. Its functions are: they define the edge of traffic lanes, traffic islands and footways – during both day and night (they reflect vehicle headlights)
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
26
Kerbs
27
• They support pavements and island structures so that edge break-up is avoided; •
They protect adjacent areas from encroachment by vehicles; • They assist in drainage of the carriageway (MoW&T, 2004). vii)
Camber
Camber, is a term used to define convexity of the carriageway cross section. Its purpose is to drain surface water from the road and avoid ponding in the surface deformations on the carriage way (O'Flaherty, 2002). A camber of 2.5% will be used for the project road. Across fall should be sufficient to provide adequate surface drainage whilst not being so great as to be hazardous by making steering difficult, the normal crossfall should be 3% on paved roads and 4-6% on unpaved roads (TRL, 1993). A minimum cross fall of 2.5% is normally recommended in the form of either a straight camber extending from one edge to the other or as one sloped from the centre of the carriageway towards both edges. The primary aim of these cross falls is to adequately get rid of surface runoff from the highway pavement (MOW&H, 2005). viii) Side Slopes According to O’Flaherty (2002), soil mechanics analysis enables the accurate determination of maximum slopes at which embankments or cuts can safely stand. However, these maximum values are not always used, especially on low embankments not protected by safety fences. The slopes of embankments and cut sections depend upon the type of soil and the height of embankment or depth of cuttings. For reasons of economy, construction of steep side slopes on embankments and cuttings is encouraged Fore slopes steeper than 1:3 cannot be counted as part of the clear zone because they are too steep. Slopes that can be traversed safely by out-of-control vehicles need to be at least 1:4 or gentler. Slopes between 1:3 and 1:4 are marginal; The back slope design in cuts with a cut drain should be designed with a 0.5 m wide ditch bottom followed by a 1:4 back slope for half a metre and then a 1:2 slope for 2.0 m; this will help to redirect a run-off vehicle to the roadside area (MoWH&C, 2004). ix)
Vertical and Lateral clearance
Typical maximum truck heights are 4.2 meters and, to allow adequate vertical clearance and the transport of abnormal loads, a 5.0 meters vertical clearance should generally be ©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
27
Kerbs
28
allowed for in the design.Lateral clearances between roadside objects and the edge of the shoulder should normally be 1.5 meters. This may be reduced to 1.0 m where the cost of providing the full 1.5 meters is high. Much smaller clearances will sometimes be necessary at specific locations such as on bridges, although a minimum of 1.0 meter will remain desirable. Minimum overall widths in such circumstances should be sufficient to allow the passage of traffic without an unacceptable reduction in speed, which will depend on the length of the reduced width section and levels of motorized and non-motorized traffic flow. Separate facilities should be provided for pedestrians where possible (TRL, 1993). viii) Roadway Markings Carriageway markings should be provided on all two-way paved roads. The edge of the carriageway should be delineated by continuous lines and may be supported by surfacing road studs or other features. The lines should be situated on the shoulder immediately adjacent to the running surface and should be at least 100mm in width. Centre line markings are also recommended on roads of at least 5 meters width designed for two lane operation in order that a driver may correctly locate his lateral position. These markings should be 100mm wide and normally be discontinuous. Except where overtaking is restricted and may be supported by the use of road studs. All markings should conform to international standards (TRL, 1993).
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
28
Pavement Design
2.4
Pavement Design
2.4.1
Introduction
29
A highway pavement is a structure whose primary aim is to support the traffic loads and transmit them to the basement soil after reducing the stresses to a level below the supporting capacity of the soil (Thagesen, 1996). a)
Types of pavements
Based upon the structural behaviour of the materials used in the construction, the pavements are generally classified into the following categories Flexible pavement and rigid pavement. i)
Flexible pavements
These are pavements which have very low flexural strength and are flexible in their structural behaviour under load (Singh, 2004).They maintain intimate contact with and distributes loads to the subgrade, they depend on aggregate interlock, particle friction, and cohesion for stability (Wright &paquatte, 1979).Since the author intends to design this type of pavement; the other will be left out. a)
Elements of flexible pavements
Most pavements consist of three superimposed layers each performing different primary functions (Thagesen, 1996). Figure 2.5 Pavement layers Wearing Course Base Course or Binder course
}
Surfacing
Road -base
sub-base
Subgrade
Source, TRL, 1993
i)
Surfacing
This is the uppermost layer of the pavement and will normally consist of a bituminous surface dressing or a layer of premixed bituminous material. Where premixed materials are laid in two layers, these are known as the wearing course and the base course (binder course) (TRL, 1993). The surfacing should be smooth and dust free, This
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
29
Road base
30
provides a riding surface for road users (Thagesen, 1996).it takes up wear and tear due to traffic, provides water tight surface against infiltration of surface water, provides hard surface that can withstand pressure exerted by tyres of vehicles (Singh, 2004).The author intends to recommend surfacing materials.
ii)
Road base
This is the main load-spreading layer of the Pavement. It will normally consist of crushed stone or gravel, or of gravely soils, decomposed rock, sands and sand-clays stabilized with cement, lime or bitumen (TRL, 1993). The functions of the base course are: •
Acts as a structural portion of the pavement and thus distribute load;
•
It prevents intrusion of the subgrade soils into the pavement (Kadiyali, 2000). The author will recommend road base materials for the road base.
iii)
Sub base
This is the secondary load-spreading layer underlying the road base. It will normally consist of a material of lower quality than that used in the road base such as unprocessed natural gravel, gravel-sand, or gravel-sand-clay. This layer also serves as a separating layer preventing contamination of the road base by the subgrade material and under wet conditions; it has an important role to play in protecting the subgrade from damage by construction traffic (TRL, 1993).The sub base is omitted when the subgrade is hard intact rock or if it is granular and has a CBR greater than 30% and without a high water table (TRL, 1993). Functions include minimizing damaging effect of frost action and facilitating drainage of free water that may get accumulated below the pavement. iv)
Capping layer
Where very weak soils are encountered, a capping layer is sometimes necessary. This may consist of better quality subgrade material imported from elsewhere or existing subgrade material improved by mechanical or chemical stabilization(TRL, 1993) .Unbound capping layers are normally made from gravely soils. A minimum CBR of 15% is recommended for material compacted to a specified density specifically 95% of the maximum dry density obtained with modified (heavy) compaction (Thagesen, 1996).
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
30
Subgrade.
vi)
31
Subgrade.
This is the upper layer of the natural soil which may be undisturbed local material or may be soil excavated elsewhere and placed as fill. In either case it is compacted during construction to give added strength (TRL, 1993) .Traffic load moving on the surface of the road is ultimately transferred to the subgrade through intermediate layers of sub base, base and wearing courses the pavement design assumes subgrade strength as the basis for designing the pavements, if the strength properties of the subgrade are inferior to the expected ones, it’s given suitable treatment to impart improvements in its performance (Singh, 2004). The author will carry out a subgrade assessment to determine its strength using UK DCP machine developed by TRL. b) Pavements design process There a different approaches to pavement design, some of which include, Analytic empirical method, terminal condition, AASTHO, mechanistic and CBR .The authors intends to use the CBR approach.
i)
Pavements design procedures
There are three main steps to be followed in designing a new road pavement these include; ii)
Traffic assessment
This involves estimating the amount of traffic and the cumulative number of equivalent standard axles that will use the road over the selected design life. Loads imposed by passenger cars don’t contribute significantly to the actual damage of the road pavements by traffic, therefore, for the purpose of pavement design, private cars are ignored and only the total number and axle loading of heavy vehicles; that will use the road during the design life are considered. In this context heavy vehicles are defined as those having an unladen weight of 300kg or more. In order to estimate the total of commercial vehicles that will traverse the pavement in the course of design life, its necessary to; the number of vehicles that that will use the road the first year the road is open, forecast annual growth rate of traffic And Select the design life (Thagesen, 1996). Manual classified counts will be carried out for this project and then project traffic using time analysis method. ©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
31
Subgrade assessment
32
The design life for this road shall be 15 years from a combination of a low reliability and high level of service. Table2.11: Pavement design life selection Design Data Reliability
Importance/Level of service Low
High
Low
10-15 years
15years
High
10-20 years
15-20 years
Source: Uganda Road Design Manual (2004)
iii)
Subgrade assessment
This is intended to determine the suitability of the subgrade soil over which the road is to be built. The strength of the subgrade is assessed in terms of California bearing ratio (CBR) and this is dependent on the type of soil, its density, and its moisture content (TRL, 1993).Overseas Road Note 31 deals more closely with the influence of water on the subgrade strength than other pavement methods. For estimation of the design moisture content, the subgrade moisture conditions under impermeable surfacing are classified into three categories. For designing the thickness of a road pavement, the strength of the subgrade should be taken as that of the soil at moisture content equal to the wettest moisture condition likely to occur in the subgrade after the road is opened to traffic. In the tropics, subgrade moisture conditions under the impermeable road pavements can be classified into three main categories: Category (1). Subgrade is where the water table is sufficiently close to the ground surface to control the subgrade moisture content. The type of subgrade soil governs the depth below the road surface at which a water table becomes the dominant influence on the subgrade moisture content. For example, in non-plastic soils the water table will dominate the subgrade moisture content when it rises to within 1 m of the road surface, in sandy clays (PI40 percent) .The water table will dominate when it rises to within 7m of the road surface. In addition to areas where the water table is maintained by rainfall, this category includes coastal strips and flood plains where the water table is maintained by the sea, by a lake or by a river. Category (2). Subgrade with deep water tables and where rainfall is sufficient to produce significant changes in moisture conditions under the road. These conditions
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
32
Subgrade assessment
33
occur when rainfall exceeds evapotranspiration for at least two months of the year. The rainfall in such areas is usually greater than 250 mm per year and is often seasonal. Category (3). Sub grades in areas with no permanent water table near the ground surface and where the climate is dry throughout most of the year with an annual rainfall of 250 mm or less. Direct assessment of the likely strength or CBR of the subgrade soil is often difficult to make but its value can be inferred from an estimate of the density and equilibrium (or ultimate) moisture content of the subgrade together with knowledge of the relationship between strength, density and moisture content for the soil in question. This relationship must be determined in the Laboratory. The density of the subgrade soil can be controlled within limits by compaction at suitable moisture content at the time of construction. The moisture content of the subgrade soil is governed by the local climate and the depth of the water table below the road surface. In most circumstances, the first task is therefore to estimate the equilibrium moisture content as Outlined in below. Estimating the subgrade moisture content Category (1). The easiest method of estimating the design subgrade moisture content is to measure the moisture content in subgrade below existing pavements in similar situations at the time of the year when the water table is at its highest level. These pavements should be greater than 3m wide and more than two years old and samples should preferably be taken from under the carriageway about 0.5m from the edge. Allowance can be made for different soil types by virtue of the fact that the ratio of subgrade moisture content to plastic limit is the same for different subgrade soils when the water table and climatic conditions are similar. If there is no suitable road in the vicinity, the moisture content in the subgrade under an impermeable Pavement can be estimated from knowledge of the depth of the water table and the relationship between suction and moisture content for the subgrade soil The test apparatus required for determining this relationship is straightforward and the method is described in Appendix B. Category (2). When the water table is not near the ground Surface, the subgrade moisture condition under an impermeable pavement will depend on the balance between the water entering the subgrade through the shoulders and at the edges of the pavement during wet weather and the moisture leaving the ground by evapotranspiration during dry periods. Where the average annual rainfall is greater than 250mm a year, the ©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
33
Material selection
34
moisture condition for design purposes can be taken as the optimum moisture content given by the British Standard (Light) Compaction Test, 2.5 kg rammer method. When deciding on the depth of the water table in Category (1) or Category (2) subgrade, the possibility of the existence of local perched water tables should be borne in mind and the effects of seasonal flooding (where this occurs) should not be overlooked. Category (3). In regions where the climate is dry throughout most of the year (annual rainfall 250 mm or less), the moisture content of the subgrade under an impermeable pavement will be low. For design purposes a value of 80 per cent of the Optimum moisture content obtained in the British Standard (Light) Compaction Test, 2.5 kg rammer method should be used. Compaction properties of the subgrade soil are determined by carrying out standard c)
Material selection
Selecting the most economical combination of pavement materials and layer thicknesses that will provide satisfactory service over the design life of the pavement (It is usually necessary to assume that an appropriate level of maintenance is also carried out (TRL, 1993). i)
Approach to design
There are various approaches of pavement design and they are classified into empirical and semi- empirical methods. An empirical method includes group index method, CBR method,. Semi- empirical method includes AASHTO method, tri-axial test, Notting ham method, California Resistance Value test, Macleod method, and Banister method. In Uganda, the AASHTO and CBR methods are most commonly applied. TRL 1993 provides a structure catalogue that can be utilized in determining the pavement thickness. ii)
Surface dressing
The design of surface dressing takes into account the type of existing road surface, traffic, the available chipping and climate (TRL, 1993). They can be applied as a single surface dressing or a double surface dressing. According to TRL, 1993, single surface dressing are suitable and adequate when applied to a bituminous layer. It’s quality must be very high in order for it to be satisfactory or non bituminous layer and their quality is enhanced if traffic is allowed to run on the first dressing for a period of 2-3 weeks. This allows the chipping of the first dressing to adopt a stable interlocking mosaic that provides a firm foundation for the second dressing. ©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
34
Material selection
35
Embedment of chippings under traffic depends upon the hardness of the layer to be sealed and the size of the chippings (TRL, 1993). Assessment of layer hardness can be based on descriptive definitions or measured using a simple penetration test probe. Details of surface category, penetration values and descriptive definitions are as shown below. The size of chippings chosen should suit the level of traffic and hardness of the underlying surface as shown in table •
Category of road surface hardness surface hardness
Road surface hardness is classified under the following Categories Table 2.12: surface category Surface Penetration at 0 Category 30 c(mm) Very hard
0-2
Hard
2-5
Normal
5-8
Soft
8-12
Very soft
>12
Definition Concrete or very lean bituminous structures with dry stony surfaces. There would be negligible penetration of chippings under the heaviest traffic. Likely to be an asphalt surfacing which has aged for several years and is showing somecracking. Chippings will penetrate only slightly under heavy traffic. Typically, an existing surface dressing which has aged but retains a dark and slightly bitumenrich appearance. Chippings will penetrate moderately under medium and heavy traffic. New asphalt surfacings or surface dressings which look bitumen-rich and have only slight surface texture. Surfaces into which chippings will penetrate considerably under medium and heavy traffic. 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 per day 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 Approximate Nunber of Vehicles Category 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 ©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
35
Binder
36
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 chippings Surface Category
Traffic ctegory
Very hard Hard
1 10 14
2 10 14
3 6 10
4 6 6
5 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 +3 Very light 0-50 Round/dusty +2 light 50-250 +1 Cubical 0 Medium
250-500
0
Flaky
-2
Medium -Heavy
500-1500
-1
Precoated
-2
Heavy
1500-3000
-3
3000+
-5
Very Heavy 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
Source: TRL, 1993
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
36
Unbound pavement materials
37
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 un–laden 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 it’s 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).
©Final Year Individual project, Upgrading Nsambya-Kirombe road to a bituminous paved surface. Kyambogo University, Kampala Uganda 2009/10
37
Natural Occurring granular materials (Road Base)
38
The main categories with a brief summary of their characteristics are shown in table Table 2.16: Properties of unbound materials Code Description GBI.A Fresh, crushed rocks
Crushed rocks, gravel or boulders GB2.A Dry- bound macadam GBI.B
Summary of Specification Dense graded, un- weathered crushed stones, .Non -plastic parent fines Dense grading, P1
View more...
Comments
