Master of Engineering in Highway & Traffic Engineering

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item: Thesis-Abstract
A Methodology for design of pedestrian crossing facilities in Sri Lanka
Kaluarachchi, RASK; Kumarage, AS
Pedestrian accommodation should be an integral part of the design of any transport infrastructure project. It can be defined as walkways and pedestrian crossings Pedestrian have a right to cross roads safely. Therefore road designers have a professional responsibility to plan, design and provide safe walking and crossing facilities. Recent accident studies identified that pedestrian comprise a significant proportion of serious injuries and fatalities while they were crossing the road without using a marked pedestrian crossing. As the majority of pedestrian accident occur while crossing a road, the need of safe and efficient pedestrian crossing facilities could be the most important pedestrian safety factor. Sight distance, Level of Service and delay to pedestrian are major terms to be considered with warrants prior to installation of pedestrian crossing at a location of road being considered. Some time there would be additional delay and hazard by introducing crossing where it is not needed or is not suitable. Pedestrian characteristics and travel behaviour in the form of relationships among parameters such as speed, density, flow and space of pedestrian need to be identified by conducting further pedestrian surveys such as flow and travel time Design of a pedestrian crossing requires a basic understanding of related human characteristics and capabilities which are dependent on age, physical and mental condition of pedestrians, who are expected to use the crossing at that particular location. So the main aim of this study is to develop a guideline to assist in determining the appropriate crossing facility for a given location of a road based on the sight distance, Level of Service, delay to pedestrians and vehicles, pedestrian speed, density, flow and space in addition to the warrants. VI
item: Thesis-Abstract
A Tool for initial environmental assessment of road rehabilitation projects
Ambalavanar, J; Bandara, JMSJ; Bandara, NJGJ
The environmental assessment process involves the prediction of changes over time in various environmental aspects as a result of a proposed project. The prediction of the nature, extent, and magnitude of environmental changes likely to result from a proposed project is aided by various tools and techniques, the choice of which depends upon the impacts of concern, data availability or lack thereof, and the appropriate specificity of quantitative models. However, the choice of the appropriate method for conducting an environmental assessment can only be guided by certain criteria, but no single method will meet all the necessary criteria. The environmental assessment is mandatory in Sri Lanka since 1988 only for the projects listed under the category of "prescribed projects" in the National Environmental Act (NEA)The road rehabilitation projects do not fall in to the above category unless it falls within sensitive areas or resettlements of more than hundred families are involved or projects located wholly or partly outside the coastal zone with a road length exceeding 10kms. However, for funding purposes foreign agencies have made this mandatory even though they exempted from the environmental assessment according to the NEA. In practice this study might consume more time depending on the size of the project. As a result we might loose foreign aid allocations and prospective donors. Therefore a quick alternative method for environmental assessment is essential. This study develops a checklist for Initial Environmental Assessment (IEA)of road rehabilitation projects which consumes only a week or so to carry out the IEA. The checklist was generated based on the literature survey, discussions with subject experts, questionnaire surveys and field observations made on road rehabilitation projects. It identifies activities, corresponding environmental impacts and suitable mitigations for each component of the road rehabilitation project. This study is unique because the attempts were made to provide much information as possible on the techniques and methods available for handling different issues in the environmental assessment process and it is specially designed to suit the Sri Lankan conditions. Further, it gives possible mitigatory measures for each impact and also comprehensively covers all relevant impacts identified in presently use checklists in Sri Lanka there by cut down the amount of time required for preparation. The RDA and other road sector organizations could use this checklist in future for their IEA studies. It is hoped fervently that, this study would provide a significant step ahead in improving the process of IEA and hence they may absorb more foreign aid funds and attract prospective donors. Also this study recommends that, the use of checklist by a panel of experts, initiating a search for new cost effective mitigation measures, include the conditions stipulated on environmental clearance in to the project contract document, deploying a strong monitoring team, make available an environmental complain form at the project site, conduct site meetings regularly to discuss the issues ' problems, report the progress to relevant authorities and providing training for the officials.
item: Thesis-Abstract
Accident analysis of Southern expressway
Chinthanie, RPD; Mampearachchi, WK
Southern Expressway, the first ever access controlled expressway in Sri Lanka, was opened for traffic to function in year 2011. Even though it has provided several safety precautions, about 2000 number of accidents have been reported during the last three and half years (2011-2013). Therefore, identifying reasons for the accidents and critical locations where majority of accidents have taken place are essential for introducing immediate safety improvements. Main objectives of this research are to identify accident-prone locations, identify possible reasons for the accidents, and calculate the accident rate based on vehicle travel kilometre. According to this research study, ten most critical accident-prone locations were identified in the Southern Expressway from Kottawa to Pinnaduwa section. Accident locations were grouped into nearest 100m distance and the ten most critical locations are 0+100 km, 5+800km, 5+900km, 8+000km, 22+100km, 27+800km, 55+300km, 58+800km, 64+800km, and 65+100km. Main causes of the accidents, as per the accident records, are the driving speed and poor road environment under rainy weather (slippery road condition). Driver fatigue also act as a key factor for some accidents. Accidents happened during night time are twice higher than that of day time. However, this trend was same in each of the section along the road. Eventhough the highest accident rate of around 3.00 x 10-6veh km was noted from Kottawa-Kahathuduwa section and Baddegama-Pinnaduwa section, accident rates in each section have reduced from year 2012 to 2013.When comparing Southern Expressway with Colombo-Wellawaya road (A2) road corridor from Moratuwa to Galle in year 2012, Southern Expressway shows higher accident rate (2.4 x 10-6 per vehicle kilometre travelled) than other corridors (1.86 x 10-6 per vehicle kilometre travelled). In addition, fatality rate in Southern Expressway has increased from 2012 to 2013, which is considerably a higher value than fatality rates of road accidents in most of the other countries. However fatality rate in southern expressway has a low value than relevant figures in A2 road and whole Sri Lanka.
item: Thesis-Full-text
Accident investigation of Southern expressway
(2018) Dharmasiri, HIMJTU; Mampearachchi, WK
Road accidents have become a normal and re-occurring phenomenon from the beginning of the operation of the expressway up to this date. This study focuses on analyzing the data collected by the Expressway Operation Maintenance & Management Division and Expressway Police Division, based on accidents from day one of the operation of the expressway up to the end of April 2016. The objective is to present accident trends between interchanges and conduct a comparison with accidents which take place in other expressways based on the accident rate (Accidents per Vehicle Kilometers Travelled). For SPSS frequency analysis, Day, Time, Location, Severity, Causes of the accidents and Conditions of locations are taken as data. Thereafter, Accidents prone locations, Causes for the accidents are analyzed with SPSS based on the three main factors, namely Human, Vehicle and Infrastructure/Environment factors. The causes of accidents and their general preventive measures are discussed based on the safety audit process. This report provides a detailed analysis on accidents within a selected time period based on various factors influencing accidents. A total of 2275 accidents, have been reported on the carriageway of the southern expressway and out of that, 14 were fatal accidents, 10.6% have caused Injuries and 88.8% have caused only property damage. This is seen as an unhealthy trend let to be continued without taking any preventative action. Most accidents have occurred when the weather condition was fair, and 36.1% occurred during the rainy weather. 40% of the accidents were reported to have taken place on a wet road surface condition. About 13 accident prone locations have been identified in between the Kottawa to Pinnaduwa section. This research would aid in the enhancement of the safety of the expressway network, and would be conducive to the planning of safety procedures in future expressway developments. Introduction of innovative changes is expected to minimize the accident rate and alleviate the severity of accidents.
item: Thesis-Abstract
Analysis of air void variations with traffic in hot mix asphalt wearing course mixtures used in Sri Lankan roads - a case study
Lakmal, KHR; Mampearachchi, WK
Over the past decades, road construction with hot mix asphalt (HMA) has significantly increased. However, many issues have risen with respect to the durability of recently constructed asphalt concrete roads. Therefore, the importance of introducing new quality control measures is a current concern. Properties of the asphalt mixture and the construction practices are important criteria for quality and durability of asphalt pavements. Present Sri Lankan practice is to measure and control, (1) Thickness, (2) Density, (3) Bitumen content and aggregate gradation, and (4) Roughness index (IRI) of the laid asphalt mat. Objective of the present research is to find the importance of measuring air void of the laid asphalt mat and the need of a combined index of significant parameters to improve quality and durability of asphalt concrete roads. Core samples were tested at 12 locations with various initial compaction levels at two aging levels, as 100 days and 225 days. In addition, performance of road sections was evaluated with various levels of initial compaction after 5 years to check the long-term aging of asphalt concrete. It revealed that initial air void content decreased significantly under traffic in a short period and it is not possible to evaluate the long-term performance of HMA roads by initial air void content alone.
item: Thesis-Abstract
Analysis of flexible pavement sections using a mechanistic - empirical method
(2015-09-17) Dulwala, NP; Mampearachchi, WK
Determining of the pavement life under given structural, environmental, and traffic conditions is considered as one of the main objectives in the pavement design and analysis. Studies in pavement engineering have shown that the design procedure for highway pavement is either empirical or mechanistic. An empirical approach is one which is based on the results of experiments or experience. Existing design methods for flexible pavements include empirical methods, limiting shear failure methods, limiting deflection methods, regression methods, and mechanistic empirical methods. The goal of the Mechanistic-Empirical Pavement Design is to identify the physical causes of stresses in pavement structures and calibrate them with observed pavement performance. These two elements define this approach to pavement design: the focus on physical causes is the “mechanistic” part, and using observed performance to determine relationships is the “empirical” part. In this study an attempt was made to study the influence on local road sections with mechanistic empirical methods. Frequently used design references in local road designs are; (1) guide to the structural design of roads under Sri Lankan conditions issued by Road Development Authority (RDA), (2) American Association of State Highway Transportation Officials method (AASHTO method) and (3) guide to the structural design of bitumen-surfaced roads in tropical and sub-tropical countries method (Overseas Road Note 31). Sometimes, design thicknesses chosen based on design guidelines are subjected to alter with the non availability of pavement construction materials in an economical distance to a construction project. The road section for the study was selected from the Northern road rehabilitation project and there were several alternative proposals for the road section due to non availability of subbase material. The design alternatives were analyzed using the Mechanistic design software KENLAYER which was verified based on an experimental study conducted in a previous study. Damage analysis was performed using KENLAYER software. Damage ratio was estimated for the pavement design alternatives and it was found that, the pavement sections designed for a design period of ten years, the sections designed using Overseas Road Note 31 methods needs earlier rehabilitation followed by AASHTO which will be failed at higher traffic category. This was identified as an indicative factor for comparing the efficiency and the performance of the design alternatives. Mechanistic tool used in this study was able to identify critical layers which will fail before the expected design life. The mechanistic tool used in this study was able to identify the best suitable pavement design composition.
item: Thesis-Full-text
Analysis of vibration levels at nearby structures due to road construction activities
Chandana, NHS; Mampearachchi, WK
Analysis of Vibration Levels at Nearby Structures Due to Road Construction Activities The purpose of this research is to analysis of vibration levels at nearby structures due to road construction activities. Vibration caused various types of structural damages and it may finally affect the project progress. Although, there are systems to control these issues, it is reported that available systems are not reliable, effective and systematic. Even though, there are many research studies about quantitative vibration studies, nobody presented systematic holistic solution for these problems. Main Objectives of this research is propose a vibration management plan prior to the start of construction and evaluate current vibration standards of Sri Lanka and propose suggestion to improvements. Firstly, existing vibration and structure damage monitoring systems of Sri Lanka and other countries were studied. Secondly data regarding existing system from experience site and Highway engineers were collected. Finally, vibration was monitored when do major vibration generation road construction activities which used heavy vibrator rollers. Damages due to vibration depends on structure type, vibration value and affected time period. Those factors are taken into account to establish a vibration management plan. This vibration management plan will provide fair solution to both parties who take vibration consequences in construction and contractors. For the survey, hilly terrain area road section with various subgrade conditions is used. On the basis of the results of this research, it can be concluded that vibration limits are exceeded its damage limits in nearby structure and current boundary limits are not in optimum range and it should change with structure condition and subgrade strength. Furthermore, Sri Lanka standard of vibration limits for construction vibration should be revised after proper analyze. According to this research analyze Type 1, Type2 and Type 3 structures prescribed limits easily can be increased up to higher limits. It will be helpful to contractor to do undisturbed work without contradicting government rules and regulation. As a result, sustainability of the road project can be improved. According to questionnaire survey 84 % engineers think existing system should improve to meet sustainable road development and 85% engineers think vibration monitoring system is required for construction activities.
item: Thesis-Abstract
Analysis on suitability of built - operate - transfer systems for Sri Lankan expressways : a case study on Colombo - Katunayake expressway (CKE)
(2021) Perera MAP; De Silva D
Sri Lankan transport network achieved a significant development during the last decade by utilizing foreign concessions and local government funds for expressway development. Road Development Authority holds the authority to operate and maintain the road system periodically and mainly travel time-saving, developed infrastructure and living standards in association with social benefit are the user benefits generated with these expressways. As a developing country, a lack of financial stability for infrastructure development by the government may lead to foreign loans and concessions. The concessions lead to rapid involvement in the fund involvement for mega infrastructure projects as the necessity and demand of the country. The Build-Operate and Transfer (BOT) concession model is becoming a trend in the privatization of infrastructure projects. For these BOT Contracts, the concession period, interest rates are becoming the critical parameters and main considerations. In this study, a model was developed to demonstrate the potentiality of applying the BOT model for an operating expressway of Colombo-Katunayake-Expressway. The demand estimation, operational and maintenance cost, and toll revenue were used as inputs to this model and financial viability was observed with different scenarios. The concession period, interest rates, and optimality of selection of BOT were decided with different criteria based on financial viability. As the Colombo-Katunayake Expressway (CKE) meets a considerable high demand for traffic in the Sri-Lankan highway network, input variables from CKE were used to demonstrate the potentiality of applying the BOT model, and optimum subsidy level was determined with the application of variable concessionary periods to minimization of the ridership guarantee, the gap in-between the accumulated revenue and accumulated costs. Also, this BOT model is modified to validate any expressway network on an urban or suburban basis by considering the traffic demand by considering the unit length costs and unit length revenues in operations with the proposed analysis for functioning expressways in Sri Lanka. By considering main operational expressways of the country, as Southern Expressway, Outer Circular Highway (OCH), and forecasted traffic on Central Expressway and proposed Ruwanpura Expressway urban and sub-urban links were defined for the developed BOT model and operational and maintenance costs and revenue for unit length basis were obtained for iv each link. Finally, this developed BOT model was described to define and evaluate any expressway link by considering different concessionaire types obtained.
item: Thesis-Full-text
Applicability and effectiveness of the park and ride system for Kandy city
Karunadasa, JMAI; Pasindu, HR
Kandy is the main city in Kandy district and Central province of Sri Lanka. As a result of increased car ownership with increase of income level among other reasons, modal share of public transport has decreased over the years. This will increase congestion of roads, reduction of mobility and reliability. One possible option is to reduce the private vehicle users to public transport modes or combination of both private vehicles with public transport mode. “Kandy City Transport Study, (KCTS)” and “Kandy Transport Improvement Program, (KTIP)” have proposed strategic plans to improve transportation system in Kandy city. Furthermore three Satellite Stations were proposed at Getambe, Katugasthota and Thennakumbura with Kandy Multimodal Transport Terminal. In this research, applicability and effectiveness of the park and ride system to Kandy city was studied. Recent studies found that 59.5% of passenger vehicles’ trips end are in Kandy CBD. Willingness to use of park and ride system among private vehicle users were assessed through questionnaire. Questionnaire was mainly focused on traveler’s background information, travel behavior data, satisfaction of present transport mode and important factors for better Park and Ride system. Trip information data and other information given by the responders were analyzed through the statistical methods. Finally acceptability of the proposed Park and Ride system was analyzed with monthly income level, average travel time, average trip length, expected waiting time on average journey and average walking distance from point of egress from the public transport mode. According to the results, acceptability of the proposed Park and Ride system mainly depends on present mode of transport, monthly income level and travel time. Travel distance, waiting time and average walking distance from the point of the egress from the public transport to destination are independent with acceptability of the proposed Park and Ride system. The most of responders were not satisfied with the current travel time, pedestrian walkways. Responders are expecting comfortable public transport system with high frequency for successful proposed Park and Ride system in Kandy city.
item: Thesis-Full-text
Applicability of rational formula in hydrological analysis of highway cross drainage structures
Dissanayake, GA; Pasindu, HR
The peak flow estimation at Highway -Waterway intersects has substantial effects on Hydraulic design aspects of culverts and bridges. Fair and accurate estimation of peak flow would be the basis in deciding the size of cross drainage structures to ensure proper transfer ofrunoff collected at inlet towards the downstream. The history of hydrology modelling varies from well-known Rational Formula to sophisticated computer aided models. Rational Formula has been used for over 150 years and still remains as the most widely used method due to its simplicity in approach. The present study considered five numbers of flood estimation techniques; Rational Formula, Fuller Formula, Snyder’s Method, Flood transportation and HEC-HMS for catchments located in four road segments where area varies from 9 - 6663 hectares (ha). All catchments are ungauged and prediction of flood flows for ungauged basins is extensively discussed in past decades and still remains a question due to accuracy and validity of assumptions made in the analysis. The study focused on different methods of time of concentration, runoff coefficient and design discharge estimations. Three empirical relationships along with Irrigation Department guideline (1984) were considered for the computation of Time of Concentration. Time of concentration results of Kirpich equation was substantially lower than other methods while UK Flood Studies Report equation was identified as the highest. Only the Bransby-William equation showed fair agreement with Irrigation Department Guideline. Peak flow estimations of flood transportation technique is highly sensitive for the drainage area ratio and relatively low drainage area ratios correspond to culvert and bridge sites caused significant deviation from other methods. Fuller formula estimations were also considerably deviated from other methods. The difference in peak flow estimation methods was not significant up to catchment area of 100 ha. Peak flow estimations of cross drainage structures in studied road segments revealed that Rational formula can be applied up to 770 ha. As a comparative assessment catchments larger than 770 ha to be modeled using Rational formula and alternative flood estimation methods.
item: Thesis-Abstract
Applicability of steel fibers to improve the properties of cement stabilized...
(2015-09-16) De Silva, MSK; Mampearachchi WK
Stabilized bases are normally designed for the heavy traffic categories or in the absence of base materials which should have the required material properties according to the specifications so that the higher strength category can be achieved. Bases can be constructed using soil or aggregates. Those are stabilized with various admixtures such as lime, sand or cement. Among them, cement stabilization is a common practice in road construction industry. The road construction industry has the experiences about the stabilization of dense graded aggregate bases with cement. Even though the content of cement has to be increased to get the higher strength capacity, shrinkage cracks may appear with the increase usage of the cement content and it has a tendency to convert the layer to a rigid pavement too. Hence, another feasible technique should be applied to achieve the required higher strength capacities concurrently to diminish shrinkage cracks and form the base withstand against higher number of heavy load repetitions as well as form the base withstand against higher number of heavy load repetitions without converting the layer into rigid. To achieve both phenomena, this research was carried out to introduce usage of a reinforcement type such as steel fibers in Dense Graded Aggregate bases. In this study, it is discussed about the high performance of Steel Fiber Reinforced Cement Stabilized bases over the conventional Cement Stabilized Bases. Based on the results, a Pavement Design Chart was developed for Steel Fiber Reinforced Cement Stabilized Bases suitable for higher Traffic Classes such as T7 and T8. This can be used in general practice without doing any calculations.
item: Thesis-Full-text
Assessment of operating speeds of rehabilitated rural roads with asphalt surfacing
Wijeratne, DDS; Maampearachchci, WK
In Sri Lanka, rural roads are not specifically designed on technical requirements. Most of the rural roads (C and D classes) have historical backgrounds as being tracks and trails coming even beyond the colonial times. Hence, most of the rural roads in Sri Lanka are almost following the same traces and not designed technically. Nowadays, rural roads are being rehabilitated. So far those rehabilitation projects underwent with merely construction improvements and proper geometrical improvements have not been adopted. It was found out that the actual speeds can be significantly greater after rehabilitation affecting the safety ofroad users. Aim ofthis study was to assess actual operating speeds, posted speed limits and to find design operating speeds that supposed to be after the rehabilitation. Finally it suggests rational speed limits to rural rehabilitated roads under purview. Most of the rural roads in Sri Lanka don’t have posted speed limits specified according to the geometric, road environment and functionality level of the road. The speed limits of 70km/h and 50km/h are the usual speed limits enforced for traffic in arterial roads which are categorized as class A and B. Since the speed limits are not categorized according to the type ofthe road, above speed limits apply to the rural roads as well. It’s hardly been seen that traffic speeds are controlled or monitored by law enforcement in rural roads. Hence the speed choice ofthe rural road drivers depends on variety ofother factors. The 85th percentile speed was taken as the operating speed. This speed was used as a basis for suggesting rational speed limit since most drivers behave in a safe and reasonable manner and do not want to get into crashes. Also it encourages drivers to travel at about the same speed. The researchers have studied number of rehabilitated roads in North Western province in Sri Lanka. Each road was divided into several sections; straight and curved. Operating speeds on straight sections were given priority in suggesting rational speed limits. As operating speeds in curves are considerably lower and enforcing lower posted speeds only based on operating speeds on curves for entire road, would not be practical since drivers tend to disrespect the speed limit. The suggested rational speed limit for all the roads under purview is 50 km/h and this speed limit will be overridden to a lesser speed limit at a curved section based on the operating and design speed. This speed limit should be notified using sign boards and shall be enforced only for the curve itself.
item: Thesis-Abstract
Cold mix for maintenance of road surfaces
Weeraratne, R; Bandara, JJMSJ
The maintenance of roads net work in the country is a very important activity and it directly effects the people and the economy of the country. At present the road maintenance system in Sri Lanka has lead to some criticism in the society though the government spends lot of money annually in order to avoid this critical problem. The identification of current road maintenance system and the materials used for maintenance works, and the identification of problems in respect of road maintenance works are considered. Materials utilized for road construction and maintenance were considered and road construction material which is frequently and widely used in Sri Lanka was selected. In this case cold mix was selected in comparison with hot mix due to the wide usage, availability in Sri Lanka, process of production, lesser environmental pollution and lesser restrictions in utilization. The main objective of this research was the investigation of possible quality improvement of cold mix by varying its composition and recommendations are made on how to use the improved material in the field more effectively under various climatic and weather conditions. In addition to changing the major components of the cold mix, examine any improvement in the quality of cold mix by incorporating a small percentage of some other binder material as a filler such as cement to fine aggregate when mixing in the cold mix and recommendations of effective way of utilization the cold mix in the field under the different climatic and weather conditions. Finally, recommendations on after care treatments for the utilization of cold mix in surfacing and maintenance works to ensure the quality and durability of the completed works. This research was not aimed to obtain a unique proportion for cold mix. Mixed proportion depends on traffic condition of road, Climatic condition of area, weather conditions and the quality of aggregates and binder material. The research leads the guidance to select the appropriate mix in respect of above situations. Based on the results of the trial mixes tested in the laboratory and in the field and the observations the recommendations are made on how to use the material in the field more effectively and after care treatments for the utilization of cold mix in surfacing and maintenance works to ensure the quality and durability of the completed works.
item: Thesis-Full-text
Cost overruns in foreiging funded highway projects in Sri Lanka
Hettiarachchi, HHNA; Bandara, JMSJ
When an infrastructure development project is planned, an accurate estimation is critical. As a result of failing the fulfillment of expected accuracy, the cost overrun of the projects would result. The cost overrun is defined as a difference between the initial project estimate at the planning stage and the accounted project cost at the time of project completion. However, cost overrun is one of the major negative consequences that may influence to the economy of a developing country, like Sri Lanka. In order to fill the aforesaid financial gap, the necessity of pumping additional funds through the consolidated fund by the GOSL would be arisen. Out of the significant impacts of which caused by cost overruns in foreign funded projects are delay in completion and curtailment of original scope of work. But both adverse impacts are restricted by the conditions and policies of funding agencies. It is the normal practice that influencing to complete the project up to the agreed scope under the specified standards by the funding agencies. Due to the fact that the highway projects would make greater impacts not only to the development of infrastructure but also to the higher cost overruns, it was decided to limit the analysis only for the highway projects. The overlooked main factors that cause to turn the project into track of the cost overrun path are; • Increase quantities • Price Changes However, there can have many factors that have supported above mentioned main factors. The objective of this research is to • To study what is cost overrun? • To identify factors behind cost overruns in Sri Lankan projects • To identify main risk factors & risk management The research would address the gap of knowledge of why highway projects overrun their cost. In addition to that, a method for minimizing cost overruns or identify cost overruns in advance will be proposed. In this research, twenty numbers of cost overrun highway projects completed within resent years and funded by different agencies were collected and analyzed. What are the main causes for cost overrun, how is a BoQ item correlate to each other item and what is relationship of cost overruns with project period or delay will be studied.
item: Thesis-Full-text
Criteria to identify optimum spacing for service areas on Southern expressway extension
(2018) Kandambi, KW; Bandara, JMSJ
Southern Expressway is the first E class highway in Sri Lanka currently spanning from Kottawa to Godagama. This expressway is 126.1 kilometers long from Kottawa to Godagama. In most expressway projects, service area which will serve passengers is common. From Kottawa to Godagama there is one service area located at Welipenna. Southern Expressway extension will extend the expressway from Matara to Hambanthota including Expressway link to Mattala. From Welipenna to Hambanthota, there is approximately 177 km. So, it is evident that there needs to be additional rest areas located in the southern extension project. Service area is an integral part of a long expressways. Purpose of the service area in an expressway is to provide services to the passengers and provide a resting place for the drivers in their long journey. Placing of the service area is very important because it will affect the accident rate in expressways. In this research using traffic data collected which include the vehicle entrance time and date to the expressway, exit time and date from the expressway, vehicle type, entered interchange and exit interchange from existing southern expressway, location for a service area is proposed by calculating the optimum distance between the service areas. Quantitative data gathered from the expressway is analyzed to obtain a criteria for deciding the optimum location for the service area of the expressway extension. According to the findings 60km was proposed for distance between service areas and 30km was proposed as the distance between the rest areas.
item: Thesis-Full-text
Design and maintenance of gravel roads for Sri Lanka.
Amarasekara, RM; Bandara, JJMSJ
A study has been carried out to gather, review, summarize literature in order to prepare a set of recommendation tor design and maintenance of gravel road for Sri Lanka, Paved roads are all weather while earth roads are not. The cost of construction and maintenance of paved roads are very high compared to earth roads. A need has always been there for all weather gravel roads to bridge the gap between paved roads and earth roads, in order to accommodate low volume of traffic on agricultural and rural roads. In this study, the available literature and practices were studied and revived by the author. who has considerable field experience in this subject, spanning a period of about two decades. It was possible after the study to present suitable recommendations, for most required items in design and maintenance of gravel roads. The surveys carried out reveal that magnitude of traffic and their composition can be accommodated with suitably designed, constructed and maintained gravel roads. The outcome of the study presents recommendations on selection of sites for gravel roads, essential geometric standards, drainage, selection of material, design procedure for pavement structure, maintenance requirements, items of maintenance and their frequencies, and the cost aspects of construction and maintenance. The study of cost aspect reveal that the gravel roads require one third of the cost that would require for traditional bitumen surfaced aggregate base (metaled and tarred) roads. Maintenance of gravel roads could be carried out on self-help basis. This would further help to bridge the gap with respect to cost, between traditional paved roads and earth roads.
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Design of pedestrian facilities in Sri Lanka
Premathilaka, LS; Bandara, JMSJ
Pedestrian facilities can be defined as walkways, pedestrian crossings, under passes, over passes and guard fences etc. In Sri Lanka, designing of highways has been mostly confined to providing the facilities for vehicular traffic. However pedestrian facilities are often neglected even though the pedestrians use considerable amount of road space. The qualitative and quantitative design for a pedestrian environment requires a basic understanding of related human characteristics and capabilities which are dependent on age, sex, physical and mental condition. However, factors such as the purpose of the trip, time of the day, weather and environmental conditions etc. will combine to determine the exact travel behavior of a pedestrian. Some of the pedestrian characteristics and travel behavior have been identified in the form of relationships among parameters such as speed, density, flow and space of pedestrians by conducting pedestrian surveys such as flow and travel time etc. The appropriate dimensions of a walkway are dependent on the location, purpose and anticipated flow or demand on the facility: It can be determined by parameters such as design speed, flow, space and density of pedestrians as these parameters can vary according to the above factors. The concept of level of service (Pedestrian Service Standards) can be introduced in order to facilitate the design of a pedestrian walkway. Pedestrian service standards are based on the freedom to select normal travel speed, the ability to by pass slow moving pedestrians and the relative ease of cross and reverse flow movements at various pedestri an traffic concentrations. The level of service can be measured in terms of space (m2/Ped), flow rate (Pedestrians/m/min), Speed (m/min) and pedestrian density (number of pedestrians/rn'') and it can be divided into any number according to the requirements. Four levels of service such as H,M,L and P were introduced under this study since the variance of the pedestrian flow can be categorized and illustrated with these four levels of service conveniently
item: Thesis-Abstract
Determination of an effective laying pattern and best block shape for concrete block pavement based on field performance
Senadeera, AA; Mampearachchi, WK
There has been an intensive process of urbanization which has brought about need for rapid construction of roads and related infrastructure during the end of the last century. Therefore development of economical road construction methods is a high priority for a developing country like Sri Lanka. Concrete block paving is one of the predominant road construction method used in most of the developing counties due to economic adaptability and this has emerged as a cost effective road construction method suitable for certain local conditions. But in Sri Lanka this technique is yet to be developed to a fully fledge road construction method. This can be attributed to a dearth of the technical expertise and knowledge. As a result, there is a great need to develop knowledge and establish proper methods of block paving. Load spreading in concrete block paving roads is accomplished by interlocking actions. Because of that concrete blocks act as a major load spreading component in concrete block paved surfaces. Therefore the aim of this research is to evaluate the effective block shape and effective block laying pattern which can improve the interlocking action. This research was covered the real ground situation and the behavior and the effects of blocks due to traffic weights. Under this study, concrete blocks were cast according to the specifications in predetermined shapes and paving was done with different block shapes and patterns in a road which contains vehicular traffic about 30CV/day. Selected 100m road length was divided to 10 equal parts and blocks were paved according to selected pattern and block shapes in each different section. Deflection was measured by using Benkel man instrument and block displacement were measured by using venire caliper. The most effective block shape and pattern were selected comparing deflection and block displacement in each combination of block shape and patterns. v
item: Thesis-Full-text
Determination of notable tolerance limits for bitumen and aggregate for asphalt concrete mixtures in Sri Lanka
(2019) Satheeban V; Mampearachchi WK
The development of corrugation along longitudinal profile is one of the most common failures in asphalt pavement. The corrugation distresses are usually more severe in road sections with high longitudinal slope than sections with mild slope. This is because the slope decreases average speed of vehicles running upward and leads to increase in the total loading time drastically. On the other hand, vehicles tend to apply brakes when running downward. The research aims at finding out how asphalt material (Bitumen & aggregates) properties have an impact on corrugation distress in sloped pavements. For this purpose a recently constructed and heavily trafficked road (Ambepussa Kurunegala Dambula A006) is considered. The standard specification for construction and maintenance of roads and bridges (ICTAD) has specified requirement for bitumen content and combined aggregate grading for mix design of asphalt with tolerances. The gradation pattern of the aggregates can have an impact on permanent distress in asphalt concrete pavements. The gradients of roads are usually not considered when selecting the combined grading type for mix design of asphalt. The specification may be adapted to suit different conditions considering various criteria. For above road project combined grading Type 1 and the bitumen content tolerance percentage by weight of total mixture was adapted as +0.3 % where standard specification states ±0.3 %. This leads the asphalt plant production crew to maintain bitumen content at higher than the design (maintain at 4.9 % in the plant though design bitumen content is 4.8 %). More than 2000 samples (each 1500 kg batch) of different Asphalt plant bitumen batching details were analyzed to conclude the predefined tolerance limits of bitumen content and combined gradation of aggregates. It has been concluded that standard values provided in ICTAD specification for bitumen content tolerance can be modified as ±0.2 % and bitumen content tolerance limit should also extend over ± values. Further the combined gradation tolerance of aggregates need no modification based on the sample analyzed in this study.
item: Thesis-Abstract
Determination of optimum nominal aggregate size for single surface dressings
Wanigasekara, WMSB; Kumara, MAW
Surface dressings are used as a road maintenance activity as well as a surfacing of a newly constructed road. One of the main decisions to be taken in designing a dressing is the selection of appropriate aggregate size. Improper selection of aggregate size could tarnish the performance of a surface dressing. The aim of this study is to find the optimum size of aggregate for a single surface dressing especially in Sri Lankan Macadam roads. General size of aggregate for a particular surface dressing could be found using commercial traffic volume and surface hardness of the road based on TRRL method. But the aggregate sizes selected in above simple method have shown inconsistent results. Therefore tests should be carried out to find most appropriate size for the surface dressings. Three sizes of aggregate were selected using above simple check for the tests. Three different surface dressings from different aggregate sizes were done. Binder type kept constant and binder rate changed according to the chip size. The performances of these three surface dressings were evaluated by measuring aggregate removal rate and skid resistance of the seal. Digital photographs of demarcated locations in surface dressings of different chip sizes were taken at pre determined time intervals. The numbers of aggregate were counted in each photo after certain time interval and using this data, the behavior of each surface dressing over a period of time can be studied. The aggregate size that could keep highest area of aggregate intact in its dressing would be a more durable chip size. The next aspect of checking performance of the dressing is the skid resistance. The techniques utilized to measure this value are Locked wheel test and Sand patch method. The main- aim of skid resistance testing was to compare three sizes of aggregate and see how they respond to skidding. -It was found that 9.5mm nominal size performed better in durability aspect and 12.5mm performed better in skid resistance aspect.