Browsing by Author "Mampearachchi, WK"

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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
Adaptation of Austroads mechanistic-empirical pavement design for tropical climates
(2022) Premarathne, RPPK; Mampearachchi, WK; Gunaratne, M
Many road agencies have employed conventional empirical pavement design methods, such as the American Association of State Highway and Transportation Officials (AASHTO) and Transport Research Laboratory (TRL) Overseas Road note 31 guidelines, to design and analyse flexible pavements. Empirical pavement design methods utilise empirical formulae based on past experiments conducted in extreme weather conditions. They have significant drawbacks permitting limited freedom for pavement designers, leading to material constraints in road projects. Such restrictions may result in high costs for hauling materials from far sites, leading to increased costs for road construction projects. Road agencies have identified the advantages of mechanistic-empirical (M-E) pavement design methods that accommodate available materials resulting in economical designs. However, performance models given in ME methods are derived under laboratory conditions and require calibrations to the field. Austroads is one of the most recognised M-E guidelines widely used in Australia and New Zealand. It accompanies a user-friendly and time-efficient software packageCIRCLY. This research was focused on adapting the Austroads M-E pavement design guidelines for tropical climates. Austroads suggests two performance models, each for fatigue cracking and subgrade rutting. This research focused on calibrating the default performance models proposed by Austroads by finding the most suitable damage exponent (b) and shift factor (SF) for tropical climates. Calibrating the default fatigue performance model was only considered. Data from two A-class roads were obtained for model development and model validation. Cumulative damage factor (CDF) representing the accumulated fatigue damage was estimated at varying damage exponents (b) and shift factors (SF) using the mechanistic design software-CIRCLY. The alligator cracking index (ACI) suggested by the Federal Highway Administration (FHWA), quantifying the fatigue damage level, was calculated using visual surveys to detect and classify pavement distresses. It could be observed that the CDF have a strong relationship with the ACI. The most robust relationship between the ACI and the CDF could be observed at the damage exponent (b)= 5.1 and the shift factor (SF)= 2.5. CDF values were computed for the model validation by inputting the calibrated damage exponent (b=5.1) and shift factor (SF=2.5) to the mechanistic design software- iii CIRCLY. ACI values were predicted by substituting these calculated CDF values for the derived regression model. When the observed ACI values were plotted against the predicted ACI values, it could be noticed that the best-fit curve for the observed ACI and predicted ACI has R2 = 0.99 and slope = 1.007. This observation emphasizes the accuracy of the derived model, thereby justifying its use for the design and analysis of flexible pavements for tropical climatic conditions. Therefore, it can be justified that adapting the Austroads mechanistic pavement design guideline for tropical climates is highly favourable by modifying the default performance relationships. The use of mechanistic tools to design and analyse pavements was strongly emphasised during the analysis steps, ensuring the reliability of such tools in pavement design and analysis. As the M-E design procedure allows the designer to use available materials, adapting the M-E design procedure will address the material constraint in road construction projects and deliver more cost-effective designs. This will finally help reduce unwanted expenditures and improve the economic aspect of road construction projects. Keywords: Mechanistic-Empirical (M-E) Pavement Design, Austroads, Modified failure functions, Alligator Cracking Index (ACI), CIRCLY, Cumulative Damage Factor (CDF), Tropical climates
item: Conference-Full-text
Analysis and numerical simulation of semi-circle bending fatigue crack propagation of asphalt mixture
(Springer, 2021) Huang, L; Zhang, P; Song, W; Feng, X; Yang, S; Pasindu, HR; Bandara, S; Mampearachchi, WK; Fwa, TF
In order to study the fatigue crack propagation characteristics of asphalt mixture, a model of fatigue crack dynamically propagating was established based on the Paris law modified with fracture energy release rate. Four different types of asphalt mixture were tested using semi-circular bending fatigue test (SCB fatigue test) to obtain the corresponding N-a curves. The extended finite element method (XFEM)was adopted to simulate the SCB fatigue tests for 4 types of asphaltmixture. The results show that the N-a curve obtained from the finite element model is highly consistent with the experimental results, which verifies the feasibility of fatigue crack propagation analysis based on modified Paris Law characterized by fracture energy release rate for asphaltmixtures. The extended finite element methodwas used to establish the fatigue crack dynamic propagation model of the asphalt mixtures. The fatigue crack propagation process of the specimen was simulated to verify the effectiveness of the method.
item: Conference-Abstract
Analysis of air void variations in hot mix asphalt wearing course mixtures used in Sri Lankan roads
(Department of Civil Engineering, University of Moratuwa., 2015-08) Lakmal, KHR; Mampearachchi, WK; Pasindu, HR
Over the past decades, the road construction with hot mix asphalt (HMA) has been increased significantly. However there were many concerns of the durability of the recently constructed asphalt concrete roads. Therefore, impotency of introduction of new quality control measures is arisen these days. The properties of the asphalt mixture as well as the construction practices are also important for the quality and the durability of asphalt pavements. The present Sri Lankan practice is measure and control of (1) Thickness, (2) Density, (3) Bitumen Content and Aggregate gradation and (4) Roughness Index (IRI) of the laid asphalt mat. The objective of this research is to find out the impotency of measuring the air void of the laid asphalt mat and the need of a combined index of the important parameters to improve the quality and durability of asphalt concrete roads. Core samples were tested at 12 locations with various initial compaction levels at two aging levels, 100 days and 225 days. In addition performance was evaluated of the road sections with various levels of initial compaction after 5 years to check the long term aging of asphalt concrete. It was found that initial air void content significantly decreased under traffic in a short period and long term performance of HMA roads cannot be evaluated by initial air void content alone.
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: Conference-Full-text
Analysis of skidding potential and safe vehicle speeds on wet horizontal pavement curves
(Springer, 2021) Peng, J; Chu, L; Fwa, TF; Pasindu, HR; Bandara, S; Mampearachchi, WK; Fwa, TF
Skidding on wet horizontal pavement curves is a major traffic safety concern. Themaximum safe driving speed against skidding is an important threshold for safe driving. However, because of the complex tire-pavement-fluid interaction mechanism and the large number of variables involved (including curve geometric parameters, pavement surface properties, properties of tire in motion, and water film thickness), currently there is no practical working procedure that allows pavement engineers to determine the maximum safe driving speed on a horizontal curve under a given wet weather condition. This paper presents a finite element model to predict the maximum safe driving speed on a wet curved roadway section based on solid mechanics and hydrodynamics. The numerical simulation model was developed and validated against experimental skid resistance values on slip angles from 0° to 90°. Based on skidding analysis, the maximum safe driving speed on a horizontal curve is derived by comparing the available tire-pavement frictional resistance and the required friction to prevent skidding caused by the centrifugal force of the vehicle concerned. An illustrative case study is presented to compare the calculated maximum safe vehicle speed with AASHTO design speed. The analysis presented suggested that the proposed approach offers a useful tool to calculate maximum safe speeds on in-service pavement curves for safe driving.
item: Conference-Abstract
Analysis of the flexible pavement sections using mechanistic - empirical method
(Department of Civil Engineering, University of Moratuwa., 2013-08) Mampearachchi, WK; Dulwala, NP; Pasindu, HR
Pavement design procedures used in road design is either empirical or mechanistic. In Sri-Lanka most of the road pavements have been designed based on the empirical design methodologies. A guide to the structural design of roads under Sri Lankan conditions issued by Road Development Authority (RDA) is used as the reference for the local road pavement designs. Overseas Road Note 31 and American Association of State Highway Transportation official’s method (AASHTO) are the other references used in the pavement designs. Pavement layer compositions given for the same road section by the different references are not in the same. In the other hand due to the non- availability of the materials and different cost constraints in the projects might subjected to change the pavement compositions rather given by the design references. So the different layer compositions are needed to be analyzed against their performances and developing improving method for analyzing is required. The quality of material properties in different layer composition can be evaluated through the mechanistic- empirical methods. KENLAYER is the mechanistic- empirical tool widely used in the pavement analysis. The output results of the KENLAYER gives the vertical stresses and strains, horizontal stresses and strains, and displacements at the specified locations. For the selected road stretch, traffic data has collected .The same section has designed using different design references and some sections are subjected to changes as available material properties. Some pavement compositions are designed with the same structural adequacy, matching with the structural Number by the varying material property which gives economic benefits. These different pavement compositions are used in analysis. Design life has analyzed for the each pavement composition using Mechanical – Empirical method. The critical layers are identified at early stage of the failure. The study concludes by identifying the best suitable pavement composition by the evaluating of the pavement performance.
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: Conference-Abstract
Analyzing the durability and the lateral drainage characteristics of open graded friction course pavement
(2019) Dedigamuwa, KV; Nawaz, RZ; Mampearachchi, WK
In Open Graded Friction Course (OGFC) is a thin permeable layer of special type Hot Mix Asphalt (HMA) which contains a combination of uniform size aggregate skeleton with minimum fines, and high asphalt content. OGFC is being used as an effective pavement material in many countries for expressway construction as it has many positive attributes in performing as a pavement material. During the operational stage of many expressways which were made out of dense asphalt, several issues were observed in wet seasons such as skidding, splash, hydroplaning. OGFC is a suitable solution as a pavement surfacing material for such existing drawbacks. Drainage characteristic of a pavement is one of the important parameters which dominantly contributes to the durability of a pavement. However, the inefficient water drainage due to the lack of drain-ability of vertical drainage caused by the clogging of OGFC lead to observe the properties of lateral drainage. Though, many studies had been carried out to address the clogging effect due to dust particles, no permanent rectification on this issue was found. Therefore, to investigate OGFC in a different way, the lateral drainage characteristics are analysed to identify the water movement on the surface of OGFC by comparing the capacities which can be endured by different types of OGFC. This study analyses the lateral drainage characteristics of OGFC pavement to find out the OGFC gradation which shows the optimum values for the combination of permeability and durability characteristics under the laboratory conditions. Further, the computer image analysis with the aid of MATLAB software is used to analyse the lateral drainage characteristics by identifying and calculating the areas of voids of cross sections captured as 2D photographs by a DSLR camera (Nikon- D3300). The proposed method is less time consuming, comparatively inexpensive and can be utilized to enhance OGFC by integrating with the traditional laboratory experiments.
item: Conference-Abstract
Animal collision induced road accidents in the Southern Expressway
(Department of Civil Engineering, University of Moratuwa., 2014-08) Mayadunnage, S; Colombage, SS; Weerakoon, DK; Mampearachchi, WK; Pasindu, HR
Declaring open the Southern expressway in November 2011 marks a major milestone of the future road network development in Sri Lanka. Ensuring road safety is one of the key considerations during the operational phase of an expressway as vehicles travel at a much faster rate, which will increase the probability of road accidents. During the period, November 2011 to December 2013, 1023 road accidents have taken place in the Southern Expressway. Out of these, 20% have resulted due to animal-vehicle collision. Animal-vehicle collisions could result in property damage, personal injury or fatalities to the commuter. This study was undertaken to analyze temporal and spatial patterns of animal induced road accidents reported in the southern expressway that would inform development of mitigation measures to reduce the incidence of road accidents caused by animal collision. Accident reports available for animal collision related road accidents during the period, December 2011 to December 2013 was collected and analyzed to identify animal collision patterns. During this period 173 road accidents have taken place. Out of these 172 accidents only involved only a single vehicle while one of the incidents involved two vehicles. Further, 98% of the incidents (169) resulted only property damages while the remaining four incidents have resulted in injury to the 10 commuters. During the study period no fatalities have resulted due to accidents due to animal collisions. There was no significant difference between the incidence of road accidents resulting due to animal collisions reported in the Galle bound section (87 incidents) compared to Colombo bound section (86 incidents) of the highway. The rate of accidents resulting due to animal collisions has reduced by 11% during the second year of operation compared to the first year. Animal collision rates fluctuated over time with highs in April and July and lows during March and May. The highest number of incidents was reported in the stretch between 80 and 90 km followed by 21 to 30 km stretch. Out of the 173 accidents recorded, 70% (121 incidents) have resulted due to collision with dogs followed by pigs (20 incidents), birds (20 incidents) monkeys (7 incidents). Out of the 20 accidents reported due to bird collision 13 have resulted due to Peacocks. Other animals that have resulted in accidents include land monitors, buffaloes, goats, porcupines and foxes which have all contributed less than 5% of the incidents. The road accidents resulting due to collision with dogs have undergone a 33% reduction during the second year of operation compared to the first year. Out of the 173 animal collision related road accidents reported 74% involved motor cars followed by vans (11%), jeeps (8%), cabs (5%), busses (1%) and lorries (1%), indicating smaller vehicles are more susceptible for animal collision related road accidents. Out of the reported animal related road accidents 58% have occurred during day time and 87% of these accidents have occurred on sunny days while the rest on rainy days. Further 83% of the animal related road accidents have taken place on clear days compared to 13% that have occurred during rainy days. Therefore, lack of visibility or whether condition may have not contributed to animal related road accidents. This study indicates that animal related road accidents show clear spatial and temporal patterns that can be used to develop mitigation measures in the future.
item: Conference-Full-text
Applicability of gneiss based mineral aggregates for the use in high friction surface treatment in terms of polishing characteristics
(Springer, 2021) Thenuwara, HV; Buddhi, PHGH; Pasindu, HR; Pasindu, HR; Bandara, S; Mampearachchi, WK; Fwa, TF
Speed and safety management of highways plays a prominent role in ensuring road user safety, especially of the vulnerable categories. Pavement Friction Management (PFM) is being considered as the best possible option in developing the road infrastructure over the other prevalent strategies, with the focus of improving user safety. High Friction Surface Treatment (HFST) is widely being used as a remedial measure to improve the friction and texture retention capacity of the wearing course, as it provides economical and sustainable solutions in upgrading the pavement performance in both as an urgent response and in the long run as well. As an urgent remedial intervention, HFST can be incorporated in the national practice of safety management in Sri Lanka, to address the concerns over the escalating numbers of grievous highway crashes. In place of the most commonly used high skid resistant aggregates, gneiss-based mineral aggregate can be a viable alternative since it delivers similar functionality to that of granites. The study examines the polishing characteristics of widely used gneiss-based roadstones in the country through laboratory experiments involving the Polish Stone Value (PSV) test. Both qualitative and quantitative analyses of the specified physical and mechanical laboratory testing are conducted to evaluate the applicability of gneiss-based mineral aggregates in the use of HFST as an alternative skid-resistant roadstone in terms of their polishing behavior.
item: Conference-Abstract
Applicability of HCM 2000 & 1986 to determine the level of service in urban arterial roads, Sri Lanka
(Department of Civil Engineering, University of Moratuwa., 2012-07) Mampearachchi, WK; Jayasuriya, WWC; Senaratne, SAMANI; Sumanathissa, RPP; Pasindu, HR
The objective of this research is to identify the applicability of Highway Capacity Manual (HCM)to determine the Level of service in urban minor arterial roads in Sri Lanka. HCM has been developed by the transport research board, USA. Currently most of the local road development agencies use HCM for capacity analysis of roads. There have been no researches carried out to identify the applicability of HCM to the Sri Lankan condition. To depict the quality of service of the roads quantitative measures of a traffic stream are required. Level of Service (LOS) is a quality measure describing operational conditions within a traffic stream, generally in terms of service measures such as speed and travel time, freedom to maneuver, traffic interruptions and comfort. Six LOS are defined based on service flow rates of roads. Letters designate each level from A to F with LOS A representing the best operating conditions and LOS F the worst. Though the local roads have acceptable LOS, the results obtained from both HCM 2000 and1986 have not reflected it. It is required to identify the factors which affect the LOS. For that a sample of two way - two lane roads were selected. For the selected sample flowvs.density curveshave been developed by considering traffic data and speed survey data. Based on the literature findings and data collected from the field, six LOS for the urban minor arterial roads have been defined.
item: Conference-Full-text
Applicability of HCM 2000 to determine the level of service in urban arterial roads, Sri Lanka
(Department of Civil Engineering, University of Moratuwa, 2012-12) Mampearachchi, WK; Jayasuriya, WWC; Senaratne, SAMANI; Nawagamuwa, U; de Silva, LIN
T16 obJective of this research is to identify the applicability of Highway Capacity Manual (HCM) to determine the Level of service in urban minor arterial roads in Sri Lanka. HCM has been developed by the transport research board, USA. Currently most of the local road eve opment agencies use HCM for capacity analysis of roads. There have been no researches carried out to identify the applicability of HCM to the Sri Lankan condition. To depict the quality of service of the roads quantitative measures of a traffic stream are required. Level of Service (LOS) is a quality measure describing operational conditions within a traffic stream, generally in terms of service measures such as speed and travel time, freedom to maneuver, traffic interruptions and comfort. Six LOS are defined based on service flow rates of roads. Letters designate each level from A to F with LOS A representing the best operating conditions and LOS F the worst. Though the local roads have acceptable LOS, the results obtained from both HCM 2000 andl986 have not reflected it It is required to identify the factors which affect the LOS. For that a sample of two way - two lane roads were selected. For the selected sample flow vs. density curves have been developed by considering traffic data and speed survey data. Based on the literature findings and data collected from the field, six LOS for the urban minor arterial roads have been defined.
item: Conference-Full-text
Applicability of HCM 2000 to Determine the Level of Service in Urban Arterial Roads, Sri Lanka
(2014-05-07) Mampearachchi, WK; Jayasuriya, WWC; Senaratne, SAMANI; Sumanathissa, RPP
Abstract: The objective of this research is to identify the applicability of Highway Capacity Manual (HCM) to determine the Level of service in urban minor arterial roads in Sri Lanka. HCM has been developed by the transport research board, USA. Currently most of the local road development agencies use HCM for capacity analysis of roads. There have been no researches carried out to identify the applicability of HCM to the Sri Lankan condition. To depict the quality of service of the roads quantitative measures of a traffic stream are required. Level of Service (LOS) is a quality measure describing operational conditions within a traffic stream, generally in terms of service measures such as speed and travel time, freedom to maneuver, traffic interruptions and comfort. Six LOS are defined based on service flow rates of roads. Letters designate each level from A to F with LOS A representing the best operating conditions and LOS F the worst. Though the local roads have acceptable LOS, the results obtained from both HCM 2000 and1986 have not reflected it. It is required to identify the factors which affect the LOS. For that a sample of two way - two lane roads were selected. For the selected sample flow vs. density curves have been developed by considering traffic data and speed survey data. Based on the literature findings and data collected from the field, six LOS for the urban minor arterial roads have been defined.
item: Conference-Abstract
Applicability of standard density in QC and QA of asphalt surfacing
(Department of Civil Engineering, University of Moratuwa, 2021-10) Rathnasiri, P; Mampearachchi, WK; Perera, HLK
The significance of quality control and quality assurance at the compaction operation in the asphalt pavement has long been recognized by the industry since the compaction maintains the volume of air in the asphalt, which has a profound effect on pavement performance and pavement service life. As a compaction quality control parameter, the degree of compaction, expressed as a percentage ratio between field density and the reference density, is used in the pavement industry. There are several methodologies to establish the reference density to formulate the degree of compaction in the present. However, for decades, measuring densities from daily laboratory compacted samples during construction (Marshall Density) has been the mainstream practice to establish the reference density in Sri Lanka. The major drawback of establishing Marshall laboratory density as a reference density is its inability to represent any unnoticed material or plant variations in the field. This study focuses on solving the aforementioned constraint by developing a new systematic approach called the ‘Standard density method’ to establish the reference density. The standard density is determined as the mean value of densities of Marshal test specimens from morning and evening operations only for a specified number of days after the commencement of construction. This study aims to evaluate the feasibility of the concept of standard density method by comparing current practice with the proposed method. In-place density readings and their respective Marshall laboratory density measurements were collected from different road projects, and the compaction performance was evaluated according to the degree of compaction (at least 97 percent of reference density) in both the existing and proposed methods. To increase the reliability of this comparison, method comparison hypothesis testing (student t-test) was developed for both the existing method and the proposed method to analyze the compaction performance. This t-test was designed to support the alternative hypothesis ‘in-place density > 97% of reference density (from Marshall density & standard density)’. According to hypothesis test results, the analysis reveals a significant correlation in compaction rates between the current and proposed methods (significant at a 5% level of significance). Moreover, the study shows that the hypothesis mentioned above can be rejected only in the standard density method if any material or plant variations have occurred in the project; in addition, these hypothesis rejections appear after a considerable time period from the commencement of the construction.
item: Conference-Full-text
Applications of molecular dynamics in asphalt pavement mixture studies
(Springer, 2021) Wan, H; Chu, L; Fwa, TF; Pasindu, HR; Bandara, S; Mampearachchi, WK; Fwa, TF
The rapid development of high-performance computing facilities and techniques in recent years has made molecular dynamics (MD) a feasible tool for studying the behaviors of asphalt mixtures under various operating conditions. MD is capable of building relationships between chemical structures of material and its macroscopic properties. This study first conducts a literature review of the various applications ofMDin asphaltmixture studies. A summary is made on the techniques and approaches adopted by researchers, and the main application areas of MD in asphalt mixture studies so far. Next, based on the basic concepts of MD, an analysis is performed to evaluate the strengths of the different techniques and approaches adopted, including the types of molecular models employed. Also evaluated are their relative abilities in explaining the behaviors of asphalt mixtures, such as mechanical properties, self-healing and rejuvenator diffusion behaviors, and the stability of asphalt-aggregate interfacial bonding under the influence of several factors. Based on the results of these evaluations, the limitations of MD applications in asphalt mixture studies would be identified. Finally, taking into consideration the strengths and limitations of MD, possible new techniques and potential new application areas are proposed and explained.
item: Conference-Full-text
Areca fiber reinforced alkali-activated black cotton soil using class f fly ash and limestone powder for pavements
(Springer, 2021) Chethan, BA; Shankar, AUR; Pasindu, HR; Bandara, S; Mampearachchi, WK; Fwa, TF
Alkali activation has gained importance in place of cement treatment in construction due to reduced CO2 emissions. The precursors that are rich in silica, alumina, and calcium can be used for soil stabilization with a suitable alkali solution. In this investigation, 0–45% class F fly ash with a constant 5% limestone powder was used to stabilize black cotton soil. These mixes were reinforced with 0.5% areca fibers and stabilized using the alkali solution. Alkali solution was prepared using 8 molar NaOH solution and Na2SiO3 solution with Na2SiO3/NaOH of 1.5. The use of limestone powder has favoured the quick UCS gain on 3 days of room temperature curing. Fiber reinforcement has shown a significant influence on flexural strength and fatigue life improvement. Areca fibers reinforcement has resulted in enormous resistance to plunger penetration during the unsoaked CBR test. However, on further 4 days of soaking, samples lost the bonding and exhibited low CBR. The SEM images showed the compact microstructure of the set mix. The formation of cementitious products is evident from the XRD micrograms due to the dissolution of silica, alumina, calcium, and other compounds by the alkali solution. When subjected to wetting–drying and freezing–thawing durability tests, the set mixeswere failed due to leaching of mineral constituents and further breaking of soil structure. Even though stabilized specimens exhibited significant strength improvement in dry conditions, they are unsuitable in wet conditions.
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Asphalt pavement texture level and distribution uniformity evaluation using three-dimensional method
(Springer, 2021) Dong, S; Han, S; Pasindu, HR; Bandara, S; Mampearachchi, WK; Fwa, TF
To supplement the research on the evaluationmethod of asphalt pavement texture, novel three-dimensional (3D) methods are proposed. First, pavement textures were measured in laboratory from asphalt mixture specimens using laser texture scanner (LTS), and the macro-texture and micro-texture were extracted based on spectrum analysis techniques. Then, macro-texture level evaluation indices f 8mac and f 9mac together with micro-texture level evaluation indices f 8mic and f 9mic were proposed based on the gray level co-occurrence matrix (GLCM) method, and the hyperparameters existing inGLCMwere discussed. Through the correlation analysis with mean texture depth (MTD) measured by sand patch method (SPM) and friction coefficient μ measured by walking friction tester (WFT), the optimum pavement texture level evaluation indices were determined. Additionally, the evaluation index σ of distribution uniformity of pavement texture (DUPT) was proposed based on the uniformity of deviations between sub-surfaces and the average surface of pavement texture. Finally, the correlations of σ with texture profiles were studied. The results show that f 8mac and f 8mic are the optimum indices for pavement texture level. MTD has significant correlation with f 8mac, and the correlation coefficient R is 0.9348; friction coefficient μ has significant correlation with f 8mic, and the R is 0.8030. The hyperparameters of GLCM selected in this study were proved effective. Moreover, the effectiveness of σ is also validated by calibratingwith standard grooved surface. It can be concluded that the proposed indices in this study are suitable to the evaluation of pavement texture level and pavement texture distribution.