Browsing by Author "Dulwala, NP"

Now showing 1 - 2 of 2

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-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.