Evaluation of resilient modulus of unbound material to implement mechanistic-empirical pavement design(MEPD) in Sri Lanka

Abstract

Road pavement design in Sri Lanka traditionally relies on an Empirical design. This conventional approach, however, is characterized by certain limitations, particularly in its reliance on indirect material properties such as the California Bearing Ratio (CBR) value. The drawbacks of this method may result in the overestimation or underestimation of pavement design, prompting a shift towards the more reliable and accurate Mechanistic-Empirical Pavement Design (MEPD) process. Despite the advantages of MEPD, its implementation in Sri Lanka encounters challenges, including the absence of laboratory and in-situ testing equipment for modulus testing, the lack of a comprehensive soil database/soil map, and the unavailability of typical modulus values for local materials. This research endeavors to address these challenges by focusing on the development of a relationship for predicting Resilient Modulus (RM) based on other index properties of the soil. Additionally, the study aims to establish a modulus-based soil database and create a soil map for MEPD designs. To achieve these objectives, soil samples were collected from 28 locations across the country, and their basic properties were determined. Modulus tests were conducted using a Light weight Deflectometer (LWD). The validity of existing relationships for predicting RM was assessed, and subsequently, a new relationship was developed specifically for local subgrade materials. Furthermore, past soil data collected on a district basis were utilized alongside the newly developed correlation to create a comprehensive Soil Map based on RM values. In conclusion, this research successfully formulated an RM predicting model tailored to locally available unbound materials in Sri Lanka within the MEPD framework. The established soil database and soil map hold significant potential to enhance the design of road pavements in Sri Lanka, contributing to a more reliable and sustainable road infrastructure. Keywords: RM, MEPD, LWD, CBR, Unbound Material