The Unbound Granular Base Course Design with Ultimate Strength Concept

Abstract

This study aims to introduce alternative design procedures for a flexible pavement base course by utilizing the ultimate strength criteria with sophisticated laboratory results of base course materials. Current pavement design mostly avoids all complicated behaviors of an unbound granular base layer considered only as a layer transferring traffic loads to underneath layers regardless on the base course deterioration. Based on the design protocol, there are only the design criterion of the horizontal tension and the vertical compression occurring at the bottom of asphalt layer and at the top of subgrade, respectively. The real behavior of a base course under traffic loads has been rarely accounted into the pavement design protocol. Nowadays, traffic is growing in terms of magnitudes and quantities far beyond the past and causing the premature deteriorations in a base course layer leading to a major damage in pavements. The study presents theoretically the more suitable approach of the stress and strain distribution in a flexible pavement using the finite element method. In this study, the pavement example of the convention pavement structure consisting of a surfacing, a base course, a sub base course, a subgrade with a single wheel load of the 750 kPa standard pressure was selected was established to investigate all pavement phenomena.The effects of a uniform design pressure and material attributes which they were generated when vehicle travels, hence stress and strain contributing between tires and pavement layers were investigated. Moreover, the new design criteria for an unbound granular layer were defined as the ultimate strength design and the bearing capacity factor resulting from the application of the shallow foundation bearing capacity concept within the California Bearing Ratio (CBR) results. Our findings were reported and used to draw up the guideline and recommendation on the current pavement analysis and design.