The confinement and modulus evaluation of unbound granular base course

Abstract

This study aims to report theoretically the possible approach of confinement evaluation of unbound granular base course using the finite element method and laboratory results in order to implement current pavement material test algorithm. As is well known, repeated load triaxial (RLT) test is used to simulate the real condition of pavement materials under traffic loads by using static confinement with cyclic actuator loads. However static confining conditions in pavement structure occur only when no vehicle travels. As the effects of traffic loads and material attributes are generated when vehicles travel, horizontal stress and confinement behaviours of pavement structure were determined. The conventional pavement diagram consists of a surfacing, base-course, sub-base and sub-grade. During the load application procedure, a single wheel with a standard pressure of 750 kPa was selected. Test results showed that horizontal stress of base course layer consists of overburdened soil and passive force from applied stress. When vehicle travels pass observed point, horizontal pressures of base course layer increase from overburdened weight and complete with passive force effect depend on applied stress and its internal friction. Seemingly, the conventional RLT test with constant confinement is unable to simulate the real behaviour of pavement structure such as resilient and permanent deformation. In this study, dynamic bearing test and the confinement evaluation of unbound granular base course were introduced to explain and define limited use of pavement diagrams subjected to various conditions in order to implement the current performance test of unbound granular base course material.