Shakedown Analysis of Unbound Granular Materials using Accelerated Pavement Test Results from New Zealand's CAPTIF Facility

Abstract

This paper reports on one aspect of an ongoing research project that is aimed at investigating the nonlinear resilient and permanent deformation behaviour of Unbound Granular Materials (UGM) using laboratory and field test results. Insufficient evidence is currently available to confirm the reliability of the proposed linkage between the Shakedown ranges defined via the Repeated Load Triaxial (RLT) test and in-situ performance of UGM. Further investigations on this specific topic were necessary to confirm predictions made by the laboratory test results by examining the results of a series of accelerated pavement tests. The examination of the relationship between laboratory shakedown parameters and field test results is described in detail. The paper shows that the shakedown behaviour of UGM observed in RLT tests can also be observed in field tests. In particular an empirical approach was formulated and calibrated to determine basecourse permanent strain rate using data from RLT and field tests for two different UGM. From the results of the tests a correlation was found to exist between the resilient strain rate and the permanent strain rate as long as the shear stresses within the basecourse material were sufficiently small.