Back-Calculation of Resilient Modulus of Lightly Stabilized Granular Base Materials from Cyclic Load Testing Facility

Resilient moduli of pavement layers are the basic input parameters for the design of pavements with multiple layers in the current mechanistic empirical pavement design guides. Field measurements are generally believed to provide accurate values to back-calculate pavement layer moduli, but the tests to measure the relevant parameters are expensive, difficult to perform, and cause disturbances to the public. Therefore, the back-calculation of pavement layer moduli from laboratory scale model testing has been a focus of recent pavement research. This paper presents a back-calculation analysis to evaluate pavement layer moduli by using a three-dimensional numerical model developed using the FLAC3D finite difference software. The pertinent measurements that are required for the back-calculation analysis were collected from a cyclic load testing facility under traffic type cyclic loading conditions, with a typical pavement structure consisting of a granular road base lightly stabilized with cement–fly ash over an expansive soft clay subgrade. This study indicates that the stabilized base material had cross-anisotropic resilient properties, with an average vertical resilient modulus of 2,875 MPa and an average horizontal resilient modulus of 1,598 MPa. From this investigation, the resilient moduli of the stabilized granular base layer and subgrade clay were reliably back-calculated from the analysis by using the FLAC3D numerical model.