Dynamic Stiffness Modulus for Pavement Subgrade Evaluation

Abstract

To avoid cumbersome traditional techniques for pavement subgrade evaluation such as the California bearing ratio and the plate loading test, several nondestructive tests (NDT) as well as suitable analysis processes have been introduced to assess the properties, the structural condition, the residual life, and the possible need for improvement of pavement soils. This paper deals with the implementation of the falling weight deflectometer (FWD), one of the most popular NDT techniques for pavement evaluation. The goal is twofold: a simplified dynamic simulation of the FWD test is first presented and consequently the dynamic stiffness modulus (DSM) is proposed as an indicator of pavement subgrade performance. Computation of the DSM requires only the central deflection measured during FWD testing and can be directly performed in the field. A preliminary analysis of field data suggests that the DSM represents the average dynamic modulus of elasticity of the subgrade material. Furthermore, it follows notably well the trends in the results of conventional nondestructive testing techniques and can be consequently adopted to describe the performance of pavement subgrade soils under traffic-induced dynamic loads.