Influence of bedrock on the dynamic deflection response and dynamic back-calculation results of asphalt pavement: Insights from the numerical simulation of falling weight deflectometer tests

Abstract

The dynamic deflection response obtained by the falling weight deflectometer (FWD) test and back-calculated modulus results play an important role in road engineering. The presence of bedrock may affect the results of FWD tests on asphalt pavement. Many numerical simulation models of FWD tests have been established to obtain the dynamic response of pavement structures without considering the influence of bedrock, which prevents us from further understanding the influence of bedrock on dynamic response of asphalt pavements. Here, we consider the bedrock under asphalt pavement structures with an analysis program based on the spectral method with fixed-end boundary conditions (B-SEM). The B-SEM is employed to observe the dynamic response of a conventional asphalt pavement during the FWD test; the results are compared with those obtained by the finite element method (FEM). Semi-rigid base asphalt pavement, rigid base asphalt pavement, and flexible base asphalt pavement are simulated by the B-SEM with different bedrock depths, and the deflection results are compared and analyzed. Additionally, the bedrock’s influence on the dynamic modulus back-calculation results is investigated. The results show that compared with the FEM, the B-SEM produces results with considerable accuracy and high computational efficiency. Furthermore, shallow bedrock has an obvious influence on the dynamic deflection responses of different pavements, as well as the accuracy of the back-calculation results. The impact of bedrock on the modulus back-calculation of pavement layers is concentrated in the subbase and subgrade, with a minimal effect on the surface layer.