FLAC3D-based Analysis on Subgrade Workaround of Asphalt Pavement Structures under Various Loading Conditions

Abstract

In order to reduce subgrade permanent deformation, it is significantly important to keep the subgrade behaving elastically. However, the subgrade workaround depth in the national design specifications of China is 0.8m for different pavement structures under various loading conditions. In fact, the minimum value of the workaround depth is dependent on pavement structures and loading conditions. Under this background, this research herein presents a FLAC3D-based model for quantitative analysis on subgrade workaround depths. In terms of the geometrical model, both the subgrade and pavement are simulated with layered structures: the subgrade model consists of two layers which are the roadbed soils and original ground soils, while the pavement consists of 3~6 layers according to the pavement types. In terms of mechanical models, subgrade is simulated with Mohr-coulomb model where Young’s Modulus, Poisson ratio, angle of internal friction, cohesion coefficient are various based on the layer material properties and pavement layers are simulated with the linear elastic model where Young’s Modulus and Poisson ratio are various based on the layer material properties. In terms of loading conditions, the various static vehicular and gravity loads are applied with the axle types considered. The FLAC3D simulation outputs are the stresses underlying pavement structures during the loading history. The calculated stresses are compared at different locations to determine the subgrade workaround depth. Through this research, recommendations are provided for determining the subgrade workaround depths for different pavement types.