DYNAMIC RESPONSE OF THE SATURATED GROUND- SUBGRADE UNDER HIGH-SPEED BRAKING LOADS

The dynamic stress responses of the layered pavement structures subjected to a variable-speed moving load are analyzed. The Dirac function is used to obtain the expression for a variable-speed moving load. Based on Biot's consolidation theory, Green's function of a layered saturated ground under moving loads is given by combining the Fourier transform, potential function decomposition as well as the transmission matrix method. The dynamic response of the layered saturated ground subjected to a variable-speed moving load can be obtained by convolving Green's function and variable-speed moving load function in the spatiotemporal domain. The results show that the variable-speed moving load has a significant effect on the dynamic stress response of the layered pavement structures. The wheel-pavement friction (braking force) mainly affects the dynamic response of the upper-layer pavement structure. In contrast, the variable-speed effect (acceleration) has a significant effect on the dynamic response of the lower-layer saturated ground, especially for the dynamic shear stress at the high-speed braking load. The effect of variable-speed braking loads on the dynamic response of saturated ground increases with growing initial speed and braking force/acceleration. The lower the stiffness of the upper-layer pavement structure, the deeper the saturated ground, and the poorer the permeability, the more pronounced the dynamic stress amplification effect induced by variable-speed braking loads.