DYNAMIC RESPONSE OF COUPLED SYSTEM OF TRACK AND LAYERED FLUID-SATURATED GROUND UNDER MOVING
HIGH-SPEED LOADS

Based on the Biot’s theory of two-phased poroelasticity medium, the dynamic Green’s functions of a layered saturated half-space under surface moving loads are derived, and then the 2.5D indirect boundary element method is proposed to study the dynamic response of the coupled system of track and layered fluid-saturated ground under high-speed moving loads. The method is verified by comparisons with those in literatures. Numerical calculations are performed by taking uniform saturated ground and a single saturated layer over a saturated half-space as models and the effects of moving velocities and of the saturated layer on the dynamic response are analyzed. It is shown that: the dynamic response of a coupled system in the case of layered saturated ground is essentially different from that in the case of uniform saturated ground; when the train speed approaches the Rayleigh velocities of sites, the resonance of the coupled system takes place, which results in a large dynamic response and significant pore pressure; the dynamic response of a coupled system is the largest in the case of undrained conditions, the second in the case of drained conditions and the lowest in the case of dry conditions. The porosity of a saturated layer, the stiffness ratio of bedrock to the saturated layer, and the thickness of the saturated layer all have significant influences on the dynamic response.