Dynamic Deviatoric Stress and Settlement of Elastic-Plastic Foundation at High-Speed Train Moving Load by 2.5D FEM

Abstract:

In order to analyze the dynamic deviatoric stress distribution law and calculate the settlement of elastic-plastic foundation by high-speed train load， a 2.5D FEM（finite element model） for elastic-plastic foundation under high-speed train load was derived. The high-speed train load was simplified to quasi-static train load and the modified train load including random excitation force. The distribution of dynamic deviatoric stress in the elastoplastic foundation at two kinds of loads was comparativly calculated. The settlement of homogeneous elastoplastic foundation was calculated by the cumulative plastic strain model of soft clay at cyclic loading. The results show that the dynamic deviatoric stress in the elastoplastic foundation is distributed in a saddle shape， and the maximum value appears in the soil near the edge of the foundation bed. When the train speed is less than the Rayleigh wave speed of the soil， the attenuation curve of the dynamic deviatoric stress in the foundation is smooth. When the train speed is close to or greater than the Rayleigh wave speed of the soil， the dynamic deviatoric stress exhibits a fluctuating attenuation under the influence of the Mach effect. The dynamic deviatoric stress distribution is more consistent with the actual situation at modified train load. The foundation settlement is relatively fast at the initial stage of high-speed rail operation， and the settlement rate gradually stabilizes. When calculating the ground settlement caused by the high-speed rail operation， the influence of train speed and random excitation force should be considered at the same time.

Key words:high-speed railway;2.5D FEM;elastoplastic foundation;dynamic deviatoric stress;settlement