2.5维有限元分析高铁荷载下弹塑性地基动偏应力与沉降

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

摘要:

为分析高铁荷载引起的弹塑性地基动偏应力分布规律并据此开展沉降计算，建立了高铁荷载下弹塑性地基2.5维有限元计算模型，将高铁荷载分别简化为准静态列车荷载和考虑随机激振力的修正列车荷载，对比了2种荷载下弹塑性地基中动偏应力的分布规律，并利用循环荷载下软黏土累积塑性应变模型计算了均质弹塑性地基沉降。研究表明，弹塑性地基中动偏应力呈马鞍形分布，最大值出现在道床边缘附近土体中；车速小于土体瑞利波速时沿地基表面和轨道中心沿深度方向土体动偏应力的衰减曲线光滑，车速接近或大于土体瑞利波速时，在马赫效应的影响下动偏应力呈波动衰减；修正列车荷载下弹塑性地基中动偏应力分布更符合实际情况；高铁运营初期地基沉降较快，随时间增加沉降速率逐渐趋于稳定；计算高铁运行产生的地面沉降时，需同时考虑列车运行速度和随机激振力的影响。

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.