列车交通荷载作用下地基土单元体的应力路径

Stress path in soil element of ground under moving traffic loads

为研究列车交通荷载作用下地基内部动应力特征以及土体单元经历的应力路径,基于2.5维有限元数值方法建立轨道-路堤-地基耦合分析模型,其中轨道在轮轴荷载作用下的弯曲变形用欧拉梁来描述,而列车荷载被简化为作用于轨道上的单个或多个移动轮轴荷载,通过基于半解析的方法推导得到了地基中的动应力解答。剖析列车轮轴荷载作用过程中地基内部土单元体经历的应力路径和其中的主应力轴旋转现象;发现当列车速度低于地基剪切波速时,不同速度的荷载作用下不同地基深度处的土单元应力路径曲线形状都很相似;而当荷载速度增大到接近或者超过地基剪切波速时,土单元应力路径曲线和应力分布均发生很大改变。分析结果为研究交通荷载作用下软土的动力特性及地基长期附加沉降提供了基础。

In order to analyze the characteristic of the dynamic stress and stress path of soil element beneath railway embankment during the passage of train moving loads, a theoretical model of track-embankment-ground was presented by employing a 2.5-dimensional finite element method. Vertical deformation of the track was described by the Euler-Bernoulli beam model, and the train moving loads were simplified as a series of moving wheel axel loads. Stress path and the rotation of principal stress axes in the soil element at different positions were obtained. The influences of train speed and shear wave velocity of the soil were studied. Analyses of stress variation and distribution in ground may be employed for studying of the dynamic properties of soil under traffic loadings and long term settlement of embankment.