移动荷载作用下土体动力反应数值模拟

在研究轨道振动荷载的产生机理基础上,归纳出一个能够涵盖速度、线路不平顺、轮重、轨枕对轮载的分散作用等因素在内的轨道荷载解析表达式,以此作为输入施加到土体模型上,利用ANSYS模拟地基土在轨道移动荷载作用下的三维瞬态弹塑性反应。通过计算得到土体不同位置位移和加速度时程曲线,并得出如下结论:荷载刚施加时地面位移会有一个突变,但是随着荷载的移动会达到一个稳定值,并随着水平面内远离轨道,该值逐渐衰减;荷载刚刚施加时加速度会有一个突变值,随着荷载的移动逐渐趋于零。轨道机车速度对竖向方向的位移和加速度影响不大。

Numerical Simulation of Soil Dynamic Response under Moving Loads

A model of moving traffic vibration loads is developed on the basis of vibration mechanism analysis. Some factors related to vibration such as the speed or bumping motion of the train, the weight of the wheels, and the dispersion effect of the sleeper car are included in this model. A three-dimensional (3D) elastic-plastic finite element model of foundation soil is then established in ANSYS. The Drucker-Prager model is chosen to simulate the soil''s non-linear characteristics. The bottom of the model is constrained within the horizontal plane. A 3D viscoelastic artificial boundary is adopted to simulate the bottom of the model and the boundary condition. Under moving traffic loads, the time-history curves of the displacement and the acceleration in various places in the foundation soil are calculated, and several conclusions are drawn. When the load is stationary, the displacement exhibits an abrupt change.However, as the load moves, the displacement maintains a stable value that decreases with distance from the track. When the load is just on, the acceleration also exhibits an abrupt change, with values trending closer to zero as the load moves. Therefore, train speed has little effect on vertical displacement and acceleration.