列车荷载作用下路轨系统及饱和弹性半空间上覆盖土层的动力响应

用解析法研究了移动列车荷载作用下下卧成层地基的路轨系统的动力响应问题。将整个系统分为上覆路轨系统和下卧土体。对于路轨系统,将钢轨简化为无限长弹性Euler梁,将枕木简化为连续质量块,同时考虑由Cosserat模型描述的道渣层。在实际工程中,地下水位往往位于地表以下几米处,因此将下卧土体考虑为成层土,其中,上层为弹性介质,下层为由Biot波动方程描述的饱和弹性半空间。在Fourier变换域内,联立铁路系统和下卧土体的动力方程,求解列车荷载作用下钢轨位移、加速度,土体位移、加速度,孔压表达式。利用数值积分方法对表达式进行Fourier逆变换,得到钢轨位移、加速度,土体位移、加速度,孔压在时域内的表达式。着重研究了弹性层厚度、密度、刚度和道渣层质量对钢轨动力响应的影响。计算结果表明,在低速情况下,这些参数对钢轨动力响应影响都很有限,但在高速情况下,这些参数对钢轨动力响应的影响都很大。

Dynamic response of railways on layered half-space subjected to moving train load

A three-dimensional study is presented,where the steady state response of a track system and layered half-space soil medium subjected to the load induced by the passage of a moving train is investigated by the substructure method.Practically,due to the ground water table being of several meters beneath the ground surface,the soil profile can be divided into two layers: the upper layer modeled by elastic medium and the lower layer by fully saturated poroelastic medium governed by the Biot’s theory.In the meanwhile,the rails are regarded as an infinitely long Euler beam,and the sleepers are represented by a continuous mass.The effect of the ballast is accounted for by introducing the Cosserat model for granular medium,and the train is described by a series of moving axle point loads,depending on the geometry of the train.The influence of the thickness,mass and rigidity of the elastic layer and mass of the ballast on the displacement respons of rails is carefully investigated.Numerical results show that the influence of these parameters is significant under high train velocity,while insignificant under low velocity.