非均布列车荷载作用下软土路基的振动分析

Ground vibration of soft subgrade subjected to a non-uniformly distributed train load

基于实测资料,假设列车轮载经钢轨传递下来的荷载由5根枕木承担。根据分担比,获得了道渣层表面非均布荷载的表达式。将道渣层视为单相弹性介质,软土地基被看成是考虑水土耦合作用的饱和多孔介质。借助势函数,利用Helmholtz矢量分解法及Fourier变换技术分别对弹性土体和饱和半空间土体进行求解,得到非均布移动荷载作用下软土地基位移、应力及孔压响应在变换域内的精确解答。利用FFT算法得到了数值结果,详细分析了荷载分布形式、观察点位置、道渣性质以及软土地基渗透系数对动力响应的影响。研究结果表明:高速情况下动力响应与低速情况有很大不同;对于软土路基,应特别注意列车高速运行时路基浅层范围内产生的孔压响应。

The ground vibration of soft subgrade subjected to a non-uniformly distributed train load is investigated analytically.Based on field test data,5 sleepers bear the dynamic loads transferred from rail,an expression of a non-uniformly distributed load is deduced by assuming that train load is distributed to sleepers with a certain proportion.Taking the ballast as elastic single-phase layer and the soft subgrade as water-saturated poroelastic half space governed by the Biot＇s theory,the governing equations of motion are solved by employing the Helmholtz decomposition theorem and the Fourier transform technique.The exact analytical solutions of the displacements,stresses,and the pore pressure of the soft subgrade are obtained in the form of integral.By introducing fast Fourier transform algorithm,the numerical results are derived;and the influences of load distribution,the position of observation,the ballast parameters and the permeability coefficient on the responses are discussed in detail.It is shown that a moving load with a high speed will generate a larger response in soft subgrade than a lower speed load;and special attention should be paid to the pore pressure in the vicinity of soft subgrade surface.