空沟对列车运行引起的地基振动隔振效果研究

Screening efficiency of open trenches to train-induced ground vibration

为研究空沟对高速列车引起地基振动的隔振效果,在已有研究基础上改进出一种新的解析研究模型。模型中首次运用了饱和半空间模型来研究地基上隔振沟对高速列车的隔振效果;隔振沟则通过在饱和半空间土体上设置3个合适宽度、截面为矩形的弹性层来模拟;中间矩形弹性层为路堤,路堤上方放置了枕木与轨道。枕木与轨道分别通过纵向异性Kirchhoff薄板与Euler梁来模拟,饱和土地基采用Biot多孔饱和介质理论来描述。控制方程通过傅立叶变换与傅立叶级数展开,在变换域中进行求解。研究表明,随着列车运行速度的提高,空沟的隔振效果明显提高;饱和土体固-液相的耦合作用对隔振沟的隔振效果的影响明显,尤其当列车运行速度超过土体表面Rayleigh波速时,随着土体渗透系数的增加,空沟隔振效果显著降低。此外,列车运行速度超过土体表面波速时,饱和土地基上空沟的隔振效果明显优于相应单相弹性地基上空沟的隔振效果。

In order to investigate the screening efficiency of open trenches to the train-induced ground vibration, a new analytical model is proposed based on existing researches. The ground is firstly modeled as a fully saturated poroelastic half-space in the research of vibration isolation to moving trains. The trenches are obtained by placing three rectangular elastic layers with appropriate widths on the poroelastic half-space. The middle elastic layer is treated as the embankment, upon which the rails and the sleepers are placed. The sleepers and the rails are modeled as transversely isotropic Kirchhoff plate and Euler-Bernoulli beams respectively. Blot＇s theory is applied to characterize the poroelastic half-space. By Fourier transforms and Fourier series, the governing equations are solved in the transformed domain. The investigation reveals that, the screening effects of open trenches improve as the train speed increases. The effects of coupling between the soil skeleton and pore water on the screening efficiency is apparent, especially when the train speed exceeds the Rayleigh wave speed of the half-space; the screening efficiency of open trenches decreases obviously as the permeability of the ground increases. In addition, the screening efficiency of the trench on poroelastic half-space is much better than that on elastic half-space to the train-induced ground vibration for the supercritical-train-speed case.