饱和软土二维-三维列车振动响应对比分析
Comparison of 2D and 3D Dynamic Responses of Saturated Soft Soil due to Metro Train Load

针对岩土工程中常用二维模型等效三维模型进行数值计算的方法，对列车运行引起的二维和三维动力响应进行了分析.根据钢轨-扣件-隧道-地基纵向模型得到作用于隧道道床上的振动荷载，基于循环流动本构模型和土-水完全耦合理论，计算了列车平均时速下饱和软土层二维和三维的振动响应规律.研究结果表明：两种模型的地表振动加速度、位移以及隧道周围超孔隙水压力在横截面内规律基本相似但数值相差较大；二维-三维地表加速度比和位移比最大值分别可达9倍和6倍，加速度振级相差可达15 dB；隧道周围的二维-三维超孔压比在1.5~3.5之间，单次振动超孔压累积值可达4.36 kPa和1.69 kPa，且在隧道竖轴左右45°及135°位置处超孔压力累积最为明显；振动荷载形式、纵向土层振动、固结速度是造成饱和土软土二维-三维列车振动响应差异的主要原因.
：As for the common practice that the two-dimensional(2D) model is approximately employed to the three-dimensional(3D) model in numerical calculation of geotechnical engineering, 2D and 3D dynamic responses induced by the metro train vibration were analyzed. Train vibration load on the track bed was determined firstly according to the rail-fastener-tunnel-subgrade longitudinal model, then 2D and 3D dynamic responses of the tunnel and the saturated soft ground were simulated based on the cyclic mobility model and the fully coupled soil-water theory when the metro train moved at an average speed. The results show thatdynamic responses of the ground surface acceleration, displacement and excess pore water pressure (EPWP) around the tunnel in 2D and 3D models are similar but significant differences exist in the quantitative manner.The maximum acceleration and displacement ratios between 2D and 3D models can be as much as ninefold and sixfold, with a maximum acceleration level discrepancy of 15 dB; the ratio of EPWP around the tunnel ranges from 1.5 to 3.5, and the accumulated EPWP in 2D and 3D models reach 4.36 kPa and 1.69 kPa, respectively, the accumulation of EPWP is obvious at the locations of 45° and 135° around the tunnel. Train vibration load, longitudinal soil vibration and consolidation rate are the three reasons accounting for the response discrepancy between 2D and 3D models