Discrete element analysis of a cross-river tunnel under random vibration levels induced by trains operating during the flood season

Abstract

Floods result in many problems, which may include damage to cross-river tunnels. The cross-river tunnel, as a new style of transportation, deserves a large amount of attention. In this paper, a large-scale cross-river tunnel model is proposed based on discrete element method (DEM). Micro parameters used in the model are calibrated by proposing a triaxial numerical model. Different in situ strata, high water pressures of normal flood-water levels and random vibration levels induced by running trains are taken into account to evaluate the dynamic characteristics of a high-stress tunnel in deformation and stress analysis. The results show that the upper half of the tunnel, including the concrete lining and the surroundings, is at higher risk than the lower half. Vibration waves transferring into the surroundings undergo an amplification process. The particles of the surroundings at the vault of the tunnel separate and move downward and then reassemble during the dynamic vibrations. The vibration levels, represented by particle accelerations, are lower under flood conditions than those under normal conditions. As train speed increases, the acceleration of the track and particles in the foundation increases, accompanied by a decrease in deformation.

摘要

目的

揭示汛期及常水位条件下地铁随机振动荷载作用下越江隧道管片及周边岩土体的动力响应及变形机制。

创新点

建立越江地铁隧道二维离散元模型,并采用随机振动荷载模拟地铁行车荷载,揭示汛期和常水位条件下地铁行车荷载对越江隧道稳定性的影响。

方法

采用离散元方法进行数值仿真。1. 基于室内三轴试验和离散元数值拟合得到土层的各细观参数;2. 采用不同接触模型对隧道内钢轨、轨枕、管片以及周边岩土体进行建模;3. 将地铁随机振动荷载施加在钢轨上,对管片及周边岩土体不同区域内颗粒的受力及变形进行监测并分析。

结论

1. 位于隧道上半部分的周边岩土体颗粒振动偏大;2. 随着距离的增大,振动波在周边岩土体内先放大后减小;3. 汛期水位条件下地铁行车荷载对管片和周边岩土体的振动影响较小,但是对隧道变形影响较大。