单圆双线地铁隧道基底粉细砂层动力响应分析

以南京地铁10号线过江段江北大堤附近典型截面为例,分别考虑了单线通行工况与会车8s、会车12s及会车16s3种典型会车工况,建立了隧道-土体有限元模型,分析了单圆双线隧道基底粉细砂层动力响应。结果表明,隧道基底粉细砂层加速度峰值随垂直深度增加而呈指数型衰减,到达23m深度时,4种工况加速度峰值已非常接近。基底下卧层土体最大位移随深度呈线性减小趋势,考虑各工况下各深度位置最大竖向位移,会车8s工况会车16s工况会车12s工况单车8s工况。列车动荷载所激发的粉细砂超静孔隙水压力约为静水压力的1%。粉细砂层最大超孔压随基底深度呈指数型衰减趋势。粉细砂层内最大孔隙水压力与总应力比值小于1,隧道基底粉细砂层不会发生液化。该结果可用于调控隧道控制截面位置基底粉细砂层动力响应与可液化性研究。

Dynamic Response of Silty Fine Sand Layer BeneathSingle-hole Double-track Subway Tunnel

A typical profile of the cross-river section of Nanjing Metro Line 10 near the North Yangtze River dike was taken as an example. Single running scenario and three typical meeting scenarios, namely 8-s meeting, 12-s meeting, and 16-s meeting scenarios were considered, and a tunnel-soil finite element model was developed to analyze the dynamical response of the silty fine sand layer beneath the singleh-ole double-track tunnel. Results showed that the peak acceleration values of the fine silty sand decayed exponentially with almost the same value when reaching a depth of 23 m for all the four scenarios. The maximal displacements of the soil layer beneath the tunnel decreased linearly along the depth. The maximal vertical displacement was observed for the 8-s meeting scenario, followed by the 16-s, 12-s meeting, and the 8-s single running scenarios. Moreover, the excessive pore water pressure induced by the dynamic load of the subway train was only a hundredth of the static pore water pressure. The maximal pore water pressures also exhibited an exponential attenuation trend. Finally, the ratio of the maximal pore water pressure to the total stress was less than 1, meaning that liquefaction would not occur in the fine silty sand layer beneath the tunnel. The investigation results can be used to regulate the dynamic response and the liquidability of the fine silty sand layer beneath the tunnel at controlled sections.