地铁循环荷载作用下交叉隧道沉降分析

Analysis of settlement of cross tunnels under cyclic metro loading

采用FLAC3D软件建立了交叉隧道的三维有限差分模型,以人工数定激励力模拟列车荷载,计算列车动荷载作用下土体的变形和应力。采用修正动偏应力长期沉降计算模型,结合分层总和法计算软土的沉降,预测交叉隧道的长期沉降规律。分析3种不同行车工况下地基长期沉降,工况1为一辆列车单独通过1#隧道,工况2为一辆列车单独通过2#隧道,工况3为两辆列车同时通过1#和2#隧道。对比不同的列车行驶速度、隧道衬砌刚度及厚度对隧道地基的长期影响。结果表明,由列车荷载引起的地基沉降主要集中在距隧道中心轴20 m范围内;在工况3下土体沉降大于工况1、2沉降之和;车速越快,沉降越小;衬砌刚度和厚度越小,沉降越大,且衬砌厚度对沉降的影响较大,衬砌刚度影响较小。

Three-dimensional finite difference model of cross tunnels is established by FLAC3 D to compute deformation and stress of soft soil under metro train cyclic loading which is modeled by artificial numerical exciting force. Modified dynamic deviatoric stress model for long-term settlement of soft soil combined with layer-wise summation method are adopted to calculate tunnel settlement and predict long-term settlement of cross tunnels. Long term settlement in three train-running cases is studied. Case 1, one train traveled through tunnel #1, case 2, one train traveled through tunnel #2, case 3, two trains traveled through tunnel #1 and tunnel #2 separately at the same time. Influences of train speed, stiffness and thickness of tunnel lining on long-term settlement of cross tunnels are studied. The results show that the settlement induced by train loading mainly distributes within 20 m from the central axis of tunnels. Sum of settlement in case 1 and case 2 is less than settlement in case 3; and tunnel settlement decreases with the increasing of train speed, stiffness and thickness of tunnel lining; while the influence of thickness of tunnel lining is more than stiffness of the lining.