苏州地铁换乘车站基坑开挖变形特性三维数值分析

3D numerical analysis of deep excavation for an interchange station of Suzhou Metro

苏州轨道交通1号线苏州乐园站为1号线(M1线)与3号线(S3线)的斜"十"字型换乘地下车站。1区基坑与2区换乘段基坑共用围护墙且基坑平面形状极不规则,基坑最大开挖深度达25.0 m,基坑开挖深度范围内存在较厚软塑-流塑高压缩性粉质黏土。因此,有必要在施工前通过数值方法预测基坑围护结构的变形,为基坑的施工方案优化提供理论参考和技术支持。采用三维快速拉格朗日方法(FLAC^(3D)),分析了苏州乐园地铁站换乘节点基坑开挖阶段围护墙的变形规律。计算结果表明:1区基坑围护结构受不同几何边界条件影响,墙体变形比较复杂,出现了墙底踢脚、向坑内刚性平移和刚性转动三种变形形态;因三维计算模型中考虑了基坑变形的空间效应,围护墙的的最大侧向变形和最大弯矩均明显小于二维模型的计算结果;2区基坑开挖引起的围护墙侧向变形明显大于1区,主要是由于较深的开挖深度和较弱的空间约束作用引起;2区基坑围护结构与平面应变条件下墙体的一般侧向变形规律基本一致,最大侧移为30.1mm。

Suzhou Leyuan Metro Station is an interchange station of Suzhou Metro Line No.1 and No.3.The excavation at the interchange part is complex and the excavation depth is up to 25.0 m.Within the depth of the excavation,the main stratum is composed of soft silty clay with high compressibility.A three-dimensional finite difference analysis with FLAC^(3D) was conducted to investigate the performance of the retaining structures during construction of the interchange part of the underground metro station and to provide some suggestions of construction measures.Based on the numerical results,the wall deformation in Zone 1 was complicated due to the boundary effect,and the maximum wall deflection was found to be about 18.8 mm.For Zone 2,the wall deformation was similar to that in plane-strain condition,and the maximum wall deflection was 30.1 mm.