圆砾层地铁车站深基坑变形特征三维数值分析

3D Numerical Analysis of Deep Station Excavation Constructed in Round Gravel Strata

以南宁轨道交通一号线广西大学站基坑工程为背景,应用FLAC3D数值计算软件对基坑开挖的全过程进行模拟分析。通过对比计算结果和监测数据,总结了圆砾层中地铁车站深基坑的连续墙水平变形及周围地表沉降变形特征。分析结果表明:基坑开挖对周围土体的影响范围约为4H(H为基坑开挖深度),总体沉降值比较小,产生最大沉降值的位置距离基坑边缘约0.6H;基坑开挖对周围环境的主要影响区为2H,次要影响区为2～4H。数值模拟结果还表明:对于埋藏有深厚圆砾层的地区,Mohr-Coulomb模型适于预估3H范围内的土体沉降,在此范围之外,地表沉降很难收敛,计算结果与实测值误差较大。

Based on the excavation of the Guangxi University Station of the Nanning Metro Line 1, this paper employs the numerical analysis software FLAC3D to simulate the complex excavation process. By implementing a deep comparison between the numerical resuhs and the monitoring data, the research draws a general conclusion about the deformation characteristics of diaphragm walls and surrounding ground surface of subway station excavations in round gravel strata. The analysis results indicate that ： （ 1 ） the influential range of the surrounding ground by excavation is about 0 - 4H （ H the depth of excavation } ; （ 2 ） the overall settlement is relatively small, and the maximum val- ue usually occurs in places within about 0.6H from the excavation border; （3） the primary influential range is 0 - 2H＇, and the secondary influential range is 2 -4H; （4） for such sites rich in round-gravels, Mohr-Coulomb model can give satisfactory predications within the 3H range, but cannot reasonably be applied outside this range because of the divergence which would produce considerable errors between numerical results and monitoring data.