天津地铁6号线车站深基坑开挖下围护结构及墙后地表变形特性分析

依托天津地铁6号线金钟街站深基坑工程,采用FLAC3D对基坑开挖及支护全过程进行数值模拟,并对其关键影响因素及墙后地表和地连墙变形的相关性进行系统分析.研究结果表明:随着基坑开挖深度的增加,开挖深度对变形的影响增大,地连墙最大侧移位置不断下移,地表最大沉降点位置逐渐远离基坑边缘;地连墙侧移、地表沉降随基坑长宽比的增加有增大的趋势,但最终数值趋于平缓;基坑插入比对基坑变形控制作用较小,而地连墙厚度对基坑变形控制作用明显;随着支撑刚度的增加,地连墙侧移、墙后地表沉降呈现减小的趋势,但支撑刚度过大不会达到预想的控制变形的效果.最终得到墙后地表最大沉降与墙体最大侧移的比值为1.15,但墙后地表沉降包络面积与墙体侧移包络面积的比值为1.82.

Analysis of ground surface deformation and retaining wall deflection characteristics under excavation of deep foundation pit of station in Tianjin subway line 6

Based on the deep foundation pit project of Jinzhong Street Station in Tianjin Subway Line 6,numerical simulation is carried out by adopting FLAC3D to analyze the complete process of excavation and support of foundation pit.The key influence factors and the correlation between ground surface deformation and retaining wall deformation are then analyzed.The results show that,with the increase of excavation depth,excavation depth will have greater influence on the deformation,the maximum lateral displacement of the diaphragm wall will keep moving down,and the maximum ground settlement will gradually moving away from the edge of foundation pit.The lateral displacement of the diaphragm wall and the ground surface settlement tend to increase with the increase of foundation pit's length-width ratio,but the final values tend to remain steady.The foundation pit deformation is less influenced by the insertion ratio,while it is obviously influence by the thickness of diaphragm wall.With the increase of support stiffness,the lateral displacement of the diaphragm wall and the ground surface settlement tend to decrease,but the excessive support stiffness will not be supposed to meet the requirement of deformation control.Eventually,the ratio between the maximum ground surface settlement and the maximum lateral displacement is 1.15,and the ration between the envelop area of the ground surface settlement and that of the lateral displacement is 1.82.