深基坑开挖和降水对紧邻既有地铁隧道的影响

Effect of Deep Foundation Pit Excavation and Precipitation on Adjacent Subway Tunnel

以深圳某深基坑工程为案例,利用Midas-GTS有限元软件建立三维数值模型,基于流固耦合理论分析基坑开挖和降水对紧邻既有地铁隧道产生的影响,以期为实际的基坑设计和施工提供有效的数据参考。结果表明:基坑降水造成的地下水渗流具有空间差异性,基坑长边侧渗流速度大于短边一侧,且地铁隧道处水力梯度较大;最大总位移出现在地铁隧道中部,且近基坑侧隧道产生的总位移比远离基坑侧隧道多一倍,其中最大水平位移发生在隧道侧边,最大沉降位移发生在隧道顶部;测斜位移曲线具有明显的拐点,临近地铁隧道的基坑长边一侧在35~40 m深度处可能形成潜在滑动面。

Taking a deep foundation pit project in Shenzhen as an case study,the three-dimensional numerical model was established by using Midas-GTS finite element software.The influence of foundation pit excavation and dewatering on adjacent existing subway tunnels was analyzed based on the fluid-solid coupling theory,which will provide an effective data reference for actual pit design and construction.The results show that the groundwater seepage caused by foundation pit dewatering has spatial difference.The seepage velocity on the long side of foundation pit is greater than that on the short side,and the hydraulic gradient at the subway tunnel is larger.The maximum total displacement occurred in the middle of the subway tunnel,and the total displacement generated by the tunnel near the foundation pit was twice as much as that far away from the foundation pit.The maximum horizontal displacement occurred at the side of the tunnel,and the maximum settlement displacement occurred at the top of the tunnel.The measured oblique displacement curve has an obvious inflection point,and the long side of the foundation pit adjacent to the subway tunnel may form a potential sliding surface at a depth of 35~40 m.