深基坑开挖对下卧地铁隧道变形正交敏感性试验研究

Study on Orthogonal Sensitivity Test of Deep Excavation above Tunnel

基于正交试验方法,以基坑场地初始水位、降水深度、土体渗透系数、隧道顶与基坑底高差为因素,把隧道最大变形、地表最大沉降、基坑底部最大隆起作为分析隧道和基坑变形的三项指标,利用数值分析方法对深基坑开挖引起下卧地铁隧道变形和基坑稳定性进行了分析,利用正交敏感性试验分析各因素在基坑开挖过程中对下卧地铁隧道变形影响的重要性次序。结果表明:在开挖深度及支护参数保持不变的情况下,地表沉降、基坑底部隆起、隧道最大变形的主要影响因素依次为场地初始水位、基坑降水深度、隧道顶与基坑底高差;工程应用表明,当隧道与基坑高差在9 m~12 m时,深基坑开挖降水至基坑底部以下0.5 m~1 m较为合适,隧道最大位移监测值为8 mm。

Based on the orthogonal test method, taking the initial water level, dewatering depth, soil permeability coefficient, and the height difference between the top and bottom of the foundation pit as factors, the maximum tunnel deformation, the maximum surface settlement and the maximum uplift at the bottom of the foundation pit as three indexes to analyze the deformation of the tunnel and foundation pit.Using numerical analysis method, the deformation and stability of underground subway tunnel caused by deep foundation pit excavation are analyzed, sensitivity analysis is used to analyse the order of importance of the influence of various factors on the deformation of underground subway tunnel in the process of excavation.The results show that when the excavation depth and supporting parameters remain unchanged, the main influencing factors of surface settlement, uplift at the bottom of the foundation pit and the maximum deformation of the tunnel are the initial site water level, the dewatering depth of the foundation pit, and the height difference between the top and bottom of the tunnel.The engineering application shows that when the height difference between the tunnel and the foundation pit is 9 m~12 m, it is more appropriate for the deep foundation pit to be excavated to 0.5 m~1 m below the bottom of the foundation pit, and the maximum monitoring value of the tunnel displacement is 8 mm.