软土深基坑开挖对隧道影响分析及设计参数讨论

Effects Analysis of Soft Soil Deep Foundation Pit Excavation on Tunnels and Design Parameters Discussion

某地铁边基坑分坑设计,邻近地铁侧设地下二层区域(小区)和地下五层区域(大区)。大区开挖引起紧邻的上、下行线隧道变形沉降差达到39.9mm。通过数值模拟分析发现,较大沉降差的原因是,大区基坑开挖后,土体应变较大的区域形成“潜在滑裂面”,类似于主动滑裂面,而两条隧道分别位于“潜在滑裂面”两侧。参数分析发现,当小区地墙穿越“潜在滑裂面”后,增加小区地墙的插入深度和刚度可以显著减小隧道沉降。因此,设计中小区地墙插入深度不仅需要考虑小区基坑开挖,更需要综合考虑大区基坑开挖引起的“潜在滑裂面”影响。

In the case of subway adjacent foundation pit design,an underground two-floor area(small zone)and an underground five-floor area(large zone)are set adjacent to the subway.The deformation and settlement difference of adjacent upper and lower line tunnels caused by excavation in large zone reached up to 39.9 mm.Through numerical simulation,it is found that during excavation,a potential slip surface was induced by the excavation of the large zone and it was similar to the active slip surface.The two tunnels were on either side of the potential slip surface,respectively.Parametric studies were conducted to study the influence of stiffness and depth of diaphragm wall on nearby tunnels.It is shown that,when the diaphragm wall of the small area crossed the potential slip surface,the increase of wall stiffness and depth can significantly reduce the tunnel settlement.Therefore,the designer should consider the influence of the potential slip surface induced by the excavation of large zone on the design parameters of the diaphragm wall of small zone.