富水砂性地层近地铁深基坑支护技术

Support'Technology for Deep Foundation Pit near Subway in Water-rich Sandy Stratum

结合工程实际,从基坑分区方式、支挡结构、地下水控制这3个方面,对富水砂性地层近地铁深基坑项目的施工技术进行了优化。采用数值分析方法研究了支护结构施工、基坑开挖、地下室回筑及降水等作业对地层变形及地铁结构的影响,结果表明:分坑分区、适当加大围护体刚度可实现对邻坑重点建构筑物的保护;砂性土地区基坑,需加强止水帷幕冷缝处理,地下连续墙应选择止水效果较好的接头形式;当止水帷幕插入比接近2,且止水帷幕端部的土层渗透系数已达10-5cm/s级别时,可有效实现止水效果。相关结论可供其他富水砂性地层近地铁深基坑工程借鉴。

Combined with the engineering practice,the construction technology of deep foundation pit near subway in water-rich sandy stratum is optimized from three aspects of foundation pit zoning,retaining structure and groundwater control.The effects of construction of support structure,excavation of foundation pit,backilling of basement and dewatering on ground deformation and subway structure are studied by numerical analysis method.The results show that the protection of key buildings and structures adjacent to the pits can be realized by dividing and zoning the pits into different areas and properly increasing the stifness of the support body.The foundation pit in sandy soil area needs to strengthen the treatment of cold joints of waterproof curtain,and the underground continuous wall should select the joint form with better waterproof effect.When the insertion ratio of the waterproof curtain is close to 2 and the permeability coefficient of the soil layer at the end of the waterproof curtain has reached the level of 10-'cm/s,the waterproof effect can be effectively realized.The relevant conclusions can be used for reference for other deep foundation pit engineering near the subway in water-rich sand stratum.