杭州庆春路过江隧道江南工作井监测分析

为了避免基坑工程设计和施工中因没有处理好承压水影响而产生的基坑工程事故，以杭州庆春路过江隧道江南工作井为例，对墙体水平位移、地表沉降、地下水位及混凝土支撑轴力进行监测分析，并提出高承压水控制和防治对策。基坑开挖过程监测数据表明：墙体水平位移与基坑平面尺寸密切相关，可通过加强中部支撑刚度，将大尺寸基坑“分隔”成数个较小的基坑，以控制墙体水平位移；地表沉降最大点发生在距离围护结构0.5倍开挖深度处；止水帷幕结合减压降水的措施，可较好地处理承压水问题，基坑下层开挖施工期间，必须保证抽水井持续降水，非正常断电会影响基坑施工安全；第1道支撑的轴力逐渐变小，甚至有可能出现拉力

Monitoring analysis of retaining structures for Jiangnan foundation pit of Qingchun road river-crossing tunnel in Hangzhou

It is common to have a foundation pit accident, when failing to deal with the effect of confined water. In order to avoid such accidents, the Jiangnan foundation pit of Qingchun Road River-Crossing Tunnel in Hangzhou was investigated. By analyzing the monitoring data of wall deflection, settlement, confined water level and strut load, we proposed how to deal with high confined water. According to the analysis of on-site monitoring data, it could be obtained that: ①The wall deflection is closely related to the plane size of the foundation pit, and through strengthening the stiffness of the central support, the large pit can "be separated" into several smaller pit to control the wall deflection. ②The maximum settlement point is 0.5 times depth of the excavation away from retaining wall. ③It is useful to treat the confined water with dewatering and cut-off walls, and during excavating the bottom of the foundation pit, we must ensure that the pumping wells keeping working; otherwise the safety of the construction can be affected. ④ The load of the first strut becomes smaller and even can be tensile force during excavation.