南通富水砂性地层地铁深基坑墙体渗漏原因分析

Causes Analysis on Wall Leaking of Metro Foundation Pit in Nantong Water-rich Sandy Stratum

富水砂性地层具有渗透系数大、无黏聚力、易液化、自稳能力差等特性,在这种地层条件下开挖基坑时,如果设计或者施工不当,就极易引发基坑事故。为积累该地层条件下的工程事故经验,针对南通某地铁深基坑渗漏事故实例,通过对基坑渗漏段监测数据、围护结构设计进行分析,从基坑所处地层条件、设计及施工3个方面总结了基坑渗漏发生的原因。1)基坑所处地层为深厚富水砂性地层,地下水位高,渗透性强;2)地下连续墙钢筋加密段存在渗水通道,降低了该段地下连续墙的水密性;3)监测数据的变化未引起施工人员足够的重视。

The water-rich sandy stratum is characterized by large permeability coefficient, non-cohesion, easy liquefaction and poor self-stability.When constructing a foundation pit in such area, accidents would be easily induced due to improper design and construction.Hence, the main causes for foundation pit leakage of a deep foundation pit of Nantong Metro are summarized from the aspects of geological conditions, design and construction of foundation pit by data monitoring on leakage section and analyzing on retaining structure design.The causes include:(1) The foundation pit is located in a deep and thick water-rich sandy stratum with high groundwater level and permeability.(2) The seepage channel existing in the encrypted section of the diaphragm wall reduces the water tightness of the diaphragm wall.(3) The variation of monitoring data did not receive serious attention.