岩溶地层地铁车站深基坑渗漏灾害成因分析

Cause Analysis of Seepage Disaster in Deep Foundation Pit of Metro Station in Karst Stratum

[目的]富水岩溶深基坑施工开挖常发生基坑侧壁或底部突涌灾害问题,应针对富水溶洞地层深基坑开挖时的渗流稳定性进行深入研究。[方法]依托佛山地铁3号线中山公园站深基坑开挖工程,对深基坑渗流特性及坑底涌水机理进行深入研究,建立了基坑-土体-溶洞三维数值模型,采用等效渗透系数法对岩溶-地层渗流场进行耦合模拟。[结果及结论]通过仿真模拟分析,获得了不均匀地层中岩溶区富水程度对基坑渗流场及涌水量的影响规律,阐明了基坑底部土体竖向平均水力坡降演变特性,揭示了该地岩溶区基坑底部突涌水机理,研究结果可为富水岩溶地区深基坑工程的设计与施工提供参考。

[Objective]In-depth study should be made on the seepage stability during deep foundation pit excavation in water-rich karst stratum in consideration of the water inrush disaster at the side wall or bottom of the pit during excavation construction in water-rich karst areas.[Method]Based on the deep foundation pit excavation project of Zhongshan Park Station on Foshan Metro Line 3,an in-depth research is conducted on the seepage characteristics of the deep foundation pit and the mechanism of water inrush at the pit bottom.A three dimensional numerical model of foundation pit,soil and karst cave is established,and the equivalent permeability coefficient method is used to make a coupling simulation of the seepage field in karst stratum.[Result&Conclusion]Through simulation and analysis,the law of water content in karst area of heterogeneous stratum influencing the seepage field and water inrush quantity of the foundation pit is obtained.The evolution characteristics of vertical average hydraulic gradient of the soil at the foundation pit bottom is clarified,and the mechanism of water inrush at the foundation pit bottom in karst area is revealed.The research results can provide reference for the design and construction of deep foundation pit project in water-rich karst area.