超深基坑深厚复合承压水管控技术研究与实践

Research and Practice of Deep Composite Confined Water Control Technology for Ultra-deep Excavation

如何综合有效地管控超深基坑中出现的复合承压含水层,已成为上海地区超深基坑明挖建设中必须解决的一个关键技术问题。以开挖深度39.44 m的上海某正方形超深基坑为例,为满足基坑和环境的双安全,开展了复合承压含水层组的围护–降水一体化设计。针对降深幅度超过32.75 m的第Ⅰ承压水采用了双止水帷幕隔断并在双止水帷幕间设置降水井的方法重点防控侧向突涌;针对埋深较深、降深幅度较大的第Ⅱ承压水采用了悬挂式止水帷幕降水;针对单井流量超过450 m^(3)/h的第Ⅱ承压水降水井,从管井构造设计及运行控制保障方面提出了相应的风险管控措施。最后通过精细的原位验证试验,确保了方案执行的可靠性,达到了预期的地下水控制目标。

How to comprehensively and effectively control the composite confined water group in ultra-deep excavation has become a key technical problem that must be solved in the ultra-deep excavation in Shanghai.A square excavation which is 39.44 m deep in Shanghai is taken as an example.To meet the safety requirements of the excavation and environment,the integral design of retaining and dewatering is made for the composite confined water group.Due to the drawdown of the first confined water is beyond 32.75 m,double water curtains were set up and a dewatering well was set between the two water curtains to mainly prevent and control the lateral surge.As the second confined water layer is deeper and with larger drawdown,a suspended water curtain was adopted.For the dewatering well of the second confined water layer with flow rate beyond 450 m^(3)/h,the corresponding risk management and control measures were proposed in terms of the well structural design,operational control and guarantee.The reliability of the programme implementation was ensured through the in-situ verification tests,so as to achieve the expected groundwater control target.