考虑参数非均匀性的深基坑悬挂式封闭止水体阻水效果分析

Effect of Non-uniformity on the Performance of Pensile Waterproof Facility of Deep Excavation Consisting of Impervious Curtain and Bottom Cement-treated Layer

采用悬挂式止水帷幕配合坑底被动区加固(封闭式止水体)措施不仅能有效解决长江I级阶地区域深基坑施工面临的地下水问题,而且与落底式止水帷幕相比表现出明显的价格优势。然而,封闭式止水体的渗透系数具有很强的空间变异性,会对止水体的阻水效果产生明显影响。鉴于此,本文首先基于确定性分析方法,探究了封闭式止水体设计参数对其阻水效果的影响,结果表明加固区存在一个临界厚度,当加固区厚度大于该值时,阻水效果不再提升。其次,基于随机场理论,研究了渗透系数空间变异性对深基坑悬挂式封闭止水体阻水效果的影响规律,结果表明渗透系数空间变异性对悬挂式封闭止水体阻水效果影响较为显著。

The newly developed waterproof technology for deep excavation,composed of pensile impervious curtain and continuous cement-treated soil layer at the bottom of deep excavation,can solve the groundwater problem caused by foundation pit at the Wuhan first terrace. And it has a good economic effect. However,the permeability coefficient of cemented-soil has a strong spatial variability,which influences the effect of water sealing obviously. In view of this,the paper explores the influence of the design parameters of closed water body on the water resistance effect based on the deterministic analysis method. The results show that,there is a critical thickness of the passive zone. When the thickness of the passive zone is greater than that,the effect of water sealing is basically unchanged.Then,a study on the effect of the spatial variation of permeability coefficient on the water resistance of deep foundation pit is carried out based on the theory of random field. The results show that,the seepage discharge of pensile impervious curtain,the surface of passive zone and total foundation pit have a normal distribution. When compared with the deterministic analysis results,it is believed that the deterministic design results will have a great probability to overestimate the actual seepage,which will make the design more secure to some extent.