不同止水帷幕插入深度下基坑降水对周边环境的影响预测分析

我国沿江沿海地区地下承压水分布特征及水文地质条件复杂,该地区基坑降水对周边环境的影响预测分析是技术难题。为研究不同止水帷幕插入深度下坑外地表沉降和坑外水位降深对坑内降水的响应特征,本文以常州地铁2号线某深基坑工程为例,采用有限元软件ABAQUS建立了基坑降水三维分析模型。结果表明:随着止水帷幕插入比的增大,基坑降水对周边环境的影响范围逐渐减小。定义止水帷幕插入承压含水层深度占其层厚的比值为插入比,当止水帷幕插入比小于1/2时,降水对坑外环境影响较大;当止水帷幕插入比大于3/4时,其止水效果与止水帷幕完全隔断承压含水层时接近,降水对坑外环境影响很小。研究成果为该地区地铁车站基坑止水帷幕优化设计提供良好的理论依据。

Prediction and analysis of the influence of foundation pit dewatering on the surrounding environment under different water stop curtain insertion depth

The distribution characteristics of underground confined water and the hydrogeological conditions in China' s coastal areas are complex，the prediction and analysis of the effect of foundation pit dewatering on the surrounding environment is a technical problem． In this study，the three-dimensional finite element model is constructed based on ABAQUS to analyze the effect of foundation pit dewatering on the surrounding environment for the foundation pit of Changzhou Metro Line 2． The results show that the influence range of dewatering on the surrounding environment gradually decreases with the increase of the depth of waterproof curtain inserted into confined aquifer． The ratio of insertion depth of water-stop curtain to the thickness of confined aquifer is defined as insertion-ratio． When the insertion-ratio is less than 1/2，the foundation pit dewatering has a great impact on the environment outside the pit，and when the insertion-ratio is grater than 3/4，the water stop effect is closed to that when the water stop curtain completely cuts off the confined aquifer，and the dewatering has little influence on the environment outside the pit． The study result provides a better basis for the optimal design of foundation pit waterproof curtain of metro stations in this area．