强透水砂卵地层深基坑地下水控制方案比选与优化设计
Comparison and optimization of alternatives to groundwater control for a deep excavation in highly permeable sand and gravel

以福州地铁2号线水部站工程为依托，针对强透水砂卵地层深基坑地下水控制问题，首先初步拟定隔水法(落底式止水帷幕、深层水平加固)、降水法以及隔、降组合法(悬挂式止水帷幕+坑内降水)等多种不同的地下水控制方案，通过对各方案的施工风险、环境影响、工程造价等比选，最终确定采用隔、降组合(悬挂式止水帷幕+坑内降水)的地下水控制方案。随后，通过对基坑坑底进行抗突涌验算，确定水部站底部承压水安全水位降深以及相应的疏干井和降压井的布置方案；进一步采用数值计算方法对止水帷幕作用下坑内降压井的稳定抽水流量、坑外水位降深以及地表沉降进行了预测，研究结果表明：该方案下车站基坑周边地面沉降值为13~22 mm，由此说明，止水帷幕的作用效果明显，且能较好地控制周边地面沉降。
In this paper, Fuzhou subway line 2 Shuibu station project was taken as a case study. For the groundwater control during excavation in the highly permeable sand and gravel, different types of groundwater control schemes were worked out initially, such as cut-off water method (fully penetrating curtains and deep horizontal waterproof), dewatering method and combination of cut-off water and dewatering (partial penetrating curtains with dewatering inside the excavation). By comparing the construction risk, environmental influence and construction costs of each scheme, finally the scheme of partial penetrating curtains with dewatering inside the excavation was determined. Then, the safety drawdown of confined aquifer in the Shuibu station was also determined through the checking calculation of anti-inrush stability, and the arrangement of corresponding dredging dried wells and buck wells were designed. Finally, by numerical simulation, steady pumping rate of buck well, drawdown outside the excavation as well as the ground settlement were predicted. The results show that the settlement of surroundings is 13~22 mm, which shows that the effect of penetrating curtain is obvious, and can control the ground settlement around the excavation better