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| 软土地区多含水层联通基坑降水引发变形及控制方法 |
| Dewatering induced deformation of multi-aquifer leaking excavation in soft soil area and its control method |
| 投稿时间：2024-09-23 修订日期：2024-12-23 |
| DOI： |
| 中文关键词: 含水层联通 数值模拟 基坑降水 地连墙变形 沉降 |
| 英文关键词:Leaking aquifer Numerical simulation Excavation dewatering Diaphragm wall deformation Settlement |
| 基金项目:国家自然科学基金项目（52178343） |
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| 中文摘要: |
| 在我国的沿海地区，土层中经常分布有多个含水层，基坑施工过程中需要进行降水。若不同含水层之间易发生越流，止水帷幕难以完全隔断基坑内外水力联系，坑内降水会造成坑外较大的水位变化，引发一系列的环境影响。因此，多含水层联通基坑降水引发的变形规律及控制方法值得深入研究。本文基于天津市某工程的基坑降水试验结果，采用有限元方法对于该工程地下连续墙底部存在粉土透镜体土层且含水层联通的基坑开展了粉土透镜体对降水引发变形影响的规律、粉土透镜体对降水引发变形影响的机理以及不同降水方案引发变形的对比研究。研究结果表明，地下连续墙墙趾深度上下含水层存在水力联通将减小地下连续墙变形，增大坑外沉降。其机理在于水力联通减小了地下连续墙两侧孔压差，但增大了坑外的水位降深。此时，基坑降水建议采用潜水和承压水独立设置滤网的“深浅井”降水体系，及时架设水平支撑，按需降水，控制基坑降水引发的变形。 |
| 英文摘要: |
| In coastal area of China, there are many aquifers widely distributed in the soil layer, which need dewatering in process of excavation construction. If it is easy for leakage between different aquifers, and difficult for fully blocking the hydraulic connection between inside and outside the excavation, it will cause a large change of water level outside the excavation in the process of dewatering, leading to a series of environmental problems. Therefore, the deformation pattern and control method caused by the dewatering in multi-aquifer leaking excavation are worthy of further study. Based on the dewatering test results of the excavation of a subway station in Tianjin, this paper adopts the finite element method to study the influence of silt lens and leaking aquifers on the excavation deformation in the toe soil layer of the diaphragm wall induced by dewatering. Moreover, the mechanism of influence of silt lens on dewatering induced deformation and the comparative study of dewatering induced deformation by different dewatering schemes are also conducted. The results show that hydraulic connection between the upper and lower aquifers at the depth of the toe of the diaphragm wall can reduce the deformation of the diaphragm wall while increasing the settlement outside the excavation. The mechanism behind this is that the hydraulic connection reduces the pore pressure difference across the diaphragm wall, but increases the drawdown outside the excavation. In this case, it is recommended to adopt the “deep and shallow well” dewatering system with independent filters for the phreatic and confined aquifers, along with timely installation of horizontal supports. Dewatering should be implemented as needed to control the deformation induced by the dewatering process. |
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