考虑群井效应下的预降水引发地表沉降计算与分析

潜水层基坑开挖前预降水处理会引起地表沉降，提前预测地表沉降数值对于实际工程具有重要意义。对于预降水处理引起的地表沉降值，采用理论计算和数值模拟的方法分别进行求解。理论计算考虑群井效应，提出预测水位降深曲线，以原地下水位和预测水位降深曲线为分界，分区计算沉降量，叠加后得最终沉降量；数值模拟采用PLAXIS 3D建模，用井单元模拟降水井，流固耦合对预降水期间周围地表沉降求解，并揭示群井效应下抽水流量和孔压变化规律。为验证理论计算方法可行性，用规范法计算结果和工程实测数据加以验证分析，结果表明，所用理论计算和数值模拟值方法能较好地接近实测值，具有一定的工程实用价值。

Calculation and analysis of land subsidence induced by pre-excavation dewatering under group well effect

Pre-excavation dewatering treatment before excavation of phreatic aquifer can cause surface settlement. It is of great significance to predict the surface settlement value in advance for practical engineering. The surface settlement value caused by pre-excavation dewatering treatment is solved by theoretical calculation and numerical simulation respectively. In theoretical calculation, the effect of group Wells was considered, and the predicted drawdown curve of water level was put forward. The original groundwater level and the predicted drawdown curve were taken as the boundary, and the settlement amount was calculated in different regions. The final settlement amount was obtained after superposition. The PLAXIS 3D modeling was adopted in the numerical simulation, and the well unit was used to simulate the precipitation well. The fluid-structure interactions was used to solve the surrounding surface settlement during the pre-excavation dewatering period, and the variation law of pumping flow and pore pressure under the group well effect was revealed. In order to verify the feasibility of the theoretical calculation method, the calculation results of the design standards and the in-situ data are verified and analyzed. The results show that the theoretical calculation method and the numerical simulation value method can approach the measured value better, and has certain practical value in engineering.