软土地区多含水层系统承压层抽水存在越流现象,地下水渗流和区域地层变形响应规律复杂.基于某超深地下工程承压水抽水试验,采用数值方法研究软土地区多含水层系统第二、第三承压层降水的地质环境响应.建立了三维有限差分模型,考虑流固耦合效应和土体小应变刚度特性,模拟了不同埋深承压含水层抽水试验,对比分析各承压层抽水引起的承压水头降深和深层土体变形时空分布特性.结果表明,第二承压层水位降深较小,但引起的地表沉降更大;第二和第三承压层抽水引起降水层的压缩变形分别占地表沉降的56.18%和77.69%.主要原因为浅部土层压缩性高,相同降深条件下引起的土层竖向压缩量更大;且第二承压层与上部弱透水层的水力联系较强,越流作用明显,导致抽水引起的地下水水位降深在深度方向的影响范围更大.研究成果对后续超深基坑降水施工及环境变形控制具有重要的参考价值.

When pumping in confined aquifers, vertical leakage could be found in the multi-aquifer system in soft deposits, and the responses of groundwater flow and strata deformation are complicated. Based on pumping tests in an ultra-deep underground project, this study performs a 3D finite-difference modeling to investigate the responses of groundwater and strata to pumping in the second and third confined aquifers. It considers the hydro-mechanical coupled and small strain stiffness characteristics of soils in the analysis, and discusses and compares the spatiotemporal distribution characteristics of drawdown and deformation induced by pumping in different confined aquifers. The results indicate that the ground settlement induced by pumping in the second confined aquifer is greater though the groundwater drawdown is smaller, and the compression of dewatering aquifers caused by dewatering in the second and third aquifers accounts for 56.18% and 77.69% of the settlement, respectively. It could be attributed to the connectivity between the second confined aquifer and its overlying aquitards, which results in a greater influential depth. In addition, the compressibility of shallow strata is significantly greater than that of deep strata. The study is significant for the dewatering construction and environmental deformation control of ultra-deep excavations.