Deep work shaft excavations have become increasingly common as a preliminary step of tunnel construction. Deep excavation above a multi-aquifer-aquitard system (MAAS) complicates the flow field and stress field surrounding the excavation, inevitably affecting the performance of excavations. However, previous studies with drained or undrained analyses ignored the effects of dewatering-induced groundwater flow on the performance of deep excavations. To better understand this aspect, this study performs fully hydro-mechanical coupled analyses to investigate the performance of a 39.5 m-deep excavation above a multi-aquifer-aquitard system, which considers dewatering in two confined aquifers. A sophisticated three-dimensional (3D) numerical model is developed to simulate the detailed construction processes of drainage, excavation, dewatering, and strut installation. The study presents a comparison of two scenarios (with and without dewatering in a confined aquifer) with respect to wall deflection, stratum deformation, pore pressure, and effective stress path. The analysis results indicate that the effective stress paths are highly dependent on stratum permeability and construction activities. The dewatering behavior significantly reduces the excavation-induced deformation, primarily due to increased effective level and consequently increased resistance on the excavated side. As a result, ground settlements decrease due to less wall deflection.

中文翻译：

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多含水层-滞水层系统上方深基坑的全水力学耦合分析


作为隧道建设的初步步骤，深井开挖已变得越来越普遍。在多含水层-滞水层系统 （MAAS） 上方进行深部开挖会使开挖周围的流场和应力场复杂化，不可避免地影响开挖性能。然而，以前对排水或不排水分析的研究忽略了脱水诱导的地下水流对深挖性能的影响。为了更好地了解这方面，本研究进行了全面的水力学耦合分析，以研究在多含水层-滞水层系统上方进行 39.5 m 深的开挖性能，该系统考虑了两个承压含水层中的脱水。开发了一个复杂的三维 （3D） 数值模型，用于模拟排水、开挖、排水和支柱安装的详细施工过程。该研究比较了两种情景（在承压含水层中有和没有脱水）在壁挠度、地层变形、孔隙压力和有效应力路径方面的比较。分析结果表明，有效应力路径高度依赖于地层渗透性和施工活动。脱水行为显着减少了开挖引起的变形，这主要是由于有效水平的增加，因此开挖侧的阻力增加。因此，由于墙壁偏转较小，地面沉降减少。