Effect of Stratum Distribution on Deep Circular Excavation with Dewatering Above a Multi-Aquifer System by Hydro-Mechanical Coupled Numerical Analysis

Dewatering in multilayered aquifers is closely related to stratigraphic configuration. However, previous studies concentrate on the excavation response to dewatering in particular strata, lacking systematic study on the influence of stratum configuration. This study developed a hydro-mechanical coupled numerical model based on the practical engineering of Shanghai Tower deep excavation. The model and input parameters were validated by field measurements. Besides, a parametric study was conducted to investigate the effect of the thickness, permeability and depth of the aquitard on excavation performances. The analysis indicated that settlements in the excavation were insensitive to the thicknesses and permeability of aquitards, while ground surface settlement increased significantly with the increase of the confined aquifer thickness. Based on the numerical analysis, a fit relationship was established to predict the maximum ground settlements of deep excavation in Shanghai considering the excavation depth, groundwater drawdown and distribution of multilayered aquifers. The applicability of the fit equation was verified by field measurements.