Fluid-Solid Coupling Effect on Numerical Simulation of Deep Foundation Pit Deformation in Soft Soil Area

Abstract

Groundwater is abundant in soft soil areas, which has a significant impact on the excavation deformation of foundation pits. In this paper, based on the monitoring of deep foundation pits with waterproof curtains in Shanghai deep foundation pits, COMSOL Multiphysics is used to model the layers of the foundation pits and establish a two-dimensional seepage-consolidation coupled model for hierarchical dewatering excavation. The feasibility of numerical simulation of regional foundation pits, the modeling method of the foundation pit seepage model is explored, and the presence or absence of waterproof curtains, and the influence of aquitards on the horizontal displacement of foundation pits and surface settlement outside the pits is analyzed. The research shows that the simulated foundation pit deformation values are in good agreement with the actual monitoring values and that the effect of dewatering and seepage has a great influence on the foundation pit deformation. The waterproof curtain has a significant effect on reducing the drop in the water level outside the pit and controlling the surface settlement. After installing a waterproof curtain, the amount of ground settlement is reduced, but the disadvantage is that the deformation of the enclosure structure increases. Finally, the influence of aquitard on the deformation of foundation pit excavation is simulated, and the distribution characteristics of the flow network diagram under different permeability coefficients are analyzed. According to the analysis of the foundation pit deformation law and flow network diagram, it is considered that the waterproof curtain can effectively reduce the influence of aquitard on foundation pit deformation.