A general solution of consolidation for a double-layer foundation soil induced by pre-excavation dewatering with bottom reinforcement considering delayed responses of water table.

This article focuses on developing a semi-analytical solution to predict water level drawdown and soil deformation inside and outside foundation pits caused by pre-excavation dewatering in unconfined aquifers. The model incorporates factors such as pit bottom reinforcement, soil stratification, and unsteady groundwater flow, using finite Fourier transform and boundary transformation techniques, and is validated against experimental data and numerical simulations via COMSOL Multiphysics. Parametric analyses reveal that increasing the thickness and reducing the permeability of the reinforcement layer effectively mitigate soil deformation and drawdown, while the compression modulus of the reinforcement layer mainly influences the ultimate deformation value. Additionally, a larger specific yield delays drawdown and deformation rates without affecting their final magnitudes, and higher permeability in the lower soil layer reduces both final deformation and drawdown, shortening settlement time. The study provides theoretical guidance for engineering design and safety assessment in foundation pit construction involving pre-excavation dewatering.