Numerical Study on Groundwater Drawdown and Deformation Responses of Multi-Layer Strata to Pumping in a Confined Aquifer

Pumping artesian water from porous media inevitably reduces the groundwater head and promotes soil consolidation, which may result in regional land subsidence. In this study, a fluid-mechanical coupled numerical model is developed to investigate the dewatering-induced groundwater drawdown and deformation responses for multi-layer strata. The relation between the stratum deformation and groundwater drawdown is discussed. The results show that the pumping process can be divided into four stages. The development of vertical deformation is inconsistent with the change of the pore pressure for the strata except for the confined aquifer at the early stage of pumping. The strata expand while the pore pressures reduce. This inconsistency may be due to the large unloading in the confined aquifer at the early stage of pumping. Soil arch comes into being owing to the constraint of the surrounding soils when the large unloading occurs in the confined aquifer; this can reduce the stratum compression and cause the expansion of the layers. It can be concluded that as the pumping continues, the decrease of the pore pressure dominates the vertical deformation and results in the soil compression in all strata.