Method for calculating pumping and recharging confined water inside and outside excavations under suspended waterproof curtain

The surrounding environment will be affected when the confined water in an excavation is pumped under a suspended waterproof curtain. The groundwater recharge can effectively control the groundwater drawdown outside the excavation so as to protect the environment. The existence of the waterproof curtain makes the head difference at two sides of the curtain during pumping and recharging of the confined water. The head difference is caused by the variation of seepage direction and path and the reduction of the seepage area. A series of equations to calculate the head difference during recharging outside the excavation are obtained by the numerical simulation regression method. The groundwater head difference during pumping-recharging action is the sum of the head difference during pumping and recharging, respectively. The proposed equations indicate that the head difference is related to the width of the waterproof curtain, the inserted depth of the waterproof curtain into the confined aquifer, the anisotropy of the aquifer, the thickness of the aquifer, and the hydraulic gradient under normal conditions. Finally, the proposed method is applied to a field case to verify its validity.