Field tests on groundwater recharge considering leakage between semiconfined aquifers

The dewatering of an excavation will cause water-level drawdown in multiple aquifers outside the excavation in the presence of multiple confined aquifers where multiple hydraulic connections exist. Recharge of all layers will result in a significant increase in cost, so one layer can be recharged and the other aquifers can be recharged by leakage. The effects of dewatering tests, single-well recharge tests, and the dewatering-recharge tests on the hydraulic connections inside and outside the excavation, the hydraulic connections between different aquifers, and the effects of interlayer recharge are studied at the site of the excavation at a subway station. Due to the significant hydraulic connection between the aquifers, the vertical cross-flow recharge is strong, and the dewatering in the excavation can cause the head of the confined aquifer to fall and the subsidence outside the excavation. Recharge of the semiconfined aquifer Ⅰ outside the excavation can effectively raise the head of the upper phreatic layer and the lower aquifer II-1, and the subsidence caused by the water-level drawdown is controlled by the interlayer recharge. For the aquifer II-2, recharge of the aquifer Ⅰ also has a certain effect on the water level, but it is still not possible to fully restore the water level. It is recommended to combine the backup recharge wells in this aquifer to control the water-level drawdown.