Deformation Behavior of Diaphragm Walls and Ground Surface During Excavation of a Circular Deep Foundation Pit Considering Coupled Dewatering and Recharge Effects

Few studies have focused on the deformation of ultra-deep circular foundation pits under the combined effects of dewatering and recharge. Therefore, a case of an ultra-deep circular foundation pit in a soft soil area was selected to investigate the mechanisms of groundwater variation induced by dewatering and recharge during excavation, and the resulting ground surface and diaphragm wall deformation. The main conclusions are as follows: (1) The model was validated against field measurements, showing good agreement in magnitude and variation trends for both ground settlement and diaphragm wall deformation. (2) With increasing dewatering rate, pore water pressure at the dewatering wells gradually decreased, forming more pronounced drawdown funnels. The reduction in pore water pressure increased soil effective stress, expanded the high-stress zone, and induced ground settlement and lateral displacement of the diaphragm wall, intensifying overall pit deformation. (3) With increasing recharge rate, pore water pressure around the recharge wells gradually increased, forming localized high-pressure zones. Ground surface heave occurred due to buoyancy from the expanded saturated soil zone, while lateral displacement of the diaphragm wall was simultaneously amplified. The affected zone expanded with higher recharge rates, enhancing overall soil deformation around the pit.