Theoretical and experimental study on drawdown and foundation pit deformation under the influence of dewatering and excavation in unconfined aquifers

ABSTRACT This paper employs a combined approach of laboratory-scale experiments and theoretical calculations to analyze the influence of foundation pit dewatering on drawdown, lateral deformation of the diaphragm wall, and surface subsidence. It also examines the proportional impact of dewatering and excavation on lateral deformation and surface subsidence. Theoretical models for calculating the drawdown caused by dewatering, as well as the lateral deformation of the diaphragm wall and surface subsidence resulting from dewatering and excavation, are derived and validated against the results of laboratory-scale experiments. The theoretical calculation results are in close agreement with the laboratory-scale experiments results, demonstrating that the proposed theory can accurately predict the drawdown and excavation deformation. The results show that during the dewatering, the drawdown drops rapidly. As the dewatering reaches a steady state, the drawdown also tends to stabilize. The lateral deformation and surface subsidence caused by foundation pit dewatering account for 6.4% and 33.6% of the total lateral deformation and surface subsidence at the end of the entire dewatering and excavation cycle, respectively. Further analysis of the impact of drawdown inside the pit on the drawdown outside the pit and the deformation of the foundation pit, the research shows that as the drawdown inside the pit increases, the drawdown outside the pit and the deformation of the foundation pit also increases.