Optimization design of foundation pit support replacement based on the structural characteristics of rainwater pump station

The foundation pit of a rainwater pump station is 16.16 meters deep and is supported by retaining piles and 4 steel pipes. The underground second floor of the pump station has a height of 8.9 meters. The original design plan did not include an effective replacement of the third support when it was removed. The removal of the third support will cause the side walls of the underground second floor to be in a cantilever state, seriously affecting the safety of the foundation pit and pump station structure. Based on the structural characteristics of the rainwater pump station, a permanent and temporary support replacement scheme was adopted. A hidden beam and a permanent concrete beam were installed 1 meter below the third support on the side walls of axes ② - ⑤ as replacement supports, which not only solves the problem of replacement supports in the foundation pit but also does not affect the use function of the pump station, avoiding the safety risks of dismantling and replacing supports in limited space. Based on the monitoring data during the excavation stage of the foundation pit, a three-dimensional numerical model of the foundation pit construction process was established using the finite element software Midas GTS. The rationality of the three-dimensional numerical model was verified from the aspects of deep horizontal displacement of support piles, steel support axial force, and column settlement. Then, the validated model was used to simulate the dismantling and support conditions of the foundation pit and predict the deformation of the foundation pit. The analysis results indicate that the optimized design scheme for replacing supports in foundation pits is safe, reliable, reasonable, and feasible, and can serve as a reference for similar engineering projects.