Study on the Control Effect of Pretreatment Measures on the Deformation of Subway Caused by the Excavation of Foundation Pit

At present, there are many control measures for the deformation of subway caused by the excavation of foundation pit. It is worthy of attention that pretreatment measures can effectively reduce the influence of deformation on the subway tunnel under different working conditions. Therefore, the finite element model is established by Midas/GTS to explore the reinforcement effect of two measures of pit bottom reinforcement and isolation pile reinforcement. The results show that: in the excavation of foundation pit, the two schemes have different effects on controlling the deformation of tunnel structure, and the inclination of diameter line is generally smaller. The deformation characteristics of each component structure of the diameter line after the pit bottom reinforcement are similar to those of the unreinforced condition, while the displacement changes of each structure after the isolation pile reinforcement become uniform and reasonable. Isolation pile reinforcement is better than pit bottom reinforcement, especially in reducing the vertical displacement of the structure. The reduction degree of the maximum horizontal displacement after the isolation pile reinforcement is about 24%–31%. Therefore, when selecting the pretreatment method, priority is given to the isolation pile reinforcement method.