Research On The Analysis Of Foundation Pit Excavation On The Adjacent Existing Metro Tunnel And Some Measures To Control Its Displacement

As the lifeline of the city,the subway is all over the underground space,due to concentration of cities,some projects can not be avoided to be adjacent to the metro tunnel.Foundation pit engineering not only affects the settlement of surrounding buildings,but also changes the stress and displacement of surrounding rock due to unloading,which causes deformation of underground pipelines and subway tunnels to varying degrees.Take the subway as the main way for the people to travel.,which carrying a large part of the city traffic.The subway tunnel accidents not only caused serious economic losses,and even endanger the life safety of the passengers,so is very important to choose a reasonable excavation scheme and engineering protection measures.This paper combines the foundation pit project of "Baoan station ~ Qianhai station" in Metro Line 11 of Shenzhen Qianhai Shuangjiehe Road(and underground)municipal engineering.Using the method of three-dimension finite element numerical simulation to research.The main results are as follows:(1)According to the existing soil mechanics theory,the phenomenon of tunnel displacement caused by soil unloading is analyzed;This part mainly introduces the calculation method of the displacement of the subway tunnel caused by the foundation pit excavation by using the elastic foundation beam theory and the Galerkin method is used to solve the beam equation of the elastic foundation,and the numerical solution of the vertical displacement of the tunnel is obtained.(2)Using the MIDAS/GTS NX finite element software to simulate the shaft excavation scheme and analysis of the influence of the excavation on the adjacent tunnel.And compared with the original monitoring data,the results of the finite element calculation are in agreement with the monitoring data,so the rationality of the simulationis verified.Using the same method to simulate Stratified excavation scheme,compared with the vertical shaft scheme excavation,the shaft excavation scheme is more beneficial to control the tunnel displacement.(3)In this project,the oversize of the tunnel caused by improper construction.There fore,the model is established to simulate two kinds of emergency measures in both loading in tunnel tunnel and backfill the soil.The advantages and disadvantages of the two are analyzed by the calculation results,and the proposed scheme is given.Research on two foundation reinforcement schemes and different reinforcement depth,it is found that the displacement of the tunnel under full hall is more sensitive to the change of the depth of reinforcement and the reinforcement of the soft soil is more favorable for the control of the tunnel displacement;Introduces the influence of the tunnel with the support in the tunnel and the dewatering of the foundation pit.