Study On Construction Impact Analysis And Control Technology Of Long-distance Continuous Shield Tunneling Through Buildings In Soft-plastic Ground

Shield tunnel construction is carried out in cities with densely distributed buildings,and the situation of adjacent buildings is everywhere.The initial ground stress field will be disturbed during tunnel construction,and ground displacement on a macro scale.The value and distribution of stratum displacement are closely related to geological conditions,construction parameters,general situation of tunnels and external overloading.Shield tunneling in soft plastic stratum faces the risk of excessive ground subsidence.Displacement,deformation and stress state of buildings above ground surface change with subsidence of underlying strata.When the building is deformed or the internal force of the structure exceeds the limit,it is very likely to cause cracking or even collapse of the building.The construction of shield tunneling in soft plastic stratum with long-distance continuous crossing through buildings has many problems,such as high construction risk,the building settlement is difficult,and the deformation control technology is still unclear.In view of the above problems,this paper relies on the tunnel between Moxie Road Station and Sujiahang Station of Suzhou Rail Transit Line 5 to analyze the risk of shield tunneling through buildings by means of field investigation and theoretical analysis.Through numerical simulation to explore the deformation and stress state of the surface and buildings during the construction of the shield,predict the settlement law of the surface and buildings,and find the key position of building settlement.Using field test means to achieve safe and stable shield crossing through buildings,and provide reference for the determination of the subsequent construction control technology.The main contents are as follows:(1)Through the on-site investigation to understand the current situation of the building and its relative relationship with the tunnel,classify the existing buildings.Then,it serves as the basis for the risk level analysis of the underpassing building group.Combined with the Suzhou rail transit engineering experience and building classification,the risk level of the Moxie Road Station-Sujiahang Station interval tunnel crossing building is determined.(2)Through FLAC3 D,the calculation model of oblique intersection between shield tunnels and five high-risk buildings is established,and the whole construction process of shield tunnels passing through existing buildings in five different ways is simulated.The plastic zone of surrounding rock,settlement of surface and building and stress of building structure are monitored in the process of tunnel adjacent construction.The displacement and deformation law and mechanical state of surface and buildings at different construction stages are obtained,and the influence degree of tunnel construction on the safety and stability of buildings is analyzed.(3)According to the characteristics of soft plastic stratum,combined with the numerical simulation results with the general situation of existing buildings,the parameters such as shield parameters,attitude correction and grouting control are optimized,and the construction control technology of shield tunnel crossing complex buildings is proposed to ensure the safety and stability of tunnel and structure.(4)According to the general situation of tunnel and its surrounding environment,a perfect monitoring and measuring system is established to collect timely and accurate construction information to guide shield tunneling and take necessary auxiliary measures.