| With the development of urbanization and the popularization of subway projects,more and more subway stations need to be built in the city center.The construction of deep foundation pits often faces the challenges of complex above and underground environments.This paper proposes the Pile Beam Plate(PBP)method,which can greatly reduce the closure time of ground traffic,avoid the relocation of some important underground pipelines,and cause less environmental disturbance.However,there are not enough data and information about the mechanical properties of the key supporting system and the related laws of the environmental disturbance and deformation characteristics caused by construction.Therefore,through theoretical analysis and numerical simulation,this pap er analyzes the key components stress deformation and environmental disturbance of the method.The work done and the main conclusions are as follows:(1)Based on the evaluation of the common subway station working methods,combined with the complex constr uction environment of the central urban area,the PBP method is proposed.The left line of the subway station constructed by the PBP method is four floors underground,and the right line is three floors underground.The station construction adopts the method of top-down cover excavation,in which the cover excavation of the right line needs to be carried out under the support of pipe curtain.This method avoids the road closure of the right line of the station and the relocation of underground pipelines.(2)In order to study the mechanical and deformation behavior of the PBP method,based on the analysis of the mechanical mechanism of the pipe curtain and the combined elastic modulus of the concrete-filled steel tubular members,a multi condition finite element model of the concrete-filled steel tubular members of the pipe curtain structure is established.Through the establishment of a multi-case finite element model of concrete-filled steel tube members of the tube curtain structure,it is believed that the existence of fixed-end constraints can significantly reduce component deformation,but the fixed-end concrete will have greater tensile stress.Through the finite element analysis(compared with the structural mechanics method)and considering the shear slip of the steel tube and concrete interface in the calculation,the results are conservative.To increase the structural resistance of the pipe screen,according to its lifting effect,the first choice is to increase the diameter of the pipe screen,and then increase the wall thickness of the pipe screen steel pipe.What is uneconomical is the interpolated section steel.(3)By establishing the finite element model of the subway station constructed by the PBP method,the regularity of the overall lateral displacement,the lateral displacement at the top of the wall,t he maximum lateral displacement and its position of the three walls are analyzed;The stress and deformation characteristics of pipe curtain structure,concealed roof and steel pipe column in construction are analyzed;The development process of surface de formation,maximum surface settlement and its location,and ground settlement with construction steps are analyzed.(4)On the basis of the above analysis,the paper selects the deformation control index of the deep foundation pit with the PBP method,divides the deformation control standard into four levels according to the surrounding environment of the foundation pit,and finally puts forward the corresponding deformation control measures.The PBP method can bring a new breakthrough for the construction method of metro station in urban central area,and has important application value.Through the above research,this paper can provide detailed reference data for the application of the construction method,provide reference for similar projects,and reduc e the safety risk in engineering application. |
