Research On Structural Stability And Construction Optimization Of Key Intersection Of Multi-layer Underground Garage

The key intersection mentioned in this paper are the intersection of shaft,cross passage and the main hole in multi-layer underground garage.There are many construction procedures in this part,and the stress conversion is complex.In this paper,structural stability and safety of key intersection of the multi-layer underground garage in the process of construction is studied.On this basis,putting forward the strengthening measures of the support structure at key intersection and then analyzing the functions of the strengthening measures.At the same time,in order to ensure the safety of supporting structure in the construction stage,the mechanical properties of the joint between the steel frame and the floor of the cross passage are studied,and the design of the joint is optimized.The main work of this paper is as follows.(1)According to the geological conditions and surrounding environment of the project,the construction sequence of the key intersection is determined,which is to turn into the main tunnel through the shaft and cross passage.Based on the two-dimensional stratum structure model,the numerical simulation of the construction process of the main tunnel is carried out,and the mechanical behavior of Drift-Pile Method with different excavation sequence is analyzed.Finally,1-4-8-5-2-3-7-6(heading No.)is selected as the best heading excavation sequence.(2)Based on the construction method described in this paper,the deformation and stress distribution of shaft,cross passage and main supporting structure of garage in different construction stages are studied by three-dimensional finite element numerical simulation.It is found that the weak parts of the support structure in the construction process are mainly located in the corner between the floor and the side wall of shaft,the connection between the shaft floor and the cross passage,the floor of cross passage,corner of cross passage roof,and the bottom corner of ingate at each layer of the cross passage,which provide the basis for the reinforcement measures of the support structure.(3)In order to reduce the deformation and stress value of the primary supporting structure of the shaft and cross passage of key intersection,and improve the safety of construction,the reinforcement measures of the shaft and cross passage structure are proposed respectively.Through the method of numerical simulation,the process of stress conversion of support structure is studied,and the effectiveness of reinforcement measures is analyzed.The results show that the displacement and the maximum tensile stress of the supporting structure can be effectively reduced by the steel frame in the cross passage,and the displacement and stress of the shaft structure can be effectively controlled by the section steel brace and section steel support of ingate,and the stress concentration degree of ingate can be reduced.(4)The three-dimensional finite element numerical simulation method is used to analyze the whole process of the test model in the relevant literature.The accuracy of the simulation method is verified by comparing the test results.Based on the above numerical simulation method,the mechanical properties of H-beam and box beam of the joint between the steel frame and the floor of the cross passage are studied.The results show that H-shaped steel and reinforced concrete column base is more suitable for the joint between the steel frame and the floor of the cross passage in the underground garage project.The research results of this paper have been successfully applied to the design of this project,which can be used for reference by similar underground garage projects.