Study On Application Of Steel Sheet Pile Combined With Reverse Construction In Civil Air Defense

A civil air defense project is located at the center of Nanchang, which is surrounded with dense buildings. Underground pipeline staggers intricately and most of the excavation depth is soil layer that has poor stability in the ground. At the same time, the scope of foundation pit is rich in water.Because of its poor construction environment, there are many restrictions on foundation pit excavation and support. Several supporting structures are commonly used at present, for example:underground continuous wall, soil-nailing wall, bored pile and so on. Because it can not work in the narrow space around the foundation pit construction, or can not effectively control the deformation, or can not achieve economic environmental protection, their application in this project has been limited. Consequently, The difficult problem of the application of the project in the supporting structure of foundation pit is caused. In the face of this problem, This paper skillfully fuses the advantages of steel sheet pile and top-down method and proposes new supporting scheme of steel sheet pile combined with top-down method through the analysis of the key point and the difficulty of the foundation pit project. According to the application of this supporting scheme in civil air defense engineering, the following works are done in this paper:(1)In order to determine the stability and security of the support scheme and to analyze and summarize the internal force, displacement and the variation law of ground surface settlement with the depth of excavation, It is necessary to calculating the deformation of the foundation pit supporting structure by the soil pressure, water pressure, internal force, overall stability of foundation pit, the pit wall and bottom uplift, steel sheet pile strength, surface subsidence and comparing of calculation results with standard values.(2)In the analysis of the supporting scheme in practical engineering application, putting forward specific requirements and effective treatment measures according to the possible construction difficulties and technical key points and providing technical support for successful application in civil air defense project.(3)Two dimensional numerical simulation of foundation pit excavation is carried out by Using MIDAS/GTS finite element software based on the hr-Coulomb Mo model. The paper Studies and analyzes the influence of the supporting scheme on the deformation of soil around the foundation pit and the structure of the building. And analysis detailedly of the deformation law in the horizontal direction on the steel sheet pile increasing with the excavation depth.(4)To ensure the use and stability of the supporting structure and adjacent buildings and underground pipelines during the construction of foundation pit. On the foundation pit project takes the information of monitoring and proposes specific requirements on the monitoring location, number and monitoring methods.