Field Test And Numerical Analysis Of The Deformation Characteristics Of Inner Bracing Soldier Pile Retaining Structure Of Deep Foundation Pit In Soft Soil

The inner-bracing soldier pile retaining system has the advantages of high reliability, no trespassing red line, strong stratum adaptability, being easy to be combined with the top-down construction method, etc..., which is widely used in deep excavation supporting system in soft soil area. However, the mechanical behavior of soldier pile retaining system and the deformation mechanism of the pit is still not very clear and needs further investigation. Therefore, it is necessary to study the deformation mechanism of the pit and the surrounding soil and its influence factors during the excavation process, then to forecast the influence of the pit excavation on the surrounding buildings, underground lines and roads, etc. so as to further discuss the design parameters of the foundation pit, which has quite both theoretical and practical significance for directing the design and construction of deep foundation pit in soft soil area. Based on the research results obtained, this dissertation uses the combination methods of field test and numerical simulation to analyze the deformation characteristics of deep pit with inner-bracing soldier pile retaining system in soft soil ground. The main contents of this dissertation can be summarized as follows:(1) A brief introduction is made on the research status and results obtained at home and abroad of the deformation of retaining wall and ground settlement caused by pit excavation.(2) A brief introduction is made on the function and features of the foundation pit engineering, the selection of retaining structure of pit, the deformation mechanism and its estimation method of foundation pit. Then, the basic principles and steps of finite element method to simulate the excavation of pit foundation is introduced, and some common constitutive models of soil used in the numerical calculation is discussed.(3) The field test data of a deep pit project with inner-bracing soldier pile retaining system in soft soil in Hangzhou city, such as the horizontal displacement, the settlement and groundwater level outside the pit and the support’s axial force, etc.., is sort out and analyzed, and the change trend is investigated.(4) The deformation mechanism of deep foundation pit with inner-bracing soldier pile retaining structure in soft soil is carried out using three-dimensional finite element and the deformation of soldier pile and ground settlement during the excavation process is investigated. Meanwhile, the effect of the factors, such as burial depth of the pile, the stiffness of the pile and inner support, the surrounding overloading and the reinforcement of the soil in the passive zone of the pit, etc.., on the pit deformation and change laws is analyzed using the numerical simulation method. The influence of these factors on the deformation of deep foundation pit with inner-bracing soldier pile retaining structure in soft soil is studied by changing these parameters in turn.