Deformation Characteristics Analysis Of Secant Piles Supporting Structure In A Deep Soft Clay-Foundation Pit Under Construction

Usually, subway foundation pits are relatively deep, and are located in areas with high density of buildings and pipelines. As a result, there is a higher requirement for the design and construction of a subway foundation pit. Deep foundation pit in the state most at risk, the need to ensure the safety of the construction pit by supporting With the development of foundation pit technology, there are more deep foundation-supporting-methods can be used in areas with different geological condition. This thesis studied the deformation of secant pile-retaining-structure in the silty-soft clay-layer during excavation, and provides references for similar foundation pit-projects. Secant pile-retaining-structure combine their strengths diaphragm wall and ordinary pile, with strong market potential, but for domestic bite pile of research are not enough, we need a lot of testing and engineering study of its applicability, the paper by studying the soft soil secant pile-retaining-structure.Retaining structure stress and deformation characteristics during the construction phase to provide a reference for the future of the same type of excavation.This thesis explained the soft soil of secant pile-retaining-structure combined Nanjing Xinzhuang subway station deep excavation site monitoring data and the finite element analysis results of excavation carried out the following analysis:(1) Mechanical behavior and deformation mechanism of deep foundation pit of a theoretical analysis of the stress mechanism and design methods;(2)Analysis of the Xinzhuang station deep foundation pit monitoring programs, and engaging pile horizontal deformation, axial force and support the monitoring data of the surrounding surface subsidence sort,.Secant pile-retaining-structure deformation of the system during the construction phase and the soft soil layer deformation of soil and silt soil related mucky layer thicker pile deformation area is relatively large, partially enclosing the pile in mucky layer may pile deformation rate is large, even convex shape. Because silt soft soil creep, after the pit envelope back body will still be sustained large deformation, while the smaller area enclosed structure with or without a thin layer of mucky mucky layer and the back cover pit after rapid deformation rate convergence;(3) Using the finite difference software FLAC3 D during deep foundation pit of the secant pile-retaining-structure force and deformation, axial force and surrounding support body surface subsidence numerical simulation analysis, and simulation results obtained with field monitoring data obtained for comparative analysis the numerical results and monitoring data is basically consistent, proven simulation software in soft soil foundation deformation characteristics Secant pile-retaining-structure having the accuracy and applicability of the structural safety of foundation pit to find the most unfavorable position by the maximum principal stress diagram and found secant pile-retaining-structure envelopes, bear most of the dirty pile of earth pressure to resist the action;(4) Numerical simulation analysis of different rock and soil physical and mechanical parameters and design parameters for secant pile-retaining-structure. Secant pile affect performance, and the impact on these parameters enclosed structure were analyzed, the results show soil bulk modulus and internal friction angle and strength of concrete piles hormone level changes in the foundation pit deformation structure and the surrounding soil settlement greater impact on cohesion, pile length and amount of bite of the impact is relatively small, there is provided construction programs in the pit design optimized to provide reference for the design and construction of deep foundation pit after the same type.