Numerical Simulation And Comparative Analysis For The Whole Process Of Deep Foundation Pit Excavation To A Project

With the continuous development of coastal areas in Qingdao,high-rise buildings in seaside of Qingdao have been continuously built,and deep foundation pit projects have also increased.The soil and geological conditions in seaside of Qingdao are complex,especially in the coastal area of the Hongdao area.There is a large amount of silty soil layer in the upper part and a hard rock layer in the lower part,which belongs to the upper soft and hard soil.During the excavation process of the foundation pit,due to the different excavation methods,overload and the complexity and discreteness of the soil layer,the deformation of the foundation pit is often unable to carry out accurate theoretical calculations.People are learning the excavation rules of deep foundation pits in other areas.On the basis of this,it is necessary to study the excavation law of deep foundation pits under complex geological conditions in the coastal area of the region.The main research contents of this thesis include:(1)Explain the development process and research status of both the foundation pit optimization and numerical analysis at home and abroad,and clearly understand the research status of these two aspects at home and abroad.(2)Introduced the basic geological conditions of Qingdao area,the common support methods in Qingdao area and the supporting schemes applicable to foundation pit under different conditions,and introduced the basic requirements of foundation pit design.(3)Taking the deep foundation pit of the International Convention and Exhibition Center project as the engineering background,using Lizheng deep foundation pit software to design and check the unfavorable profile of the foundation pit.Through the analysis of the design verification results,it is found that all the indicators meet the requirements of the specification.,indicating the safety and reliability of the design.(4)Establish a three-dimensional finite element model of Midas GTS,and compare the numerical simulation results with the measured values.The effects of factors such as the stiffness of the foundation pit retaining structure,the arrangement position of the anchor,the prestress value and the spacing of the anchor on the deformation of the foundation pit are studied.(5)Through the comparative analysis of the finite element calculation results under different working conditions,the influencing factors analysis and optimization of the foundation pit are discussed.The conclusions drawn in this paper mainly include:(1)Using the rational deep foundation pit software to design and check the unfavorable profile of the foundation pit.Through the analysis of the design verification results,it is found that all the indicators meet the requirements of the specification,indicating the safety of the design scheme.reliability.(2)Through the horizontal displacement of the slope of the hotel foundation pit,the vertical displacement of the slope top,the deep horizontal displacement and the axial force of the anchor,the maximum horizontal displacement of the pile top is 42 mm,the maximum vertical displacement of the pile top is 17 mm,and the maximum level of the envelope structure.The displacement is 35.3 mm.(3)After analyzing the simulation results of the deep foundation pit of the hotel,the variation of the deep horizontal displacement of the foundation pit and the axial force of the anchor is consistent with the variation of the monitoring value,and the reliability of the foundation pit model is verified.(4)After comparing the results of the finite element model of different thickness retaining structures,it is concluded that as the thickness of the retaining structure increases,the horizontal displacement of the retaining structure decreases linearly below the prestressed anchor.(5)Different prestressing is applied to the anchor rod.After comparing the results of the finite element model,it is concluded that the change of the prestress value of the anchor has little effect on the horizontal displacement of the foundation pit and the basal uplift.(6)Different vertical positions are set for the bolts.After the comparison of the results of the finite element model,it is concluded that with the decrease of the vertical arrangement position of the anchors,the displacement in the foundation pits is gradually reduced,and the horizontal displacement of the pile tops is gradually increased.(7)After comparing the results of the finite element model of horizontal spacing of different bolts,it is concluded that as the horizontal spacing of the anchors becomes larger,the horizontal displacement of the deeper layers of the retaining piles above the basement increases continuously,and is embedded in the soil.The horizontal displacement of the retaining pile part did not change significantly.