Optimization Of Deep Foundation Pit Support Scheme And Finite Element Analysis Of Deformation Of Retaining Structure

At present,various types of underground spaces for various purposes are constantly being developed and utilized in major and medium-sized cities in China,and various deep foundation pit projects are emerging one after another,such as high-rise building basements,underground rail transit,large underground parking lots,urban reservoirs,underground civil air defense projects,etc.With the increasing scarcity of urban construction land,more and more deep excavation projects are being constructed in areas with dense surrounding buildings,staggered underground pipelines,and complex geological conditions.Excavation of foundation pits will inevitably affect the surrounding soil,which in turn will have adverse effects on surrounding buildings,groundwater,underground pipelines,and surrounding road surfaces.With the continuous deepening of foundation pit depth and the complex and ever-changing construction environment,the standards for engineering quality and safety are increasingly improving.Therefore,conducting research on the design,construction,and monitoring of deep foundation pit engineering has significant practical guidance significance.Based on the background of a deep foundation project of a rainwater storage tank in Hefei City,this paper uses the main methods such as analytic hierarchy process,fuzzy comprehensive judgment method,numerical simulation method and percentage method to compare and optimize the two kinds of foundation pit support structure schemes,conduct three-dimensional finite element analysis of the foundation pit support structure,and further optimize the original foundation pit scheme.The main contents include the following aspects:（1）Summarized the current research status of deep foundation pit engineering design theory,optimization of foundation pit support schemes,and design optimization both domestically and internationally,and elaborated on the research content and significance based on the project.Summarized the common types and applicable conditions of support structures in foundation pit.（2）Explored the basis and principles for optimizing the support scheme of deep foundation pits.By using the Analytic Hierarchy Process and Fuzzy Comprehensive Judgment Method,qualitative and quantitative calculation and analysis were conducted on the safety,economy,construction period,and technical feasibility of the two foundation pit support schemes in this project,The results show that the fuzzy comprehensive judgment value E₁ of Scheme 1 is 2.404,the fuzzy comprehensive judgment value E₂ of Scheme 2 is3.277,and E₁ is less than E₂.Therefore,the support scheme for this foundation pit project has been determined as the second type.（3）According to the measured data,the surface settlement displacement,pile displacement,internal support force and column settlement deformation of the foundation pit in different excavation stages are analyzed.With the continuous excavation of the foundation pit,the internal force of the retaining structure increases,and the internal support has a significant limiting effect on the soil around the foundation pit.The horizontal displacement of the pile body increases with the excavation depth,and the maximum displacement point appears near the excavation face.Combined with the numerical simulation analysis,the change laws of the two are basically consistent,and the simulation results meet the requirements of monitoring and measurement standards,which verifies the rationality of the numerical simulation.（4）The"space effect"of foundation pit is analyzed on the basis of 3D foundation pit model.The research shows that the surface settlement displacement presents a"concave"shape,and the maximum settlement is about 0.153%H,which is about 15m away from the middle edge of the long side of the foundation pit.The displacement of the pile body presents a"bulge"phenomenon along the pile body,and the maximum displacement is about 0.110%H,which occurs near the excavation surface.The maximum surface settlement around the foundation pit occurs in the middle area around the foundation pit,and the settlement at the corner area of the foundation pit is small.（5）The finite element software is used to optimize the pile diameter,pile spacing and pile embedded depth.The pile diameter is optimized from 1.2m to 1.1m,and the pile spacing is optimized from 1.5m to 1.8m.Through numerical simulation analysis,the results are in good agreement with the original foundation pit support scheme.Figure[53]table[21]reference[62]...