Study On Optimization Of Deep Foundation Pit Retaining Scheme And Construction Mechanical Effect

Foundation pit engineering is a systematic engineering integrating geological engineering,geotechnical engineering,structural engineering and geotechnical experimental technology.There are many factors that affect its stability.Now,deep foundation pit projects are increasing year by year.There are also more and more problems in the construction and design of deep foundation pit support.For example,in the process of foundation pit construction,it is necessary to ensure the stability of the foundation pit itself,the safety of adjacent buildings and underground pipelines,and the economy and rationality of the support scheme,so as to save the investment amount for the construction unit and reduce the cost for the construction unit.Through this study,it can provide a reference for the design scheme of deep foundation pit support projects of similar scale,provide the key technology in the construction process,summarize the change rules of slope vertical deformation,horizontal deformation and internal force of each soil nail in the process of deep foundation pit soil nailing wall support,and provide relevant technical support for the design of similar foundation pit support schemes in the future.The main research contents of this thesis are as follows:(1)The characteristics of different supporting methods for deep foundation pit are analyzed.According to the stratum lithology and hydrogeological conditions of this project,the design calculation is made by using the rational design software,and three supporting schemes,namely soil nailing wall,underground continuous wall and row pile+anchor rod,are comprehensively compared and analyzed in aspects of slope stability,construction convenience and technical economy,and it is concluded that the best supporting scheme for this project is soil nailing wall.(2)Three-dimensional numerical method is used to simulate and analyze the foundation pit construction process,and the vertical and horizontal variation laws of slope and axial force of soil nails are studied for different excavation depths,different soil nail spacing and different arrangement modes.At the same time,the settlement and inclination rate of high-voltage tower foundation near the foundation pit are studied,in order to determine the position of maximum deformation of slope top,the position of maximum axial force of single soil nail on the maximum deformation section,the position of soil nails with large axial force in the vertical section of foundation pit and the relative stress of soil nails.(3)From the actual construction,it is concluded that the excavation of foundation pit should be layered vertically according to 1.4m per floor,and the length of each section in the horizontal direction along the A-K axis is 25 m,so as to ensure the reasonable connection with the supporting process.In structural construction,the key points of construction quality in processes such as drilling holes,planting soil nails and concrete slope ensure the quality of supporting structure,thus ensuring the safety of foundation pit.(4)According to the characteristics of foundation pit shape,deformation monitoring points(8 in total)are arranged at the top of slope,and the results of horizontal and vertical displacement of each monitoring point are compared with those of numerical simulation,which proves the rationality of supporting parameters.