Study On Evaluation And Optimization Of Deep Foundation Pit Retaining Scheme

Nowadays,there are more and more super high-rise buildings in cities.Skyscrapers have become the symbol of landmark buildings in every city,the beautiful building name card of every city and the symbol of modern civilization.With the increasing above ground height of buildings,the depth of underground structure is getting deeper and the plane size is getting bigger and bigger.As well as the rise of urban rail transit projects and underground comprehensive pipe gallery projects in various cities,there are more and more deep foundation pit engineering projects.With the development of deep foundation pit engineering to ultra deep,super large and super tight,many safety accidents have also been caused.Design error is the primary factor that causes deep foundation pit accidents,therefore,to ensure the safety of deep foundation pit engineering,deep foundation pit engineering design is the key,adopt scientific management method in the design stage,make the design reach zero error,deep foundation pit safety accidents will be greatly reduced.The design of deep foundation pit support scheme is the key to the design of deep foundation pit engineering.Before the detailed design of deep foundation pit support,an optimal support scheme should be selected first.In this context,this study first analyzes a large number of foundation pit supporting cases and references to books and manuals related to foundation pit engineering to select 9 main influencing factors from many factors affecting the optimization of deep foundation pit supporting scheme,and then uses the improved principal component analysis method to select the principal components of the main influencing factors.Finally,a scientific and objective optimization model of deep foundation pit supporting scheme is determined by trial calculation comparison with improved BP artificial neural network and MATLAB software code program.The main research contents are as follows:(1)In the numerous factors influencing the deep excavation,the select,the size of the foundation pit excavation depth,the number of dominant soil type,soil,the soil average heavy,soil,on average,cohesive force,the average friction Angle of soil,underground water and the safety of foundation pit and surrounding buildings neighboring relations the nine main influencing factors,as the influence factors of deep foundation pit support scheme set,The qualitative factors are quantified by the relative standard,which lays a foundation for determining the principal component of the influencing factor set.(2)Determine the principal components of the influence factor set of deep foundation pit supporting scheme,reduce the 9 related factors to 5 unrelated principal components,and accelerate the convergence speed of BP artificial neural network model.(3)Some methods to improve the traditional BP artificial neural network are proposed from three aspects of network topology,gradient descent method and activation function.By using improved BP artificial neural network and using Matlab software to write code program,the optimization model of deep foundation pit support scheme is established through trial calculation and comparison.There are 50 figures,11 tables and 76 references in this thesis.