Study On Reasonable Supporting Structure Of Deep Foundation

In recent years,the economic policy of continuous stimulation to speed up the pace of metropolitan construction,the country's large and medium-sized cities show the features of the prosperity of the central area of the city,and the untapped suburbs.At the same time,the problem of traffic congestion is becoming more and more prominent,and it is urgent to improve the service capability of urban passenger transport system.In the engineering field,the deep foundation pits of the subway station are increasing,and the internal force and deformation regularity of different types of deep foundation pits are needed to study for every engineering and technical personnel.In this paper,a deep foundation pit project in Guangzhou subway is taken as an example.The support scheme of the deep foundation pit is calculated by using the Lizheng deep foundation pit 7.0 and the numerical simulation software MIDAS GTS NX respectively.The Lizheng deep foundation pit 7.0 based on the "technical regulation of building foundation pit support",the results are larger than those of numerical simulation software.The calculation results of the norms are more conservative.By the numerical simulation software establishing the three-dimensional numerical analysis models about underground wall thickness and embedding depth,then they are used to study the effects of different variables on the horizontal deformation of the foundation pit,the surrounding surface subsidence,the bending moment of the envelope structure.Influence of relative settlement of steel columns.The main contents of this paper are as follows:(1)By reading a large number of documents,the deep foundation pit engineering research status are discussed from the deep foundation pit engineering design theory and reasonable research methods.The classification form of supporting structure and inner supporting structure and their respective application scope,internal force and deformation calculation method of supporting structure and inner supporting structure are expounded in detail.(2)The advantages and limitations of the Lizheng deep foundation pit software are studied in detail.Using the software to calculate the support structure,the horizontal displacement,vertical settlement and.stability checking results of this project are less than those in the specification value of the foundation pit engineering manual".So it is safe.(3)Combined with geological survey report,the definition of material properties,the determination of foundation pit and peripheral load,the finite element model of MIDAS GTS NX finite element software is used to establish the three-dimensional finite element model,to gain the horizontal foundation deformation,vertical settlement,Moments,support axial force analysis results.By comparing with the results of the calculation of the Lizheng deep foundation pit,it is concluded that the calculation result of the Lizheng deep foundation pit is too large and conservative.(4)The influence of the variation of the thickness and the embedment depth of the diaphragm wall on the internal force and deformation of the foundation pit is analyzed by numerical simulation.lt is concluded that there is a critical value for the deformation of foundation pit.The reasonable value of wall thickness and embedded depth is studied based on displacement safety reserve coefficient.In engineering practice,the increase of wall thickness and embedded depth can effectively control the deformation of foundation pit.(5)By comparing the results of the finite element software and the actual monitoring results,the difference of lateral deformation is 2.2,the difference of settlement is about 4.12,and the trend is consistent.It is proved that the numerical simulation results of the foundation pit project have reference significance and guiding role for the design of foundation pit support structure and foundation pit excavation.