Nonlinear Soil Spring In Deformation Calculation Of Foundation Pit Retaining Structure And Its Engineering Application

At present,the member system finite element method is often used to calculate the deformation of the retaining structure of foundation pit.However,the traditional member system finite element method,which uses linear elastic spring to simulate the soil in the passive area,is unreasonable,which leads to the fact that engineers often calculate the "skirting" deformation that is not found in the actual monitoring.This makes the design of retaining structure of foundation pit engineering divorced from the reality.In order to make the deformation calculation of foundation pit more close to the actual monitoring results,the spring reflecting the nonlinear deformation characteristics of soil should be used in the passive area during the calculation,that is,the nonlinear spring.The parameter selection of nonlinear soil spring in passive region is one of the main contents of this paper.In this paper,the shortcomings of the traditional finite element method of bar system are explained,the form of nonlinear spring is emphasized,and the hyperbolic function soil spring model is established.Based on the field monitoring data,the nonlinear spring parameters of the soil in the passive zone of more than 30 foundation pits are analyzed.For a typical project,the nonlinear spring parameters of soil are obtained by in-situ test method,and the back analysis work is carried out.The relationship between the parameters obtained by back analysis and the parameters obtained by insitu test is discussed.The empirical values of nonlinear spring parameters of soil layers in Shanghai area under different in-situ test and back analysis are basically obtained.By using the finite element software,the two calculation sections in the specific project are analyzed by the improved finite element method of bar system.In the analysis process,the increment method is used and the nonlinear spring parameters are adjusted,and the ideal calculation results are obtained.Compared with the results of linear spring,it is proved that the nonlinear spring in passive zone proposed in this paper is feasible,reasonable and applicable,which is conducive to improving the algorithm of foundation pit deformation.