Deformation And Stress Analysis Of Foundation Pit Excavation Based On Modified Mohr-Coulomb Model

With the development of society,urban rail transit came into being.The excavation problem occurs frequently in the process of railway construction.Subway construction is usually carried out in the urban areas,but the surrounding environment is more complex.There are a variety of roads,pipelines,surrounding buildings.So the deformation and stress caused by excavation is worthy of consideration.In this paper,finite-element element software MIDAS/GTS was adopted to analyze the deformation and force in the excavation of the subway pit based on a subway project in Kunming.1.The constitutive model of the soil adopted throughout this paper is a modified Mohr-Coulomb model,the parameters of which are analyzed by Joint Sensitivity Analysis of Single Factor and orthogonal analysis of variance.Besides the influence of these parameters on the deformation and the maximum force of the foundation pit and is studied.2.It is difficult to ascertain these three parameters in the constitutive model of the Mohr-Coulomb,such as Eref50,Erefoed and Erefur.The parameters Erefoed/Erefoed =1?2?3 and Eurref/Eref50=3?4?5?6 are designed as 12 schemes.In these 12 schemes,the surface subsidence of the foundation pit,the bottom of the pit,and the lateral movement of the wall are analyzed,Three kinds of suitable schemes are initially selected,and compared with the results of the actual monitoring data.Finally,the data most suitable for the project are Eref50/Erefoed =1 and Erefur/Eref50=6.The deformation of the pit is the most reasonable and consistent with the actual situation in the model established by this set of parameters.3.Through the comparison of the above twelve programs,the most appropriate ratio is chosen.And the ratio is used in the numerical simulation of foundation pit excavation.The deformation of the foundation pit under various working conditions is analyzed comprehensively and systematically(including settlement,Uplift,wall swings).4.The stress analysis of foundation pit excavation is also carried out in the process of numerical simulation,The distributions of supporting axial force,walls bending moment and active earth pressure are analyzed.Two methods are used to fit the actual earth pressure distribution curve,and four methods are used to determine the ultimate active value of the foundation pit.By academic calculation and numeric simulation,it is proved that the numerical simulation is reasonable and correct.The stability and strength of the inner brace are analyzed by using the maximum axial force in the theoretical calculation and numerical calculation.It is proved that the support design is reasonable and safe.5.The method of parameter determination reflects the adjustment method of the numerical model.That is,the most reasonable numerical results can be obtained by adjusting the ratio of Eref50,Erefoed and Erefur,which can be used to predict the deformation of the foundation pit.