The Research Of Finite Element Method For Stability Analysis And Its Application In The High Embankment Of High Speed Railway

In recent years,with the maturation of the finite element technique,finite element limit equilibrium method and strength reduction finite element method as two principal kinds of finite element method for stability analysis have been rapidly used.FEM for stability analysis combines many advantages of FEM and introduces the stress-strain relationship into stability analysis,therefore calculation can be made to get more rational calculation result.It is for this,this kind of method is being popular with many authors and is being applied to analysis of the complicated problem. Some research work focusing on two kinds of FEM for stability analysis is displayed in this paper.Based on Hooke-Jeeves algorithm,FES software is compiled by Fortran95and VB.NET.Through examples,the correctness and practicability of the software are verified,and the effect of parameters of the software on computing result is discussed.Based on Drucker-Prager yield criterion under the plane strain condition for associated flow,the calculation accuracy of strength reduction finite element method is studied by using ABAQUS finite element software.The applicability of two kinds of FEM in stability analysis about high embankment of high-speed railway is evaluated.Our works are as follows:(1)The principles of two kinds of FEM for stability analysis are introduced and deduced the equations between Drucker-Prager yield criterions and Mohr-Coulomb criterion,which can trabsform one criterion to another under the plane strain condition in ABAQUS finite element software.(2)FES software for finite element limit equilibrium method is compiled by Fortran95and VB.NET.Aiming at the shortcoming of Hooke-Jeeves algorithm as low efficiency in local optimum searching,by setting two searches,reducing global search area and threshold of Hooke-Jeeves algorithm of the second search,the computational efficiency and calculation accuracy of the software are improved greatly. Through two standard examples,the reliability of the FES software is verified,and discussed the effect of parameters of the software on computing result.(3)By the data of triaxial tests,the parameters of Mohr-Coulomb nonlinear perfect elastoplastic model for subgrade of high-speed railway are obtained.Through ABAQUS finite element software,the analysis model of high embankment of high-speed railway is established. Based on Drucker-Prager yield criterion under the plane strain condition for associated flow,the computational accuracy of strength reduction finite element method,taking the run-through of plastic zone as unstability criterion,is studied and analysed the effect of model boundary,mesh element size and type on computing result. (4)Based on the analysis model of high embankment of high-speed railway,the applicability of two kinds of FEM in stability analysis about high embankment of horizontal and sloping foundation is evaluated.The results show that:The difference of the safety factor between strength reduction finite element method and Morgenstern-Price method is greatly affected by foundation deformation.Only when foundation deformation is small,the safety factor of strength reduction finite element method is less than Morgenstern-Price method and the safety factor of the two methods are very close.Computing result of finite element limit equilibrium method can reflect well the influence of foundation deformation.When foundation is relatively soft,the safety factor of finite element limit equilibrium method is less than Morgenstern-Price method and the safety factor of the two kinds of methods are differen-tial,but finite element limit equilibrium method requires better accuracy of FEM stress calculation.Only based on rational stress field,can be obtained actual results with using this method.