Realization Of Large Deformation Cosserat Finite Element Numerical Method And Its Applications

With the increase of deformation,the bearing capacity no longer increases,but decreases after the bearing capacity reaching the peak for triaxial shear text of dense sand and overconsolidated clay.That is,strain softening occurs.Slope and foundation failure is a progressive process for such soil.The progressive failure is often accompanied by large deformation problem.In this,the research work mainly in the following aspects:1.Through calculation safety factor of slope stability,the correctness of introducing strength reduction method to ABAQUS is verified.ALE provided by ABAQUS introduces the strength reduction method,it is testified the feasibility by contrast with large deformation results calculated by Cui-Ying Zhou.The reduction necessity and method of Poisson's ratio is given in this paper.2.When the non-associated flow rule is adopted under conditions of plane strain,Drucker-Prager(DP5)yield criterion matches Mohr-Coulomb(M-C)yield criterion.In this,material parameters of Drucker-Prager(DP5)yield criterion can be obtained in Cosserat theory.The foundation bearing capacity is analyzed by the degradation of Cosserat,the result is compared with the results of DP5,M-C in ABAQUS and Nazem.They are exact match.The correctness of Cosserat element program is proved.3.Make use of the secondary development function of ABAQUS,interpolation subroutine SDVINI is writing by FORTRAN.Combining eight-node quadrilateral Cosserat element,the Cosserat continuum theory is successfully introduced into the large deformation method of RITSS.The correctness of Cosserat-RITSS is proved by contrasting it with large deformation results calculated by Nazem and Tian.4.It is theoretically proved that the solution of safety factor for critical failure and steep slope is consistent by using gravity increase method and strength reduction method.Write programs to implement gravity increase method in Cosserat element.The safety factors under large and small deformation conditions obtained by using Cosserat-RITSS and Cosserat-FEM are consistent with strength reduction method of ABAQUS.5.The progressive failure process of slope is analyzed with strain-softening behavior by using Cosserat-RITSS and Cosserat-FEM.Strain softening reduces the safety factor of slope for small and large deformation.The Cosserat-RITSS developed in the paper can consider both strain softening and large deformation,it has an outstanding characteristic.6.Progressive failure of axisymmetric circular foundation penetration is analyzed by Cosserat-RITSS.The results illustrate it is not safe to use the ideal elastoplastic constitutive relation in the analysis for the soil with strain softening.