Numerical Simulation Of Geotechnical Engineering Based On PFEM And Cosserat Continuum

The particle finite element method(PFEM)is an emerging numerical simulation method,which has a solid mathematical foundation of the finite element method and the advantages of the meshless method in dealing with large deformation and complex boundary problems.It has a wide range of applications in fluid dynamics and large deformation of rock and soil.This paper first implements the PFEM method calculation process based on the commercial software ABAQUS,and uses the implemented PFEM method to simulate the foundation bearing capacity,collapse problems and slope stability problems.The results show that the PFEM method implemented in this paper is suitable for large deformation problems in geotechnical engineering,and can simulate the entire failure process;due to the use of boundary recognition technology,the topological relationship between particles is optimized,and the change of free surfaces is well described;at the same time,the mesh is continuously re-divided during the large deformation calculation process,and the mesh quality is also guaranteed.In addition,this paper treats boundary recognition and meshing as two independent processes,and uses different types of elements for analysis,which proves the feasibility of quadrilateral elements in the PFEM method and lays the foundation for subsequent research.The triaxial test results of loose sand and dense clay show that such rock and soil materials are often accompanied by strain softening when they fail.In actual engineering,strain softening will cause progressive failure characterized by the formation of shear bands.In the numerical simulation,the strain softening will also cause the governing equations to lose well-posedness in the nearby localized region,and the solution of the problem will have an ill-conditioned mesh dependence.In order to solve the mesh-dependent behavior caused by strain softening in the large deformation of rock and soil,this paper introduces the Cosserat continuum theory into the previously implemented PFEM method,and uses the quadrilateral eight-node Cosserat element subroutine developed by the predecessor to realize Cosserat-PFEM method.Subsequently,this method was applied to the progressive failure analysis of the sliding slope and the passive earth pressure analysis of the retaining wall.The results show that the Cosserat-PFEM method can effectively improve the mesh dependence caused by strain softening in large deformation problems.The bearing capacity curve,shear band form and displacement mode under different mesh sizes all show strong consistency.The Cosserat-PFEM implemented in this paper provides a new idea for solving such problems.