Cosserat-particle finite element method for large deformation analysis of rock and soil

The particle finite element method (PFEM) inherits the solid mathematical foundation of the finite element method and possesses the capability of modeling the problems with large deformation and complex boundary, so it has been widely used in the fields of fluid-structure coupling and geotechnical engineering. While in the process of large deformation of rock and soil, strain softening and strain localization often occur. In order to keep the well-posedness for the large deformation problem, it is necessary to introduce the regularization mechanism into the constitutive equation. The Cosserat continuum theory is one of the effective methods to introduce the regularization mechanism. Combining the PFEM with the Cosserat continuum theory, the Cosserat-PFEM method is developed. Besides, unlike the traditional PFEM using triangular elements, in the Cosserat-PFEM method the boundary recognition and the mesh generation are carried out independently, which makes it possible to use quadrilateral elements, so as to improve the numerical accuracy and overcome the tendency of triangular elements to simulate the strain localization. The examples show that the developed Cosserat-PFEM method and the programme explored based on the ABAQUS software are reliable and efficient, and expand the application scope of the PFEM. It is also demonstrated that the Cosserat-PFEM has the capability to simulate large deformation problems and keep the well-posedness of the problems, and is suitable for the simulation of large deformation and progressive failure problems.