Hybrid finite–discrete element modeling of geomaterials fracture and fragment muck-piling

The essential components of hybrid finite–discrete element methods (FEM/DEMs) available in literature are reviewed in this paper first, which include contact detection and interaction between individual bodies, deformability, and transition from continuum to discontinuum through fracture and fragmentation, and temporal integration scheme. Among them, the transition from continuum to discontinuum through fracture and fragmentation is introduced in detail since it is regarded as the key component and makes the hybrid FEM/DEM superior to the continuum-based finite element method (FEM) and the discontinuum-based discrete element method (DEM). An integrated development environment (IDE) is then developed for a hybrid FEM/DEM using C++ and OpenGL on the basis of the authors’ enriched FEM-based codes and the open-source combined FEM/DEM libraries available in open-source repositories. The proposed IDE not only simplifies the use of the hybrid FEM/DEM through graphically building numerical models and visually displaying calculated results in real time but also provides a platform for further developing the hybrid method. The proposed development is then used to model the quasi-static failure of rock in uniaxial compression tests and dynamic fracture of rock in impact tests, which are well documented in literatures, to calibrate the hybrid method. Finally, several engineering problems are modeled to demonstrate the application of the hybrid method in geotechnical engineering. The models of particle flow through a draw point and rock-falling along a staged slope demonstrates the benefits of the proposed development in dealing with the discrete systems in 2D and 3D, respectively. Compared with DEM, the hybrid method is more versatile in dealing with deformable, irregular-shaped and breakable discrete particles. The modeling of rock fragmentation by blast and resultant fragment muck-piling demonstrates the key feature of the hybrid method in dealing with the transition from continuum to discontinuum through fracture and fragmentation. Compared with FEM, the hybrid methods are more robust and efficient in dealing with rock fragmentation after the rock fracture occurs, especially in modeling resultant fragment movement, tertiary fracture, and fragment muck-piling.