Abstract: Reasonable characterization of fracture process zone is key to nonlinear fracture simulation of quasi-brittle materials, such as concrete and rock. This paper, based on a framework of cohesive zone model, presents an extension of the frictional contact model between discrete blocks in the deformable discrete element method. In this model, we adopt a new cracking criterion by combining the mixed-mode BK fracture energy criterion with to the Mohr-Coulomb criterion with tension-cutoff, and formulate nonlinear interface constitutive equations capable of modeling tension-shear and compression-shear mix-mode loading conditions. And Voronoi tessellation is used to eliminate the dependence of fracture propagation paths on the geometric division of discrete blocks. Through parametric analysis of the Galvez asymmetric three-point bending beam tests and adopting suitable softening parameters, we achieve a good agreement between the results of this model and the test data, verifying its capability in simulating uniaxial tension and mixed-mode fractures.

Key words: discrete element method, cohesive zone model, Voronoi tessellation, mixed-mode fracture