IMPLEMENTATION OF A COHESIVE CRACK MODEL IN GRAIN-BASED DEM TECHNIQUE FOR SIMULATING FRACTURE IN QUASI-BRITTLE GEOMATERIAL

ABSTRACT: This paper presents a grain-based discrete element model for simulating the quasi-brittle failure of rocks under mechanical loading. In this approach, the development of crack along grain boundaries controls the degree of damage in rock. A cohesive crack model based on the theory of “Non-linear Elastic Fracture Mechanics (NLEFM)” is implemented into the UDEC distinct element numerical code to define the constitutive behavior of the grain interfaces under different modes of fracturing. Implementation of the crack model in the grain-based simulator aims at enhancing the capability of the UDEC-Voronoi scheme to simulate the micro-cracking mechanisms more realistically similar the micro-cracking mechanisms. Rock heterogeneity, due to the presence of different mineral grains, is introduced to the model by considering the mineral composition of real rock and contrast in mechanical properties of the constituent minerals. The elastic properties of the grains and the strength properties at grain boundaries are extracted based on the experimental data. Then, the capability of the model to replicate the mechanical behavior of Lac du Bonnet (LDB) granite under compression and tension is evaluated. To do so, a series of uniaxial and triaxial compression and Brazilian tests is simulated. The mechanical response of the numerical models is found to be in good agreement with the response of the real rock observed in laboratory.