Numerical modeling of rock mechanical behavior and fracture propagation by a new bond contact model

• A bond contact model for rocks was proposed based on experimental data.
• The bond contact model was successfully calibrated to match experimental data.
• Two limitations frequently encountered in DEM simulation of rocks were solved.
• An agreement is observed between simulations and experiments on cracking patterns.
• The mechanical behaviors of DEM flawed samples match the experimental data well.

This paper presents a numerical investigation into mechanical behavior and rock fracture using the distinct element method (DEM). Based on a series of laboratory tests on the bonded granules idealized by two glued aluminum rods, a normal force dependent bond contact model was proposed and implemented into a two-dimensional (2D) DEM code. This 2D DEM code was used to carry out a series of numerical simulations, including uniaxial and biaxial compression tests, direct tension and Brazilian tension tests, whose results were compared with experimental data to calibrate the proposed model and identify the microscopic deformability and strength parameters. In addition, the validated model was then used to simulate crack propagation and rock fracture in single-flawed and double-flawed samples with different flaw inclinations, and the simulations were then compared with experimental observations. The numerical results demonstrate that the proposed bond model incorporated into the distinct element method is able to capture the main mechanical behaviors of crystalline rocks (Lac du Bonnet granite and Hwangdeung granite). The limitations associated to a low strength envelope angle and high ratio between tensile strength and compressive strength frequently formed in DEM simulations of rock behaviors are solved. In addition, five distinct stages of the stress–strain curve and the marked stresses can be clearly identified by lateral strain, volumetric response and the cumulative number of bond failures. The mechanical behavior and rock fracture patterns obtained from DEM simulations are in good agreement with experimental observations and the model captures both the geometrical control and the general strength value for crystalline rocks.