This study aims to demonstrate the capacity of the Discrete Element Method (DEM) to model and simulate fracture in brittle rock, capture the crack propagation process and determine crack propagation rates for various levels of external loading. In the numerical experiments reported here, a macroscopically homogeneous body of brittle rock, containing a single pre-existing crack, was subjected to tensile stress loading. Simulations concerned with model I crack growth process in 3D were carried out. The process of fracture has been observed under various steady state and dynamic conditions. The numerical results obtained reproduce qualitatively and quantitatively a variety of observed fracture phenomena. Specifically, this study examined the onset of cracks, single dominant cracks that grow across the specimen, crack bifurcations and branching. The density of fractures that can be nucleated and grow to a significant size with and without arresting each other, crack growth speed and stress distribution, all have been consistently and systematically analyzed. Suggestions on potential future developments are made and discussed.
Fracture and failure mechanics are very important in mining, manufacturing, materials processing, mineral processing, civil and mechanical engineering, and many other disciplines of science and engineering. Yet, due to the complexity of fracture phenomena, no theoretical models of broad applicability are currently available (Bieniawski 1967). The simulation of crack propagation is therefore considered an open question in numerical rock mechanics. Although, a significant body of experimental research on fracture of materials was carried out since the early days of fracture mechanics (circa 1940s) (Poncelet 1946, Mott 1948), often in parallel with the development of fracture mechanics theories as well as with the development of experimental and observational techniques themselves, the experimental results were often done on particular classes of material such as glasses and other very brittle materials. Indeed, a number of specific experimental observations on the behavior of growing cracks in brittle materials were made in the 1940s for which generally accepted explanations based on physical principles are still lacking. Likewise, quantitative numerical modeling, based on both continuum and discrete methods, as a basis for understanding dynamic crack growth is still in a preliminary stage.
From the rock mechanical point of view, fracture mechanics is a branching field of rock mechanics which plays an essential role in elucidating the behaviour of rock-like solids. It is widely applied in various areas such as building seismic resistance (Guanglun, Pekau et al. 2000, Zhu, German et al. 2011), metal fatigue (Orowan 1939, Barsom & Rolfe 1999) or dynamic earth faulting. In the mineral industry, the understanding of fracture dynamics is critical. In cave mining, for instance, knowledge of fracture behaviors could help engineers determine the stability of rock structures, predict the evolution of discontinuities, plan undercut and extraction level layouts, and optimize the use of drilling and blasting in an attempt to maximize operational efficiency and minimize potential hazards. Thus fracture mechanics continues to be rich in challenging and important problems.
