DEM investigation of the fracture mechanism of rock disc containing hole(s) and its influence on tensile strength

Macroporosity, pores or holes are common in rock mass, and play important roles on mechanical behaviors of rock mass. The aim of the numerical study presented in this paper is to investigate the fracture mechanism of rock disc containing hole(s) and its influence on tensile strength using the discrete element method (DEM). With special reference to experimental tests, the methodology of using triangle blocks in the Universal Distinct Element Code (UDEC) to simulate tensile fracture process in Brazilian disc tests has been validated herein. First, the properties used in the UDEC Trigon model were determined depending on numerical calibrations to the published experimental results. Secondly, the fracture process of the rock disc containing a central or eccentric hole was simulated numerically, and the numerical results were compared with the experimental tests available. Special attention was given to the effect of the hole size and location on the tensile fracture pattern and tensile strength of the specimen. A series of numerical simulations were implemented to suggest a critical scope in which the hole plays an important role on tensile fracture onset and propagation and then determining the tensile strength. Thirdly, the influence of multiple holes on the initiation and propagation of tensile cracks inside a specimen were simulated. Fracture mechanism of disc containing two holes and its influence on tensile strength were highlighted. The effect of the hole numbers (void porosity), hole sizes and their distribution on tensile fracture patterns and strength were also investigated.