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To optimize the excavation of rock using underground blasting techniques, a reliable and simplified approach for modeling rock fragmentation is desired. This paper presents a multistep experimental-numerical methodology for simplifying the three-dimensional (3D) to two-dimensional (2D) quasi-plane-strain problem and reducing computational costs by more than 100-fold. First, in situ tests were conducted involving single-hole and free-face blasting of a dolomite rock mass in a 1050-m-deep mine. The results were validated by laser scanning. The craters were then compared with four analytical models to calculate the radius of the crushing zone. Next, a full 3D model for single-hole blasting was prepared and validated by simulating the crack length and the radius of the crushing zone. Based on the stable crack propagation zones observed in the 3D model and experiments, a 2D model was prepared. The properties of the high explosive (HE) were slightly reduced to match the shape and number of radial cracks and crushing zone radius between the 3D and 2D models. The final methodology was used to reproduce various cut-hole blasting scenarios and observe the effects of residual cracks in the rock mass on further fragmentation. The presence of preexisting cracks was found to be crucial for fragmentation, particularly when the borehole was situated near a free rock face. Finally, an optimization study was performed to determine the possibility of losing rock continuity at different positions within the well in relation to the free rock face.
Kucewicz et al. (Fri,) studied this question.