Multi-criteria assessment of rock bump hazard

A series of laboratory tests was carried out for 50 samples of different rock types (sandstones, siltstones, limestones, shaly silts) to evaluate the tendency of rocks to rock bumps. The tests were carried out using the Instron 8802 servohydraulic press in the uniaxial compression mode with the press clamp velocity travel of 0.1 mm/min. Five specimens were tested from each group of the same rock types. As the result, complete stress-and-strain diagrams including the post-peak deformation section were obtained. Evaluation of the rock bump hazard was performed using several criteria in order to compare their accuracy. Results of the calculations revealed that different criteria can give different estimates of the rock's tendency to bumps even for the same rock type. Based on analyzing the experimental data, it was concluded that the energy-based rock bump hazard indicator, defined as a difference value covering the entire rock fracture process, is the most reliable criterion.