Experimental investigation and failure characteristics of slit-cut method in rockburst prevention

Abstract

Rockburst has become one of the most serious threats to the safety of workers, equipment, and excavations in deep underground engineering. However, the prevention of rockburst risk remains an unsolved problem. The slot-cut method was put forward, aiming at the problem of strain burst for tunnel projects. The mechanism and method of slot-cut prevention of delayed rockburst were discussed by laboratory tests, theoretical analysis, and numerical simulation. The mechanical responses, failure patterns and failure indexes of granite specimens were analysed. The rockburst process and deformation evolution law of test specimens with different crack parameters were studied in great detail. Based on the experimental results, a comprehensive discrimination of rockburst proneness was explored. The results demonstrate that the peak stress and damage index of pre-cracked granite initially decreases and subsequently increases with crack angle, and the pre-peak and post-peak elastic modulus with different crack numbers decreases linearly, indicating that a change in the crack number significantly affects the bearing capacity of granite. The failure mode of the granite specimen belongs to the tension-shear composite type. Meanwhile, it was found that both the brittleness index and ejection energy with different cracks show an U-shaped for the pre-cracked granites, confirming that the crack angle of 60° has been found to be the threshold for rockburst proneness. Ultimately, the combination of the rockburst energy index describing rock ejection qualitatively and the optimized residual energy index considering elastic energy at post-peak stage quantitatively provides a judgment criteria to comprehensively characterize the rockburst proneness of granite by the slit-cut method. When compared with original index, the results of the comprehensive discrimination exhibited good accuracy. Therefore, the experimental phenomenon and judgment criteria prove that the slit-cut technology can be well applied to the rockburst prevention.