Experimental study on energy dissipating characteristics of rockburst fragments under different loading rates

The experiments on coarse-grain cuboid granite are performed for simulating ejection process of strain rockburst under different loading rates by using self-developed triaxial rockburst test system. Based on a new method for measuring surface energy per unit area, the quantitative analysis of energy dissipation of rockburst fragments is realized by with analyzing the stress-strain curve. Then energy dissipating characteristics of rockburst fragments under different loading rates are studied. The experimental results show that: (1) Under the triaxial compression with one single free face, rockburst ejection occurs when some conditions are met including that the vertical loading rate exceeds a certain rate, gathering enough elastic strain energy and dissipating proper energy through rock splitting on the surface of the free face and rock shearing in potential rockburst near the free face. (2) With the increase of loading rates ranging from 0.5~30 kN/s, the broken degree of rockburst fragments linearly declines. (3) Among the fragments under different loading rates, the coarse sheet fragments mainly come from surface of rockburst notch and are created by tension failure, and the medium-granular, fine-grained prismatic fragments and powdery tiny fragments mainly come from the interior of rockburst notch and are created by shear failure. (4) Under different loading rates, energy dissipation is mainly caused by shearing, and the percentage of energy dissipation caused by shearing reaches about 97% to 99%.