Experimental study on energy dissipation of fragments during rockburst

In this study, rectangular prismatic coarse-grain granites were analyzed through an application of a modified true-triaxial rockburst testing system. Various loading rates were considered in a process in which one face was kept free and loading conducted on the other five faces. Using a proposed surface energy per unit area measurement method, the energy dissipation due to the formation of rock fragments during the rockburst process was quantitatively analyzed. The experimental results show that rockburst occurrence depends on several conditions, including - specifically the tangential loading rate exceeding a certain threshold, the presence of considerable amounts of stored strain energy, the dissipation of energy through rock splitting on the free face, and the shear failure in the potential rockburst pit. With increases in the loading rate from 0.5 to 4.0 MPa/s, the fragmentation and energy dissipation of fragments decline linearly. Lamellar coarse fragments are found to be primarily induced by tension failure from the rockburst pit surface. Blocky medium, fine fragments and white powdery tiny particles are mainly induced by shear failure from the rockburst pit interior. Under various loading rates, the dissipated energy of fragments induced by shear is more than 90% of the total dissipated energy.