Physical and numerical study of strain burst of mine pillars

Strain burst is a spontaneous dynamic failure of rock that can cause serious injury to the miners and damage to the underground excavations. To simulate the strain burst in the lab, a steel beam was designed and connected to the compression loading machine. The beam acts as an energy absorber and is in direct contact with the rock specimen which is under uniaxial compression loading. Upon failure of the specimen, the absorbed energy in the beam is transferred to the rock specimen to simulate the strain burst in underground pillars. Based on the physical tests, rock fragment velocities of more than 4 m/s were measured using a high speed camera. The interaction between the steel beam and the rock was modeled using a hybrid discrete-finite element computer program. The effect of different parameters such as pillar’s length and diameter, friction coefficient between pillar and roof, compressive strength of pillar, rock post-peak behavior, roof stiffness, and pillar and roof rock densities on the intensity of the strain burst were studied. The strain burst intensity was defined as the kinetic energy of the simulated rock. Dimensional analysis was applied to find relationships between the dimensionless parameters in the numerical simulation. The proposed scaling model together with the numerical analysis appears to be able to show the significance of different parameters involved in the strain burst. In particular, it is shown that the pillar diameter and its uniaxial compressive strength have significant impacts on the induced kinetic energy during a strain burst.