Experimental verification of the intrinsic strainburst proneness of various rock types

Abstract

A portion of excess strain energy is converted into kinetic energy after the peak load in Class II rock. That is the intrinsic potential energy for strainburst. Therefore, the intrinsic strainburst proneness of the rock can be quantitatively assessed by the excess energy released from the rock, which can also be expressed by an intrinsic ejection velocity. This study aims to validate the idea of using the intrinsic ejection velocity as an index for the strainburst proneness of rock. Servo-controlled uniaxial compression tests were first conducted on 13 types of rocks. The intrinsic ejection velocities of rock specimens were assessed on the stress–strain curves. It was showed that the ejection velocity was greater than zero in twelve of the thirteen rock types, indicating that the twelve rock types were intrinsically prone to strainburst. The intrinsic ejection velocity was less than 5 m/s in eleven rock types, while up to 7.2 m/s in one. True triaxial tests were then conducted to examine the intensity of the bursting in six of the burst-prone rock types. The mass of the ejected rock fragments and the bursting sounds were recorded and analyzed afterward. The results showed that the orders of both the mass of the ejected rock fragments and the intensity of the bursting sounds were consistent with the order of the intrinsic ejection velocities of the rocks. It seems that the intrinsic ejection velocity is an appropriate index for the strainburst proneness of rock.