Dynamic compression mechanical behavior and damage model of singly-jointed samples

The dynamic mechanical behavior of jointed rock mass plays a key role in the blasting excavation from mining and tunneling engineering. To investigate the influence of joint parameters (e.g., joint length, joint position and joint type) on the mechanical behavior of singly-jointed samples, dynamic impact compression tests are performed on prefabricated rock-like samples using the Split Hopkinson Pressure Bar system. The test results show that the dynamic stress-strain curves of the samples can be divided into elastic phase, plastic phase, unstable crack propagation phase and post-failure phase. Although the dynamic failure modes of all samples are tensile failures, as recorded by a high-speed camera, the joint position demonstrates an important effect on the crack propagation. It is found that the absorption energy, transmission energy and absorption energy per unit volume are all in a positive linear relation with the strength coefficient, while the reflection energy shows a negative linear correlation. The dynamic peak strength of jointed sample increases with the decrease of the joint length, and increases as the joint closes, whereas it decreases as the distance of the joint from the center of the sample decreases. Combined with the strength damage of jointed samples, the damage weight theory for joint positions of singly-jointed sample is proposed and verified. The theory indicates that the damage weight reduces linearly by similar to 50% from the sample center to the edge. In addition, a damage model is proposed and verified for the singly-jointed samples to reflect the correlation of damage factor induced by different joint parameters.