Experimental investigation on the dynamic response of rock with different brittleness under coupled static-dynamic compression

Abstract

Abstract Deeply understanding the failure characteristics of brittle rock under the combined action of static geo-stress and dynamic disturbance is is crucial for the assessment of deep underground rock structure stability. In this study, the dynamic response characteristics of rocks with different brittleness under coupled static-dynamic loads, are investigated using the Splitting Hopkinson Pressure Bar (SHPB) impact tests on granite, green sandstone, and red sandstone. The influence of brittleness index(Bd) on stress-strain, dynamic strength, energy absorption, and failure characteristics under different axial pre-stress (APS) was analyzed. The results show that all the stress-strain curves appear to strain rebound, and the rebound deformation of the red sandstone (with the smallest Bd) is the smallest. With a rise in APS, the dynamic strength increases, then falls, and achieves its maximum when the pre-stress is 30% of uniaxial compressive strength (UCS). In addition, the energy absorption density (ηa) and the energy utilization efficiency (Ka) both show a trend of first increasing, and then decreasing as the APS increases, and the higher the Bd, the greater ηa, and the smaller Ka. Furthermore, when the APS is greater than 0.3 UCS, the crack propagation velocity (CPV) increases with the increase of APS, and the CPV is directly proportional to Bd. At 0.7 UCS, the fractal dimension of the fragments after failure reaches the maximum, indicating a more uniform distribution of fragment size.