Study on dynamic loading characteristics and energy evolution of sandstone with double cracks

Abstract

To obtain the mechanical characteristics and energy evolution law of sandstone with double cracks under dynamic load, the test is carried out by using the SHPB test system, and the failure process of the sample is recorded by the high-speed camera system. The stress-strain curves under dynamic load and the failure characteristics of the sample are obtained, and the effects of crack angle and impact pressure on the mechanical characteristics of sandstone with double cracks are analyzed. The results show that the compressive strength of the specimen decreases initially and increases afterwards with the increase of the crack angle under dynamic load, and the compressive strength of the specimen increases gradually with the increase of the impact pressure. At the pressure of 0.03 MPa, the peak strain increases initially, followed by decreases with the increase of crack angle, and shows the opposite law with the increase of impact pressure. Under dynamic loading, the crack tip first starts to crack outwards along the axial direction, and the penetration of the rock bridge lags. The macroscopic cracks of 0° and 90° sandstone are mostly tensile cracks, while those of 30°, 45°, and 60° are mostly shear cracks. With the increase of crack angle, the failure mode changes from tensile failure to shear failure and then to tensile failure. The fractal dimension increases with the increase of impact pressure, and increases and then decreases with the increase of crack angle, and the fractal dimension increases with the increase of energy dissipation per unit volume. In addition, in the process of rock burst prevention and control, the size of the dynamic load and crack angle should be evaluated in advance. When the dynamic load in this area is large, the surrounding rock pressure relief should be carried out in advance to increase the dissipation energy. When there are 60° and 45° crack angles in the rock mass, the stress propagation path should be changed by structural regulation based on grouting filling micro-fracture modification.