Research on rock failure characteristics under combined action of uniaxial stress and explosion

Blasting technology is widely used in deep rock mass engineering, and the surrounding rock damage and crack propagation caused by blasting are usually affected by ground stress. The failure and propagation of cracks in boreholes surrounding rock under the combined action of uniaxial stress and blasting load are comprehensively studied. Explosion tests, mechanical analysis, and finite element modeling are used to verify these results from the perspectives of numerical simulation and field engineering. The LS-DYNA numerical software is used to verify the explosion experiment, and the corrected constitutive model is used to simulate the effects of different uniaxial stresses on rock loosening and shaped charge blasting failure characteristics. The fracture network is processed by ImageJ software, and the fracture morphology and fractal characteristics of rock surface are analyzed. Then, the change of fracture mode of uniaxial stress-induced shaped charge blasting is analyzed by means of elastic mechanics, and the mechanism of directional crack propagation is discussed. The results show that the crack initiation occurs along the zone of maximum tensile stress around the hole during loosening blasting. The application of uniaxial stress can restrain the speed and length of crack growth and control the direction of radial crack growth, which makes the crack propagation parallel to the stress direction more advantageous. In the process of shaped charge blasting, with the increase of uniaxial stress, the damage in the shaped charge direction gradually forms a complete failure plane, which significantly inhibits the crack growth in the non-shaped charge direction. This leads to fewer cracks, but faster spreads, and fewer fractal dimensions of cracks and rock damage. Finally, the test of cutting the top and relieving pressure of coalmine by shaped charge blasting has been carried out, and satisfactory results have been obtained. In deep rock mass engineering, it is suggested to use shaped charge blasting under anisotropic ground stress to achieve directional blasting so as to better maintain the integrity of surrounding rock and obtain a smoother blasting surface.