Experimental study on failure mechanism and geometric parameters of blasting crater under uniaxial static compressive stresses

In deep mining and rock engineering, it is important to understand the failure mechanism of a blasting crater under coupled dynamic and static loads, and further investigate the quantitative relationships between its parameters and the static stress. In this study, lab-scale crater-blasting experiments on sandstone specimens under different uniaxial stresses are performed to investigate the characteristics of the blasting craters and the blasting fragments as well as their representative failure mechanisms. The relationships between the diameter, area, volume of a blasting crater, and the stress–strength ratio (SSR) are analyzed quantitatively. The results show that the blasting crater can be divided into block, transition, and flaky failure zones. Correspondingly, the blasting fragments can be classified into block, transition, and flaky fragments. The block failure zone and the block fragments are caused by tensile and high-temperature burn damage. The transition failure zone and the transition fragments are the results of tensile and shear damage. The flaky failure zone and the flaky fragments are produced mainly by tensile damage. The relationships between the blasting crater parameters and the SSR can be divided into three stages: linear growth stage, slow growth stage, and rapid growth stage. The static stress has a significant influence on the blasting craters parallel to it, whereas it has a negligible effect on those perpendicular to it. Besides, the static stress leads to oversized fragments and has the most significant influence on the flaky failure zone. Finally, a blasting design method considering static stresses is proposed.