Formation mechanisms of different kinds of blast-induced cracks and their extension characteristics in rock mass

Different kinds of cracks, including radial cracks, circumferential cracks, and spalling cracks, are formed in rock blasting. Understanding the extension characteristics of these cracks is essential for improving rock fragmentation results. However, few publications have comprehensively focused on various blast-induced cracks, and their formation mechanisms and extension characteristics are still unclear. In this study, the formation mechanisms of different kinds of blast-induced cracks are theoretically analyzed from the viewpoint of inner and outer blasting effects. Numerical models are subsequently developed to study the extension characteristics of different kinds of blast-induced cracks. Finally, based on the tunnel blasting excavation, the extension of cracks induced by cutting and surrounding blastholes is numerically simulated. The results show that rock blasting can be classified into inner and outer blasting effects. Under the inner blasting effect, radial cracks are formed in various stress states, with circumferential cracks occurring specifically in the tensile-tensile state. Under the outer blasting effect, spalling cracks form around the free surface of rock mass. In brittle rocks subjected to blast loading with higher peak values, circumferential cracks occur more frequently. In practice, it is advisable to improve rock fragmentation results by adjusting the formation of different kinds of blast-induced cracks.