Study on the direction effect of stress wave superposition and fracture distribution in rock mass during cylindrical charge blasting

In deep hole blasting, the initiation position plays a decisive role in determining the propagation direction of the shock wave, subsequently influencing the distribution of the explosive stress field and rock fractures. Leveraging the superposition principle proposed by Starfield, the propagation and superposition rules of the explosive stress field generated by chain-like spherical charges are derived. This forms the basis for constructing an equivalent cylindrical explosive model. By introducing a delayed loading method for the chain-like spherical explosives, numerical simulation of stress fields is carried out through the superposition of cylindrical explosives using the discrete element method. The focus is on investigating the directional effects on the distribution pattern of rock fractures under different propagation directions. The findings indicate that due to the phase delay of explosive stress waves, a significant directional effect is present in the superposition of stress waves from cylindrical explosives and in the distribution of fractures. The superposition of stress waves is stronger along the propagation direction, with the growth rate of superimposed stress amplitudes increasing initially and then diminishing. The range of fracture distribution also gradually expands along the propagation direction. For different propagation directions, when blasting occurs from the bottom or top sides individually, fractures generally exhibit a“funnel-shaped”distribution along the propagation direction. When blasting occurs simultaneously from both ends towards the center, fractures are most developed near the center of the borehole, exhibiting an overall“spindle-shaped” distribution. When blasting initiates from the center towards both ends, fractures are slightly broader near the ends of the borehole, indicating a relatively uniform overall distribution. The fracture distribution patterns aptly mirror the distribution laws of superimposed stress fields under different blast propagation directions. The superposition effects of the equivalent cylindrical explosives under different propagation directions provide a rational explanation for the development and evolution of fractures within rock formations, thus revealing the underlying mechanisms of the directional effects. © 2024 Academia Sinica. All rights reserved.