Analysis of dynamic characteristics of through-wall cracks between 2 boreholes in the directed fracture controlled blasting

摘要

Through-wail cracks between 2 boreholes in the directed fracture controlled blasting have been always concerned by researchers. Dynamic characteristics of through-wall cracks between 2 boreholes and lateral crack propagation of boreholes in the double-borehole slot mode and the synchronous blasting of boreholes were examined using the explosive loading digital dynamic caustics experiment system. And die effects of borehole loading mode and borehole clearance on through-wall cracks between boreholes were examined using distinct lattice spring model numerical analysis, based on the experiment model. Findings show that the tips of through-wall cracks between boreholes did not meet directly but staggered, continuously propagated after meeting, and moved closer to the existing anisotropic crack direction. The velocity and acceleration of crack propagation fluctuated. K_I rapidly decreased from the maximum value, then gradually increased after a repeated volatility, and began to decrease after it reached the second peak. During the process of crack propagation, K_(II) was basically smaller than K_I. The dynamic energy release rate rapidly decreased from the maximum value, reached the second peak after the volatility, and gradually decreased again. The borehole loading mode and borehole clearance had significant effects on through-wall cracks between boreholes.