Effect of in-situ stresses on fracturing performance of crater blasting under different resistance lines

In deep underground mining, high-stress condition plays a key role in rock blasting. However, the mechanism of rock breaking by blasting under high-stress conditions is still unclear. Therefore, crater blasting experiments and theoretical analyses were conducted to study the effect of in-situ stresses on rock fracturing. A 3D theoretical model considering stress concentration on the blasthole wall was conducted to further investigate the fracturing mechanism of crater blasting under in-situ stresses. The experimental and theoretical results allowed the following conclusions: 1) Long resistance line (over 6 cm) results in a decrease crater volume along with increasing confining pressure; 2) the influence of confining pressure on blasting gradually changes from negative restraining to positive promoting with decreasing resistance line (less than 5 cm); 3) Radial fracturing was restrained and the reflected tensile fracturing was promoted in the direction of higher in-situ stress. While, radial fracturing was promoted and the reflected tensile fracturing was restrained in the direction of lower in-situ stress. Reducing resistance line of crater blasting and increasing between spacing hole are the best to take advantage of the in-situ stress to promote the rock fragmentation by blasting.