Effects of in-situ stress and delay time on rock damage under shaped charge jet blasting

Abstract

In-situ stress and delay time in shaped charge jet blasting (SCJB) have significant effects on rock damage. In this study, the stress distribution pattern and damage mechanism of rock around the blast hole under coupled in-situ stress and blast loading are studied using theoretical analysis and numerical simulation. The effect of SCJB on rock crushed zone, jet erosion length and crack propagation characteristics under in-situ stress was explored. The results show that the SCJB method achieves directional crack extension and increases the crack extension length. Under equibiaxial in-situ stress condition, the crushed zone is circular, and the radius of the crushed zone, jet erosion length and crack length decrease with increasing in-situ stress level. Under an anisotropic pressure condition, on the other hand, the crushed zone is elliptical; the greater the difference between horizontal and vertical pressure, the more pronounced the anisotropy of the crushed zone. As the lateral pressure coefficient k decreases, the horizontal crack length tends to decrease whereas the vertical crack length increases. The vertical crack length of the delay blast hole increases with the increase of the delay time.

Keywords

shaped charge jet blasting / in-situ stress / crack propagation / delay time

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