Abstract: To improve the efficiency of the rotary-percussive drilling, it is necessary to understand the rock-breaking mechanism under tooth impact. Current research efforts in this regard are mainly focused on the numerical or experimental simulations of rock breaking under tooth impact. Thus it is important to investigate the rock-breaking mechanism under tooth impact at low velocity. In this paper, the crushing pit morphology resulting from single-tooth impact is first analyzed; and then the physico-mechanical models are developed for classifying different crushing areas. Considering the low-velocity and confining pressure effects in single-tooth impact, the theory of spherical cavity expansion is revised, from which the stress and strain solutions are obtained in the area around the cracked pit of the rock. Analytical solutions are obtained for different regions using Matlab; and the effects of confining pressure, particle velocity and rock mechanical parameters are analyzed on the dimensionless stress and displacement of the three different regions. The applicability and capability of the proposed model are shown by comparing the numerical results with those yielded from the LS-DYNA code.

Key words: rotary-percussive drilling, spherical cavity expansion theory, tooth, rock dynamics, numerical simulation