Experimental Investigation and Numerical Analyses for Red Sandstone Rock Fragmentation

Abstract

The effects of initial stress conditions and rock breaking parameters on rock fragmentation were investigated through indentation tests and numerical analysis with a discrete element method (DEM). Different initial stress conditions and the thrusting velocity of the cutter were the focus in the design of indentation tests. Some indicators were used to reflect the instability of the thrusting force, rock breaking efficiency, failure patterns, and the fluctuation of force-penetration response. The indentation results show that rock failure patterns have a closed correlation with initial stress conditions and loading rate. All tests showed several distinct chipping phases, and obvious chiseled pit and crushed rock could be observed on the top surface of each rock specimen. Moreover, rock brittleness was evaluated by the fluctuation of force-penetration curves; this study also revealed the changing law of peak and mean thrusting force. In addition, the numerical simulation of indentation tests reproduced the development process of rock fragmentation and crack propagation. Increasing confining stress restrained the propagation of vertical and lateral cracks, whereas the axial stress had the effect of restraining the propagation of radial cracks. However, there is a critical confining stress that causes different results of fractured depth. Therefore, this investigation is beneficial for optimizing the cutting parameters to promote rock breaking efficiency.