Rock fails in shearing as a tuned critical system

Shearing is the most widely exploited method to fracture and remove rock formations in many man-made rock-opening activities. During shearing, rock breaks into chips due to the periodic nucleation, propagation, and coalescence of numerous micro-cracks. The crack interactions along with the rocks complex physical properties lead to extreme challenges in reaching a consensus on the rocks failure behavior in shearing. In this paper, force-drop events, as a quantitative measure of the global rock breakage occurrence, were recorded and analyzed. A power-law distribution with a tunable cut-off between the frequency of the force-drop events and their magnitudes is shown. The obtained results, for the first time, reveal the rocks tuned critical behavior in shearing which is intrinsically similar to its failure behavior widely observed in earthquakes.