Numerical investigation into the stress evolution and failure mechanism of deep-buried hard rock under blasting loads

With the production activities continue progressing into deeper underground spaces, the rising ground stress poses new challenges in the fracturing of hard rock. Previous research mostly focused on the outer actions of blasting on conventional rock mass, while research on the inner actions of blasting via discrete element method (DEM) is relatively scarce, especially for deep-buried hard rocks under high ground stress. Relying on the pre-cracking project of hard rock protective layer in the thousand-meter deep well of Pingdingshan coal mine, this paper aims to numerically investigate the fracture mechanism of deep-buried hard rock under blasting loads via DEM. To this end, the algorithm of simulating explosion load is improved. The improved algorithm ensures a more reliable correspondence between numerical results and engineering practice, significantly enhancing the accuracy and credibility of calculations. After the calibration of mesoscopic parameters on the basis of laboratory tests, a series of parametric study, including confining pressure, peak blast stress and lateral stress coefficient, have been performed to understand the effects of in-situ stress on the behaviors of rock blasting. The obtained numerical results exhibit that confining pressure inhibits the fracture growth: under low confining pressure, confining pressure mainly inhibits the development of fractures in sparsely fractured zone while the crack growth in densely fractured zone and crushed zone is also inhibited under high confining pressure. According to the stress state, hoop peak stress is more sensitive to confining pressure than radial peak stress. Rock breakage in the vicinity of blasthole is essentially controlled by the radial peak stress, while crack propagation in the far-field is mainly induced by the hoop peak stress. With different lateral stress coefficients, the failure characteristics of rock mass are principally related to the hoop stresses in the vertical direction. The obtained numerical results and mesoscopic analysis are capable of providing new insights into the fracturing mechanism of deep-buried hard rock.