Experimental Investigation and Numerical Simulation on the Crack Initiation and Propagation of Rock With Pre-Existing Cracks

Abstract

Rock mass behavior is determined not only by the properties of the rock matrix but also mostly by the pre-existing cracks in the rock mass. Before the overall failure of rock, the crack initiation and propagation around the tip of pre-existing cracks (i.e., pre-crack) will occur and contribute to rock failure. In this paper, the deep granite from a gold mine is taken and made to specimens with the pre-crack of 0.3 mm thickness. Uniaxial compression tests are carried out on the pre-cracked specimens. The acoustic emission (AE) sensors and digital image correlation (DIC) system are employed to record the failure characteristics of the specimens. The extended finite element method (XFEM) with the non-local stress field calculation is used to simulate the crack initiation and propagation of pre-cracks. The crack patterns, opening and shearing displacements of the cracked surface, and the crack length development are obtained from numerical simulations. Finally, the effects of friction of crack surface on the crack pattern and crack propagation are investigated and discussed. It has been found that, for pre-cracked specimens, crack initiation and propagation will occur when the stress is much smaller than the rock compressive strength. And in the range of pre-crack angle 30-60°, the larger the pre-crack angle is, the larger the compressive strength is. The crack patterns from numerical simulations have a good agreement with those from experimented DIC results. Moreover, the order of crack propagation speed is consistent with the order of the compressive strength. The crack pattern and crack propagation are affected by the friction coefficient of the cracked surface.

Effect of Joint Density on Rockburst Proneness of the Elastic‐Brittle‐Plastic Rock Mass

“…e failure behavior of jointed rock mass under different stress environments is highly complex [24][25][26]. e initial crack or local high stress will damage the rock mass and reduce its strength.…”

Experimental Investigation on Shear Failure Mechanism of Rock Mass with Intermittent Joints

“…As a complex engineering geological body, natural rock mass has a large number of discontinuities such as joints, fissures, and faults with different scales [20][21][22]. At present, the shear strength characteristics and deformation laws of two-dimensional regular structural plane are mainly studied by direct shear test [23][24][25].…”

Stability Assessment of Ground Surface along Tunnels in Karst Terrain Using Improved Fuzzy Comprehensive Evaluation

“…Because of the complex karst phenomena, the ground collapse in karst terrain has the characteristics of invisibility, burstiness, and mass occurrence [1,2]. Once the ground collapse happens in the karst terrain, it may cause great casualties and economic losses [3][4][5][6][7]. Recently, more and more efforts have been made in the development and utilization of underground space, and thousands of tunnels have been constructed in karst terrain all over the world, resulting in the fact that hundreds of ground collapses caused by tunnel construction have happed [8][9][10].…”