Experimental study on mechanical behavior of rock-like materials containing pre-existing intermittent fissures under triaxial compression

It is of important practical significance for ensuring the stability of fractured rock engineering to investigate the influence of pre-existing fissures on the mechanical behavior of rock under three-dimensional stress. The rock-like material specimens containing two unparallel open penetrating fissures are fabricated in the laboratory. And then a series of conventional triaxial compressive tests on rock-like material specimens are carried out by using the MTS815.02 rock mechanics servo-controlled testing system. On the basis of experimental results, the stress-strain curves, strength and deformation parameters and failure modes are analyzed. The main conclusions are drawn as follows: (1) The stress-strain curves of pre-fissured specimens show multi-step softening, and some curves have two peak strengths; (2) The peak strength, crack damage threshold and peak axial strain of intact and pre-fissured specimens all increase linearly with the increase of confining pressure. The sensitivity to the confining pressure of intact specimen is the highest, and the sensitivity of pre-fissured specimens decreases from fissure angle 45° to 30° and then to 60°; (3) The failure modes of pre-fissured specimens are determined by the fissure angle and confining pressure. When the confining pressure is smaller, it is mainly affected by the fissure angle. Whereas the confining pressure is higher, which is mainly influenced by the confining pressure, and the rock specimens exhibit a shear mode.