Experimental Investigation on Strength and Crack Mechanism of Rock-Like Samples with Open-Closed Cross-Flaws under Uniaxial Compression

Abstract

Abstract Rock masses with open-closed cross-flaws are common in nature. The open-closed cross-flaws usually control the strength of rock masses. However, studies about the influence of open-closed cross-flaws on cracking behaviors and mechanical properties of rock masses are rare. In this study, rock-like samples containing open-closed cross-flaws with different geometries were fabricated to be conducted uniaxial compressive tests. The cracks observed in the tests were classified to nine types, and two new crack modes were described and identified. Two failure modes, failure caused by tensile cracks and failure caused by the combined effect of tensile and shear cracks, were observed. The failure caused by the penetration of the rock bridge is not observed, indicating that the rock bridge is not a potential penetration path for the samples with cross-flaws. Experimental results show that, when α=0°, the peak stress decreases from 32.2 MPa to 17.0 MPa as β increases from 0° to 90°. When α=90°, the peak stress increases from 22.5 MPa to 40.0 MPa as β increases from 0° to 90°. The inclination angle of the open flaw has an obvious effect on the strength of samples. When the inclination angle of the open flaw is 0°, the peak stress is the lowest (17.0 MPa). When the inclination angle of the open flaw is 90°, the peak stress is the largest (40.0 MPa). The samples with an open flaw of large inclination angle tend to have great compressive strength. For samples with open-closed cross-flaws, the open flaw has a greater influence on the strength and failure mode than the closed flaw.