Failure strength and fracture characteristics of rock with discontinuity under indirect tension

Abstract

Large-scale discontinuities can significantly affect the mechanical properties of rock masses. However, the tensile behavior of rock discontinuities is often less investigated. To study the statistical characteristics of failure strength and fracture characteristics of rock discontinuities, Brazilian disc tests were conducted on limestone specimens with a single natural discontinuity at different load-discontinuity angles (beta). In this study, beta = 0 degrees and beta = 90 degrees correspond to the discontinuity parallel and perpendicular to loading direction, respectively. The results show that Brazilian failure strength (BFS) can reasonably represent the tensile strength of rock with discontinuities, by comparing the BFS and tensile stress in the disc center at peak force. The two-parameter Weibull distribution can capture the statistical BFS characteristics of rock discontinuities parallel to loading direction (beta = 0 degrees) and at different loaddiscontinuity angles (beta not equal 0 degrees). All specimens with discontinuity at different load-discontinuity angles show more plastic deformational behaviour than intact rock specimen. With increasing beta, the mean BFS of limestone with discontinuity increases before reaching a plateau at beta = 45 degrees. The single plane of weakness theory best explains the BFS of fractured limestone with beta. Only a specific segment of preexisting rock discontinuity could affect the fracture process. When beta = 0 degrees, interfacial cracks and alternative cracks formed. When beta not equal 0 degrees, mixed failure mode with shear and tensile failure occurred, particularly when beta = 30 degrees and beta = 60 degrees. The findings can contribute to better understanding the failure and fracture characteristics of rock with discontinuities, particularly the interaction of pre-existing discontinuities with stress-induced fracturing.