Dynamic and damage properties of artificial jointed rock samples subjected to cyclic triaxial loading at various frequencies

Abstract Jointed rock samples with dip angles of 15°, 30°, 45°, and 60° (0° corresponds to the horizontal axis) are manufactured artificially, and a series of cyclic triaxial loading tests are performed at different frequencies (0.1, 1.0, 3.0, and 0.5 Hz) to assess the effects of the frequency on the dynamic characteristics, number of cycles until failure, irreversible strain, dissipated energy density, and failure mechanisms. Analysis of the test results and the phenomenon of cyclic loading reveals that frequency has a significant effect on the dynamic characteristics of the jointed rock samples. With the increasing frequency, the number of cycles until failure increases, the maximum value of the contractive volumetric strain increases, and the volume expansion significantly decreases. A higher frequency corresponds to a higher irreversible axial strain, but the irreversible volumetric strain exhibits two different trends, depending on the dip angle. Further, a higher frequency corresponds to a higher initial average axial stiffness and a higher dissipated energy density. Two new damage variables are defined in this study (the density method and residual strain method), which can describe the three stages of fatigue damage in jointed rock samples subjected to cyclic loading (initial damage, damage accumulation, and accelerated stage).