Mechanical Characteristics and Failure Characteristics of Jointed Rock under Axial Unloading and Radial Unloading

In this research, we used precracked rock-like materials (simulating jointed rock masses) to assess the triaxial compression of cracked specimens under axial unloading and radial unloading paths. The research goal was to comparatively analyze and research the mechanical characteristics of cracked specimens to ascertain how deformation properties, strength properties, and failure features influence the overall mechanisms in context. The test results showed that the failure of specimens did not appear at peak stress under axial unloading and radial unloading. The elastic stage, yield stage, and failure stage of the stress-strain curves were not clearly defined in the testing process. However, the stress drop and the strain of resilience of the lateral strain-axial strain curve happened under this path because the lateral strain was significantly greater than the axial strain. This in turn led the volumetric strain to remain in a state of expansion throughout the testing process. The mechanical properties under this path are mainly influenced by the crack inclination angle, the unloading speed of radial pressure, and the initial confining pressure. However, there is a difference in the influence of these three factors on their mechanical parameters; that is, the influence of the crack inclination angle is the greatest, followed by that of the initial confining pressure, while that of the unloading speed of radial pressure is relatively small. Finally, the failure characteristics of specimens often present mixed tension-shear failure under axial unloading and radial unloading.

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