Loading and unloading test of hard rock and its elastoplastic damage coupling model

Deep-buried engineering and test results show that hard rocks behave as part of an elastoplastic damage coupling process. The coupling effect can contribute to the weakness of the surrounding rocks and the extension of the water channels. As a result, the coupled elastoplastic damage model is the basis for a stability analysis in deep engineering. In this paper loading and unloading tests were conducted on T2b marble in the Jinping II hydropower station. Based on the tests the effects of the confining pressure on the strength, the failure strain and the dilation were analyzed. According to the plastic shear failure and the parameters weakness mechanism, the damage-evolution function reflecting the weakness character, the loading function and the plastic potential function regarding plastic hardening were proposed. The activation of the damage and plastic process was then studied. The coupled elastoplastic damage model was finally established. Through simulating the test curve, the proposed model was verified. This model could play an important role in the stability analysis of deep-buried hard-rock engineering. Z. Li et al.: Loading and unloading test of hard rock and its elastoplastic damage coupling model