A damage model of rock-like materials subjected to incremental cyclic loading considering unloading rate and water content

Abstract

：A series of experiments were conducted to study the damage response of rock-like specimens on the water content and the unloading rate of the incremental amplitude cyclic loading experiments. Under the conditions of five unloading rates and three water contents, the influence of the incremental amplitude cyclic loading on the rock-like specimens was analyzed. The damage characteristics of the rock-like specimens were discussed, and a damage model was proposed. The test results indicate that the rock-like specimens are sensitive to the water content and the unloading rate of the incremental amplitude cyclic loading. Compared to the monotonic uniaxial compression tests, the rock-like specimens’ elastic modulus and failure stress subjected to incremental amplitude cyclic loading are generally lower. As the unloading rate increases, the failure stress generally decreases, while the elastic modulus first decreases and then increases. Moreover, water can amplify the effect of the unloading rate on failure stress, elastic modulus, and damage variable of rock-like specimens. The influence of the unloading rate on the damage variable has a critical value. A lower unloading rate below the critical value has little effect on the damage variable. In contrast, an enormous unloading rate that exceeds the critical value will enhance the damage variable. The established damage model is suitable for describing and assessing the plastic strain damage variable and the energy damage variable of rocks with different water contents subjected to an incremental amplitude cyclic loading with different unloading rates.