不同张开度裂隙类岩体循环加卸载下滞回环特征与损伤变形分析

为探究张开度和不同应力等级循环加卸载复合影响下裂隙岩体的损伤特性和裂纹演化规律，利用水泥砂浆制备不同张开度单裂隙类岩石材料，基于RMT-150B岩石力学试验机对类岩石材料开展了3种等级的应力循环加载试验，分析了裂隙类岩石材料的应力—应变曲线特征、滞回环面积变化规律、动弹性模量变化规律及损伤特性。试验结果表明：类岩石材料的强度随应力循环等级的增大而出现弱化现象，同时循环过程中加卸载曲线形成的滞回环由刚开始的“密集型”转为“稀疏型”；类岩石材料滞回环的面积随着循环次数的增大呈递减趋势，而滞回环面积随张开度的增大呈递增趋势；当循环应力和循环次数相同时，类岩石材料的动弹性模量随着张开度的增大呈递减趋势；随着应力循环等级的增大，类岩石材料的损伤变量随着循环次数的增加呈现为递减—缓慢增长—急剧增长趋势，且不同应力等级下裂纹的演化各不相同。

Hysteresis Characteristics and Damage Deformation Analysis of Fractured Rock Mass with Different Crack Opening Under Cyclic Loading and Unloading

In order to explore the damage characteristics and crack evolution law of fractured rock mass under the combined influence of opening and cyclic loading and unloading of different stress levels，four kinds of single fractured rock materials with different opening （0.1，0.2，0.4，0.8 mm） were prepared by cement mortar，and three kinds of cyclic stress loading tests were carried out on rock-like materials based on RMT-150B rock mechanics testing machine.The characteristics of stress-strain curves，hysteretic loop area，dynamic elastic modulus and damage of fractured rock materials were analyzed.The test results show that the three kinds of stress cyclic loading roughly correspond to the three stages of pore compaction，elastic deformation and stable propagation of microcracks，and the peak strength of rock-like materials decreases with the increase of cyclic stress grade，the phenomenon of strength weakening occurs，and the hysteresis loop changes from “dense” to “sparse” at the beginning.Under the condition of the same stress level，with the increase of the number of cycles，the hysteresis loop area decreases sharply at first and then tends to be stable.In addition，there is an obvious difference in the decrease of the hysteresis loop area with different crack openings，the smaller the crack opening is，the smaller decrease of the hysteresis loop area is.Under the same number of cycles，the hysteresis loop area increases with the increase of crack opening and cyclic stress grade，and in the same cyclic stress grade and crack opening，the dynamic elastic modulus increases sharply at first and then tends to a stable value with the increase of the number of cycles.When the cyclic stress level and cyclic times are the same，the dynamic elastic modulus of rock-like materials decreases with the increase of crack opening.Under the same crack opening and cycle times，the dynamic elastic modulus increases at first and then decreases with the increase of cyclic stress grade，and with the increase of stress cycle grade and cycle times，the damage variable of rock-like materials shows the trend of decreasing first，then slow growth and then sharp increase，corresponding to the change law of the transition of hysteretic loop from “dense” to “sparse”.And the crack evolution of rock-like materials is different in different cyclic stress levels.