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.

http://www.goldsci.ac.cn/article/2021/1005-2518/1005-2518-2021-29-3-392.shtml