Experimental study on mechanical properties of marble under alternation between short-time creep and low-cycle fatigue

The deep engineering rock mass is subjected to the creep loads caused by stress adjustment. At the same time, during construction and operation, it will be intermittently subjected to the cyclic loads such as blasting, earthquakes and traffic loads, and their influences on the creep behavior are not clear. To explore the mechanical properties of the deep rock under the alternation of short-time creep and low-cycle fatigue, the tests with different stress levels and different fatigue amplitudes are carried out, and the acoustic emission tests are carried out simultaneously. The test results show that: (1) The creep-fatigue interaction will significantly accelerate rock failure, and the failure strain is larger than that of pure creep failure strain. (2) The strain increment and creep rate caused by creep and fatigue at all stress levels show a "V" change law, and the creep rate after fatigue at all levels is not less than that before fatigue. (3) The acoustic emission ring counts are evenly distributed in the creep section, with a surge in the fatigue section. When the fatigue amplitude is less than or equal to 2 MPa, the variation law of b value is "rise - small fluctuation - sudden drop", and when the fatigue amplitude increases to 4 MPa, b value is "fall–rise–fall". (4) The acoustic emission failure point and nuclear magnetic scanning show that the fracture evolution law develops from inside to outside in the cross section and extends from the middle to both ends in length direction. The rock failure is mainly shear failure, and the smaller the fatigue amplitude, the more the rock powder.