Study on the Influence of Coal Stress Damage on Impact Tendency Under Cyclic Loading and Unloading Effects

This article aims to explore the response characteristics of coal impact tendency to cyclic load. Through the mechanical damage test of coal sample under cyclic load, the deformation and damage of the coal sample under different cyclic stress, cyclic rate, and cyclic times were analyzed. The development and distribution characteristics of microcracks of the coal sample after cyclic loading and unloading were compared and analyzed by means of scanning electron microscope and nuclear magnetic resonance, and the relationship between ultimate strength, damage variable, and impact tendency of a coal sample under cyclic load was revealed. The results show that the peak strength strain of the specimen increases with the increase of the number of cycles, and the stress decreases with the increase of the loading and unloading rate. The results show that the ultimate strength and impact energy index of the samples are reduced to varying degrees after different loading and unloading cycles, and the loading and unloading times and loading and unloading rate have a significant impact on the impact tendency of the samples. The research shows that the internal mechanism of the weakening of the impact tendency of the coal sample structure damage and mechanical strength reduction under cyclic loading and unloading is that the impact tendency is significantly affected by the number and rate of loading and unloading. This study can provide some ideas for the prevention and control of rock burst.