Experimental study on creep disturbance mechanics and acoustic emission characteristics of coal under different stress control

Under the influence of the continuous expansion of the depth and scope of underground coal mining and the frequent stress disturbance of mining activities, how to ensure the long-term safety and stability of the roadway under the superposition of high static load stress and external disturbance stress is particularly important. In the deep complex geological environment, the surrounding rock shows strong creep. The damage and failure mechanisms of coal under long-term creep disturbance at various burial depths were investigated using conventional triaxial testing supplemented by acoustic emission technology for damage monitoring. Four groups of creep interior tests at varying confining pressures were carried out, and then creep impact and disturbance testing was executed under different stress levels. The results show that (1) the peak strength and peak axial strain of coal increase progressively with increasing confining pressure under standard triaxial compression,The peak strength has a linear relationship with the confining pressure, and the slope is 1.88. The peak strength during graded creep and creep disturbance is lower than that during conventional triaxial testing at the same confining pressure, failure occurs at 54.2 % −80 % uniaxial peak strength, which reflects the deterioration effect of creep disturbance on coal strength. Under the creep impact process, the greater the stress level and impact velocity are, the greater the peak strength of the coal sample. (2) In the process of graded creep and creep disturbance of coal samples, the higher the stress level is, the greater the strain increase caused by creep. The improved nonlinear creep model is used to fit and quantify the creep parameters of coal under different stress levels. (3) Acoustic emission (AE) signal parameters can effectively reverse the development of microcracks and progressive damage in coal at different stages of triaxial loading and under different creep stress levels. This method is strongly coupled with the stressstrain curve of coal and can be used to evaluate and predict coal damage. The research results can provide guidance and a reference for the long-term stability of coal roadways under mining disturbances. •The mechanical properties of coal samples under uniaxial and triaxial creep disturbance are systematically studied.•The self-developed experimental equipment combined with AE technology was used to carry out multi-angle analysis.•The nonlinear viscoelastic-plasti