Experimental study on mechanical acoustic emission characteristics of prefabricated fractured coal rock under graded static-dynamic combined loading

Abstract

In order to study the failure evolution characteristics of fractured coal rock under combined loading of graded pre-static load and different dynamic load amplitude levels, the coal rock with strong impact tendency of prefabricated fractures with different inclination angles was taken as the test object. The combined loading test of graded pre-static load and dynamic disturbance was carried out by using the rock dynamic and static triaxial mechanical test system, and the whole process of coal rock failure was monitored in real time by acoustic emission. The results show that under the condition of “graded pre-static load + dynamic disturbance” loading, the overall stress level of strong impact-prone coal rock decreases first and then increases with the increase of fracture dip angle, and the peak strain and ultimate strain increase first and then decrease. The “stress-strain strengthening” phenomenon appears in intact and local coal rock containing prefabricated cracks, and the bearing capacity is improved in varying degrees. The change of ringing count of acoustic emission of coal rock with strong impact tendency is positively correlated with the change rate of stress-strain in the process of combined static and dynamic loading. The acoustic emission activity of coal rock with 30° and 45° dip angle shows high frequency and high amplitude response characteristics under high dynamic load amplitude. The test results are helpful to improve the understanding of the mechanical properties and fracture evolution characteristics of deep coal rock mass under the action of high ground stress and increasing dynamic disturbance, a theoretical reference for the prediction and control of mine mining dynamic disasters.