Determination of bursting liability of coal-rock combined body based on residual energy release rate index

Coal-rock bursting liability is the natural attribute and the key influencing factor of coal-rock rockburst disasters. The coal-rock combined body was taken as the research object to accurately judge the bursting liability of coal and rock，and the uniaxial cyclic loading and unloading test was carried out on the coal-rock combined body，The elastic strain energy of the combined body under different stress levels was obtained，and the function between the elastic strain energy and the stress level was established. A new method for calculating elastic strain energy at peak stress time was proposed. A residual energy release rate index that comprehensively considers the peak strength，elastic strain energy，energy dissipation of the failure process and failure time of the specimen was proposed based on this，and the bursting liability judgment interval was given in combination with the existing indicators，and the rationality was verified. The results show that：(1) With the increase of the stress，the elastic strain energy shows a “slow-fast-slow” growth law，which corresponds to the compaction stage，elastic stage and plastic stage of the stress-strain curve. (2) The evolution laws of input energy density，elastic strain energy and dissipated energy density are similar to the evolution law of stress，all increasing with the increase of the stress. The increase of input energy density is the largest，and the increase of dissipated energy density is the smallest. (3) The elastic strain energy of the combined body at different stress levels was obtained through the experiment，and the functional relationship between the elastic strain energy and the stress level was established，that is，the square of the stress at any time had a good linear relationship with the elastic strain energy. A new method for calculating elastic strain energy at peak stress time was proposed. (4) Considering the peak strength of the specimen，elastic strain energy，energy dissipation in the failure process and failure time and other factors，a new bursting liability identification index was proposed：the residual energy release rate index WT，which is the ratio of the residual energy obtained by subtracting the post-peak dissipative energy density from the pre-peak elastic strain energy and the dynamic failure time represents the energy release in unit time when the coal-rock is impacted and damaged. This index is closely related to compressive strength Rc，bursting energy index KE，elastic energy index WET，and dynamic failure time DT. The evaluation interval of the residual energy release rate index WT was given：when WT≤0，the coal rock has no bursting liability；when 0＜WT≤14.5，the coal rock has a weak bursting liability；when WT＞14.5，the coal rock has a strong bursting liability. (5) The multi-sample method was used to verify the rationality of the proposed residual energy release rate index WT. This index was used to evaluate the bursting liability of coal seams in 8 mining areas，the results show that the evaluation accuracy of the residual energy release rate index WT is as high as 93.75%. The proposed new index to evaluate the bursting liability of coal rock has high accuracy and good rationality，which can reflect the actual bursting liability of coal and rock，and has good promotion and application value. © 2023 Academia Sinica. All rights reserved.