Experimental study on energy dissipation and fragmentation characteristics of gas-bearing coal under combined dynamic and static loading

LIU Huaiqian; ZHAO Hongbao; WANG Lei; MA Qing; YU Meilu; HU Hao; WANG Chunhua

doi:10.13225/j.cnki.jccs.2024.1362

Abstract：To explore the energy dissipation and fragmentation characteristics of gas-bearing coal under combined dynam-ic and static load,the impact experiment of gas-bearing coal under different impact velocities and axial compressive stress ratios was carried out with the help of the self-developed observable combined dynamic and static loading test system of gas-bearing coal.The energy evolution laws and energy dissipation characteristics of gas-bearing coal fracture were stud-ied.The debris ejection mechanism and its distribution characteristics were discussed,the intrinsic relationship between the energy dissipation density and the debris fractal dimension of gas-bearing coal was clarified.The results show that:①The energy conversion of gas-bearing coal during impact is synchronous,and the time curve of dissipation energy cor-responds to the deformation stage of coal sample,that is,it is found that when the bearing capacity of gas-bearing coal is lost after impacted,the dynamic stress-strain curve is parabolic,and the time curve of dissipation energy can be divided in-to elastic-energy storage stage,elastic-plastic-energy dissipation stage,plastic-energy dissipation stage and energy release stage.Especially,when the axial load causes the gas-bearing coal to be in an elastic-plastic or plastic state,the time curve of dissipation energy is divided into the elastic-plastic or plastic energy dissipation stage and the energy release stage.When the gas-bearing coal still has bearing capacity after impacted,the dynamic stress-strain curve is barbed,and the de-formation stage can be divided into elastic stage,elastic-plastic stage,plastic stage and rebound stage.the time curve of dissipation energy is correspondingly divided into elastic-energy storage stage,elastic-plastic-energy dissipation stage,plastic-energy dissipation stage and energy-rebound stage.The energy rebound stage can lead to coal wall spalling or road-way rockbursts.②The dissipation energy of gas-bearing coal increases with the impact velocity increasing,the dissipa-tion energy ratio is basically constant,which is between 31.1%-34.0%.The fractal dimension of debris increases exponen-tially with the increase of energy dissipation density.There is a critical axial compressive stress ratio,which makes the dis-sipation energy and its ratio decrease first and then increase.The fractal dimension of debris is segmented with the change of energy dissipation density:when the sample is in the continuous energy-storage stage,the fractal dimension of debris decreases with the increase of energy dissipation density,when the sample is in the continuous energy-release stage,the fractal dimension of debris increases with the energy dissipation density increasing,and at this point,slight disturbances can lead to coal-rock instability.These conclusions enrich the basic theory of the dynamic coal-rock-gas disaster induc-tion mechanism and can provide theoretical support for the monitoring,early warning and prevention technology of dy-namic disasters in composites.