Energy Evolution Law And Application Of Coal And Rock Mass Under Cyclic Loading

In this paper,based on the engineering background of rock burst prevention and control in No.17 coal seam of Junde Coal Mine,from the perspective of energy evolution in the whole process of coal and rock assemblages under load,the complex stress environment in the coal and rock assemblages area of the working face is simulated through uniaxial cyclic loading and unloading tests and triaxial cyclic loading and unloading tests.The deformation and failure characteristics and energy evolution law of coal and rock mass are obtained,and the energy evolution mechanism and energy evolution path of coal and rock mass under cyclic loading are revealed.The impact energy driving mode of surrounding rock in the mining face area of Junde Coal Mine No.17 coal seam is discussed.The law of impact appearance of No.17 coal seam was analyzed by numerical simulation,and the pressure relief scheme of large diameter borehole was proposed.The field test was carried out to verify the pressure relief effect and solve the problem of dynamic pressure appearance of coal mining face in this coal seam.The main results are as follows:(1)The coal-rock mass under cyclic loading experienced three evolution stages:initial energy accumulation stage,rapid energy accumulation stage and rapid energy dissipation stage.The evolution process was greatly affected by the coal height and confining pressure in the coal-rock combination structure.(2)The coal height has a weakening effect on the mechanical properties and energy accumulation of the coal-rock mass under cyclic load.With the increase of the coal height,the peak load,the number of cycles,the energy storage limit,the time of energy evolution and the stored energy of the mass all have a decreasing trend,and the combined specimens are more prone to damage and destruction.Confining pressure of coal rock under the action of the circulating load combination of mechanical properties and strengthening effects of energy accumulation,with the increase of confining pressure,coal and rock combination of internal native crack closure reinforcement,plastic deformation and shear failure has been suppressed,peak load and cycle times,time limit,the evolution of energy storage,storage of energy and dissipation can both increase the proportion of,However,the shorter the energy dissipation period is,which can explain the transient characteristics of rock burst.(3)The impact energy driving mode of "roof-coal seam" coal-rock combination system was studied.Thick sandstone roof coal seam clamping,hindered the coal seams and coal rock interface in the pressure,the deformation resulted in the coal seam is repeated compaction,the accumulation of a large amount of elastic energy,mining disturbance caused by the change of the confining pressure,change system on coal reservoir to the path of the energy storage limits,when storing energy than new confining pressure of the energy storage limits,energy is suddenly released,the impact pressure,Therefore,changing the complete structure of the coal-rock system can change the conditions of stress state failure energy accumulation,so that the energy evolution of the coal-rock combined system tends to the low-energy area,thus slowing down the appearance of rock burst.(4)The numerical simulation of the mining situation of No.17 coal seam in Junde Coal Mine shows that the energy distribution is greatly affected by the occurrence of coal and rock strata,and the smaller the coal-rock ratio,the greater the energy accumulated in coal body.The large diameter pressure relief drilling scheme can improve the energy state of No.17 coal seam in Junde Coal Mine.According to the feedback of microseismic monitoring data,the pressure relief scheme can slow down the mine pressure in the process of mining No.17 coal seam.This study plays an important role in preventing and controlling rock burst in No.17 coal seam of Junde Coal Mine,further enriches the application of energy evolution theory of coal-rock combination in engineering practice,and provides an important reference for preventing and controlling rock burst in coal mine.