| China is a big country of coal production and consumption.With the energy consumption structure turning to the new normal high quality stage,the state puts forward higher requirements for the innovative development of coal energy,safe and efficient development.However,due to the complex geological conditions of coal seams in China,mine disasters and accidents occur frequently,which seriously restrict the safety of mine production.In this paper,based on the occurrence characteristics of coal seam in a high gas mine in Shanxi Province,the specimens of tectonic coal combination were made,and the mechanical,acoustic emission and permeability variation laws of tectonic coal combination during loading and fracture were studied.The following conclusions were obtained:Based on the occurrence characteristics of coal seam in a high gas mine in Shanxi Province,the pilot experiment of the ratio of raw coal and tectonic coal was carried out by using the coallike material specimen preparation experiment system,and the mechanical properties of raw coal and tectonic coal with different ratios were obtained.Finally,the appropriate mechanical parameters are selected according to the prototype basic parameters,and the composite specimens of different structural coal thickness are made.The uniaxial compression mechanics and acoustic emission characteristics experiments of different structural coal thickness combinations were carried out,and the compressive strength and elastic modulus of structural coal combination specimens decreased gradually with the increase of structural coal thickness ratio,and the average decrease of compressive strength was 0.375 MPa;the peak stress and strain of tectonic coal combination increased with the increase of tectonic coal thickness ratio,and the variation range was 3.25%-4.14%;combined with fractal theory,the fractal dimension of fracture network in different loading stages of tectonic coal combination is processed,and the fractal dimension values of specimens are generally distributed between 0.88 and 1.31.Based on the characteristics of acoustic emission behavior,it is obtained that the acoustic emission of tectonic coal combination is relatively stable and the energy change is small before the loading and fracture.The acoustic emission of all raw coal specimens increases significantly before the loading and fracture,and the energy change is intense.The permeability test experiment was carried out by using the automatic permeability tester of coal rock core,and it was obtained that the permeability of tectonic coal combination was negatively correlated with axial pressure,confining pressure and gas pressure.Further analysis shows that the influence of axial pressure on the permeability of tectonic coal combination is greater than that of confining pressure during the same loading process.Combined with the evolution relationship between stress and fracture in the loading process of tectonic coal combination,the interaction characteristics between mechanical loading environment and permeability of tectonic coal combination are discussed.Based on the above conclusions,this paper obtains the fracture,acoustic emission evolution characteristics and permeability characteristics under the influence of different factors in the process of loading and fracture of coal with different structural coal thickness ratio,which provides a theoretical basis for mining pressure relief gas drainage and mine gas disaster prevention. |
