| At present,coal resources rank among the top of consumed energy in China,but due to the complex and varying geological structure,in the process of mining,rock fracture,roof fall,roadway deformation and other disasters caused by impact ground pressure are encountered from time to time,and its coal mining has always been a difficult problem that requires long-term solutions.Therefore,understanding the stability of the surrounding rock is the theoretical basis for ensuring safe coal mining.In this paper,the mechanical properties and energy dissipation of coal-bearing sandstone are analyzed by comparing the static-load uniaxial compression test and dynamic-load uniaxial compression test,and the scale characteristics of impact crushing specimens after dynamic compression test and the relationship with their energy dissipation are compared by introducing digital image processing technology with the help of 3D scanner.The main research results are as follows:(1)The stress-strain dynamic compression curves of coal sandstone under different impact air pressures were obtained by conducting uniaxial compression tests on coal sandstone specimens under static and dynamic loading conditions using the split Hopkinson pressure bar(SHPB)system.The mechanical properties of uniaxial compression of coal sandstone under static load and the calculation methods of basic physical parameters(modulus of elasticity and Poisson’s ratio)are mastered;the basic parameters of dynamic mechanical properties of coal sandstone specimens are studied and understood by conducting a variable-section separated Hopkinson compression bar test(SHPB test apparatus system)on the specimens,and the strain rate effect of dynamic stress is obtained,and the strain rate effect of coal sandstone specimens is obtained.The strain rate effects of dynamic stresses were obtained,and the strain rate effects of coal sandstone specimens were compared with those of dynamic stresses under static and dynamic load conditions,with emphasis on the strain rate effects of both.(2)The impact crushed coal sandstone specimens were collected after the variable section separated Hopkinson pressure bar test(SHPB test system),firstly,they were grouped and classified according to the impact air pressure,and then a simple macroscopic analysis was performed according to their macroscopic morphology and the corresponding strain rate and energy;secondly,the coal sandstone specimens were scanned by a 3D laser scanner,and then The 2D images were digitally reconstructed to obtain the macroscopic morphology of the crushed coal sandstone specimens to qualitatively analyze the damage characteristics of the crushed coal sandstone specimens under different impact air pressure;on this basis,the impact crushing shape indicators,such as overall shape parameters,roughness,angularity and surface texture,and specific surface area,were obtained by image processing technology to analyze the influence of these shape indicators on the crushed coal sandstone specimens after impact crushing.The applicability of these shape indicators to the scale characteristics of crushed coal sandstone specimens after impact crushing was analyzed,and the sensitivity of these shape indicators describing the scale characteristics of crushed coal sandstone specimens under different impact air pressures was explored and evaluated.(3)Combining the energy dissipation calculation principles studied and summarized by previous authors,the relationships between incident energy,reflected energy,absorbed energy and energy dissipation density of coal-based sandstone specimens at different impact air pressures are calculated and analyzed separately;the energy dissipation density strain rate effect is emphasized,and for calculating the specific surface energy of coal-based sandstone specimens after the variable-section separated Hopkinson pressure rod test(SHPB system device)The equation of energy consumption is quoted,and the strain rate effect of specific surface energy of coal-based sandstone specimens is analyzed and investigated.An attempt is made to reveal the mechanism of rock material crushing and deformation through energy consumption relationship.Figure 34,Table 9,Reference 85... |
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