Study on mechanical properties and crack propagation of coal specimen based on CT scanning technology
The mining areas in central and eastern regions of China have been entering the deep mining phase.The inner cracks development inside the coal are intensified with the enlargement of tectonic stress and mining-induced disturbance effect,which leads to the increased occurrence of coal rib instability.To study the mechanical properties and crack propagation law of coal mass under a high in-situ stress envi-ronment,this study achieved the accurate identification of each component in coal specimen based on CT scanning technology.A three-dimensional reconstruction model and the refined numerical model of the coal specimen were established.Assisted by the UCS test,the impacts of the spatial distribution charac-teristics of each component in the coal specimen on the deformation parameters,peak strength,and crack propagation path were investigated.The experimental results showed that a larger inclination angle of the preexisting crack led to a lower value of initial modulus Ei,then the specimen was prone to a lon-gitudinal splitting failure.The smaller inclination angle of the preexisting crack incited a lower peak strength σc,then the specimen was prone to a combined tension-shearing failure.Moreover,a greater volume proportion of high-density impurities facilitated a higher value of the elastic modulus Et,thereby the brittleness of the coal specimen could be amplified.Plus,the greater volume proportion of the preex-isting crack was positive to the appearance strain hardening characteristics of the specimen,besides,the crack volume proportion and complexity after the compression failure of the specimen also increased re-markably.The propagation path of the cracks mainly extended along the preexisting cracks horizontally and longitudinally,the generation of bifurcate cracks accompanied the process due to the rapid expansion.Moreover,a more complex tendency distribution of the preexisting cracks encouraged a gen-eration of bifurcate cracks.In addition,the propagation paths of cracks often bypass the high-density im-purities if the preexisting primary cracks didn't touch the preexisting,otherwise,the propagation paths of cracks tended to penetrate the impurities and expand thereof.The following numerical simulation results were consistent with the laboratory test results,both exhibited identical propagation modes of the micro-cracks,which vindicated the reliability of the refined numerical model.
CT scanningthree-dimensional reconstructionmechanical propertiescracks propagationrefined numerical model
万方数据
维普
