Deformation and Fracture Characteristics of Coal Gangue Interbedded Samples under Loading and Unloading Conditions

The dynamic sedation of the coal mine production is alternate or superimposed in coal rocks, which causes crack unevenness due to the presence of jacquards, causing unregistered coal blocks. By observing the deformation and fracture characteristics of coal-rock interbedding specimens with different gangue ratio under different stress paths, this paper studies the fracture instability mechanism and fracture characteristics of coal-rock interbedding, analyzes the progressive failure process and fracture opening model of coal-rock interbedding, and uses GDEM software to simulate the triaxial loading and unloading failure characteristics of coal-rock samples. The results show that the ratio of gangue inclusion has a significant effect on the structural strength of coal rock interbedding; with the unloading, the coal rock interbedding of the top coal body will be damaged and destroyed to varying degrees and asynchronously, the coal rock interbedding of the top coal body will present various forms of failure characteristics according to the changes of horizontal stress gradient in the vertical direction; the progressive failure process of coal rock interbedding under loading and unloading conditions can be divided into three stages. As the jigs are raised, the crack nonstable expansion stress of the composite coal body sample is gradually increased; and the rising ratio of the jacket X is not complete. The striped conjugated shear failure characteristics are more obvious; the different combined coal gangue tester shows microcrack near the peripheral loading boundary, and as the loading axis pressure increases, the fracture distribution range and density are increased; the rock layer is present. The tensile fracture is destroyed, and the coal seam exhibits shear destruction of intensive cracks; different test pieces produce significant tensile destruction on one side of the unloaded boundary; the greater the loaded axial pressure of the specimen, the greater the damage degree of the specimen after unloading; the damage degree of two coal and one rock specimens is the largest, the damage degree of one coal and one rock specimens is in the middle, and the damage degree of one coal and two rock specimens is the smallest.

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