Influence of Partial Crack Length of Rock in Assemblage Body on Mechanical Characteristics of Coal-rock Assemblage Body
In view of the influence of different lengths of cracks in the roof and floor rocks during coal mining process on the mechanical characteristics of coal-rock assemblage body specimens formed by residual coal pillars and roof and floor rocks,five numerical simulation models of coal-rock assemblage bodies with different lengths of cracks are established using the particle flow analysis program PFC in numerical simulation software.Uniaxial compression numerical simulation experiments are conducted to obtain the influence of crack length on the strength,deformation,microcrack variation,and acoustic emission variation characteristics of coal-rock assemblage body specimens.As the length of partial cracks in the rock increases,the peak strain and peak strength of the coal-rock assemblage body specimens containing cracks show a trend of first increasing and then decreasing,while the elastic modulus shows a variation trend of monotonically decreasing,the microcracks show a trend of first increasing,then decreasing,then increasing,and then decreasing.When the crack length is 4 mm,the maximum number of microcracks in the coal-rock assemblage body is 4802,and when the crack length is 36 mm,the number of microcracks is the lowest.The failure of coal-rock assemblage body mainly occurs in the coal body part of the assemblage body,and research is of great significance for understanding the influence of crack length on the mechanical characteristics of coal-rock assemblage body specimens and the stability of coal-rock assemblage structures.
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