弱胶结顶板砂岩力学特性及声发射演化规律试验研究OA

The composite roof structure of weakly cemented strata in coal mine engineering exhibits deformation and failure charac-teristics such as small deformation scale,sudden instability,and phase transition-like behavior.Revealing the characteristics of in-formation associated with the instability and failure of weakly cemented strata rock masses is the foundation for achieving effective roof control and disaster prediction.To accurately obtain the mechanical behavior,acoustic emission characteristics,and crack evolu-tion laws of weakly cemented roof sandstone,uniaxial compression tests and acoustic emission tests were conducted on weakly ce-mented roof sandstone from Shilawusu Coal Mine.Combined with the Gaussian mixture model,cluster analysis was performed on the acoustic emission AF-RA parameters.The results show that the weakly cemented roof sandstone has heterogeneity and deform-ability.The closer the sandstone in the upper part of the roof is to the roof surface,the larger the axial strain at peak strength.A neg-ative linear correlation exists between the sandstone layer position and axial strain,indicating that sandstone closer to the roof has stronger deformability.During the loading process,acoustic emission signals show obvious stage changes,with the A-value and b-value exhibiting oscillatory evolution characteristics in different loading stages,reflecting the development and evolution process of internal cracks in the rock.The proportions of micro-tensile cracks and micro-shear cracks vary in different stress stages,with shear failure dominating overall.For sandstone adjacent to the roof,the proportion of micro-shear cracks reaches 75.48%before peak stress,while that of shallow layers is 57.42%.This shows that shear failure is the dominant instability mode of weakly cemented roof sandstone.The closer the sandstone layer is to the roof,the more obvious its shear failure characteristics and the more developed the shear cracks.The stage changes of acoustic emission signals and the evolution of crack types can be used as precursor information for roof instability.