EXPERIMENTAL STUDY OF COAL CONSIDERING DIRECTIVITY EFFECT OF BEDDING PLANE UNDER BRAZILIAN SPLITTING AND UNIAXIAL COMPRESSION
LIU Kaide，LIU Quansheng，ZHU Yuanguang，LIU Bin
(State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China)
Abstract：In view of the characteristics of B10 coal layers with significant horizontal bedding in Huainan mining area，tensile and compressive mechanical properties in the directions of vertical and parallel to the coal bedding plane are researched by the Brazilian splitting and uniaxial compression tests. The results show that：(1) Tensile strength in the directions of vertical and parallel to the coal bedding plane are discrete，but the former discrete level is much more. Comparing the mean values in both directions，the former is obviously less than the latter，tensile strength has obvious anisotropy. (2) The random distribution of macroscopic coal composition and its differences on physico-mechanical properties are the important conditions which lead to the discreteness of tensile strength. Moreover，banding distribution characteristics of macroscopic coal components and directivity of coal cleat system are the internal causes to decide the anisotropy of coal mechanical properties. (3) Comparing the axial stress-strain curves in the directions of vertical and parallel to the coal bedding plane under uniaxial compression，the former pre-peak deformation characteristics are similar；the mechanical properties are stable；the post-peak stress drops quickly and the brittle feature is apparent. However，the latter pre-peak and post-peak deformation characteristics of each curve are different；and mechanical properties are unstable. Meanwhile，the axial peak strains of all coal samples are less than 1%. Thus，the deformation features are in a brittle failure state. (4) Fracture failure patterns of coal samples in the directions of vertical and parallel to the bedding plane are respectively given priority to shear and fracturing failure under uniaxial compression；and the uniaxial compression strength and deformation parameters in both directions are obviously different. In other words，the anisotropy is apparent. (5) The uniaxial compression characteristics in the direction of vertical and parallel to the coal bedding plane are discrete；but the latter discreteness is much more obvious. (6) The uniaxial compressive strength is much greater than the tensile strength，uniaxial compression strength in the directions of vertical and parallel to bedding plane are respectively 40.1 and 14.7 times of tensile strength.
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2013, Vol. 32 
