Abstract Using self-made meso-shear test equipment for gas-containing coal and rock,the researchs on the evolution process of cracking and development,macroscopic crack morphology,and meso-crack coalescence mode of raw coal containing horizontal and vertical surface cracks,are carried out under different loading speed conditions. Results show that horizontal surface crack influenced the numbers of macrocrack development,made macroscopic shear crack morphology of raw coal containing horizontal crack manifested H or H+L type;while,vertical surface crack had no effect on the number of macroscopic crack development;raw coal containing vertical crack showed L type. Effects of original cracks on the development and evolution of the new crack were limited to the local area near predetermined shear plane,cracks far from predetermined shear plane and rock samples defects far from predetermined shear plane induced by making of raw coal samples,whose shape were not changed significantly,had no significant effect on the macroscopic crack development near shear plane. Nearby predetermined shear plane,later macro main crack will cause pre-generated right side crack closed. Vertical original crack on the left side of the shear plane had no effect on crack initiation and expansion of macro main crack. Meso-analysis show that,horizontal surface original crack made coal rock failure mode complex and diversification,including compressed failure,shear failure,tension failure,and combination mode,lead crack initiation location to appear at the original crack nearby predetermined shear plane,while vertical surface original cracks less affected the coal rock failure mode.
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Received: 09 April 2012
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