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Abstract Based on the theory of particle flow and the particle flow code(PFC)，an equivalent crystal model reflecting the mesoscopic structural features of rock mineral was established with the combination of models of bonded particles and smooth joints. The suitability and reliability of the equivalent crystal model of rock were validated with the experimental and calculated data. The mechanism of fracturing and the strength of rock under loading condition were revealed from mesoscopic viewpoint. Under the uniaxial tensile condition，the surfaces of macro fractures were found to be approximatively perpendicular to the loading direction and the fractures were primarily due to the tensile failure of bond on the boundary of crystalline. Under the uniaxial or triaxial(low confining pressure) compression，the surfaces of macro fractures were parallel to the loading direction and the fractures were primarily due to the tensile failure of bond on the boundary of crystalline，which led to the splitting failure of rock macroscopically. Under the triaxial compression with the high confining pressure，the surfaces of interpenetrating macro fractures cross oblique to the loading direction were primarily due to the tensile failure of bond in the crystalline，and the tensile and shear failure of bond on the boundary of crystalline，which led to the macro shear failure of rock. For hard brittle rock such as granite，the lower ratio between the tensile and uniaxial strength of the rock，can be reproduced by adopting the equivalent crystal model，and its strength properties can be reasonably described with Hoek-Brown strength criterion.
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Received: 28 May 2014
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2015, Vol. 34 
