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Abstract It takes migmatitic granite of Xingshan iron mine as the object to study the failure criterion of brittle hard rock. According to the physical and mechanical parameters from laboratory experiments and grains section scanning，micro-geometric model of migmatitic granite grains were built based on particle flow theory and PFC programs，loading codes were developed and some functions were adjusted by Fish language to simulate uniaxial and triaxial( = 40 MPa) compression experiments. Based on comprehensive comparison and analysis of the complete stress-strain curves，acoustic emission and “crack” monitoring results from laboratory and simulation，the micro-mechanical characteristics and the cracks revolution laws from microcosm to macrocosm of migmatitic granite were obtained. On this condition，cohesion weakening and friction strengthening(CWFS) failure criterion model parameters of brittle hard rock were optimized and verified through laboratory curves of unixial rigid loading，relation curves between cracks and friction energy with plastic strain，and FLAC simulation. The optimized CWFS model parameters of initial cohesion，residual cohesion，initial friction angle，residual friction angle and critical plastic strain ， of migmatitic granite are 23 MPa，4.3 MPa，0°，46.3°，0.001 5 and 0.003 7 respectively，which is of great significance in theory and practice on the study of fracture mechanism，mechanical constitutive relations and engineering stability of rock mass during open pit mining transferring to underground mining in Xingshan iron mine.
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Received: 27 October 2011
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2013, Vol. 32 
