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Abstract According to direct shear tests performed on artificial discontinuous intermittent joints，the mechanical mechanism of weakening process of discontinuous joint rock bridge during shearing is described，i.e. tensile failure of micro-unit rock bridge under shear loads results in the mechanical properties weakening of rock bridge. And the development law of weakening zones in rock bridge is also investigated. Based on the above analysis，assuming that rock bridge micro-unit strength is of Weibull random distribution and the minor principal stress of rock bridge micro-unit is adopted as the random distribution variable，model for explaining the weakening process of rock bridge is set up；and a parameter ，which is named as the degree of weakening，is defined to characterize the degree of rock bridge weakening during shearing. And then，based on direct shear tests，rock bridge weakening mechanical model that takes shear displacement as random distribution variable is derived from analogy method. Finally，the change laws between the degree of rock bridge weakening and parameters m， are analyzed . The results show that the new model can properly reflect the weakening and failure process of rock bridge during shearing.
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Received: 24 March 2010
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