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Abstract Rheological experiments of hard metamorphic-volcanic breccia specimens in dam foundation under triaxial compression with seepage pressure are carried out on the advanced rock servo-controlled triaxial rheology testing equipment. Based on experimental results of hard rocks，the creep properties of metamorphic-volcanic breccia specimens under different confining pressures are studied；and the variation of seepage rate with time in the stage of completed process of hard rock creep is analyzed. The results show that，when the applied stress level is considerably less than fracture stress，the creep deformations of metamorphic-volcanic breccia specimens are not obvious，and the main creep form is named steady state creep. On the other hand，when the applied stress level is greater than or less than but close to fracture stress，the creep deformations and accelerative creep characteristics become more obvious. Meanwhile，cracks of metamorphic-volcanic breccia specimens appear and spread. The metamorphic-volcanic breccia specimens show significant volume expansion phenomenon under triaxial compression；and circumferential creep deformations are obviously higher than those of axial creep deformations. The seepage rate of metamorphic- volcanic breccia in stage of steady state creep is not changed with time significantly. But in the stage of creep acceleration，the seepage rate increases evidently；and the seepage acceleration at confining pressure of 2 MPa is greater than those at confining pressure of 6 MPa. The results can provide dependable reference for the establishment of rock rheological model and parameter identification.
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Received: 13 January 2010
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