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Abstract The mechanical properties of clastic rock of dam foundation in a hydropower station in virtue of conventional physical and deformation analysis are very complex. Triaxial rheological tests were therefore conducted using the automatic triaxial servo-instrument to investigate the rheological properties and permeability of such rock under hydro-mechanical coupling. The axial，lateral and volumetric deformation curves versus time were measured and the rheological deformation properties and rheological rate law were discussed accordingly. The evolution process of permeability during rheological period was analyzed in detail. The scanning electron microscope(SEM) experiments were performed for the rock specimens after failure to study the mechanism and mode of macro-micro failure. The results show that the clastic rock has a pronounced rheological behavior. The rheological curves have a transient period initially，a steady period thereafter and an accelerated period finally at the last loading step. The rheological deformation were increased when the stress and seepage pressure applied were increased and were reduced if the confining pressure was increased. The finally failed specimen have the characteristics of large axial compression deformation，obvious ductile volumetric dilation and large steady rheological rate. The relationship between the rheological rate and the applied stress can be described by an exponential function. The coefficients of permeability fluctuate during the rheological process possibly because of the heterogeneity of specimens，but overall decrease. During the stage of steady period，the coefficients of permeability decrease linearly. It is shown that the fluctuation has no significant effect on the permeability evolution. Furthermore，the permeability coefficients decrease as the confining pressures increase.
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Received: 08 June 2013
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2014, Vol. 33 
