Creep behaviour and permeability evolution of cataclastic sandstone in triaxial rheological tests

Abstract

This article reports the results of triaxial creep tests of cataclastic sandstone cored from the dam foundation of a hydropower station. Meanwhile, the permeability measurements are performed in course of creep tests under hydro-mechanical coupling. The creep behaviours of studied rock and their effects on the permeability evolution have been analysed in detail. The results show that the studied rock exhibits pronounced irreversible time-dependent deformations. The strain rate increases by exponential functions as the deviatoric stress increased and the confining pressure decreased. The long-term strength can be defined at which the critical point of expansion strain rate is greater than the compression strain rate. In addition, important plastic deformation, obvious dilation and large strain rate are observed in the last stage of experimental tests. The permeability change shows some mutative correlation with the material porosity during the time-dependent deformation. But the trend of change is decreasing with the increase of deviatoric stress for all specimens. During the stage of steady creep, the permeability variation slowly decreases quasi-linearly. It indicates that the fluctuation has no significant effect on permeability evolution. These results may provide the basis for the establishment of hydro-mechanical coupling creep model and the long-term stability analysis of structures.