Abstract: Triaxial compression creep tests on the quartz–mica schist from Danba, China, are carried out to illuminate the schist’s anisotropic creep characteristics. Samples are divided into two sets by the axial load direction, which is perpendicular or parallel to the rock bedding plane. Creep tests under different confining pressures used the multistage loading mode, which shows the creep variation of the quartz–mica schist, including instant deformation, attenuation creep, stable creep, and acceleration creep. A creep model with the Kachanov creep damage rule is adopted to describe the acceleration creep stage, and to estimate the rock creep parameters of the quartz–mica schist. The good agreement between the fitting and test curves indicates that this model can suitably describe the creep properties of a quartz–mica schist. Long-term yield strength, fracture morphology, instantaneous deformation parameters, and steady-state creep strain rate based on the results from the two sets of tests show that there are significant anisotropic creep properties in the quartz–mica schist. The relatively higher strength, shear modulus, bulk modulus, and viscosity of these samples, in which the bedding plane is perpendicular to the axial load, show that these samples perform better in terms of anti-deformability and damage resistance compared with the parallel sample set. The samples in which the bedding plane is perpendicular to the axial load mainly have shear failure modes; the other sample set show lateral expansion when the samples are damaged. The instantaneous deformation and stable creep rate of both test sets increase with increase of stress level.

Key words: triaxial creep test, anisotropy, creep damage model, Kachanov creep damage rule