The shear rheological behavior of rock mass discontinuities dictates the long‐term stability of rock engineering. However, the interplay between shear creep, stress relaxation, and long‐term strength of red sandstone discontinuities, particularly under the influence of morphological characteristics, remains inadequately understood. This study systematically investigates these time‐dependent properties through graded loading shear creep and stress relaxation tests on discontinuities with varying morphologies, quantified by the slope root mean square ( Z 2 ). Key findings reveal that the steady‐state creep rate decreases, while the stress relaxation rate increases with Z 2 , both exhibiting exponential growth with shear stress. Novel semiempirical rate equations incorporating Z 2 and shear stress were proposed to predict these behaviors. The long‐term strength, determined via improved methods (transition creep, isochronous curves, and relaxation), ranged from 66.4% to 82.3% of the instantaneous shear strength (9.71 MPa), with values derived from stress relaxation tests being slightly higher. Although the Burgers model effectively captured the attenuation and steady‐state stages of both shear creep and stress relaxation (average R 2 > 0.945), significant disparities in the fitted parameters indicated that these two processes are related but not entirely equivalent. The findings provide quantitative insights and predictive tools for assessing the long‐term deformation and stability of rock masses.
Zhang et al. (Thu,) studied this question.