Abstract：To investigate the creep mechanical properties of layered rock slopes with varying dip angles following excavation unloading, layered phyllite was selected as the research subject. Multistage loading-unloading triaxial creep tests were conducted to establish a creep model for layered rock masses, taking into account both the anisotropic characteristics associated with different dip angles and the time-dependent strain-softening mechanism. The influence of varying dip angles on the creep mechanical properties, long-term strength, and deformation and failure characteristics of layered phyllite was analyzed. The experimental results indicate that: (1) Layered phyllite experiences three sequential stages during multistage loading-unloading triaxial creep: decelerating creep, steady-state creep, and accelerating creep. Notably, dip angles of 0° and 90° have minimal impact on these three creep stages. In contrast, rock with a dip angle of 60° transitions into the accelerating creep stage more rapidly and exhibits the shortest creep duration. (2) The creep rate is significantly influenced by the dip angle, demonstrating anisotropic characteristics. At the final stress level, the increase in circumferential strain surpasses that in axial strain, indicating a pronounced effect of rock lateral dilatancy. (3) The long-term strength initially decreases and then increases as the dip angle rises, reaching its maximum near 45°–60° and approximately following a “U-shaped” pattern. (4) An elasto-plastic variable body incorporating a dip angle factor was introduced to establish the LSVISC creep model, which effectively reflects the multistage loading-unloading creep characteristics of rock masses with varying dip angles. The experimental data align well with the model curves, accurately characterizing the multistage loading-unloading triaxial creep mechanical properties of phyllite under different dip angles and quantifying the “U-shaped” variation of creep parameters with respect to dip angle. This study provides a theoretical foundation for exploring the creep mechanical properties and long-term stability design of layered rock and soil masses in slope engineering.
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2025, Vol. 44 
