Abstract: For the safety and long-term stability of underground engineering, it is important to clarify the shear time-dependent performance of deep-seated anchored and filled jointed rock masses. Shear creep tests on anchored and filled jointed rock masses under constant normal stiffness (CNS) boundary conditions were conducted, and the influence mechanisms of different combinations of filling degree Δ, joint roughness coefficient JRC, filling material strength σ_cj , and normal stiffness kn on the tangential and normal creep characteristics of the anchored and filled jointed rock masses were analyzed. A fundamental relationship equation among macroscopic stress difference, mesoscopic stress, and time was established. Combined with mesoscopic computed tomography (CT) experiments, the evolution law of pore volume fraction was analyzed. On this basis, an improved nonlinear shear creep equation of the Nishihara model considering the combination of macroscopic and mesoscopic scales was established. The research results indicate that: 1) The four influencing factors of Δ , JRC,σ_cj  and k_n mainly lead to the differential evolution of the climbing-shearing behavior between rough asperities and the wear behavior of the filling material, which in turn affects the tangential and normal creep characteristics of the anchored and filled jointed rock masses; 2) Δ  is the main factor affecting the tangential creep performance of the anchored and filled jointed rock masses, and the influence degrees of JRC, σ_cj and k_n  on the tangential creep performance of the anchored and filled jointed rock masses are relatively close; 3) A localized coordinated deformation failure mode of the anchoring-induced compression and fragmentation zone was proposed to reflect the overall time-dependent deformation evolution characteristics of the anchored and filled jointed rock masses; 4) An improved Nishihara nonlinear creep model was constructed, and its parameters were verified and subjected to global sensitivity analysis. The model can effectively describe the accelerated creep stage of anchored and filled jointed rock masses and can provide theoretical guidance for the long-term structural slip failure prediction of deep-seated rock masses.

Key words: constant normal stiffness boundary, shear creep, anchored and filled jointed rock masses, integration of macroscopic and mesoscopic scales