Study on the Fractional‐Order Creep Constitutive Model of Rock Considering Chemical–Stress–Seepage Damage

ABSTRACT

Accurate characterization of rock creep under coupled chemical–stress–seepage conditions is essential for deep rock stability. A three‐dimensional fractional‐order creep constitutive model is developed. Chemical, stress, and seepage damage are quantified by elastic modulus degradation, the Kachanov evolution, and permeability–pore‐pressure gradient evolution and combined into a total damage variable. This variable is introduced into an Abel‐type fractional dashpot, and the governing equation is converted into an explicit time‐power series form through the Riemann–Liouville integration and the Beta function. The model is extended to three‐dimensional stress states and validated by step‐loading triaxial creep tests under varied pH, seepage pressure, and stress levels. Results show that stronger corrosion, higher seepage pressure, and higher stress increase the fractional order and time‐power coefficients, reduce viscosity, and promote accelerating creep. Fitting gives coefficients of determination R ²  > 0.85, supporting long‐term deformation prediction and stability assessment of rock masses under coupled multi‐field environments.