An advanced stress–strain framework for rockfill materials incorporating cyclic degradation and energy dissipation under low-frequency loading

Abstract Existing constitutive models like the Duncan-Chang model inadequately capture hysteretic effects and residual strain accumulation in rockfill materials under low-frequency cyclic loading (e.g., from reservoir water-level fluctuations in dams). This study investigates the mechanical evolution of rockfill materials under such loading, specifically addressing the Duncan-Chang model’s limitations in describing hysteresis and lag effects. Triaxial cyclic loading–unloading tests were conducted on two representative rockfill materials (limestone and sandstone) under varying cyclic stress ratios ( CSR ), cyclic stress mean ratios ( CSMR ), and confining pressures. Results informed the development of an enhanced Duncan E-B model incorporating CSR , CSMR , and confining pressure effects. Experimental findings revealed that, as cyclic loading increased, the unloading modulus remained relatively stable, while the loading modulus followed a hyperbolic evolution pattern and gradually approached the unloading modulus. For limestone rockfill, the cumulative axial strain increased from 0.48 to 2.67% when CSR increased from 0.25 to 1.00 after 20 loading cycles. The unloading modulus was influenced by CSR , CSMR , and confining pressure: it decreased with increasing CSR due to particle disturbance, but increased with higher CSMR and confining pressure. The predicted strain increments showed good agreement with the experimental results, with the coefficient of determination R 2 exceeding 0.87 for the validation cases. Application to a 247 m-high dam showed that deep water-level fluctuations (> 50 m) significantly amplified upstream slope deformation. Under the same 10 loading cycles, a 110 m drawdown increased the face-slab deflection by 222.13 mm, compared with 17.88 mm for a 10 m drawdown. This study provides a robust tool for evaluating long-term dam safety under cyclic hydraulic loads and offers insights for optimizing the design of high concrete face rockfill dams.