Dynamic Deformation and Stability Evaluation of Red-Bed Interbedded Rock Filler Under Cyclic Loading with Wetting–Drying Effects: A New Shakedown Criterion
摘要
To investigate the dynamic response and long-term stability of red-bed interbedded rock filler (RBIRF), a series of cyclic triaxial tests were conducted under coupled wetting–drying and dynamic loading conditions. The influences of soft–hard rock ratio (SHR), number of wetting–drying cycles, confining pressure, dynamic stress amplitude, and particle breakage level on the cumulative deformation behavior were systematically examined. Based on a newly developed shakedown framework, the dynamic stress characteristics and critical shakedown states of RBIRF were analyzed. The results reveal that axial cumulative plastic strain is jointly controlled by structural composition and environmental effects, exhibiting pronounced dependence on SHR and wetting–drying history. A lower SHR enhances the skeletal interlocking and reduces deformability, whereas repeated wetting–drying weakens particle cementation, promotes crushing, and amplifies plastic strain under cyclic loading. Increasing confining pressure effectively restrains deformation, while higher cyclic stress accelerates particle rearrangement and secondary strain acceleration. The evolution of cumulative strain includes three stages: slow growth, acceleration, and re-acceleration. Particle breakage, characterized by the fractal dimension (D), shows a strong positive correlation with plastic strain, indicating that breakage acts as both a byproduct and a trigger of macroscopic instability. On this basis, a new quantitative stability criterion, defined by the reciprocal of the strain–cycle slope (1/as), was established to classify long-term stability into plastic shakedown, plastic creep, and incremental collapse zones. The proposed criterion effectively captures the critical transition from stable to unstable states under multi-factor coupling, providing a reliable theoretical and practical basis for evaluating long-term performance and optimizing the design of red-bed subgrade filler.
Highlights Established a coupled test system considering wetting–drying, dynamic loading, and heterogeneity of RBIRF. Clarified a three-stage deformation mechanism via particle breakage, skeletal reorganization, and stress transmission evolution. Proposed a new 1/as-based shakedown criterion for quantitative evaluation of long-term dynamic stability.