Study on the evolution law and numerical simulation of the mechanical properties of rockfill under dry-wet cycle conditions

The mechanical properties of rockfill materials degrade markedly under dry-wet cycles, uneven settlement of rockfill dams over time. This study employed numerical simulations of crushable triaxial compression on rockfill samples subjected to various dry-wet cycles, utilizing the particle discrete element method. The macroscopic mechanical behavior and the micrscopic degradation mechanisms of rockfill under these cycles were subsequently analyzed. The research findings are presented in detail below: (1) Macroscopic law: As the number of dry-wet cycles ( N ) increases, the peak stress of rockfill decreases while the volume strain increases. After N reaches a certain threshold, the peak stress and volume strain show minimal change. The shear strength, cohesion ( c ), and internal friction angle ( φ ) of rockfill exhibit an exponential relationship with N . With the progression of cycles, the rate of particle breakage ( B _r ) and the increment in particle count diminish. (2) Microscopic mechanism: As N increases, the dense chain regions, areas of particle breakage, fracture distribution, and displacement field within the sample all expand overall, while the average coordination number rises significantly. However, beyond a certain N , these microscopic changes become less pronounced. (3) Damage evolution: The parameters A , B , and C of the modified Duncan-Chang model follow an exponential relationship with N . As N increases, these parameters exhibit exponential growth, with a marked increase during the early cycles, which stabilizes in the later cycles.