Qiuling Yao ¹ XiPing Yan ² Zebin Wu ¹ Huiqing Hao ² MeiHong Ma ^2,3*

• ¹ China Institute of Water Resources and Hydropower Research, Beijing, Beijing Municipality, China
• ² Tianjin Normal University, Tianjin, China
• ³ State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing, China

This study investigates the backward erosion piping mechanism and its dependency on model size through a series of experiments and numerical simulations. The numerical simulations were conducted using the finite element method (FEM), where the dike foundation was modeled in 3D, and the seepage flow was simulated under various hydraulic gradients. In parallel, physical experiments were carried out using small-scale dike models for verification. Experiment results shown that in dikes without blanket layers, hydraulic gradients increase steadily as the piping channel develops, leading to upstream erosion and failure. Conversely, dikes with a blanket layer exhibit a stabilizing effect, where the hydraulic gradient initially decreases before increasing, creating a self-healing phenomenon that halts further channel progression. The study also reveals that the size effect-reflected in hydraulic gradients-diminishes with larger model dimensions, becoming negligible beyond a certain threshold. Furthermore, the interaction between model width and depth is significant, with their combined effects influencing the progression of piping. These findings offer valuable insights for designing more resilient dike systems and improving flood protection strategies.