Abstract

This study investigates the nonlinear rheological effects on debris flow dynamics within multi-stage energy dissipation systems. Addressing the limitations of the constant-viscosity Bingham model under high-shear conditions, we developed a 2D multiphysics model combining stepped spillways and a regulation basin using the Phase-Field method. We systematically compared the Bingham model against the Herschel–Bulkley–Papanastasiou (HBP) model across various flow behavior indices. Results reveal three key mechanisms: (1) In rapid stepped-drop zones, the HBP model captures shear-thinning behaviors, correcting Bingham’s velocity prediction biases. (2) In bottom gentle zones, deceleration in moderate-to-strong pseudoplastic fluids triggers a “low-shear to high-viscosity” positive feedback, spontaneously forming a high-stiffness unyielded cushion that enhances energy dissipation. (3) Shear-thinning behavior significantly reduces the macroscopic viscosity of the fluid near structural boundaries. This apparent viscosity reduction causes the debris flow to generate dense and high-frequency transient impacts upon initial contact with the retaining wall. The traditional Bingham model often severely underestimates this critical initial destructive force. This research elucidates non-Newtonian phase-transition laws under cascading topographies, providing a robust theoretical basis for designing impact-resistant disaster mitigation structures.

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