Abstract ID: 3.13188 | Accepted as Talk | Talk/Oral | TBA | TBA

Debris and mud flows pose significant natural hazards, often resulting in severe damage and loss of life. Understanding their behavior, particularly in curved channels, is crucial for improving risk assessment and predictive models. As these flows navigate along bends, centrifugal forces cause a height difference between the inner and outer banks, a phenomenon known as superelevation. Analytical models describe this effect by relating superelevation to flow velocity, typically using a forced vortex approach. However, these models rely on simplifying assumptions, such as a linear flow surface and a rectangular cross-section, while neglecting complex rheological behaviors and solid-fluid interactions. Consequently, an empirical correction factor is introduced, though its mechanical basis remains unclear and is primarily determined through field and laboratory studies. This study enhances the forced vortex approach by integrating depth-resolved numerical simulations using a coupled SPH-DEM model, where SPH represents the fluid phase (fines and water) and DEM captures the coarse solid particles. The model is first validated against laboratory-scale superelevation experiments before being applied to analyze the effect of water content on flow behavior. Results reveal that higher water content leads to increased superelevation and influences the flow surface shape. Mud flows tend to exhibit convex upward surfaces, whereas granular debris flows display concave downward shapes. This distribution is governed by the equilibrium between boundary stresses and centrifugal forces. By balancing centrifugal forces and basal normal stresses along the channel boundary, we establish a correlation between the analytical model’s correction factor, material type, and water content. However, we notice significant variations in the correction factor throughout the bend, prompting questions about the presence of additional variables not accounted for in the model, like a run-up component. Large-scale SPH-DEM simulations of a real debris flow event at Illgraben (Switzerland) demonstrate good agreement with field data, highlighting the model’s potential for real-world applications. These findings contribute to a more accurate representation of debris flow dynamics in curved channels, improving hazard assessment and mitigation strategies.