General equations for landslide-debris impact and their application to debris-flow flexible barrier

Abstract

The runup height and impact load of landslide debris are the key parameters for design of debris hazard mitigation structures. However, the movement of obstacle (e.g., deformation of flexible barrier) still cannot be quantitatively considered in the existing analytical models. This study proposes general equations for landslide-debris impact under vertical jet and momentum jump modes. Especially, the influence of flow regime and obstacle movement (in the form of a modified Froude number), state of granular material, compressibility (density change), and flow resistance within the jump volume are explicitly considered in the momentum jump model. Through comparison between model prediction and experimental results, it is found that the vertical jet model prediction agrees well with the physical measurements. While the discrepancy between the momentum jump model and experimental results mainly comes from the inappropriate characterization of the unsteady flow properties (velocity and flow depth). Systematic parametric study demonstrates that the functionality of debris-flow flexible barrier primarily relies on the deflection of barrier, and the state of granular material also affects the impact load of dry granular flows.