Influence of release mechanisms on flow velocity and depth in dry granular flows: an experimental investigation

Debris flows are an extremely rapid and unpredictable phenomena with a dynamic that remains poorly understood. Further complicating the problem, human settlements are often located in regions prone to debris flows. Despite the acknowledged hazard, comprehending the intricate behaviour of debris flows remains a challenging task. Laboratory experiments serve as a crucial tool, enabling the simplification of complex channel geometries and facilitating detailed observations. However, the often-overlooked influence of release mechanisms on resulting flows presents a significant gap in current practices. This paper addresses the simplification of release mechanisms, commonly reduced to dam break schemes or, less frequently, double gate systems regulating flow discharge. To isolate this issue, focus is placed on the influence of different release mechanisms only on dry dense granular flows. Flume experiments are carried out and recorded with a high-speed camera. The videos are analysed using the Particle Image Velocimetry (PIV) technique, providing insightful results on flow velocity, depth, and velocity profiles. The findings highlight the role played by the release mechanism in influencing both flow depth and velocity. This factor has the potential to modify outcomes when studying the interaction of debris flows with mitigation structures. This highlights the need to consider the release mechanisms in the study of granular flows, particularly when proposing new criteria for the design of structures or estimating the forces acting on them.