Flume investigation of the influence of rigid barrier deflector angle on dry granular overflow mechanisms

Abstract

Mass-wasting processes are often intercepted using rigid barriers, which are sometimes equipped with deflectors to prevent overspilling. Despite the engineering value of deflectors, they are currently only installed using empirical and prescriptive approaches because flow interaction mechanisms are not well understood. A 5 m flume was used to study dry granular flow deposition and overflow processes with and without deflectors of varying angles. The deflector angle was varied as 0°, 30°, 45°, and 60° with respect to the horizontal plane. For the geometric and material parameters adopted in this study, experimental results reveal that deflector angles greater than 45° develop steep ramp-like deadzones that result in effective energy dissipation as approaching flow impacts the deflector, whereas deflectors less than 45° rapidly develop shallow ramp-like deadzones, which promote high-energy overflow. Deflectors of at least 45° are required to develop upward overflow launch angles, whilst deflectors of 30° or less result in downward overflow launch angles. Upward launch angles indicate that a steep deadzone develops and effectively dissipates flow energy. An orthogonal deflector increases launch lengths by 40% compared to a bare rigid barrier.