A laboratory study of the retarding effect of breaking mounds in 3, 6 and 9 m long chutes
Kristín Martha Hákonardóttir, Tómas Jóhannesson,
Felix Tiefenbacher, Martin Kern
VÍ-G01007-ÚR02; May 2000
A series of laboratory experiments in 9 m and 3 m long experimental chutes using 0.1 mm glass particles and 2 mm sand particles, was performed to investigate the effect of scaling of supercritical, high Froude number granular flow interacting with obstacles. The experiments were followup work on laboratory experiments performed in a 6 m long chute in the summer 2000 (Hákonardóttir, 2000), where basic understanding of the retarding effect of avalanche breaking mounds was established. It was verified that the collision of the flow with a row of breaking mounds leads to the formation of a jump or a jet whereby a large fraction of the flow is launched from the experimental chute and subsequently lands back on the chute. The retarding effect of the mounds was investigated quantitatively by direct measurements of the velocity and runout length of the flow along with the geometry of the jet. The effect of several aspects in the layout of the mounds on their retarding effects was examined. It was observed that a row of steep mounds with a height several times the flow depth, a breadth similar to the height and narrow gaps between individual mounds can lead to a 30-40% reduction of the runout length of the flow past the mounds.