Innovation of permeable groundsills for local scour control

in International Symposium (poster paper), 國際研討會(全文海報發表)
標題Innovation of permeable groundsills for local scour control
AuthorsWu, 吳嘉俊, 陳宥達, 張之馨, & 謝采樺
出版日期Jul 13 2017 12:0

Groundsill is one of the common practices implemented for torrent control. It serves the purposes of controlling longitudinal scour in stream channels as well as checking channel gradients. Nevertheless, groundsills often dissect aquatic habitat, and the unavoidable local scour at the groundsill toe every so often endanger the safety of the structure. Therefore, the objective of this study is to investigate the feasibility of permeable groundsills in a laboratory setting under different hydraulic and sediment conditions while varying the structure permeability.
This study was conducted in a semi-circular hydraulic flume using 1:50 scaled groundsill models, which included solid slabs representing the typical groundsills and two permeable groundsills with 7% and 68% permeability. Flume experiments was run under three sediment sizes, three flow rates, and three channel gradients. Laser profiler was used after each experiment to scan the channel topography, and the elevation data were used afterwards to acquire the maximum scour depth, extent of the scour as well as the location where maximum scour occurred.
Experiment results indicated that permeable groundsills could effectively control the scour depth and the extent of scour. However, sediment from upstream channel was still trapped by the permeable structures but with less uniformity. Non-uniform deposition on the backside of the permeable groundsills provided a gateway for stream flow to easily go through the voids, which changed the overflown flow depths as well as affected the scour mechanics. These vital adjustments not only eased the scour extent and diversified the flow regime, but also facilitated the restoration of habitat environment.
Within the scope of this study, groundsill with high permeability was not recommended for high-gradient torrents. On the other hand, low permeable groundsill was found capable of reducing local scour depth and overflow flow depth at low flow rate stream channels with gradients less than 6%.

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