以渠槽试验观测透水与不透水性固床工之冲刷及破坏差异.PDF

2015 年中華水土保持學會年會及學術研討會論文摘要集 以渠槽試驗觀測透水與不透水性固床工 之沖刷及破壞差異 [1*] [2] 孫崇育 許少華 摘 要 台灣坡陡流急，洪峰期間河床沖淤變化激烈。為穩定河床，常以固床工來穩定河床高層 ， 當水流經過固床工時，對固床工下游產生局部沖刷。近年來由於生態保育意識抬頭，提倡須以友善環 境作為考量的河工結構物 ，而傳統的構造物只考量安全方面，對生態有嚴重的影響。本研究以固床工 的透水性與不透水性對於局部沖刷的差異性，分別探討水流經過兩種固床工所產生的流況及沖刷現 象。水流經過透水性固床工會同時產生兩種流況的型態 ，因兩種流況會相互消能，所以對於不透水性 固床工之基腳淘刷破壞影響較小，不透水性固床工發生破壞是因靠近固床工下游被捲起的床砂達到固 床工基礎時，會沿著固床工底部的基礎向上游淘刷。 關鍵詞：局部沖刷、流況、不透水性固床工、透水性固床工、基腳破壞 。 Difference on Erosion and damage between permeable and impermeable groundsill by observation in flume tests Chong-Yu Sun[1*] Shaohua Marko Hsu[2] ABSTRACT Due to the characteristics of Taiwans geographical features, steep slope and fast flow, scouring and depositing are quite severe during flood peaks. In order to stabilize the riverbed, it is common to use groundsills to stabilize the riverbed elevation. While flow passes through the interface between groundsill and riverbed, local scour usually occurs downstream of the groundsills. In recent years, due to the rise of ecological consciousness, the concept of environmental friendly was introduced into the consideration of river structures. Concern on the traditional structures was mainly on safety, which usually creates serious impacts on ecology. This study investigated the differences of permeable and impermeable groundsills to local scour. Discussion on flow conditions and scours in the two kinds of groundsill was addressed. Flow passes through permeable groundsill will produce two flow patterns, and less impact compared to impermeable groundsill in footings damage. When damage occurs to an impermeable groundsill, usually due to degradation moves upstream from a scour hole and reaches the base of groundsill. Key Words: local scour, flow pattern, watertight groundsill, per