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Experimental study of riverbed girdle arrangements in the downstream of Sabo dam
|關鍵字:||free over-fall flow|
Most hydraulic structures failures in Taiwan (such as the Sabo dam) were due to the scouring of downstream protective structures. The result of recent research on the local scouring of free over-fall flows are referenced in this study. A pressure transducer that has no effect on the flow filed was laid to measure the pressure distribution in the downstream channel. The three best riverbed girdles lengths for varied flow could then be proposed by reducing the pressure on the maximal pressure position. A scouring experiment for varied slopes was processed to determine scouring characteristics. In contra-position to the riverbed girdles, a scouring experiment without a riverbed girdle was also carried out. According to the experimental data, the scouring volume of the scouring hole decreased and scouring occurred farther from the Sabo dam. To compare the relationship between the scouring experiment without riverbed girdle the average maximum scouring depth decrease 58% was determined. The area of the scour hole and the shape factor were partitioned 2.63 and 2.53 times. (That is a slender scour hole). When the trench bed with the riverbed girdle dispose, the flow impact upon the riverbed girdle trench surface would have a coast-down force and qualitative energy dissipation, compared with the non riverbed girdle dispose, to obtain an action debility of about 32~35 percent and an energy decrease of 58 percent. When the trench bed gradient becomes steep, the potential impact of a free over-fall flow wash will wax, lead sediment particles to be washed away easily by the flow, thus causing the wash phenomenon to prick up. Riverbed girdles can be divided into types Ⅰ and Ⅱ because the circulation zone influences a small opening between the dam and riverbed girdles possess a flow action with a smaller design mode allied to type Ⅲriverbed girdles. For the economy cost and convenience of riverbed girdle design, type Ⅰ riverbed girdles will be more suitable for engineering requirements.
|Appears in Collections:||土木工程學系所|
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