透水柵與梳子壩之共構試驗研究

Abstract

The bottom infiltration screen which has the ability of the water infiltration, the energy reduction and the sediment transport adjusting is one of the strategies to control debris flow. In the past researches, we can find that debris flow affected by the infiltration screening device. There is a repeated phenomenon of move and stop of the debris, at last it stagnated and lost the efficiency of the screen device. In order to advance the available time of infiltration screen, we place a slit dam to displace the traditional check dam. After experiment in the laboratory, we find that the slit dam instead of the traditional check dam can extend the effective service time of the screen device. This study have experimented according to the important factors which are opening width of the slit dam, the upstream bound inclination angle of the infiltration screen, and the bar length. This study selected three different elevation angles of 33˚、35˚、37˚, three different opening widths of 1cm、2cm、3cm in two openings and three different bar length of 30cm、40cm、50cm. We obtain the dimensionless formula for cumulative opening width length (Σb/20), bar length (L/d50), inclination angle (θ), sediment screening ratio (S) as follows: S = 0.0152 × (L/d50) + 1.6094 × (Σb/20) + 0.9807θ - 1.1792 R^2 =0.6704

透水柵具有脫水、減勢和調節土石流攜出土砂規模的能力，是防治土石流的主要工法之一。過去研究發現，土石流受透水柵篩分作用影響，會產生流動、停積、再流動、再停積之重覆現象，直到透水柵淤塞失去篩分功效。經渠槽試驗後發現，以透過性佳的梳子壩取代原本共構防砂壩的設計，可以有效延長透水柵有效使用的時間，取得更好的防砂效果。 本研究以梳子壩開口寬度、透水柵柵面向上游仰角及柵面長度為重要因子進行試驗，設計開口數皆為2開口寬度1cm、2cm、3cm的梳子壩三組、透水柵柵面向上游仰角33°、35°、37°三組、柵面長度30cm、40cm、50cm三組。觀察對土石流運動、堆積型態之影響，得到梳子壩狹縫密度(Σb/20)、無因次柵面長度(L/d50)及透水柵柵面仰角(θ)與土砂篩分比(S)之無因次回歸公式： S = 0.0152 × (L/d50) + 1.6094 × (Σb/20) + 0.9807θ - 1.1792 R^2 =0.6704