土石流通過梳子壩之水理特性研究

Abstract

近年來生態意識抬頭，為追求生態系與人類安全之平衡，於土石流防治工法上經常設置具通透性之梳子壩。然而目前對於梳子壩設計模式上之研究，模式大都僅包含幾何因子，對於土石流通過梳子壩之特性描述並未完全。本研究目的即藉模擬土石流通過梳子壩之水理特性與因次分析方法，以暸解各相關參數對於梳子壩攔蓄土砂能力之關係並探討梳子壩之篩分能力，進而推衍出一套梳子壩貯砂模式。將本研究渠槽試驗數據配合前人研究資料進行迴歸分析，得一貯砂模式： P＝2.26•(C)0.13•(b/D50)-0.93•(Σb/B)-0.45•(q/√(gD503))-0.22•σ0.25 R2=0.77 式中：P=梳子壩貯砂率(即經由壩所阻攔之土砂量與總來砂量之比值)；S=坡度；C =土石流臨前泥沙體積濃度；b=梳子壩開口間距；D50 =土石中值粒徑；B=河寬；水流經梳子壩束縮之單寬流量(q)；粒徑分布因子(σ=√（D84.1/D15.9)，適用範圍b/D50＝1.34∼11.97，Σb/B＝0.3∼0.85，σ＝1.2∼5.8 藉由此貯砂率模式結合集水區及溪流等調查資料，可作為梳子壩設計時，壩體開口寬度、開口密度及有效壩高等主要幾何因子之設計依據。

In recent years, people pay more attention to our ecological environment. The traditional check dam has been replaced by penetrative comb typed dam in the prevention of debris flow for the balance between ecosystem and safety. The problem is that the current available researches on comb typed dam design are all based on its shape. They do not describe the properties of debris flow passing the comb typed dam. Therefore, in our research, we simulate the properties of debris flow passing the comb typed dam and implement the dimensional analysis to find out the relationships between related factors and the impoundment capability. A mathematical model of the impoundment capability is then derived from the above discussion together with the regression analysis based on available literatures as the following: P＝2.26•(C)0.13•(b/Dm)-0.93•(Σb/B)-0.45•(q/√(gD503))-0.22•σ0.25 R2=0.77 Here, P = block rate (blocked debris/total debris); S=gradient；C=debris load per unit volume before the arrival of debris flow; b = comb typed width; D50 = median diameter of debris; B=rive breadth; q=unit discharge of water flow passing the comb typed dam; distribution factor (σ=D84.1/D15.9) ， b/D50＝1.34∼11.97，Σb/B＝0.3∼0.85，σ＝1.2∼5.8 Based on this model and on-site data of river, major factors like comb typed width, density and effective height can be calculated during the design of comb typed dam.