Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/33461
標題: Flume Experiment of Alluvial Fan at the Confluence by Debris Flow
土石流入匯主流形成沖積扇型態之渠槽實驗
作者: 安軒霈
An, Shiuan-Pei
關鍵字: debris flow
土石流
alluvial fan
classification
沖積扇
型態分類
出版社: 水土保持學系
摘要: 本研究透過兩組實驗渠道,模擬山區土石流入匯主流時,在主流中形成沖積扇之過程。實驗渠道I中,主槽提供三種不同之清水流量、六種不同之渠床坡度,支槽以固定清水流量調配三種不同乾砂通量,以提供三種不同之支槽土石流濃度。實驗渠道II則有三種土石流濃度、三種主槽流量共九組實驗條件。兩組實驗渠道之支槽皆以交匯角90°之模式入匯主流。 經觀察實驗現象後,可將土石流入匯分為土砂流動擴散與土砂持續停淤、擠壓擴張兩個階段。在土砂流動擴散階段時可用土砂擴散福祿數 判斷其擴散型式。而在土砂持續停淤、擠壓擴張階段,則可將沖積扇型態分為四類:無法發生溯源淤積、過渡型沖積扇、輕度溯源淤積型沖積扇與重度溯源淤積型沖積扇。本實驗以主槽總輸砂質量對土石流總供砂質量比做為四型沖積扇之分界標準。而在輕、重度溯源淤積型沖積扇方面,則探討主、支槽輸砂率比對溯源淤積時刻延後、沖積扇體積型態因子與沖積扇長度型態因子的影響,且提出主、支槽輸砂與水流條件對沖積扇長寬比影響之模式,發現當主支槽流量比與主槽有效輸砂能力增加時,會明顯地增加沖積扇長寬之比例。
In this study, we use two experimental flumes to simulate the forming process of alluvial fans which were formed by debris flow at the confluence in mountain region. There are three discharge, six slopes for main flume and three debris flow concentrations for tributary flume in experimental flume I. In experimental flume II, there are three discharge for main flume, and three debris flow concentrations for tributary flume. The confluence angles of two experimental flumes are 90 degrees. The process that the sediments flow into the confluence can divide into two parts: first, the sediments diffusion, and second, sediments deposition and pushing expansion. In the process of sediment diffusion, we can differentiate the forms of diffusion by the sediments diffusion Froude number. In the process of sediments deposition and pushing expansion, the form of alluvial fans can divide into four parts: no alluvial fan, transitional alluvial fan, slight retrogressive depositing alluvial fan, and heavy retrogressive depositing alluvial fan. The ratio between mass of sediments that transport in main flume and mass of sediments that supply in the tributary is used to differentiate the form of the alluvial fans. We discuss the delay of retrogressive depositing, the factors of alluvial fan form by volume and by length in our study. We also offer a formula which explains how the flow in main river and tributary to influence the ratio in length and width of the alluvial fan.
URI: http://hdl.handle.net/11455/33461
Appears in Collections:水土保持學系

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