全球氣候變遷影響下，極端的氣候事件增加，高強度降雨所造成之災情變的更加嚴重且頻繁，土石流與洪流事件也隨之增加。台灣山麓沖積扇經常成為各村莊、部落的聚集地。若產生土石流災害，對人民生命安全及財產的損失將造成嚴重的威脅。本實驗利用小尺度的三維渠槽，搭配雷射光與相機進行研究，並於流量率定時探討桶倉(silo)內粒流動之情形，再藉由改變水砂比(n)以及積水深度對沖積扇(alluvial fans)型態之縱剖面、橫剖面、扇緣堆積形態以及頂積層(topset)與前積層(foreset)角度進行分析及探討。

本實驗主要控制參數為顆粒粒徑、水砂比(n)、積水深度，其水砂比為水流量(Qw)與顆粒出流量(Qs)之比值(Qw/Qs)。研究結果顯示桶倉開口大小與顆粒粒徑是主要影響流量的因子，流動情況與流出開口之順序與顆粒是否在不動區內有極大之關係。縱剖面堆積高度與積水高度和顆粒粒徑有關，且積水深淺時，縱剖面呈現一凹向上之曲線形態。橫剖面型態則為一凸向上之剖面，並隨著縱方向越來越大而更加明顯，並於積水深度較深時，幾乎趨於凸向上之剖面甚至呈直線，而形態也越趨於一致。沖積扇堆積範圍與水砂比大小有關，但積水深越深，因受水體阻擋而使得堆積形態趨於相似。頂積層角度於水砂比越大或積水深越深而變小；前積層角度則於積水深變深時略增。

Under the impact of global climate change, the slope-land disasters such as landslides and flash floods caused by highly intensive rainfalls occur more frequently. Alluvial fans at foothills in Taiwan often accommodate villages and infrastructures, and are high-risk areas for the landslides and debris flows. In this study, the formation for alluvial fans is explored by using experimental study. A small-scale flume-basin model was setup with silo, laser lights and camera to investigate the fan forming processes. By changing the sediment concentration (i.e., the ratio of sediment discharge(Qs)to water discharge (QW)) and the base-level water depths, the longitudinal profiles, cross profiles, fan shapes, angles of topset and foreset angle have been analyzed. The size of the silo opening and particle size control the particle discharge. The longitudinal profiles of the fans depict a concave shape, while the lateral profiles are convex. The angles of topset slope decrease with decreasing sediment concentration, while the foreset slopes with tail water are close to the friction angle of the sediment.

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