本研究以渠槽實驗模擬非凝聚性土石壩因壩體強度不足而導致滲流及溢流破壞，造成土體受淘刷及沖蝕作用而使壩體發生潰流之過程。實驗之壩體由非凝聚性之均勻顆粒之越南矽砂所構成，因此壩體的滲透性高，其破壞形式可分為兩種：1.土石壩於小流量下，壩體內部受到滲流作用而產生溯源淘刷之漸進式破壞，滑動崩壞面朝上游發展後引發土體潰流。2.土石壩於大流量下，上游壩頂發生溢流破壞而造成土體潰流之過程。 實驗內容分為兩部份：第一部分為壩體在穩定及非穩定之條件下，因滲流作用而造成壩體崩壞，由實驗資料可得到壩體滲流破壞之無因次崩壞長度與崩壞時間之關係為 ，當坡度及單位寬入流量愈大，壩體崩壞速率愈快。第二部份為壩體發生溢流破壞時，在不同壩長之條件下分析壩體潰流之歷程。本實驗結果對於非凝聚性土石壩因滲流及溢流破壞引發壩體潰壩危險之預警與疏散避難有所助益。 The processes of non-cohesive landslide dams breached by seepage and overtopping failure are experimentally examined in this study. The landslide dams are on a flume with a bed slope varying from 8° to 24°. The processes of dam breaches have two different forms: one is at small discharges and the seepage surface arises until seepage line reaching the downstream end of dam, then followed by progressive head-cutting process until dam collapsing. The second is at larger discharges when the dam overtopping occurs on the upstream side and the dam collapses quickly. The experimental data for both stable and unstable cases of head-cutting processes are analyzed by the dimensionless equation to fit the relationship between the collapsed length and elapsed time. When the overtopping breach occurs from the upstream of the dam, the failure processes are faster for the cases either at higher slopes or with shorter dam widths. The experimental results of this study is useful for prevention and evacuating the landslide-dam breach induced by the seepage and overtopping.
