本研究以渠槽實驗模擬斜坡上之天然土石壩受滲流破壞而造成溯源崩塌，其破壞土體逐漸飽和，進而轉化為土石流之過程。壩體受滲流破壞轉化成土石流之過程可分為三個階段：1.壩體受滲流水流沖蝕而使得土體發生崩塌。2.崩塌土體會呈暫時性堆積、停止之情形，待水流與崩塌土體充分混合達到飽和狀態。3.崩塌土體流體化而轉化成土石流向下游面流動。坡度、單位寬入流量越大，則崩塌土體流體化之速度越快。 實驗內容包含土石壩之滲流破壞及壩體受滲流破壞轉化為土石流之情形。土石壩滲流破壞之無因次崩塌距離與崩塌時間之關係為l'=at'+b(t')^2，當坡度、單位寬入流量越大，則壩體崩塌速率越快。土體流動實驗中，當坡度、單位寬入流量越大，則土體流體化之速度越快。土體之流動情形呈間歇性之流動，土體表面之流速分佈成栓部形狀。中值粒徑d50=1.48 mm及d50=0.58 mm之流動土體體積濃度約在0.31?0.47及0.25?0.47之間。本實驗結果對於天然土石壩滲流崩塌破壞轉化為土石流之預警及避難有所助益。 The characteristics of debris flow generated by the seepage failure of landslide dams are experimentally studied using an inclined slump with slope verying from 16° to 24° in this study. The failure of landslide dams is triggered by toe failure first, then followed by progressive head-cutting process. The head-cutting process induced by seepage can be divided to three phases. First, the dam slumped by seepage erosion. Second, the unsaturated soil became saturated by the mixing of upstream water flow. Third, the saturated slumped block moved as debris flow. The liquefaction process of the slumped block becomes more quickly when either the slope or the inflow increases. The experimental data of the characteristics of the head-cutting are analyzed by dimensional analysis. The dimensionless equation fits the relationship between the collapsed length and elapsed time well. The parabolic velocity profile be at fluid surface was observed in the experiments. Concentration of debris flow, is 0.25~0.47 for large grains and 0.31~0.47 for small grains.
