台灣因獨特地形與氣候而致土石流現象發生頻繁，滑坡災害成為新興但急迫的研究議題。本研究主要探討水面下滑坡之動態行為；研究藉探討不同條件（渠道坡度、玻璃珠試體重量、玻璃珠試體含水量），觀察玻璃珠顆粒試體迅速進入水中所產生動態行為（玻璃珠顆粒流形貌、對波浪之高度與速度的影響）；此外，也與大多數實驗採用之滑體做比較。研究數據之分析採用質點影像測速法(particle image velocimetry [PIV])。
本研究獲得下列三項主要實驗結果：
1. 玻璃珠顆粒滑入水中後，顆粒流前緣持續前行而與表層玻璃珠顆粒分離，可形成水面下玻璃珠顆粒流三種形貌變化，包括前端部分、拉伸部分、崩落/停滯部分。
2. 玻璃珠顆粒試體的顆粒速度越晚減緩，對波浪的影響越久。從波浪之高度與速度推測，水面下玻璃珠顆粒流對波浪有兩階段影響：由抽出閘板後0.20 秒~ 0.40 秒，係直接影響波浪；由抽出閘板後0.40 秒~ 0.55 秒，則為間接影響波浪。
3. 滑體直接滑入水中才出現減速狀況，而玻璃珠顆粒試體甫入水中（在渠道底面與水面線交會處）即出現受阻擋樣貌。
本研究結論，在初期水面下玻璃珠顆粒流的形貌變化會影響波浪的速度與高度；不宜以滑體作為前期條件來模擬水面下滑坡動態行為。
根據本研究發現，研究者提出下列二項後續研究方向，俾利於形成滑動成因假設與預防對策：(1)以現地條件進行實驗，觀察水面下顆粒流對波浪影響程度；(2)觀察試體滑動條件如何影響水面下顆粒流堆積形貌。

Land-sliding is an urgent and inevitable urgent research topic in Taiwan where landslide-disaster occurs frequently due to her unique topography and climate. The study aims to investigate the dynamic behaviors of the subaqueous mass movement. With different channel slopes and concentrations of the water-glassbead mixture, the dynamic behaviors of the rapid moving mass were observed, where the specimens were suddenly released and sliding into the water. In this study, the motion of glass-bead specimens is also compared to the ones of sliding-body specimens. The particle image velocimetry (PIV) was adopted for analyzing the velocity fields.
There are three main issues in the study:
1. While the glass-bead granular flow slides into the water, the flow behavior can be approximately divided into three sections: the front section, the stretch section, collapsing/stagnation section.
2. The deceleration of the glass-bead specimen is related to the induced wave at the water surface. Two stages, direct and indirect impacts, are found for the impact of the subaqueous granular flows: from 0.20 s to 0.40 s after the gate opening is the direct impact period; and from 0.40 s to 0.55 s is the period of the indirect impact.
3. The difference between the behaviors of the sliding rigid-body and granular flows is significant.
The study comes to two conclusions: (a) The height and velocity of the water waves are influenced by the morphology of the subaqueous granular flow. (b) For simulating the dynamic behavior of subaqueous landslide, it is not appropriate to apply the sliding rigid-body as the pre-condition.
Two suggestions are proposed for further research: (a) the effects of the subaqueous granular flow on waves under the conditions according to the field observation/measurement; (b) the influence of the sliding conditions of the specimen on the morphology of the deposit.

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