現地礫石型土石流潛勢溪流上游之崩塌面，常見坡度甚陡之風化裸露層，其破壞型態可分為快速之塊體崩落與漸變之坡面破壞兩種型態。而在921地震及512汶川地震中，均可在現場岸例中，觀察到地震力作用下崩塌坡角會隨地震強度而降低。本研究為期二年，分別探討堆積土體坡面受重力及地震力崩落機制及過程；第一年主要研析不同粒徑之均勻球型顆粒之坡面破壞實驗，配合流動粒子影像法分析堆積顆粒之斜坡崩落特性，瞭解非穩態運動下之定量與定性關係。今年度(第一年度)計畫內容擬以理論及實驗方式兩方面進行無孔隙水之乾顆粒流崩落研究，所得定量關係並與現地案例進行驗證。本研究乃藉由不同粒徑之顆粒材料、邊坡傾角與渠道寬度，以室內渠槽實驗模擬現地邊坡之破壞行為，同時配合前人之相關理論基礎，針對坡面型態、崩塌角變化、速度剖面分佈、動量守衡關係進行研析，以求進一步瞭解崩落機制及其相關運動之動態參數特性。第二年擬探討顆粒體於震動台上受水平震動之崩落效應，同時對不同頻率與震幅條件下之顆粒流動機制及坡面減坡過程進行研析，並與921地震及512汶川地震之現場岸例比對。經由本研究成果，可由事後崩落現場或崩落過程，了解崩塌規模與作用力之關係，對於防救災措施改進及危險區域劃定有相當助益。The processes of rock avalanching and slope sliding are significantly related to the physical properties of granular material. The collapse process of granular slopes driven by gravity and seismic forcings will be explored in this study in the time span of two years. In first year, the relaxation of dry dense granular avalanching pattern will be experimentally investigated by employing a transparent plexiglass chute with flow imaging analysis methods. On the other hand, the quantification and qualitative analysis of unsteady flows are also confirmed. The mechanisms of the granular collapse with combining different frequencies and amplitudes under the horizontal vibration will be explored in the second year. The failure phase of stony debris flow usually appears a steep slope and exposed regolith. The failure pattern could be divided into two processes, including the faster avalanching and a transition with slope reducing. The whole process depicts a short time, unsteady, and non-uniform flow. There are many opening questions have not been addressed and quantified. The aim of the current study is to present results of experimental investigations of collapses for granular slope. In the second year, the relaxation process of slopes under horizontal seismic forcings will be examined by employing shaking table with particle image analysis. The proposed theoretical model was established to explore flow dynamics for suddenly released media and under seimic forcings. Furthermore, the study could contribute to an advanced understanding of real geophysical phenomena and will be beneficial for slopeland hazard mitigation and hazard map zoning. 研究期間 : 9808 ~ 9907
