通過三角壩之表面滲流破壞量測

Abstract

此篇論文主要討論來自上游定水頭壓力所造成的滲流侵蝕破壞，而現實生活中藉由滲流產生的破壞到潰壩的過程通常緩慢。經過挑選出適合的實驗材料後，且利用三角壩之特殊角度及高嶺土、黑砂與水的固定比例，即能建造出小規模的實驗寬壩以模擬出相似於真實情況的潰壩過程並得到足夠破壞演化進行分析。分析過程包括配合各種定量及定性的工具用以了解內部流況及表面破壞，以簡易雨量計及上游水位變化原始資料將會得到流量資料對照當時破壞情形，以雷射掃瞄裝置搭配攝影器材取得連續資料，結合粒子追蹤及模糊概念的應用配合不協調網絡測繪的概念，即可藉由影像處理方法得到DTM。侵蝕現象雖皆大致包括類似坡痕(scarp and crack)、泥流(mud wave)、沖積扇(fan)、趾部(toe)及破壞隆起處(bulging)之地貌變化，但每一組實驗的細部演變皆不盡相同，最終會討論造成潰壩的滲流破壞其相同和相異之處，並加以比較，且歸納出潰壩形成的相關因素。

The failure of a dyke due to groundwater seepage followed by breach incision and widening is examined in this research. To investigate the flow pattern through the dyke and the downstream surface failure, wide triangular dams are studied in laboratory experiments. The materials used are sand and kaolinite. The mixing ratio between the two materials, the water quantity and angle of the dyke constituted are determined on the basis of preliminary experiments. The water flow through the dyke and the state of the downstream dyke face are monitored throughout the failure process. For this purpose, a throughflow hydrograph is measured using a combination of mechanical and imaging methods. Using laser scanning, the surface topography during the failure process is also characterized in detail. Some of the failure patterns appeared in laboratory experiments are similar to what have been discovered and interpreted through field investigation, including main scarp, minor scarp, mud wave, zone of bulging, and alluvial fan. Although the above failure pattern all occurred in each experiment, their development proceeds differently, as reflected by the evolution of the height of failure and width of breach.