| Summary: | 碩士 === 朝陽科技大學 === 營建工程系碩士班 === 100 === Due to the increasing extreme weather conditions in recent years, the frequency and magnitude of composite disasters are greatly increased. For example, in 2009, when Typhoon Morakot intruded Taiwan, there were severe disasters in both central and southern parts of Taiwan, including incidents as the whole village of Hsiaolin was wiped out, and occurrences of severe debris-flow disasters in Toukeng Creek. This study were completed through debris-flow flume experiments and a two dimensional numerical model FLO-2D. The flume experiments and FLO-2D simulation results were used to analyze the characteristics of debris fans deposited in the mainstream-tributary intersection.
Forty five sets of flume experiments, three intersection angle (30 °, 60 °, 90 °), three tributaries of the slope (13 °, 16 °, 19 °) and five volume concentration (0.45, 0.50, 0.55, 0.60, 0.65), were proceed in this research. According to the debris fans piling up in the mainstream-tributary intersection, four types of debris fans were classified as tributary deposited, part of mainstream deposited, completely mainstream deposited, and barrier-deposited and overflow.
The test results showed that the velocity of debris flow increased with the increase in the slope of tributary, also increased with the decline in the volume concentration. In general, when the angle of mainstream-tributary intersection increases, the debris flow squeeze the main river channel behavior becomes more obvious, the smaller deposition width, the larger deposition thick. In particular, the intersection angle of 90 °, most likely to form a short period of barrier lake, the impact to the upstream and downstream riversides is also the highest. Using the FLO-2D two-dimensional numerical model to simulate the flume experiments by the artificially building flume DEM, simulation results have similar trend with the flume experiment results.
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