| Summary: | 碩士 === 朝陽科技大學 === 營建工程系碩士班 === 96 === For concept of debris-flow hazards mitigation, traditionally, the protective equipment, which is designed based on the rigid retaining concept of concrete structures (such as debris barrier or reinforced concrete gravity dam), costs large sums of money. However, the flexible steel system has been used in Europe and U.S. for many years. In addition to the rock-fall disaster prevention, it also can be used in such disaster as snow-slide or debris flow. It is seldom seen that the flexible steel system is used to block debris flow in Taiwan. Therefore, this research will make a further study on the flexible retaining system is an important issue in debris-flow hazards mitigation construction.
The flexible steel net was installed in the upstream of Shan Pu Keng River, Shanan Village, Shueili Township, Nantou County. After flexible steel net set up, there were some typhoons which caused heavy rainfall leading to debris flows. The flexible steel net blocked the debris flows individually. After that, rocks and sediments filled in the flexible steel net. In this research, the depositions of debris flows and situations of block of flexible steel net, as well as compare with the results of flume tests in Lab to discuss the situations of sediments, grain deposition rate, volume concentration reduction rate, sediments flow rate, change of spring and change of vibration meter, etc.
From observation of field and flume tests in Lab, it can be found that the slope of river bed become smooth and the impact force of debris flows decreased make debris accumulate gradually in upriver after flexible steel net is struck again and again by debris flows. For the volume concentration reduction rate, the results of flume tests in Lab shows that the volume concentration for all cases after passing the net is reduced to below 0.2. Volume concentration, 0.012, in the sediment is better than in the higher the volume concentration, which means that when debris flow is in the lower the volume concentration, the power of flow is great and more debris can pass flexible steel net. The analytic results of spring elongation and vibration meter illustrate that flexible steel net form function of rock gabion after flexible steel net block debris. Due to the retaining structure produced, which can effectively decrease impact force of the next debris flow. Through the results of field observation and flume tests in Lab, they can be known that flexible steel net can effectively decrease the volume concentration of debris flow, the amount of flow of debris flow, the impact force and the destructive force, to reach the destination of debris-flow hazards mitigation.
Key Word: Debris Flow, Debris-Flow Hazards Mitigation, Flexible Steel Net
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