Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/13000
標題: 混合礫石非平衡運移與河床演變之研究
Transport of Nonuniform Gravel and Channel-Bed Evolution
作者: 洪大川
Hong, Ta-Chung
關鍵字: Gravel
礫石
Channel-Bed
Evolution
河床
演變
出版社: 土木工程學系
摘要: 大多數人類皆比水而居,河川演變過程關係著當地文明之興衰。研究非均勻混合礫石運移機制,不僅可以增進吾人對於河床沖淤變化與河流泥砂運動理論之瞭解,且對於集水區治理、水土保持等具有更廣泛的應用價值。 本研究針對台灣天然陡坡河川之特性,進行礫石輸移率之渠槽試驗。參考前人之研究,試驗設計採用固定級配與單寬流量,四種起始坡度(S=2 ~ 5 %),含超載減載共計4組試驗。整個試驗係於國立中興大學土木工程研究所渠道輸砂試驗室進行。 根據試驗資料,分析礫石輸移率、礫石粒徑、渠床高程與曼寧n值隨時間之變化,並發現在陡坡超載試驗中,渠床會逐漸細化而產生分層之現象,與Solari等人(2000)之試驗結果相似。 本研究並以數值模擬與試驗資料相互驗證比較,結果顯示就定性而言,數值模式可初步模擬一維之河床淤積與沖刷現象。天然河川之河床演變過程相當複雜,未來仍應針對粒徑分佈變化等項目,作更深入之分析與研究。
Most of mankind lives beside rivers. The rise or decline of civilization is related to the evolution of rivers in that area. An understanding of the nonuniform gravel transport mechanism and the change of river-bed is very helpful to many engineering applications such as watershed management and the soil and water conservations. A series of experiment were conducted to study the sediment transport rate of nonuniform gravel for mountain rivers with steep gradients. With consideration of the existing data, the experimental design adopted a fixed particle size distribution and a constant flow discharge, four levels of slope, which amounted to four experiments for both overloading and underloading conditions. All experiments were carried out in a steep flume in NCHU. Based on the experimental data, the temporal variations of sediment transport rate, sediment size, bed profile and Manning''s n value were analyzed. It was found that the sediment size of surface bed material decreased with time at a fixed location for the overloading experiments with steep slope gradients. The phenomenon was similar to the experimental results of Solar et al. (2000). A one-dimensional numerical model was performed to simulate the evolution of the bed profiles. Both the overloading and underloading conditions can be simulated with the model. However, the mechanism of the variation of bed material size has to be incorporated into the model in the future in order to simulate the more complicated natural river evolutions.
URI: http://hdl.handle.net/11455/13000
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