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A Study of Sea Bed Change of Different Submerged Dike on Sloping Bottom
|Authors: ||Ming-Hua Wu|
|Contributors: ||NTOU:Department of Harbor and River Engineering|
Sloping beach;Shore protection;Submerged dike;Hydraulic model test
|Issue Date: ||2011-06-30T07:37:16Z
|Abstract: ||經回顧定床試驗並整理得知，於距灘線30~50cm處，增設第二道潛堤，其在波浪溯上、水位抬升、景觀及經濟效益等多方面考量下有不錯之成效。因此本文分別在兩種不同粒徑的鈄坡海床上建置一道或兩道離岸潛堤，並配合後方兩種不同的鈄坡海堤(礫石或階梯)進行規則波水工斷面模型試驗，並針對不同潛堤配置進行碎波位置、相對溯上、水位抬升、平衡海灘斷面下海床之侵淤與潛堤之穩定性之觀測與分析。 由試驗結果得知不論海床底質及改善配置為何，設置潛堤確實能強制將波浪於外海碎波，進而減緩海岸侵蝕而有穩定海灘的作用。但當第一道潛堤設置距灘線距離約為1/2波長時，趨勢則較不明顯。另得知在長時間波浪作用下海床底質為粗砂時，消波塊孔隙間因海床底質堆積，造成消波塊間的牽制力消失、潛堤孔隙率降低，最後形成消波塊個別遭受波浪作用而逐漸往外海滾落及移動，潛堤遭受海床底質的覆蓋而形成類似沙堆(Sand bar)地形。 另本論文所提改善方案方面，在平衡海灘斷面試驗下顯示，增設第二道潛堤，對海岸侵蝕均有顯著減緩之趨勢。而第二道潛堤採C1配置(開口錯開)，在穩定海床減緩侵蝕，較B1配置(開口共線)有較佳之成效。|
Abstract A series of hydraulic model tests of regular waves acting on movable sandy sloping beaches equip with detached submerged dikes and incline sea dikes were carried out to investigate their influences on the locations of wave breaking, the height of run-up, the rise of mean water level, the beach erosion, and the stabilization of submerged dike. Two types of sandy beaches, two sets of submerged dikes, and two kinds of incline sea dikes were used selectively in setting up the different layouts. The results show that the deployment of submerged dikes can cause the earlier breaking of incident waves, reduce the beach erosions and stabilize the sandy beach, and two sets of submerged dikes is better than one set. Such benefit is not dominant, however, when the distance between the shoreline and the location of dike is around one-half of wave length. Under the long term wave actions, the coarse sandy seabed can accumulate sands between the armor units, forms a sand bar and decline the anchorage force between the units, and that cause the armor units individually moved by the wave forces. In the evaluations of different shore protection layouts, the increase of second set of submerged dikes can largely reduce the coastal erosion, and arranging the opening of two sets of dikes in stagger way is better than in collinear way.
|Appears in Collections:||[河海工程學系] 博碩士論文|
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