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標題: | 透過式調整型防砂壩經營管理及土砂密實度之縮尺試驗研究 Sustainable Management Investigation for Through-Type Adjustable Check Dam Considering Soil Compactness: a Small-Scale Experimental Approach |
作者: | 夏佳宏 Chia-Hung Hsia |
指導教授: | 廖國偉 Kuo-Wei Liao |
關鍵字: | HEC-RAS,經營管理與操作矩陣,縮尺模型,土砂密實度, HEC-RAS,Management and operation matrix,Reduced-scale model,Soil compactness, |
出版年 : | 2023 |
學位: | 碩士 |
摘要: | 為更深入瞭解透過式調整型防砂壩在影響範圍內土砂運移情況和對保全對象的影響,本研究使用縮尺模型進行實驗模擬土砂運移趨勢,並與HEC-RAS數值模擬進行驗證,以確保這兩種研究方法的準確性。首先,通過第一組試驗與數值模擬的驗證,確保了縮尺模型的準確性。其次,由於目前對於縮尺模型土砂密實度的相關研究文獻較少,本研究的第二組試驗將有助於補足相關的研究內容,使用不同土砂乾單位重代表不同土砂密實度,希望能夠找到其與透過式調整型防砂壩影響範圍內土砂沖淤變化之間的關係。透過這些研究,可以確保防砂壩的有效運作,同時最大限度地減少對保全對象的不良影響。
探討本研究廍仔溪HEC-RAS數值模擬結果,當遇到大坑雨量站25年重現期的一日暴雨量572mm以及保全對象5K+065第二固床工下游沖刷坑臨界最大沖刷或淤積深度達1m作為面臨特定事件或土砂狀況時,必須考慮調降或調升調整型防砂壩的措施。當操作者在遇到特定情況時,可參考經營管理與操作矩陣,根據「防砂壩上游影響範圍內的淤砂坡度」和「下游保全對象的沖刷深度」這兩個因素,在對應矩陣中找到相應的數值,以確定所需的預鑄塊調降支數。 根據室內渠槽試驗結果,保全對象5K+065第二固床工下游沖刷坑淤積量為42.26平方公尺,平均淤積深度為1.75公尺,然而數值模擬顯示淤積量為51.57平方公尺,平均淤積深度為2.07公尺,兩者的平均淤積深度之間存在著15.46%的差異,兩者間存在的差異,主要是由於HEC-RAS數值模型和室內渠槽試驗在上游可沖刷土砂深度的不同所致。這種差異可以被視為數值模擬和實驗模型之間可接受的誤差範圍。此外,本研究也證明了HEC-RAS數值模型以及經營管理與操作矩陣的準確性和可靠性。 土砂密實度對透過式調整型防砂壩影響試驗結果顯示,夯實上游土砂確實會使土砂的運移變得更加困難,夯實後的土砂具有較大的乾單位重和密實度,因此在水流作用下更難被沖刷或運移。相較之下,未夯實的上游土砂具有較小的乾單位重和密實度,更容易受到水流的影響。除此之外,夯實上游土砂對補充下游5K+065第二固床工沖刷坑土砂是不利的。夯實上游土砂使得對保全對象的土砂補充變得困難。因此,在數值模擬和縮尺試驗中,建議都需要考慮乾單位重此一重要的物理性質。 In order to better understand the migration of soil and sand movement in the through-type adjustable check dams and its impact on the the downstream protection objects. This study used reduced-scale model to simulate the trend of soil and sand migration and verified it with the HEC-RAS numerical simulation to ensure the accuracy of these two methods. Firstly, through the first set of tests and numerical simulations, this study can ensure the accuracy of the reduced-scale model. Secondly, since there is less literature about the sand compactness of the reduced-scale model. The second set of tests in this study will help to complement this research by using different dry unit weight to represent different sand compactness in the hope of finding the relationship between the through-type adjustable check dams. Through this study, the effective operation of through-type adjustable check dams can be ensured while minimizing the negative effects on the protection targets. The HEC-RAS numerical simulation results of Buzi stream shows that when meet the 25-year retrun period of the maximum daily rainfall of 572mm at Dakeng rainfall station and the critical maximum scour or silt depth of the 5K+065 scouring pit reached 1m. It is necessary to consider lowering or raising the adjusting blocks of the through-type adjustable check dams. When the operator encounters a specific situation, the operator can refer to the management and operation matrix and find the corresponding values based on the two factors " upstream sand deposition slope " and " the sand erosion depth of downstream protection target facility " to determine the number of adjusting blocks that need to be reduced. According to the results of reduced scale model experiment, the siltation volume of the 5K+065 scouring pit is 42.26 square meter and the average siltation depth is 1.75 meter, but the numerical simulation shows that the siltation volume is 51.57 square meter and the average siltation depth is 2.07 meter. There is a difference of 15.46% between the average siltation depth of these two research methods. The difference is mainly due to the difference in the scouring depth of sand in the upstream of HEC-RAS numerical simulation and reduced scale model experiment. This difference can be considered as an acceptable error between the numerical simulation and reduced scale model experiment. In addition, this study also proof the accuracy and reliability of the HEC-RAS numerical simulation and the management and operation matrix. The results of the soil compactness test on the effect of the through-type adjustable check dams showed that compacting the upstream soil does make the migration of soil more difficult. The compacted soil has a higher dry unit weight and compactness, so it’s more difficult to be scoured or transported by water. In contrast, the uncompacted upstream soil has smaller dry unit weight and compactness, thus more vulnerable to the effects of water. In addition, compacting the upstream soil has negative effect to the siltation of the 5K+065 scouring pit. Compacting the upstream soil makes it difficult to replenish the soil of the protection target. Therefore, it is suggested that this important physical property of dry unit weight needs to be considered in both numerical simulation and reduced-scale model. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/91266 |
DOI: | 10.6342/NTU202303423 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 生物環境系統工程學系 |
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