以二維水理分析探討系列固床工之最佳配置方案

Abstract

為減緩溪床坡度、防止縱橫向沖蝕、控制流心、穩定兩岸坡腳，興建固床工為目前國內外普及的工程方法，當保全範圍較大時、系列固床工更是常見之方法。然而溪流的土砂運移為一個動態的過程，系列固床工造成河段縱向廊道不連續對生態環境與景觀產生破壞，在台灣，許多坡度平緩溪的河道上亦設有固床工；固床工的存在、個數以及間距已成為現今工程與生態界的關注焦點之一。雖然各界對於系列固床工的各項檢討已存有相當的共識，然而目前多數的研究的重點在於固床工型態(如高度與寬度)對於鄰近下游土砂的影響，且因為已實際施作的案例因時間尚短，資料量過少無法建立管理與操作規則。因此，本研究擬藉由縮尺寸模型實驗與二維數值模擬推估土砂運移的趨勢，進而計算合理的系列固床工配置方案，冀望合理設置固床工數量與改善生態環境外，嘗試提出的系列固床工配置方案，經由分析固床工調整下之模擬結果，使上下游水保設施有明確的助益並確保下游保全對象的安全性，且提供更加多元的改變方案以供穴研究參考。

To reduce the slope of the riverbed, prevent erosion in both longitudinal and transverse directions, control the flow, stabilize the slopes on both sides, and prevent the outflow of soil and debris, the groundsill has become a widely adopted engineering method both domestically and internationally. When dealing with larger conservation areas, series of river training works are commonly employed. However, the sediment transport in rivers is a dynamic process, and the implementation of series groundsills can cause discontinuities in the longitudinal corridor of the river, leading to damage to the ecological environment and landscape. The presence of groundsills, the number of works, and their spacing have become a focal point of attention in the fields of engineering and ecology. Although there is considerable consensus on various aspects of series of groundsills, current research primarily focuses on the influence of the configuration of groundsills (such as height and width) on sediment downstream. Additionally, due to the limited duration of implemented cases, there is insufficient data available to establish management and operational rules. Therefore, this project aims to estimate the trends in sediment transport through scaled physical model experiments and two-dimensional numerical simulations. Based on this, reasonable configurations of series of groundsills will be calculated, aiming to achieve proper placement of the number of groundsills and improve the ecological environment. More importantly, the proposed configuration schemes for series of groundsills are intended to ensure clear benefits to upstream and downstream water conservation facilities and ensure the safety of downstream conservation objectives by regulating sediment transport through river training works.