圖書典藏及影音數位平台

石門水庫原興建時並無設置底層排砂專用通道，颱洪時期入庫泥砂僅能經由溢洪道、排洪隧道及永久河道放水孔等既有非排砂專用設施排除，水力排砂能力有限，北區水資源局於民國101年完成水庫壩前發電鋼管改為排砂專用隧道後，實際操作整體排砂比已可達34%~37%。然經檢討石門水庫入、出庫砂量，現況排砂能力尚無法達到入、出庫砂量平衡之目標。基於水庫永續利用及操作安全等考量，水利署水利規劃試驗所（以下稱水規所）及北水局於99~103年辦理「石門水庫大灣坪防淤隧道工程可行性規劃」與「石門水庫阿姆坪防淤隧道工程可行性規劃」，以提升水庫防洪與防淤功能。藉由防淤、清淤隧道，搭配既有設施更新改善工程，導引排放颱洪期間入庫渾水至水庫下游，俾達到水庫「清渾分治」目標。 由於過去規劃設計以水工模型試驗為主，數值模擬方面則多以一維或二維數值模式為輔；近年來因高速計算技術應用隨電腦運算效能提昇而逐漸普遍，且石門水庫增設防淤隧道甚多複雜流場，如自由液面流與壓力流之互相轉換、象鼻軟管虹吸現象、潛沒式孔口流、水躍交波等流場特性，若單採用一維或二維數值模式，計算上易造成較大誤差。因此在水理計算方面，本計畫導入三維數值模擬，輔助工程設計；另外在阿姆坪沖淤池動床模擬，則因凝聚性土壤沖淤機制複雜，故仍選用二維動床模式。

The Shimen Reservoir is lack of desilting construction using the hydraulic force. Since the maximum heavy rainfall results from the climate change due to global warming with high likelihood, there is problem with the capacity of desilting and discharging flood through the present facilities. To enhance the desilting and drainage ability in the Shimen Reservoir, two projects, i.e. Feasibility Study of Dawanping Desilting Tunnel Project in Shimen Reservoir and Feasibility Study of Amuping Desilting Tunnel Project in Shimen Reservoir, were carried out in 2011 by the Northern Region Water Resources Office WRA (Water Resources Agency). These two projects primarily enhance the capability of flood prevention and desilting during typhoon events in order to achieve the goal of separating the clear water and turbidity water. Thus, the project of new sediment bypass tunnels for Shimen Reservoir was proposed and it is expected to achieve the annual average desilting amount of 1,350,000m3. In the annual average amount, 710,000m3 is expected to be delivered through the Dawanping tunnel and the remaining amount of 640,000 m3 was done by the Amuping tunnel. In the past, the hydraulic design and plan are implemented based on the experiment and the numerical simulation, performed by 1D or 2D numerical models, is merely used for assistance. In this project, there are many complex flow fields in this project, such as transformation between free surface flow and pressure flow, siphoned flow in the elephant nose, submerged orifice flow and hydraulic jump with cross wave. Accordingly, 1D and 2D numerical models is difficulty used in the simulation of the aforementioned flow field. Recently, because of advanced development of high-performance computing technology in association with high computing power, the numerical simulation is widely applied in the hydraulic analysis and design. Therefore, a 3D numerical simulation model should be more appropriate for the complex flow field of interest. Although the 3D numerical model can improve the quality and efficiency of hydraulic design, there are no suitable 3D sediment transport models nowadays. Therefore, the 2D numerical simulation model is also required to simulate the desilting in the Dawanping basin.