圖書典藏及影音數位平台

南水局為了解白河水庫繞庫防淤渠道完工後之排砂效率與水庫既有之溢洪道、庫區防淤隧道、主出水工等洩水設施，未來營運階段之操作時機，並研擬排砂策略以提高整體排砂效率，作為後續營運參考，爰辦理白河水庫繞庫防淤渠道水工模型試驗。本項模型試驗目的包括繞庫防淤渠道之水理流況、水庫整體防淤功能與排砂效率，研提整體評估水庫防淤策略，除了冀期改善工程計畫順利推動外，亦提供未來排砂設施操作及啟動時機參考。模型試驗進行空庫時期三種閘門操作方式加以比較，方式一為流量45立方公尺/秒以下在繞庫渠道閘門全開條件下進行加砂試驗、方式二為莫拉克颱風後地形進行流量45立方公尺/秒以下在繞庫渠道閘門全關及庫區防淤隧道閘門全開條件下加砂試驗(莫拉克颱風後庫容動床地形泥砂已壓密)、方式三為流量45立方公尺/秒以下在繞庫渠道閘門全關及庫區防淤隧道閘門全開條件下進行加砂試驗(舖設浚渫砂量1,250萬立方公尺庫容動床地形)，如下表所示。比較排砂效率後得知，方式三總排砂效率56.7%最佳，方式一總排砂效率46.4%次佳，方式二總排砂效率45.0%最小，試驗結果顯示，空庫時期因方式三庫容動床地形有擾動，所以排砂效率最佳，反之因方式二庫容動床地形泥砂已壓密，所以排砂效率最差。

The main purpose of this project is to understand the sediment sluicing efficiency of new bypass channel on Baihe Reservoir by physical model experiments. An undistorted reservoir model with a 1:50 scale ratio between the model and the prototype was built to conduct the experiments. The physical model of the reservoir was built with a fixed bed for the upstream reach and a movable bed for the downstream reach. It was tested with both clear-water and sediment flows under the unsteady flow conditions. The main experimental results are summarized as follows：1. This new bypass channel uses a PMF frequency flood (discharge is 1,026 m3/s) as the input flow and the maximum inflow discharge into the channel is 200 m3/s(design discharge). When floods occur, sediment bypasses from this channel to the downstream river and into the reservoir. The experiments of sediment bypass channel are executing and the results will provide for engineering design.2. Typhoon Morakot was simulated under the condition with new bypass channel and old flush tunnel gate opened. The maximum discharge of inflow is 270 cms and the maximum concentration of inflow is 116,502 ppm. The sediment sluicing rate of the new bypass channel is about 68.7% and the sediment sluiced rate of the old flush tunnel is 3.4%. The total sediment slucing efficiency of the new bypass channel and old flush tunnel is about 72.1%.3. Empty flushing of reservoir sediment was simulated under two conditions：(1) new bypass channel gate are opened (case1) , and (2) old flush tunnel gate and opened (case2). The discharges of the inflow are less than 45 cms(i.e. 45,19,9,4,2 cms) in 30 days. The maximum discharge of inflow is 45 cms and the maximum concentration of inflow is 23,028 ppm. The total sediment slucing efficiency of the new bypass channel is about 46.4% (case1). The total sediment slucing efficiency of the old flush tunnel is about 56.7% (case2).