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自民國93年艾利颱風過後，石門水庫產生大量淤積導致庫容減少，同時高含砂濃度入流亦影響民生供水能力，水庫泥砂的問題開始被凸顯出來，近年來在政府特別預算的支持下，相關研究成果提出了改善與治理的對策，亦已對石門水庫的活化產生很大的貢獻。但在水庫泥砂課題涵蓋範圍相當廣，且每部分都相當複雜的情況下，不管在學術或實務面上，每一個面向其實都還是存在若干值得進一步深入探討的問題，尤其在本計畫隸屬於科專經費的前提下，更凸顯技術突破的需要性，其中水庫泥砂監測技術研發改良，建立適合臺灣使用之監測調查方法為水庫防淤問題中首先要解決之課題。在台灣有進行泥砂監測之水庫中，以石門水庫之泥砂監測資料比較齊全利於量測成果比對，爰此成立本計畫進行研究與探討，以提供水庫防淤策略研擬與操作參考。為評估水庫最佳防淤策略，水庫的來水來砂特性為重要關鍵，對於洪水監測，各水庫已施作多年，但泥砂監測資料目前僅石門與曾文水庫有較多資料，其他水庫並不完整，且泥砂監測過程中問題頗多，故建立水庫泥砂資料是目前水庫整體防淤策略重要基本工作，依據「水庫泥砂監測技術暨防淤操作策略研究」計畫之水庫入庫泥砂監測技術初步規劃，各水庫泥砂濃度觀測儀器設置之步驟，主要先從入庫邊界渾水明渠流之緩流區及各排放口開始，原因在於水庫管理單位希望能掌握入庫含砂濃度進而得知入庫總砂量，以及得知各排放口或取水工附近高泥砂濃度變化情形，進而調整水庫放水與取水時間。石門水庫羅浮站在右岸斜坡建置分層抽水取樣設施及懸浮質濃度自動化觀測點，雖已提供較有根據的入庫泥砂估計，但受邊壁效應影響使其量測之河道泥砂濃度可能存在相當程度的變異性，如何獲得斷面代表性的含砂濃度，為河道輸砂觀測相當重要但較欠缺的一環。因此本研究擬配合羅浮既有側岸幫浦、TDR含砂濃度與光學濁度設備，嘗試於主深槽建置一觀測樁，以提供主深槽的分層取樣與即時觀測，內部將包含分層抽水幫浦以及TDR含砂濃度等自動化觀測設備；並以觀測樁作為中繼固定點，規劃設計岸壁至觀測樁間的鋼索道（cableway）取樣量測系統，提供斷面泥砂濃度量測作業所需之設備(如附圖1~圖3)，預計此透水觀測樁直徑至少16英吋、厚度8mm，基礎最深點至少要接近原始河床標高接近EL.230公尺，穩定的鋼索要與現有結構結合(如圖4)。透過上述工作，可評估主深槽與河岸、不同量測系統測定結果的變異性，並研擬如何率定側岸或觀測樁量測點結果以獲得斷面代表性濃度，期能提供更精確的水庫上游入庫砂量推估及粒徑組成。

This study featured the construction of an observation pile in the river channel, of which to provide sediment sampling at different depths and real-time monitoring. The observation pile system comprised of motor pumps, TDR Suspended Sediment Concentration (SSC) probes and automated monitoring system components. A SSC sampling and measurement system was designed to be attached on a cableway, routing from the river bank to the mid river channel using the observation pile as a relay point, which provided the platform to measure the SSC profile over various depth in the mid river channel. Through SSC measurement from the observation pile, observation variations between river channel and river bank, and between different monitoring systems could be evaluated. Data calibration according to observation pile and river bank are also investigated to generate a more reliable and representative SSC cross-sectional profile, which would eventually provide a more accurate estimation of upstream inflow sediment load and the corresponding particle size distribution.Design specifications of this observation pile are maximum water level of EL +252m, maximum flow velocity of 5 m/s, partial scouring depth at design of 2.5m and floating log weight of 20 tons. The pile adopted CISS PILES (Cast-in-steel-shell piles) as design, with pile diameter of 0.8m and total length of 26.5m. External pile casing is A36 stainless steel tube of 15mm thick, while the internal of the steel pile is filled with reinforcement steel cage and cement mortar with compressional strength of fc’=280 kgf/cm2. The observation pile is driven into the ground for 14m below in-situ ground surface.Attached facilities of the observation pile mainly included working platform, guardrail ladder, cable adjustment base, SUS steel protection casing for TDR probes, motor pump protection lid, anti-collision device (comprises of 45 scrap tires and fixing cable), submergible motor pump power configurations, liquid interface detection control configurations, 10m pipeline protection cover, submergible motor pump fixing base, steel cable and steel cable base of the observation platform.This study completed sediment transport monitoring during flood events with both manual observation and automated TDR measurement operation in the three typhoon events of Typhoon Chan-hom, Soudelor, and Dujuan. During Typhoon Dujuan, the measured SSC values from manual motor pump sampling between river bank and observation pile were high in concentration variation during flood rising section but were more consistent later in the flood recession section.In this study, existing cableway foundation of the river bank sampling system is integrated with the top and the platform of the observation pile, providing attachment support to the sampling pipelines and signal transmission cables of the observation pile. This cableway also accommodated an equipment delivery system for maintenance staff during high water level, and could facilitate in new sampling facility setup and other flood observation facilities in future.