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年度	100	專案性質	實驗性質
專案類別	研究專案	研究主題	調查
申請機構	國立台灣大學	申請系所	地質科學系
專案主持人	賈儀平	職等/職稱	教授
專案中文名稱	利用熱脈衝流速儀量測井孔地下水流之研究
中文關鍵字	地下水；熱脈衝流速儀；水力傳導；井孔
專案英文名稱	Research on borehole groundwater flow measurement using heat-pulse flowmeter
英文關鍵字	Groundwater； heat-pulse flowmeter； hydraulic conductivity；borehole
執行金額
執行期間	2011/11/26 至 2012/11/25
計畫中文摘要	地層的透水性是地下水質監測、污染物傳輸速率與污染範圍評估、地下水污 染整治的重要依據，目前的污染場址調查多採用現地水力試驗來估算含水層的平 均水力傳導係數，然而含水層多為非均質，地下水流通常集中於少數透水性較高 的區段，若能量測地層透水性隨深度變化，咸信將明顯提升地下水污染監測與整 治工作效益。因此本研究嘗試在實驗室研發改進近期發展之熱脈衝流速儀，藉由 設計水流模擬系統，測試與校正量測結果，在現地偵測井孔中的優勢水流，並估 算含水層水力傳導係數隨深度的分布。 本研究分為「實驗室井管水流模擬系統建置」、「熱脈衝流速儀實驗室測試」 及「熱脈衝流速儀現地測試」三個項目。井管模擬水流系統係藉由重力及水位差 來驅動水流，並控制流速，以此分析流速儀量測流速與井管平均流速之關係，探 討量測誤差大小與來源。熱脈衝流速儀實驗室測試結果顯示，無論裝設導流器與 否，量測流速皆大於井管平均流速，兩者呈線性關係，然而其誤差隨著水流流速 降低而增大，其中流速儀置放位置與摩擦損失為最主要誤差來源；此外，在低流 速狀態下，熱的自然對流效應顯著影響量測誤差。裝設導流器可有效增加通過流 速儀的水流流速，然而當流速超過雷諾數門檻，層流狀態轉換為亂流，誤差將大 幅增加。現地試驗證實熱脈衝流速儀可量測井孔中分段水流垂向流速隨深度的變 化，藉由實驗室測試得到之校正公式，可解析地層垂直方向上分層透水性分布， 測試結果發現在高透水性之礫石層仍存在透水性差異。本研究整合分析流速儀在 實驗室和現地測試結果，經由校正分析，將可偵測出井孔中優勢地下水流；若配 合現地水力試驗的分析結果，可定量分析水力傳導係數及地下水流在垂直方向上 的變化，預期可提升我國地下水污染場址水文地質調查與整治的品質與效益。
計畫英文摘要	Hydraulic conductivity of an aquifer plays a very important role in monitoring, site characterization and remediation of groundwater pollution. Hydraulic testing can be used to obtain an equivalent hydraulic conductivity of the whole aquifer. However, an aquifer is often heterogeneous and groundwater flow often concentrates in few highly permeable sections. It is desirable to delineate the preferential flow or the distribution of hydraulic conductivity. Recently developed heat-pulse flowmeter provides a promising technique for continuously characterizing the vertical distribution of hydraulic conductivity in a borehole. The objective of this project is to develop and improve heat-pulse flowmeter measurement techniques for investigating the variation of hydraulic conductivity with depth in an aquifer. A carefully designed water circulation system was established in the laboratory to evaluate the accuracy and precision of flow velocity measured by heat-pulse flowmeter in various conditions. We found a linear relationship between the measured velocity and the averaged velocity for the laminar flow. The measurement error increases as the averaged flow velocity decreases due to free convection. A calibration formula was developed based on the laboratory test data. Field test results at two sites indicated that heat-pulse flowmeter measurement can detect the locations of preferential groundwater flow in gravel aquifers. By integrating the results of hydraulic test, the vertical distribution of hydraulic conductivity in a borehole can be delineated. The result of this research is expected to provide an emerging technology which can significantly improve the quality and efficiency of site investigation and remediation of groundwater pollution.