張力計延遲效應對觀測動態毛細壓力以及排水模擬的影響

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Title:	張力計延遲效應對觀測動態毛細壓力以及排水模擬的影響
Authors:	鄭名良;CHENG, MING-LIANG
Contributors:	水文與海洋科學研究所
Keywords:	動態毛細壓力;張力計延遲
Date:	2017-06-09
Issue Date:	2017-10-27 13:06:58 (UTC+8)
Publisher:	國立中央大學
Abstract:	傳統上保水曲線在靜止狀態下量測。但許多實驗證據發現飽和度與毛細壓力的關係，在改變不同邊界條件下排水速度會有所不同，因排水速度不同改變的保水曲線稱為保水曲線的動態效應。但張力計本身並不能及時反應水壓的快速變化，張力計的延遲不可避免會對量測造成影響，而實驗量測動態毛細壓力卻大多忽略張力計延遲效應。本研究進行一系列室內沙箱實驗量測靜態和動態保水曲線。並且透過實驗量化延遲係數 k。探討影響延遲係數的因素。此外進行沙柱排水實驗量測累積出流量，來了解靜態和動態保水曲線和張力計延遲效應對模擬一維排水的影響。研究結果發現，在修正毛細壓力後靜態和動態保水曲線的差異更為明顯。修正後的保水曲線，VG 參數 n 增加但α卻減少，使得採用修正前與修正後保水曲線模擬的一維排水累積出流量之間差異不大。模擬結果顯示流量1.11cm3/s 的動態保水曲線用於模擬沙柱排水，與實驗結果最為相近。延遲係數的測試實驗結果發現，陶瓷頭經長時間使用會造成其延遲係數會減少，延遲係數與玻璃砂顆粒大小成反比，以及延遲係數隨有效飽和度增加而增加。;Traditionally, the water retention curve is measured at rest. However, the experimental evidence found that the desaturation rate changes the water retention curve known as the dynamic effect of water retention curve. It is difficult to observe the dynamic effect because the tensiometer itself does not respond to the rapid changes in water pressure. The tensiometer delay will inevitably have an impact on the measurement, while the experimental measurement of dynamic capillary pressure mostly ignores the tensiometer delay effect. In this study, a series of indoor sandbox experiments were performed to measure static and dynamic water retention curves, and we also perform the experiments to quantify the delay coefficient k. To explore the factors that affect the delay factor. In addition, the sand column drainage experiment was conducted to measure the cumulative flow rate to understand the effects of static and dynamic water retention curves and tensor delay effects on simulated one-dimensional drainage simulation. The results show that the static and dynamic water retention curves are more pronounced after the modified capillary pressure by considering delay effects. Nevertheless, the VG parameters of the modified water retention curve n increases but the α is reduced, making the difference between the simulated one-dimensional drainage of the cumulative outflows with the original and modified water retention curve is insignificant. The simulation results show that the simulated sand column drainage with the dynamic water retention curve with a flow rate of 1.11 cm3/s is closest to the experimental results. The result of the experiments for delay coefficient shows that the delay coefficient of the ceramic head significantly reduced when the head has been used for a long time, the delay coefficient decreases as the decrease of the glass sand size increases, and the delay coefficient increases with the effective saturation.
Appears in Collections:	[Graduate Institute of Hydrological and Oceanic Sciences] Electronic Thesis & Dissertation

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