使用自然電位觀測輔助一維非飽和層滲流參數推估;Estimations of unsaturated hydraulic parameters in 1D soil column by using self-potential observations

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Title:	使用自然電位觀測輔助一維非飽和層滲流參數推估;Estimations of unsaturated hydraulic parameters in 1D soil column by using self-potential observations
Authors:	陳鎮傑;Chen,Chen-Chieh
Contributors:	應用地質研究所
Keywords:	自然電位法;飽和度;TDR;砂柱試驗;HYDRUS – 1D模式;Self-Potential technique;saturation;TDR;sand column test;HYDRUS – 1D model
Date:	2016-08-29
Issue Date:	2016-10-13 14:56:32 (UTC+8)
Publisher:	國立中央大學
Abstract:	含水層的非飽和層物理特性與特徵參數是決定地表下的氣體、水和溶質傳輸非常重要的因子，藉由各種試驗、儀器與地球物理方法來探討就顯得非常重要。本研究之目的為利用自然電位法配合實驗室砂柱實驗，找出電場、真實含水量兩者間對應的關係，並嘗試推估壓流電位(Streaming potential)，將訊號即時反應當地含水量，以求能了解地下含水層的水文地質參數。本研究先利用一維砂柱進行二組砂樣（＃30、＃60）的入滲試驗，並利用TDR（Time Domain Reflectometry）量測入滲時砂樣真實含水量資料，結合測量砂柱內的自然電位法訊號，輔助觀測找出非飽和層土壤含水量等滲流參數之間的關係。本研究另外藉由土壤特徵曲線試驗以及落水頭試驗，代入RETC(Retention Curve)模式反推估出砂樣的土壤特徵參數，並與砂柱實驗結果反推估的參數做討論。試驗結果顯示(1)砂柱中的濕鋒移動過程可即時反應於自然電位訊號，會因為砂樣的粒徑粗細、飽和狀態與TDR同時施測與否造成電位差異。(2)自然電位訊號與含水量的關係在#30與#60砂樣中皆呈現與驗證組不同的結果。(3)依據土壤特徵曲線與砂柱試驗中含水量資料反推估的參數，在#30砂樣：殘餘含水量(θr)顯示相差一個order，空氣入滲係數(α)顯示相差0.072，材料孔隙係數(n)相差兩倍；在#60砂樣：θr顯示相差0.017左右，α顯示相差0.057，n顯示相差0.31左右。結果反應差異頗大，來自砂樣建模與量測方法不同所造成。(4)將自然電位訊號利用VG公式反推估含水量變化在#30砂中有較好的的結果。;The hydraulic properties in unsaturated soils control the movement of gas, water and solute in shallow aquifer systems. It is crucial to obtain such hydraulic parameters for accurate predictions of flow and contaminant transport in unsaturated soils. This study aims to obtain the relationship of streaming potential and water content dring an infiltration process and uses the self-potential observations to assess the estimations of unsaturated hydraulic parameters for soils. A one-dimensional sand column with #30 & #60 sand was used to conduct constant head infiltration tests. The variation of water content in the column was measured by TDR (Time Domain Reflectometry) during the infiltration test. The observations of the infiltration test in a vertical sand column are then used in HYDRUS-1D model to obtain parameters of the Van Genuchten formula. The results show that the migration of the wetting front in the sand column can be detected in real-time by the self-potential observations. However, the measured signals might be influenced by the grain sizes、TDR signals and saturation conditions. The results of self-potential observations and water content are different in #30 and #60 sand cases. The results of estimated water content in #30 sand case show better estimation of Van Genuchten formula as compared with the results of pressure plate estimations.
Appears in Collections:	[Graduate Institute of Applied Geology] Electronic Thesis & Dissertation

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