應用地電阻量測方法於環境監測與實驗室入滲試驗技術之研究

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Title:	應用地電阻量測方法於環境監測與實驗室入滲試驗技術之研究 A Study of Using Geoelectric Resistivity Method in Environmental Monitoring and Infiltration Lab Test
Authors:	陳力齊 Li-Chi Chen
Contributors:	張竝瑜嘉南藥理科技大學：環境工程與科學系碩士班
Keywords:	地電阻法電阻率泥火山擬合含水率 water content fit mud volcanoe Resistivity
Date:	2007
Issue Date:	2008-12-03 11:15:35 (UTC+8)
Abstract:	本研究主要是探討地電阻法技術之精準度與解析度，研究分為(1)野外實測部分，以及(2)砂箱入滲中尺度試驗，與(3)小尺度之實驗室土壤飽和度-電阻率試驗，並運用此三個不同之試驗結果比較分析，相互驗證並校正此方法的誤差。野外實測的地點在高雄縣燕巢地區燕巢烏山頂泥火山，監測時間自2006年7月至2007年5月，平均電阻率範圍介於3.36 ~ 9.43 Ω‧m，結果發現在地表3公尺以上電阻率變化最大，可能造成此因素的原因有很多，在地表易受到多種天氣因素和地表乾濕所影響。其中在監測期間2006年12月26日晚，屏東縣恆春鎮外海發生三起芮氏規模6.7、6.4、5.2強震，在地震後，靠近泥火山附近，近地表3公尺處電阻率有明顯上升2~5Ω•m，可能的解釋為在地震後較多量氣體因地震沿斷層裂隙帶釋放，因此導致此區電阻率增高。中尺度的砂箱入滲試驗是模擬台灣地區一次性大雨一小時後，電阻率的變化，發現灑水區電阻率較降雨前下降約200~575Ω‧m，並隨時間增加，電阻率升高。造成此原因主要為蒸發散、水分滲透，表面蒸發使得淺處土壤含水量減少，造成電阻率升高；而過多水分可因重力逐漸滲透至底部，造成0.5公尺以上的土壤含水率降低，電阻率升高。小尺度的實驗室土壤飽和度-電阻率試驗，根據Archie’s law經驗式擬合出電阻率與體積含水率的關係式，結果分別為泥火山：y = 285.47 x -1.0707；砂箱槽體：y = 2473.6 x -1.0182。並利用上式推估現地與砂箱的含水率，其範圍分別為泥火山：24.2% ~ 63.59 %；槽體土壤：3.16 ~ 10.67 %。為驗證推估的含水率是否合理，因此在槽體實驗中，實際量測各位置不同深度之體積含水率。結果實測值與推估值有所差異，並將這些數據作深度分析，發現各深度的關係式皆不相同，若僅用一個關係式代表計算，將產生較大之誤差。 This study concerns about the accuracy and precision of the Geoelectric Resistivity Method in monitoring subsurface changes in a time-lapse sense. The study includes (1) in-field long-term monitoring of, mud volcano activities, (2) an infiltration experiment in a large sand box, (3) an experiment of saturation-resistivity relationships for mud and sand samples in the laboratory. Using the results of the three separate experiments, we tried to examine the accuracy and precision of this method. Our in-field monitoring site is located at the Wushangting mud volcanoes, which are on the Chishan Fault line, in Yanchao, Southwestern Taiwan. The measuring period is from July 2006 to May 2007. The average resistivity is between 3.36 ~ 9.43 Ω‧m. During the monitoring period, the major changes of reisitivity are between the surface and a depth of 3-m. On December, 26th, 2006, three earthquakes occurred measuring as high as 6.7, 6.4, 5.2 at the Richter scale outside the sea of PingTun county. And the epicenter is about 100 km southwest from the monitoring site. After the earthquakes, the resistivity is found to be raised up 2~5 Ω‧m between the surface and a depth of 3-m. There are a lot of reasons that may cause the changes of resistivity, for example, the temperature, the humidity, the earthquake activities and its subsequent influence, i.e., gas or fluid emission from the subsurface. After examine the weather records during the monitoring period, we suggest that the most possible reason causing the decrease of resitivity in the monitoring site is the subsequent influence of the earthquake activities. We simulated a heavy rain event in the sand box experiment and monitored the variation of resistivity one hour after the rain teminated. The resisitivity in the sand box decreases about 200 ~ 575 Ω‧m in comparison with that before the rain initiated. In addition, the resistivity in the sand box had increased gradually with time since the rain stopped because the surface evaporation and water migration. Soil samples for the lab saturation-resistivity experiment were collected near the monitoring site and in the sand box. From the lab results of saturation-resistivity relationships, we tried to estimate the water content in the field and in the box. The water content for the monitoing area is between 24.2% and 63.59 %, and for the sand box between 3.16% and 10.67 %. We took samples and measured the water content in different positions and depths in the sand box in order to verify the accuracy of the estimated water content. The results show that the estimated water content is different from the estimate value if a universal relationship is applied to the estimation calculation. Furthermore, if we establish separated relationships for different depths, the estimated water content can be more represented to the true water content. Therefore, caution should be made when we apply a single, lab-established relationship of saturation-resistivity to estimate the water content in the filed resistivity measurements.
Relation:	校內外完全公開
Appears in Collections:	[Dept. of Environmental Engineering and Science (including master's program)] Dissertations and Theses

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