https://scholars.lib.ntu.edu.tw/handle/123456789/86174
標題: | 土石流監測與預警系統之研究─子計畫:雨量與地下水電導度(EC)監測方法之研究(Ⅱ) | 作者: | 范正成 | 關鍵字: | 土石流;臨界降雨線;地表最大加速度;地文因子;水文因子;費雪區別函數;多變量常態分佈法;地下水;電導度;滲流;水質試驗;debris flows;critical rainfall line;peak ground acceleration (PGA);physiographic factor;hydrological factor;Fisher’s discriminant function;multivariate normal distribution;groundwater;electrical conductivity;seepage;water quality tests | 公開日期: | 2003 | 出版社: | 臺北市:國立臺灣大學生物環境系統工程學系暨研究所 | 摘要: | 本報告分為兩大部分:第一部份以彙集歷年雨量資料與土石流發 生之時間,將發生及未發生土石流的雨場事件予以數化,求出這兩個 群組的基本統計量。再由兩群組間重疊的部分,利用多變量常態分佈 法求取機率式臨界降雨線;第二部分則探討EC 值對管湧式土石流發 生的影響。 本研究之第一部份以南投縣為主要研究區域,選定二十八個集水 區為樣本,並經過Mann–Whitney–Wilcoxon 檢定之後發現下列四種 因子—崩坍地面積、土地利用因子、土壤粒徑大於四號篩百分比與有 效集水區面積對土石流之影響較大。並引用多變量分析中之費雪區別 函數求出南投地區土石流預警的建議公式。921 集集大地震後,土石 流危險溪流的勢能增加,故以地表最大加速度PGA,配合隨時間遞減 之影響函數,求取各集水區地震後修正臨界降雨線之通式。利用多變 量常態分佈法建立各樣本溪流之機率式土石流臨界降雨線。 本研究第二部分主要目的是在探討地下水電導度與土石流發生 之關係。土石流發生區堆積土層或溪谷兩岸之邊坡長期受到滲流沖蝕 的影響,會因細粒料不斷的流失,使得土體本身之結構趨於不穩定, 最後導致土體全面性崩潰。因此,本研究進行現地因次分析,並設計 滲流槽試驗以進行研究。本研究以南投縣豐丘為主要區域,選擇豐丘 野溪上游附近土壤為樣本。將採回之土樣配合因次分析進行滲流箱試 驗,探討當土體破壞時,地下水電導度變化與主要的影響離子,以及 評估地下水電導度觀測方式之可行性。其結果顯示,當地下水電導度 值呈現上升趨勢時的20~60 分鐘內,即可能發生大規模崩塌,水質試 驗結果顯示,So42-及HCO3-為使電導度值上升的主要成份。 There were two parts in this study. In the first part, the rainfall data and the occurrence time of debris flow were collected, and the rainfall events in which debris flow occurred and did not occur were digitized, and finally, the basic statistical parameters of the two sample groups were obtained. Using the overlapped portion of the two groups, multivariate normal distribution were used to evaluate probabilistic critical rainfall lines. The second part of this study was to investigate the effects of EC on the occurrence of debris flow induced by piping. In the first part of this study, the Nan-Tou county was selected as the test site and 28 watersheds in this area were selected as the samples.After examination by using the Mann-Whitney-Wilcoxon test, four factors were relatively highly related to debris flow occurrence. The four factors were : landside area, landuse factor, percentage of the soil particle greater than sieve No.4 and effective watershed area. Equations for predicting debris flow occurrence in the Nan-Tou area were proposed by using Fisher’s discriminant function of multivariate statistical analysis. After the Chi-Chi earthquake, the potential of debris flow of the streams increased. Accordingly, the peak ground acceleration (PGA) of the earthquake and a function decreasing with time were used to revise the critical rainfall line for each watershed after the great earthquake. Then, the probabilistic critical rainfall lines of debris flow were established by using multivariate normal distribution for each sample stream. In the second part of this study, The main purpose of this study is to investigate the relationships between electrical conductivity of groundwater and debris-flow occurrence. If the soil deposited in the stream with a high potential of debris flow or located at the sides of the stream was eroded due to seepage for a period of time, fine particles of the soil might be carried away and subsequently, the whole soil deposit or the slope might collapse. Therefore, field dimension analyses were conducted and accordingly, seepage tanks were designed and fabricated. In this study, Feng-Chiu a small village of Nan-Tou prefecture was selected as the site. The soil samples were collected from the upstream site of Feng-Chiu. Then, by using the obtained data and properties, the seepage experiments were designed and carried out. Therefore, when soil was collapsed, variation from electrical conductivity of groundwater might be observed. It was found that about 20 to 60 minutes after the increase apparent of the electrical conductivity of groundwater, slumps occurred. The water quality tests were conducted, and it was found that two compositions, namely, SO4 2- and HCO3 -, induced the electrical conductivity value to increase. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/10760 | 其他識別: | 912625Z002027 | Rights: | 國立臺灣大學生物環境系統工程學系暨研究所 |
顯示於: | 生物環境系統工程學系 |
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912625Z002027.pdf | 8.86 MB | Adobe PDF | 檢視/開啟 |
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