行政院國家科學委員會專題研究計畫成果報告:土石流災害防治之研究（以南投縣陳有蘭溪為研究對象）─子計畫：土石流發生危險度即時分析及評估系統（III）
Date Issued
2001
2001-07-31
Date
2001
2001-07-31
Author(s)
DOI
892625Z002045
Abstract
The main purpose of this study was to analyze the hydrologic and physiographic criteria of debris flow occurrence for a watershed. There were two parts in this study. In the first part, the equations for evaluating the critical rainfall line of debris flow occurrence were developed, and accordingly, the relationship between the decline of the critical rainfall line due to the Chi-Chi earthquake occurred on September 21, 1999 and the time period after the earthquake was evaluated. Then, a method for determining the probabilistic critical rainfall line of debris flow occurrence was proposed. The second part of this study was to investigate the effects of seepage on the occurrence of debris flow induced by piping.
In the first part of this study, twenty-eight watersheds were selected in the prefecture of Nan-Iou as the test sites. After examination by Mann-Whitney-Wilcoxon test, the following five factors were found to be highly related to the occurrence of debris flow. They were: land use factor, percentage of soil particles greater than sieve No.4, watershed area, length of main stream and average slope steepness. Aside from these, Fisher¡¦s discriminant function was used to derive the equations for debris flow warning.
After the 921 Chi-Chi earthquake, the potential of debris flow for each stream was considered to be higher. The critical rainfall lines were analyzed and revised by using a factor of peak ground acceleration (PGA) and a fUnction decreasing with time. Besides, multivariate normal distribution and characteristic curves were used to evaluate probabilistic critical rainfall lines. Subsequently, the probabilistic critical rainfall lines may be used for criteria of warning systems of debris flow occurrence.
In the second part of this study, the soil samples were collected from Feng-Chiu and Sheng-Muh where debris flows occurred rather frequently in Nan-Tou. After tests, the particle size distribution curves and basic soil physical properties were obtained. Then, using the obtained data and properties, the experiments of seepage were designed and carried out. In this study, Dupuit Assumption was used to analyze the rectangular earth dam model, so that the critical hydraulic gradient, line of seepage (LOS) and equations for calculating critical piping might be evaluated. It was found that the critical hydraulic gradients for the soil samples collected from Feng-Chiu and Sheng-Muh were both 0.288. It also found that the critical seepage angles for the soil samples collected from Feng-Chiu and Sheng-Muh were 35 and 37 degrees respectively.
Subjects
debris flow
critical rainfall line
peak ground acceleration (PGA)
characteristic curve method
seepage
critical hydraulic gradient
piping
line of seepage
SDGs
Publisher
臺北市：國立臺灣大學生物環境系統工程學系暨研究所
Type
report
File(s)![Thumbnail Image]()
Loading...
Name
892625Z002045.pdf
Size
16.23 MB
Format
Adobe PDF
Checksum
(MD5):2ee9508fe902a5a55ee54d76dde9ae04