| Summary: | 碩士 === 國立成功大學 === 土木工程學系碩博士班 === 100 === The aim of this study is to investigate the influence of the strength of precipitation to the stability of slope land along highways those spreading in the watershed of river Da-Jia during typhoons Toraji, Mindulle and Morakot. By collecting the historical precipitation data in site, the completed rainfall events during those typhoons can be obtained and be adopted to calculate the accumulated rainfall(R) and rainfall intensity(I) of the watershed. Furthermore, the concept of rolling rainfall intensity is proposed to illustrate that accumulated rainfall and rainfall intensity are not only the factors that led to the damage of slope land along the highway, the effect of duration of the rainfall intensity has to be included. Furthermore, accumulated rainfall and rolling rainfall intensity are also used to establish the snake line that is the analysis model of rainfall hydrograph and can be expressed the variations of accumulated rainfall and rolling rainfall intensity with time.
In addition, both physiographical conditions and the rainfall data in area where disasters were occurred were collected. The physiographical conditions can be classified as four factors which as elevation, degree of slope, direction of slope and geologic condition and with Log-Pearson Type Ⅲ Distribution, the rainfall data is used to calculate the recurrence interval and classified it according to the severity of the disasters in the past for frequency analysis. By combining the results of classification and analysis with the snake line, the critical rainfall envelope of the study area can be defined. The disaster event occurred on June 10, 2012 is verified with the critical rainfall envelope. It is shown that the critical rainfall envelope can be the basis for the disaster capacity of mountain highway slope.
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