| 摘要: | 近年來因全球氣溫暖化，導致世界各地極端氣候災害不斷發生，2009年8月8日，台灣南部遭受莫拉克(Morakot)颱風的侵襲，莫拉克颱風形成之豪雨為南部帶來嚴重的洪水災害。此次的洪水災害，探究其原因最主要是因為河堤潰堤所致，而本研究必須蒐集多方資料，以程式模擬河堤、壩體或是擋土牆在極端豪雨的影響下，找出可能造成破壞的原因，以降低未來災情產生的機率。 本研究目前是以高雄縣舊寮一號堤防為模擬樣本，其資料是由經濟部中央地質調查所和交通部公路總局材料試驗所提供，關於此堤防的地質狀況以及附近地層的鑽探資料顯示，堤防附近是屬於現代沖積層，地層大致分為兩層，上為卵礫石層和下方的岩盤；而其鑽孔資料皆位於荖濃溪沿岸橋樑附近，其中大津橋與舊寮一號堤防的相關位置最接近，而模擬舊寮一號堤防所輸入的參數，目前是取用大津橋的鑽孔資料來進行分析。本研究使用的軟體為GeoStudio 2007，並以其中一個模組SLOPE/W，進行邊坡穩定分析，以現地土壤不同的內摩擦角、水位高、堤外土壤掏刷深度三種變數來探討堤防的破壞機制，再加上不同水位差的變數，考慮滲流狀況；而以上的分析結果顯示，某些狀況下所求得的安全係數會小於1，達到破壞標準。 另外，本研究進行了堤防基礎可能的破壞模式分析，根據作用於堤防基礎上的力學機制，分析結果為堤防基礎可能會產生滑動破壞以及傾倒破壞，而不會有承載力破壞的發生，對照了當時堤防破壞的相關資料或照片，破壞狀況與計算結果相當地吻合。 In recent years due to the global warming, extreme weather resulted disasters around the world continue to occur. In August 8, 2009, the southern part of Taiwan suffered from serious floods from heavy down pouring rain of Typhoon Morakot. To explore the main reasons for the flood disaster, which results in levee and floodwall breach, this study must collect extensive information to use the program to simulate the embankment and levee behavior when heavy rain occurred, aiming to find out the reasons for potential damage, and to reduce the probability of future disaster. In this study, we have chosen Chiu Liao 1st Levee, in Kaohsiung County as the case study example, the relevant data is provided by Directorate General of Highways, materials testing Lab under the Ministry of Economic Affairs. About geological conditions close to the study site, based on the boring logs collected for this study, the strata is divided into two layers, the first layer consists of mostly gravel material and the second layer is the bedrock; the borehole locations are near the Lao Nung River, where Da Jin Bridge is the closest bridge to Chiu Liao 1st Levee. The software GeoStudio 2007 is adopted in this study, and one of the modules- SLOPE/W is employed for slope stability analysis. Different internal friction angle of soil, the water level, the scouring depth of soil are chosen to be three variables to explore the levee failure mechanism, the analysis was also coupled with the water level difference, and seepage condition; the above analysis results show that the values of factor of safety obtained in some cases are less than 1, reaching the failure state. In addition, this study conducted the retaining wall failure analysis, including sliding failure, overturning failure and bearing capacity failure. It was found that the bearing capacity failure is unlikely to occur under all scenarios; however, the sliding and overturning failure can occur when the water level changes with the consideration of seepage conditions. |
