- 學位論文
降雨對邊坡穩定性的影響—以九份地滑地為例
A Study on the Effect of Rainfall on the Stability of Slope—A Case Study of Joufen Landslide
摘要
台灣山坡地面積約佔75%，近年來又大量地開發建設，因此坡地災害頻傳，綜觀坡地災害的成因，崩塌地本身的地形、地質條件，例如順向坡地形、土岩層的破碎帶等等均會造成坡地的危險；外加的力量例如地震、暴雨、房舍的加載、坡角的開挖等等，也很容易引起邊坡的崩塌，一般來說，坡地不穩定的發生常常起因於兩種以上的誘因，再加上有人群的聚集或經過，如此的坡地不穩定現象就會因為威脅到人身安全而變成災害。 九份地區由於先天地質條件欠佳，政府近年又積極開發，使之成為重要而著名的觀光景點，同時也使得土地利用過於緊繃，再加上台灣北部雨量豐沛，降雨量不但多而且密集，使得九份山坡地於民國八十五年開始發生較明顯的滑動，尤其九二一大地震後，使得滑動速率更顯著，也使得整個九份地滑地的安全性受到重視。 本研究承接前人進行的研究、監測，以有限元素法軟體PLAXIS對九份地滑地進行穩定分析，由於引起地滑的主因有數種，本研究依據監測資料所得結果，針對降雨造成的各種現象例如地下水位上升、砂頁岩浸水軟化等進行數值分析，並比對現地監測數據，期望突顯出降雨的強度與九份地滑地位移的關係。
並列摘要
75% of Taiwan is covered in mountains and hills. Lately, there has been enormous demand for slope development, and slope disasters, therefore, have occurred quite frequently. Looking at the causes of these disasters, the geography of the site itself, the geologic conditions, such as dip slope, or fracture zone in the strata could a certain threat to the safety of a slope; the collapse of a slope is often the result of external forces such as earthquake, storm, the weight of buildings and the excavation of slope toe. In general, the instability of a slope is usually the result of more than 2 causes. On top of that, if there are people gathering or passing by in the vicinity, the slope instability will then threaten the safety of people, even causes a disaster. The geologic conditions of Joufen are not very good, and in recent years, the government has been working to develop this place into one of the important tourist attractions, resulting in the over-stress on the land uses. Meanwhile, the precipitation in Northern Taiwan is rich, and the rain often comes hard and concentrated. As the result of all of the above causes, the slopes of Joufen have started to develop noticeable slides since 1996. Particularly after the 921 Earthquake, the rate of sliding is getting more and more significant and as the result, the safety of the landslide areas at Joufen is taken more and more seriously. Following the research and monitoring of the predecessors, it is the intension of this study to perform the stability analysis on the landslide areas at Joufen using finite element software PLAXIS. Since there are several causes to the occurrence of landslides, numeric analysis is performed for the phenomena from the rainfalls, such as the rising of groundwater table and the saturated softening of sand shale, according to the data obtained from monitoring, and the result is compared to in-situ monitoring data, hoping to highlight the relation between the intensity of precipitation and the displacement in the landslide areas at Joufen.