本研究以出磺坑背斜之北段為研究範圍，主要目的在檢討本區之水文特性與山坡地滑動潛勢之關係。 本區出露之岩層主要為卓蘭層、錦水頁岩、桂竹林層與上福基砂岩；主要地質構造自西而東，依序為錦水背斜、仁隆向斜與出磺坑背斜。褶皺之軸線大致以北偏東三十度之方向延伸，彼此互相平行。 邊坡穩定分析採用FORTRAN程式語言編寫之STABL 6軟體，其理論基礎依據二維極限平衡法分析邊坡之穩定性。先選取鑽井岩心進行岩石力學弱面直剪試驗，求得分析時所需的力學參數凝聚力c與內磨擦角ψ，作為程式分析之根據。並以現地地表地質調查所取得之岩層位態，進行圖解法邊坡穩定分析；再配合水系分佈與密度圖與坡度分析圖，進行綜合檢討山坡地之穩定性。 研究結果顯示坡度小、岩層傾角小、水系分佈與密度較為緊密之坡地，順向平面滑動潛勢較低；坡度大、岩層傾角大、水系分佈與密度較為疏鬆之坡地，順向平面滑動潛勢較高。於河流侵蝕處的兩岸，河岸順向坡處滑動潛勢相對較高，而另一岸則相對較穩定。而於曲流轉彎處的兩岸，河道凹側以侵蝕作用為主，坡腳之底切作用導致滑動潛勢較高；凸側則進行堆積作用，整體坡度較緩，滑動潛勢相對較低。 This study area is situated at the northern part of Chuhuangkeng Anticline, the main purpose of the study is to analyze the relationship between hydrologic characteristics and the sliding potential of the land slope. The main rock strata outcrop in the study area are Cholan Formation, Chinshui Shale, Kueichulin Formation and Shangfuchi Sandstone; the main geologic structures lying from west to east are Chinshui Anticline, Jenlung Syncline and Chuhuangkeng Anticline respectively. Fold axes strike approximately in the direction of N30oE and are nearly parallel to each other. With a basis of 2-D Limit Analysis, STABL 6 program in FORTRAN language has been used in slope stability analysis Direct shear tests on rock cores were performed to obtain the cohesion c and the angle of internal friction ψ, which in turn are the basic mechanical factors in programmed slope stability analysis. Graphical slope stability analysis has also been performed based on rock strata attitudes collected in field survey and mechanical factors. Overall analysis has been done by considering all the results from slope stability analyses as well as the drainage density and distribution maps. The study shows that the slope with lower gradient, lower strata dips, and dense drainage density and distribution bears the least sliding potential; while the slope with higher gradient, higher strata dips, and loose drainage density bears the most sliding potential. The dip slope in one side of the river banks gives relatively higher sliding potential than the opposite. At the place of meander turning, strong stream erosion happens at the outer part of the meander, and the under-cutting action at the toe of the river bank results to potentially unstable slopes; while the deposited inner part of the rivers show stable, gentle slope.
