| Summary: | 碩士 === 國立中興大學 === 水土保持學系所 === 96 === The characteristics of geological environment of Taiwan include frequent earthquake, abundant rainfall, and strong erosion, thus leading to various of geological disasters. The study site is Luchang Area of Miaoli, NW Taiwan. The geological environment of this site is a steep land with high stream-flow velocity and strong geological activities. The purpose of this paper is to explore (1) the characteristics of geological environment, (2) the reason of the unstable slope and (3) the sensitivity analysis of slope. Future mitigation plan of the study area can then be derived.
The results of this study showed that the influencing factors of slope instability for the Luchang Area include rock fall at the west slopes, thick colluvium, sliding planes for dip-direction slopes, headward and sideward erosion of channel, as well as fast seepage of ground water. Two slide planes were recognized from geological profile model. One is potential slide plane on the dip-directional slope, another plane is located in the colluvium near Luchang river sides. Large landslide will occur when the continuous accumulated precipitation was greater than or equal to 1250mm, and tensional cracks occurred at central Luchang terrace. The degree order of sensitivity analysis for six parameters of soil dynamics versus safety factor are horizontal seismic coefficient (Kh)＞soil friction angle (ψ)＞water table (WT)＞vertical seismic coefficient (Kv)＞cohesion (C)＞unit density (rt). After revealing past earthquake data (mostly with intensity < 4, as well as Chi Chi earthquake), the soil friction angle of the site is concluded to be greater than 35 degrees, slope failure of the site will occur when the intensity of earthquake approaches to 6.
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