| Summary: | 碩士 === 國立臺北科技大學 === 環境工程與管理研究所 === 99 === There is about seventy-five percents area of hilly lands in whole Taiwan island, all of the forest roads managed by Forestry Bureau are located in this area, and their slopes were usually eroded, collapsed and destroyed on the part of roads by typhoons and torrential rains, that is owing to their special geographies, including cliffy terrains, steep hillsides and fragile geologies. One of the forest roads, Yilan ROAD “NO.1” , it’s geology is also fragile, and constantly induced landslides collapsing and sliding after Chi-Chi earthquake. Torrential rains and typhoons. In July eighteenth 2005, one of the typhoons called Haitang severely attacked Yilan ROAD “NO.1” , and caused traffic interruption and the Tai-Pin-Shan Forest Recreation Area was forced to close for nearly one year.
Slope damages usually happened in some period within a rainfall or after a rainfall, and mostly because of the water infiltration phenomenon, it rose water level from the groundwater saturated layer, and added the unsaturated layer’s unit soil weight either, both increased the sliding forces of the unit soil, moreover, the soil particles contented much water, the soil lost it’s shearing strength quicker, and this kind of condition occurred in different periods and influenced each other, it induced slopes fractures and deformations at the most weak plane after rainfalls, moreover, it induced collapsing and sliding.
The study chiefly analyzes how effective that the piling to prevent hillside from sliding was, and takes the treatment of 12.8K at Yilan ROAD “NO.1” for example, and applies Stable and Plaxis formulas to measure landslide stability before and after treatment within general time, a torrential rain and an earthquake, three kinds of conditions, and makes a reference of landslide treatment for the forest roads under Forestry Bureau control. The results show that in the case of unknown depth, recommended using PLAXIS formulas to analysis is more in line with the status. In the round of monitoring tubes has been set and grasp the sliding depth, we can use STABL formulas to analysis. In addition to the program’s advantage is popular, if we limited the sliding depth, the result is in keeping with status. The study of piling can enhance the safety factor of 0.15. In status of heavy rain, the piling of Yilan ROAD “NO.1”. 12.8K B7-B8 cross-section safety factor should upgrade from the 0.96 to 1.09.
Hillside sliding is one of the common damages, all of the forest roads managed by Forestry Bureau are located in hillside, nine of them connect forest recreation areas, are the chief traffic roads fir tourism. To protect passersby safety, suitable treatments are necessary. Landslide treatment strategies chiefly combine the method of restraining and the method of prevention, recent year, the main forest roads managed by Forestry Bureau (for instance, Yilan ROAD “NO.1” and Tengihih Forest Road) adopted piling to prevent sliding trend when they took place deep layer sliding, and apply hillside monitoring to measure the sliding depth. Rate and scope before treatments, these kind of method becomes a basis of assessment, and outcome is extremely wall.
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