| Summary: | 碩士 === 國立屏東科技大學 === 水土保持系 === 91 === "Transportation Infrastructure" is an important part of national fundamental constructions. In view of the recently increasing demands of transportation convenience, our government started the national secondary freeway construction project in 1984. The south second highway is one of important highways in south area, which intersects three counties of Kaohsiung, Tainan and Pintung and includes main lanes and branches there of from Hsinhwa, Tainan, to Chouzu, Pintung. The total length is 96 km. The highway also intersects complicated geological areas of Mudstone, Sandstone and gravel formations. Besides, while constructing the south second highway, the excavated slopes and cut slopes has caused the strata stability failed, and the rainfall intensity in south area is large and concentrated. So many landslides and failures occur in slopes along the national freeway, which shows there are many topics worth to discuss regarding the slope protection engineering methods along the highway. Therefore, this study is first to investigate the basic characteristics of slopes along the highway in discussing the relationships between that characteristics; then choose Kuanmiao Rest Area as the plot for the installation of monitoring devices in observing soil erosion depth, vegetation cover rate, soil toughness and earth temperature. To sum up the above two parts, the conclusions are summarized as follows:
1. From investigation results, there are seven current slope protection methods along the south second highway, which are the free frame method, pre-cast concrete frame method, vegetation belt pavement method, soil bag pavement method, vegetation net pavement method, wire-netting with hydroseeding method, and bag and carpet method. In regard with the degree of damage, it is found that performing a single vegetation method or engineering method is worse to performing complex engineering method. Therefore, it is recommended to use complex engineering method to let both the vegetation method and engineering method go into effect.
2. Results have shown that there is a negative relationship between the vegetation cover rate and soil erosion. As the vegetation cover rate is more than 30~50%, the soil erosion is conspicuously lower; As more than 70%, it has even no erosion gullies. Therefore, the success and failure of the slope protection methods along the south second highway are closely relating to their vegetation cover rate.
3. From the results of soil erosion experiments, the observed value of erosion depth has significant difference to the estimated value by the formula, where the difference between the pre-cast frame method area and bare area is most, about 6 times to 8 times difference. Therefore, that shows it is required to remove sediment for stability of slope.
4. Considering different engineering methods, it is found that the variation of earth temperature of bare slope area is most; of the vegetation net pavement area and the damaged vegetation net area in east are the next; and of the pre-cast frame method and the bag and carpet method are lowest.
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