The South Cross-Island Highway (also named TAI.20th highway)is a maior critical highway contributed to economic, transportation, national defense and recreation business in the southern Taiwan. The highway with a total length of 209 km starts from Tainan City run through Central Mountain range and terminates at Guan-Shang in Taitung. The highway passes through Yu-Jin, Bei-Liau of Tainan Hsian, and Jia-Shian, Mei-Shan of Kaoshung Hsian, and enters Taitung Hsian at Ya-Kou tunnel. In Taitung Hsian, the highway goes through Shiang-Yang, Li-Dau, etc., and Hai-Duan, then leaves the Cordille'ra Central.
The complicated geology structures, fragile stratum & special topography along the highway and heavy rainfalls brought by the annual typhoon and monsoon season has been recognized as major factors trigger collapsing and sliding of the highway slopes. This can jeopardize the traffic line.
Jia-Shian to Ya-Kou section of the highway was selected to be investigated and studied in the research. The stratum along the section from Jia-Shian to Mei-Shan contains mainly Sandstone, Argillite and slightly metamorphosed Sedimentary Rocks. The section between Mei-Shan and Ya-Kou are mainly predominated by Slate and Phyllite. Those are classified as Sanhsia Group and its equivalents, Lushan Formation and Pilushan Formation. In the studied section, slopes failures mostly occurred at the northern slopes with steepness within 20°-50°and the U turns having large radius of curvature. The elevations of the collapsed slope fall between 400-1200 meters. Enduring head winds of the southwest air current during summer season, the northern slope aspect should be well drained and treated to prevent weathering of the rock on slope surface. According to the differences and its influential scopes of various factors, such as formation property, slope instability, slope aspect, landslide and geological fault etc., weighing number was established for counting each factor related to slope failures by GIS system. The total weighing number would be used to show the situation of disaster danger being classified in the result layouts. The GPS/GIS technology integration would be use to establish the potential disaster database system for the studied section located at the highway. Further more, two inquiring subsystems of theestablished database systems were set up on the basis of the actual requirement, and using the visual basic (VB) program language under the GUI interface enviroment.
It is believed that the research can be a reference to help planning and designing of the highway slope stability treatment and disaster prevention engineering in the future.
