Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 101 === Different protection methods, such as geotextile blankets for erosion control, soil nails, and ground anchors, are often used to protect slopes. The effect of these engineering works at extreme climate condition, e.g., uneven distribution of rainfalls with high intensities in recent years, is worth studying. In this research, the effect of some slope protection works were studied through numerical analysis by using the package software named GEO-Studio. The Tieliku landslide in the catchment area of the Shihmen Reservoir was taken as the case for this study.
The engineering properties of the soil were obtained from the in-situ soil samples tested in the laboratory. The numerical model consisted of two slopes, steep and gentle, in plane-strain condition. The rainfall data was that from the Sinlaku rainfall. The engineering works analyzed were the vegetation cover by hydro-seeding method in conjunction with soil nails, the anchored geosynthetic slope system, and the geotextile blanket for erosion control. The following three programs were employed in the analysis. First, the SEEP/W program is for analysis of the change in pore pressure, considering both saturated and unsaturated modes. Second, the SIGMA/W program is for stress and strain analyses. Third, the SLOPE/W program is for stability analysis of the slope.
The conclusions are made as follows. (1) The foreign soil from hydro-seeding has a low coefficient of permeability and can delay the increase in pore pressure. In addition, the soil nails can reduce the displacement of soil as well as decrease significantly the plastic zones in the slope. (2) With increased infiltration depth, the axial force in the anchor increases, and the location of maximum tensile force shifts from close to the slope face initially to the middle of the anchor, while the maximum shear force and the maximum bending moment are close to the surface. In general, the axis force in a nail is relatively more important than its shear force and the bending moment. (3) The geotextile blanket provides a drainage path along the slope face, thus it reduces infiltration as well as the plastic zone, the displacement, and the axial force in the nails. Moreover, the axial forces are lower than those in the case of vegetation cover with nails. (4) Though use of a geotextile blanket alone may reduce infiltration, soil nails are still needed if the soil has inadequate shear strength to keep the slope stable.
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