抄録
Two dimensional stability analysis along mid-section by limit equilibrium method with back analysis is popularly used in the world for stability analysis of landslides. However, the residual shear strength of the soil is mainly dominated by the clay mineralogy and may give the different shear strength than the calculated value by back analysis. The residual shear strength of 18 soil samples collected from shallow and deep sliding zone of Okimi landslide in Niigata prefecture, Japan have shown less than 15% variation in shear strength. The average of those shear strengths have been utilized to conduct the 3-D stability analysis of each landslide blocks. The sliding surface contour map has been prepared according to the check boring information to estimate the shearing surface depth. Likewise, available piezometer data and ground topography has been used to estimate the water level throughout the landslide area. New coefficient called stability correction factor (Cf) has been introduced to compare the ratio of calculated factor of safety with unit value by 2-D stability analysis along various sections and 3-D stability analysis. The value of Cf by all methods is found to be consistent when the sliding block has uniform width throughout and primary data are abundant. However, the value of Cf has considerably varied in the block having nonuniform width and less primary data. As the 3-D stabil-ity analysis proposed in this paper is simple 3-D form of simplified Bishop's 2-D method, the calculation process is very simple and can give better solution for the stability analysis of landslide than the method in common practice.
