抄録
In order to increase the accuracy of stability analysis of the first time slide in the bedrock, it is important to clearly perceive the characteristics of geological structure, the residual strength acting on the slickenside surface of discontinuities, and the peak strength of the fractured mudstone in the slip surface zone.
Concerning the landslide of the Neogene mudstone discussed in the present report, it was found that the slip surface has been formed by being strongly controlled by the strikes of bedding and fault planes, cutting through the fractured mudstone. The residual and peak strength parameters obtained from the ring shear test and the triaxial compression test were as follows: cr=7kPa and φr=16° for the slickenside surfaces; cf′=75kPa and φf′=36° for the specimens of mudstones having opening cracks; cf′=95kPa and φf=42° for the mudstones having internal cracks and microcracks. For the stability analysis a new method was introduced to assess the parameters of average shear strength along the slip surface, and applying the strength parameters mentioned above, c′=11kPa and φ′=17.5° were obtained.
