Average shear strength parameters along the slip surface of various types of landslides: Shimajiri-mudstone landslides, Okinawa

To discuss a more rational determination of average shear strength parameters, a stability analysis that considers both the slide patterns and slip surface conditions has been done by applying the results of laboratory shear tests of the slip-surface soils. The Shimajiri-mudstone landslides, which are the focus of this paper, had different slide patterns, while the slip-surface conditions varied from one landslide to the other. Measured shear strengths were applied in the stability analysis depending on the magnitude of displacement and slip-surface conditions of the landslides and the average shear strength parameters have been calculated with reasonable accuracy. Ranges of average shear strength parameters at the time of reactivation are presented based on the distance of movement and slip-surface conditions of the landslides. Thus, for the application of measured shear strengths in stability analyses of landslides, it is important to grasp an appropriate perception of the actual slip-surface conditions and estimate shear strengths of slip-surface soils more accurately.