Abstract
Landslide strength is the most important value among parameters that influence the cost of landslide prevention works. However, it is difficult to determine the precise value of the landslide strength. The landslide strength can be generally calculated by the back analysis, assuming that a stability factor of an objective slope is approximately equal to 1.00. In the case of an inactive landslide, the landslide strength may be underestimated by the assumption that the stability factor is equal to 1.00. This underestimation results in an over design of the prevention work. Therefore, it is necessary to determine a reliable value of the landslide strength for inactive landslides individually.
In this paper, the authors proposed a new simple method to determine the landslide strength for landslides of colluvial deposits having a gentle and long slope in the Yuya Peninsula, northwestern Yamaguchi Prefecture. The landslide strength obtained by the back analysis has previously been used to estimate the stability factor of a landslide block that occurs in landslide protection regions in the peninsula. It is pointed out that the landslide strength is related to the slope angle and thickness of landslide deposits. Residual strength of each colluvial deposit that constitutes the landslide blocks is also measured by ring shear tests. Accordingly, the validity of the method is approved in order to determine strength parameters of an inactive landslide of colluvial deposits having a gentle and long slope.
