The movement mechanism of crystalline-schist landslide associated with underground erosion

Abstract

It has been estimated that creep movement is caused by underground erosion in the crystalline-schist debrismass landslide. However, it is not sufficient to explain the movement mechanism of landslide.
Then, the authors carried out monitoring of sediment discharge caused by underground erosion, landslide mass deformation and measurement of underground water paths in Zentoku landslide mass, Tokushima prefec-ture, Japan, to clarify the movement mechanism of such type of landslide. From the results of analysis about the factor affected to underground erosion using these monitoring and measurement results, it is considered that (1) water paths are formed along/above the shear zones, where underground erosion is caused (2) sediment discharge caused by under ground erosion is affected by the factors of not only groundwater discharge but also landslide activity (3) high landslide activity makes the debris mass structure subjected to underground erosion in the landslide mass. Consequently, the investigation has made clear that the mechanism of creep movement consists of the link of two processes, one is underground erosion caused by landslide activity, and another islandslide activity caused by underground erosion.