EVALUATION OF LANDSLIDES IN RESERVOIRS BY FOCUSING ON THE DEGREE OF SATURATION OF GOUGE

This paper examined the time dependent behavior of landslide by focusing on an actual landslide behavior observed at the dam site, which was built on Sambagawa metamorphic belt (mainly formed with crystalline schist), which was formed in Mesozoic and Paleozoic era. In concrete terms, we cite two examples and categorize them based on landslide moving speed; a landslide caused by decrease of reservoir level during initial impoundment; an intermittent landslide caused by submergence and rainfall. We also studied the actual phenomena by conducting unconfined compression tests of clay samples obtained near the sliding surface. As a result, it was qualitatively clarified that the plastic behavior of clay became a liquid flow condition when increasing the saturation degree of the clay and the strength of the clay also decreased. In conclusion, we suggest confirming either by laboratory tests or site investigation whether or not the change in the degree of saturation causes an extreme decline in the strength of a sliding surface gouge.