Experimental study with ring shear apparatus on the may 2004 landslide-debris flow at bettou-dani valley, Haku-San Mountain, Japan

Abstract

In May 2004, a landslide occurred at the right flank of the Jinnosuke-dani landslide, and transformed into a debris flow after fluidization. By analysis of the monitored video images of the debris flow, field investigation on the source area of the landslide, and a series of simulation tests with a ring-shear apparatus on the initiation of the rainfall-induced landslide and its traveling process, the initiation and traveling mechanisms of the debris flow traveling in the valley were investigated. It is shown that concentrated groundwater flow was the main reason for the landslide initiation, and a rapid decrease of the mobilized shear resistance even under naturally drained condition caused the rapid landslide motion. During the debris motion in the valley, high potential for grain-crushing of deposits in upstream and lower potential for the downstream deposits controlled the traveling and depositing process of the debris flow. Different grain-crushing potential of the valley deposits played an important role in the debris flow traveling and depositing processes. © 2007 Springer-Verlag Berlin Heidelberg.