Abstract
During the heavy rain on June 29, 1999, four slope failures occurred around the Taishi-do area in Zentoku landslide, Tokushima, Japan. Based on field investigation after these failures, and the monitored records of the three-dimensional shear displacement me-ters before the failures, it was made clear that 1) the failures were limited comparing to the rainfall ; 2) One of the failures showed precursory displacement of creeping failure. To clarify the failure mechanism, field investigations including one-meter depth of soil temperature survey, temperature measurements of spring water and groundwater in borehole were conducted, and pore water pressures generated at failure were estimated through back-analysis. Thereafter, the relationship between the location of failed slopes and flowing groundwater veins, and the relationship between groundwater vein and precursory displacement of failures were analyzed. It is found that: 1) Slope failure occurred above or near groundwater vein ; 2) There were two types of groundwater veins, one was surficial vein type with high water temperature, and the other was deep vein type originating from a depth between 49 and 70m with low water temperature ; 3) The precursory displacement of the creeping failure was associated with the groundwater vein.
