高速高圧リングせん断試験機の開発と地すべりにおける急速載荷時のせん断強度変化

Abstract

Sassa has developed a high-speed high-stress ring shear apparatus in 1988 for study onfast moving landslides, which followed the first high-speed (low stress) ring shear apparatusdeveloped for debris flow study in 1984.In use of this newly developed ring shear apparatus, rapid normal stress loading testswere performed during shear, under the condition in which both of porous end plates of thesample box are kept to be drained. It is a kind of model test simulating the rapid loading onslopes by a moving landslide mass.Pore pressure generated by rapid loading caused a great decrease of the apparent frictionangle during motion in both of clayey soils taken from the Jizukiyama landslide and sandysoils from the Denjou torrent of the Ontake debris avalanche. Dissipation of pore pressuretook a few ten hours in the Jizukiyama soil and some ten seconds in the Denjou torrent depositin the manner similar to one dimensional consolidation theory.Finally a computer simulation of the Ontake debris avalanche in use of the rapid loadingtheory by Sassa was briefly introduced.