Abstract
Rock specimens consisting of smectite-bearing fine tuffs of the Upper Miocene Ikutawara Formation from the Ikutahara-Minami landslide area in Engaru Town, northeastern Hokkaido, Japan, were analyzed.
The rocks belong to a hydrothermal clinoptilolite zone, and consist of clinoptilolite and minor quartz, feldspar, smectite and pyrite phases. The rocks are divided into two groups on the basis of their smectite content; approximately 7 wt% and very small amounts of smectite-bearing fine tuff.
For rock core specimens perpendicular and parallel to the lamina plane, point load (axial test) and uniaxial compression tests were performed using laboratory testing equipment with specimens under a forced dry-state, dried in an electric oven at 60 ± 3 °C for1day, and a forced wet-state, saturated with distilled water for 10 days.
For these rock specimens from the boundary area of soft and semi-hard rocks, comparative tests revealed that the smectite content influences the point load and uniaxial compression strengths, according to discrepancies in the coefficient of variation of both strengths.
The uniaxial compression strength is approximately 20.0-22.6 times as much as the point load strength under the forced dry-state, and approximately 10.8-11.4 times that under the forced wet-state.
