Uniaxial compression tests on siliceous mudstone of the Wakkanai Formation under high temperature conditions

Mochizuki, Akihito  ; Sato, Toshinori  ; Wada, Junichi*

For the geological disposal of high-level radioactive waste, research and studies are being conducted in Japan and abroad to contribute to the mitigation of the upper temperature limit (100C) in the buffer material assumed in the current disposal system. In this study, uniaxial compression tests under several temperature conditions, some of which exceed 100C, were conducted to understand changes in rock properties under high temperature conditions, using siliceous mudstone (Wakkanai formation) from Horonobe, Hokkaido, as a case study. The uniaxial compressive strength of the rock increased with heating temperature. The uniaxial compressive strength of specimens heated above 100C was comparable to that of specimens desiccated before testing. Mineralogical observations by scanning electron microscopy showed no evidence of alteration of pore structure or minerals, as observed in other rocks in previous studies. In conclusion, the increase in strength of siliceous mudstone with heating temperature observed in this study is considered to be due to the drying of the specimens with heating.