砂岩の破壊靭性に及ぼす湿度の影響

抄録

The effect of the humidity on the fracture toughness in sandstone in air was investigated experimentally. Rocks used in this study were Berea sandstone, Shirahama sandstone and sandstone obtained at Kushiro coalmine (Kushiro sandstone). Double-Torsion method was used in this study to measure the fracture toughness to compare the results to those of subcritical crack growth. All measurements were conducted under the same temperature and different relative humidity to investigate the effect of the humidity.
It was shown that the humidity affected the fracture toughness. The fracture toughness decreased with the increase of the humidity. The decrease of the fracture toughness was more remarkable when the content of clays in rock was higher. It is considered that the amount of clays had a significant effect on the change of the fracture toughness of sandstone. Degradation of clays with increasing the water content is considered to affect the decrease of the fracture toughness. It was shown that the decrease of the fracture toughness with increasing the humidity was less than the decrease of the stress intensity factor for subcritical crack growth. This was caused because stress corrosion had less effect on the fracture toughness. It is concluded that the crack growth in sandstone is affected by the humidity and the content of clays.