岩石におけるサブクリティカル亀裂進展の組織・環境依存性

Abstract

In order to make realize long-term stability of rock mass, it is necessary to study the time-dependent fracture problem in rocks.Subcritical crack growth due to stress corrosion is considered to be one of the key factors of the time-dependent behaviors in rocks. It is known that subcritical crack growth is affected by the environmental condition. Thus, it is important to research the dependence of subcritical crack growth in rocks on the environmental condition. Especially, water is known to be a corrosive agent of stress corrosion in rocks.In this study, Double Torsion (DT) test was carried out by using granite and andesite under various temperature and relative humidity, and the dependence of subcritical crack growth on water vapor pressure was investigated quantitatively.It was shown that subcritical crack growth in rocks was facilitated as water vapor pressure became large. For andesite, activation energy was estimated from the experimental results, and crack velocities under various temperature and water vapor pressure were calculated. The theoretical values of crack velocity agreed well with observed values.For granite, considering the dependence of subcritical crack growth on the crack density of pre-existing microcracks as well as the dependence of water vapor pressure, crack velocities were calculated theoretically. The theoretical values were consistent with observed values very well. It is concluded that crack velocity can be predicted by considering the environmental condition and the crack density of pre-existing microcracks.