Effects of relative humidity and temperature on subcritical crack growth in rock

Abstract

In order to ensure long-term stability of structures in a rock mass, the study of time-dependent fracturing is essential. We have therefore investigated the effects of relative humidity and temperature on subcritical crack growth in rock experimentally on samples of Kumamoto andesite, Oshima granite, Berea sandstone, Shirahama sandstone and Kushiro sandstone using the Double Torsion method. All experiments were conducted in moist air. Our results show that, in experiments conducted under the same relative humidity, crack velocity in igneous rocks increased with increasing temperature, in agreement with previous studies. On the other hand, the change of the crack velocity in sandstones at a given stress intensity factor was unclear when the temperature increased under a constant relative humidity in air. Our results also show that, in experiments conducted at the same temperature, crack velocity increased dramatically with increasing relative humidity. This increase is much larger than that expected from the conventional concept based on the theory of stress corrosion. The increase of the crack velocity was larger for sandstone which contained larger amount of clays. We conclude that subcritical crack growth in rock in air is affected remarkably by the relative humidity and the existence of clays.