Subcritical crack growth in rocks under aqueous environment

Abstract

Subcritical crack growth is one of the main causes of time-dependent fracturing in rock. In this study, subcritical crack growth in rock was investigated in distilled water (pH=6) and aqueous solution of sodium hydroxide (NaOHaq, pH=12). Especially, comparing the results in water to those in air, the effect of water was investigated. Additionally, the effect of pH in aqueous environment was also investigated. Rock sample were andesite and granite. The relation between the crack velocity and the stress intensity factor was determined by Double-Torsion method. All experiments were conducted with controlling temperature. It was shown that the crack velocities in water were higher than those in air. These results are in accordance with the results by many researchers who reported that the crack velocity increased in water. Comparing the results in NaOHaq to those in water, however, it was shown that the crack velocity at the same stress intensity factor didn?t change even though pH of surrounding environment changed. This result doesn?t agree with conventional concept that the hydroxyl ion accelerates subcritical crack growth in silicate materials. It is concluded that water accelerates the crack velocity and pH has little effect within the environmental conditions in this study.