Effect of water on the strength and creep lifetime of andesite

Abstract The authors’ research group has investigated the close relation between the time-dependent behaviors under various loading conditions through laboratory tests, theories, and constitutive equations. It is well known that water accelerates the time-dependent behaviors of rocks; water enlarges the loading-rate dependence of strength and shortens the time to failure (creep lifetime) under constant stress level (ratio of creep stress to strength). This paper introduced the theory in the previous studies based on the rate process theory and the stochastic process theory, and found that the theory disregarded the effect of a change in water conditions on the strength and creep lifetime of rocks. The theory was briefly modified and then applied to the strength, creep lifetime, and their variability in both dry and wet conditions. To validate the modified theory, strength tests and creep tests were conducted under uniaxial compression with Sanjome andesite. The constants in the modified theory were calculated from the strength, and then the creep lifetime collected from the creep tests was examined with the formulae derived from the modified theory. The test results in dry and wet conditions were consistently elucidated by the modified theory, which indicates that the strength and creep lifetime of Sanjome andesite are approximated by the simple formulae in the theory. Creep lifetime was estimated from strength, and the results in dry conditions were estimated from those in wet conditions and vice versa, based on this study.