Effects of water on time-dependent behavior of granite.

Abstract

Effects of water on time-dependent properties of granite are investigated experimentally using partially saturated rocks. Granite specimens, all cored from the same block, were tested to failure under constant strain-rates at confining pressures from 0.1 to 200 MPa. The strain-rates in these tests were varied from 10-4 to 10-7s-1. The compressive strength decreases linearly as the logarithm of the strain-rate decreases. The strain-rate dependence of the strength is enhanced at high confining pressures. The strain-rate effect on the strength of wet granite is more apparent than that of dry granite at lower confining pressure ranges. The dilatant strain increases exponentially with applied stress except just prior to the ultimate failure. The change of the velocity during the deformation is smaller when water exists in the rock specimen than that in dry sample experiments. The acoustic emission rates are much smaller under wet conditions than those under dry conditions. Some of the present results are explained by a theory based on the subcritical stress corrosion cracking.