Effects of water on rock strength in a brittle regime

Failure strengths of granite and andesite have been measured under various conditions of strain rate and confining pressure both in the dry and wet st ates. Constant-stress creep tests for granitic samples have been also condu cted. All specimens show that the failure strength decreased linearly as th e logarithm of the strain rate decreased, The strain rate dependence of the failure strength is increased at higher confining pressures. The strain ra te effect is more apparent on the failure strengths of wet samples than dry samples in lower confining pressure ranges. In the constant-stress creep e xperiments, the creep failure strength decreased as the logarithm of the ti me to failure increased. Time-dependent failure strength of all rocks obser ved in the regime of the present study may be interpreted by subcritical cr ack growth assisted by the stress corrosion mechanism. (C) 2001 Elsevier Sc ience Ltd. All rights reserved.