Innovative laboratory testing

Three laboratory test techniques were developed to study and quantify damage development in loaded rock specimens and to provide data for use in the calibration and solution of numerical models. Damage-controlled tests involved incremental loading-unloading cycles with the stress at volumetric strain reversal (crack damage stress sigma(cd)) and elastic properties calculated for each successive cycle. Damage was quantified by measuring the irreversible volumetric strain upon unloading and the degradation of rock strength and elastic properties. In long-term loading test, a creep stress greater than sigma(cd) was applied to the specimen until failure. The time to failure was dependent upon the ratio of the creep stress to sigma(cd), and to confining pressure. It was shown that sigma(cd) is a reasonable estimate of the long-term rock strength. Damage was quantified by measuring the degradation of elastic properties through periodic unloading-reloading cycles. The test data were used for the calibration of Itasca's PFC stress-corrosion model. Five types of thermoporoelasticity tests were designed to determine seven of the nine thermoporoelastic parameters required for the modelling of the thermoporoelastic response of rock. Tests were performed by applying increments of confining pressure, temperature or pore pressure on the rock specimen, and measuring the changes in confining pressure, specimen volume and pore pressure. The measured values of five parameters were found to agree reasonably well with the estimated values. (C) 2004 Elsevier Ltd. All rights reserved.