High pressure / High Temperature Geomechanical Triaxial Test Cell with Integrated Pore Pressure Monitoring and Acoustic and Strain Transducer Arrays

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The research program to be supported is that of Dr. Diederichs at Queen's University and involves early damage detection in rock under confined, high temperature loading. The equipment being requested here will form an important cornerstone in the experimental work related to excavation damage around shafts, tunnels and caverns designed for long term storage of nuclear waste. The long term stability and limiting permeability of the host rocks for such a repository depend on controlling the levels of damage development around the excavations during construction, operation and over the long term life of the repository. This long term phase includes temperature and porepressure influences. Long term lower bound strength of massive rock has been linked with the measurable onset of observed damage at intermediate stress levels enroute to ultimate failure. This damage threshold and the subsequent damage propagation within the sample can be monitored with highly accurate strain measurement during testing or with acoustic monitoring ("listening" for micro-acoustic emissions associated with cracking). Of particular interest in terms of fundamental research, however, is the dependency of damage initiation stress thresholds on confining stress, temperature and pore pressure of rocks. These conditions are to be expected during the containment lifespan of an Ontario-based waste repository. Possible candidate rocks include granitic rocks, limestones, shales and possibly massive metamorphic complexes. These rocks are expected to behave differently under the expected repository conditions, necessitating investigation of the type proposed here. The equipment requested integrates all of the monitoring needs into one purpose built system and provides a unique and highly controlled testing environment.