Precision controlled vertical actuator for advanced hydro-thermal coupled confined and long term testing for nuclear waste repository geomechanics

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Dr. Diederichs at Queen's University is involved in research related to damage detection and prediction in rock under a variety of loading and boundary conditions as a predictor for long term performance adjacent to and around underground nuclear waste repositories. The equipment being requested here will form a critical 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. Long term lower bound strength of massive rock has been linked with the measurable onset of observed damage at intermediate stress levels on the way to ultimate failure. This damage threshold and the subsequent damage propagation within the sample can be monitored with highly accurate load and strain control through monotonic or cyclic stress/strain path testing. The tests to be performed during the course of this research require a full time dedicated actuator/load frame with a high level of customizable control and flexible physical configuration options including the capability to integrate with a state-of-the-art confinement cell acquired previously for this work and the future direct shear and fracture testing. The equipment requested here is a servo-controlled loading frame with high capacity, high-stiffness and state of the art digital control technology that makes it possible to conduct unconfined compression, triaxial, post yield, direct and indirect tension, creep and fracture toughness measurement tests and cycled strain/load tests. The system has leading edge controller, application software and high-flow, high-response servo-hydraulics (valves) allow for manipulation of the control loop using any combination of feedback signals (ie: axial load, stroke and strain, circumferential strain, onfining fluid intensifier pressure and stroke, pore fluid pressure, etc). Within the next 4 years at least 10 graduate students will use the system within the context of the research discussed but also in a secondary capacity in a number of other projects.