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The permeability of sandstone was measured in triaxial tests. Within the range of confining pressures used here, permeability as a function of differential stress was found to decrease until a minimum value was reached at about 60–70% of the fracture strength, i.e., at a stress that lies between the crack-initiation stress and the stress corresponding to the volumetric strain reversal. Thereafter, permeability started to rise, and at about 85–90% of the fracture strength its rate of increase was greater. The permeability method was not sensitive enough to mark the point of crack initiation and the onset of crack coalescence. However, differential stress versus volumetric strain curves were, in general, similar to differential stress versus permeability curves. Thus, the permeability method can be successfully used to study the fracture mechanism of rocks.

This report presents a preliminary evaluation of design concepts for the eventual sealing of the shafts, drifts, and boreholes at the Waste Isolation Pilot Plant Facility. The purpose of the seal systems is to limit the flow of water into, through, and out of the repository. The principal design strategy involves the consolidation of crushed or granular salt in response to the closure of the excavations in salt. Other candidate seal materials are bentonite, cementitious mixtures, and possibly asphalt. Results from in situ experiments and modeling studies, as well as laboratory materials testing and related industrial experience, are used to develop seal designs for shafts, waste storage panel entryways, non-waste containing drifts, and boreholes. Key elements of the ongoing experimental program are identified. 112 refs., 25 figs., 1 tab.