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The potential seismic risk for an underground nuclear waste repository will be one of the considerations in evaluating its ultimate location. However, the risk to subsurface facilities cannot be judged by applying intensity ratings derived from the surface effects of an earthquake. mining circles that the damage caused by an earthquake is significantly less in the subsurface than it is at the surface; mines have operated f o r a substantial period of time in some of the most seismically active regions of the world. It is common knowledge in If the smaller damage effects of earthquakes in the subsurface are to be used in assessing the hazard to an underground nuclear waste repository, then a quantitative data base is needed to replace the general precept that earthquake damage is minimal to nonexistent in the subsurface. The purpose of this study was t o develop such a quantitative data base. A literature review and analysis were performed to document the damage and non-damage due to earthquakes to underground facilities. Damage from earthquakes to tunnels, mines, and wells and damage (rock bursts) from mining operations were investigated. Damage from documented nuclear events was also included in the study where applicable.

A small number of heated block tests have been performed, with the objective of determining the usefulness of large-scale field testing in site characterization for an underground nuclear waste repository. These tests have been research oriented, involving independent control of the state of stress and temperature in a specimen of rock having a volume of 8 m3. The heated block test is a logical candidate to obtain information on repository design and licensing, particularly for validating predictive repository model performance. A description is given of the preparation, field work, and analysis that comprised the heated block tests at the Colorado School of Mines (CSM) experimental mine and G-tunnel on the Nevada test site. These demonstrations of the heated block test showed that additional refinement is possible and especially that the method was effective in gathering meaningful data not obtainable by any other means. Such data included the apparent coupling of the effects of independently controlled stress and temperature on the deformation behavior of jointed rock, and on the conductivity of a single fracture to injected water.

We describe a new technique for measuring the deformation and load bearing capability of large intact and jointed in situ rock specimens under applied uniaxial stress. The specimen configuration is an equilateral triangular prism of constant cross section with one end still connected to the rock mass. The free end of the specimen is loaded by a triangular flat-jack package. Displacements are monitored along and across joints; strains are measured on the surface of the specimen. Forty-six tests have been performed at five sites on solid and jointed specimens over a range of effective diameters from 6 to 50 in.; on surfaces with orientation ranging from horizontal to nearly vertical; and on a wide variety of rock types including granites, sandstones, amphibolites, and chloritic schists. The technique has been used to measure the effect of specimen size on the strength of intact rock and frictional characteristics such as maximum and residual shear stress, normal and shear stiffness, and friction angle on natural joints with surface areas up to 750 square inches.