Characterization of drained and undrained response of thermally loaded repository rocks
The fluid pressure and mechanical response of a potential repository rock to heating is shown to be characterized by the isothermal parameters of the classic stress-strain theory for a porous medium, in combination with some nonisothermal parameters describing the fluid, solid, and pore volume expansivities. The isothermal coefficients are described in terms of easily interpretable parameters by noting that the fluid response can be formulated within the limits of drained and undrained behavior. The low permeability-high thermal conductivity environment generally considered to be ideal for nuclear waste storage would appear to favor an undrained response, at least within the isolate pores and cracks of a fractured rock medium. Several cases are presented that provide a qualitatively correct demonstration of the effects of heating in this environment. These include fluid pressure increases in excess of temperature-induced increases in in situ stress, elastic strain and the potential for inelastic crack propagation, and porosity-permeability augmentation. If the rocks are dry, or of a high permeability such that fluid flow takes place at constant fluid pressure, similar rock material alterations are possible. This follows from the fact that when the temperature is raised to some high value, say 80/sup 0/ or 90/sup 0/C, and then decreases to its ambient value, the final volume of a polycrystalline substance will generally be greater than the initial one. Hence the effect of temperature is irreversible because of the differential thermal expansion of the composite mineral grains and the generation of new grain boundaries. The increase in porosity during such a heating episode is calculable and empirically related to increases in permeability.
- Research Organization:
- Univ. of Illinois, Urbana-Champaign
- OSTI ID:
- 6919804
- Journal Information:
- Water Resour. Res.; (United States), Journal Name: Water Resour. Res.; (United States) Vol. 18:2; ISSN WRERA
- Country of Publication:
- United States
- Language:
- English
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12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
58 GEOSCIENCES
580300 -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
COMMINUTION
FRACTURING
HIGH-LEVEL RADIOACTIVE WASTES
MANAGEMENT
MATERIALS
MECHANICS
PERMEABILITY
POROSITY
RADIOACTIVE MATERIALS
RADIOACTIVE WASTE DISPOSAL
RADIOACTIVE WASTE STORAGE
RADIOACTIVE WASTES
ROCK MECHANICS
ROCKS
STORAGE
TEMPERATURE EFFECTS
THERMAL FRACTURING
UNDERGROUND DISPOSAL
WASTE DISPOSAL
WASTE MANAGEMENT
WASTE STORAGE
WASTES