Ground Shock Attenuation for Deep Basing in Saturated Layered Geologies.
Abstract
Finite difference code calculations were conducted using the 2-D CRALE code to determine if distinct stratigraphic layering would substantially contribute to attenuation of stresses and motions at depth beneath large nuclear bursts over saturated geologies. Three geologies were examined: In Case 1, there were five distinct layers of soft rocks above the bedrock at 2300 ft. In Case 2, layers were homogenized to eliminate diffraction at interfaces. Case 3 was the same as Case 1, but with 1% hysteretic compaction in layers above the bedrock to simulate air entrainment. The burst was represented as a shallow-buried isothermal sphere containing 7.5 Mt of energy. The results show only minor differences between waveforms and peak stresses for the three cases. Peak stresses attenuated approximately as the square of the depth, i.e., omega max alpha D-2 (similar to attenuation observed in hard rock). Layering in media above the bedrock (Case 1) reduce stresses in the bedrock by only 10-15% (as compared with the homogenized media in Case 2). In the three cases, stresses above 1.5 kb were experienced to depths between about 3200 and 3800 ft. It is concluded that the effects of typical layering in saturated sedimentary soft rock layers will not substantially reduce peak stresses beneath near-surface bursts. Deep base facilities in such geologies would probably need to be placed at depths equivalent to those required in hard rock. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1980
- Accession Number
- ADA096352
Entities
People
- K. N. Kreyenhagen
- S. H. Schuster