Ground Shock Attenuation for Deep Basing in Saturated Layered Geologies.

Abstract

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., ma x a 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.