Geologic and Engineering Properties Investigations
Abstract
The Dugout event was a row cratering experiment in which five 20-ton nitromethane charges spaced 45 feet apart at depths of 59 feet in dry basalt were detonated simultaneously. The explosion produced an apparent crater about 135 feet wide, 285 feet long, and 35 feet deep. Preshot and postshot NX core and calyx hole drilling, trenching, laboratory analysis of core samples, and analysis of photographs have revealed preshot structure, the extent and characteristics of the ejecta and fallback, the zone of blast fracturing, the zone of bulking, and a sheared zone. As revealed by preshot drilling, the upper basalt layer consists of about 40 feet of vesicular basalt overlying, with a gradational contact, about 50 feet of dense basalt. The vesicular basalt has been subdivided into four types on the basis of vesicle content and fabric. From 2 to 14 feet of silt overlies the bedrock. Unconfined compressive strength for 6 samples ranges from about 7,000 to 17,000 psi. Samples of dense basalt tested triaxially show a greater increase of strength with confining pressure than does a sample of vesicular basalt. Dynamic laboratory tests gave a compression wave velocity of 16,000 ft/sec for dense basalt and about 13,000 ft/sec for slightly vesicular basalt, and they indicated that Poisson's ratio averages about 0.25.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 24, 1964
- Accession Number
- ADA382354
Entities
People
- R. J. Lutton