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Geotechnical validation of pre-dug, backfilled egress concept.
Barton-N; Bush-DD; Bakhtar-K
NTIS: PB/85-163608, 1983; :1-179
Large-scale tests were conducted on quartzitic gravel and crushed sandstone to investigate pertinent geotechnical properties for backfill support of egress shafts. Such shafts are envisaged for rapid launching of deep-based missiles. The backfill support is designed to resist shaft closure under dynamic loading and must also drain rapidly to a lower catch chamber to allow launching. Large-scale tilt shear tests were performed to measure the internal shear strength of the two backfill materials. Shaft filling and emptying tests were conducted in a 12-ft-deep, 3-ft-diam model section of shaft drilled in sandstone. One-half of the model was smooth bored, the other half was rough surfaced to represent drill and blast surfaces. Vertical and horizontal pressure cells indicated that stress only built up during the first 1 to 1-1/2 diam of filling, owing to the high sidewall friction of 38 deg for the rough shaft and 31 deg for the smooth shaft. Interface sliding tests were performed to confirm these figures. Static and dynamic deformation tests were also performed and indicated moduli as high as 56,000 psi, which will give excellent shaft support. Both the shaft support characteristics and the ease of emptying of gravel look particularly promising.
Quartz-dust; Rock-mechanics; Geology; Environmental-technology; Environmental-engineering; Environmental-control; Structural-analysis
CP; Final Contract Report
NTIS Accession No.
Terra Tek, Inc.
Page last reviewed: September 2, 2020
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