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FREE-FIELD MEASUREMENTS OF EARTH STRESS, STRAIN, AND GROUND MOTION
Rept. for Mar-June 1953
SANDIA CORP ALBUQUERQUE NM
Pagination or Media Count:
Earth cover provides protection to underground structures against the effects of air shock loading. Part of this protection may result from attenuation of stress with thickness of the cover. Measurements of vertical earth stress at three depths and at five ground ranges were made during Shots 9 and 10 of Operation UPSHOT KNOTHOLE to detect and evaluate stress attenuation with depth. A practical system for measuring free-field earth stresses and strains resulting from transient loads has been tested with sufficient thoroughness to establish its feasibility. Arrays of directionally sensitive earth stress and strain gages and accelerometers were installed 5 ft deep to record these parameters during Shots 1, 9, and 10 of UPSHOT KNOTHOLE. Duplicate instrumentation showed that stress measurements were reproducible with average deviations of 16 per cent and strain measurements with average deviations of 35 per cent.
APPROVED FOR PUBLIC RELEASE