Project's officer's final report : Operation Distant Plain, Events 1, 2A, 3, 4, and 5. Project 3.02A, Earth motion and stress measurements
Ingram, James K.
Technical reportAbstract: Ground motions and stresses within the upper 10 feet of soil were measured on the Distant Plain events detonated in Canada in 1966-67. Events 1, 2A, 3, and 5 were detonated at the Drowning Ford Test Site, Defence Research Establishment, Suffield (DRES), Alberta, Canada. Event 4 was detonated at a remote mountainous site near Hinton, Alberta. Ground motion measurements were unsuccessful for the aboveground detonation (Event 1). Motion data of good quality were obtained for the remaining detonations of the test series (Events 2A, 3, 4, and 5). Acceleration and velocity measurements were made in the vertical and horizontal directions. In addition, a limited number of vertical stress measurements were made. Sixty-four data channels were successfully recorded on Event 2A, 32 for Event 3, 35 for Event 4, and 33 for Event 5. Data waveforms, except for Event 4, are included in Appendix A. Event 4 waveforms are included in Chapter 5. Detonation of the surface gas bag, Event 2A, produced no crater. Airblast-induced ground motions for this event were greater than for Distant Plain Events 3 and 5 and Flat Top II and III. This was the result of significant explosive energy going directly into airblast formation rather than partitioning to the ground through crater formation. Distant Plain Events 3 and 5 and Flat Top II and III were identical in yield and geometry, but differed in site location. An additional variant was introduced by Distant Plain Event 5 which was detonated in frozen ground. In spite of these variations, the ground motions were -s-imilar in amplitude and waveform. The variances between Distant Plain Event 3 and Flat Top are attributed to slight differences in test site soils, explosive coupling, and instrument canister placement. The effect of the frozen ground on Distant Plain Event 5 motions was generally limited to the horizontal vector near the surface. This was manifested as higher amplitude and frequency accelerations than for unfrozen ground. The thin frozen surface layer allowed greater coupling of the high-frequency components which are attenuated by dry alluvium. Distant Plain Event 4 primary ground motions in the region of tree 4 blowdown were down and away from the point of detonation at early times, then upward due to elastic rebound and., later, refracted energy from depth. Measured upthrust motions were small in the region instrumented and did not contribute significantly to the blowdown process.
Weapons Effects Laboratory (U.S.)Engineer Research and Development Center (U.S.)
Distant Plain (Operation); Explosion effects; Ground motion; Soil stresses
Technical report (U.S. Army Engineer Waterways Experiment Station) ; N-71-3.
Approved for public release; distribution is unlimited.