Dynamic response of concrete arch bunkers : Event DIAL PACK, Project LN314A
McGrath, Robert K.
Technical reportAbstract: Event Dial Pack, a 500-ton TNT surface burst detonated at the Defence Research Establishment, Suffield, Ralston, Alberta, Canada, on 23 July 1970, provided an opportunity to test and collect data pertinent to the design of structures to resist the airblast overpressure and ground motions resulting from a simulated nuclear detonation. The objective of Project LN314A, discussed herein, was to determine the gross response of buried prefabricated concrete arch shelters subjected to a traveling airblast overpressure wave_. The particular concrete arch tested was originally designed and evaluated to resist conventional weapons and to meet certain requirements as to size, weight, ease of installation, and ease of transportability. Three 1/2-scale arches were tested at Event Dial Pack. One was located at 90 psi and two at 49 psi. The structures were buried in pits with a compacted soil below the footings and then backfilled with native soil with 2 feet of soil above the crown. The motion response of the structures was generally in the vertical direction. The vertical displacement was from 1-1/2 to 2-1/2 inches. Upon excavation and examination of the crack patterns, it was determined that the damage mechanism in all three cases was the same, only varying in degree. The structure at 90 psi showed the greatest damage and the structure oriented at 45 degrees at 49 psi showed the least. The arches showed evidence of flexural stresses at the haunch, which caused crushing on the intrados, and tension cracks on the extrados. Tension cracks were visible on the intrados at the crown and across the entire floor. The test results indicate that the protective structure with compacted soil below the footings and lightly compacted backfill can resist up to 90 psi with only slight damage. It is recommended that for planning and deployment purposes, the capability of the structure be established as up to 90 psi when no mechanical compacting equipment is used for soil placement. When mechanical devices are used for compacting the backfill material, overpressures approaching 100 psi can be resisted without excessive damage to the structure.
Weapons Effects Laboratory (U.S.)Engineer Research and Development Center (U.S.)
Blast effects; Bunkers (fortification); Concrete arches; Dial Pack (Event); Dynamic loads; Shelters; Underground facilities
Technical report (U.S. Army Engineer Waterways Experiment Station) ; N-71-8.
Approved for public release; distribution is unlimited.