The 500-Ton event called DIAL PACK was conducted on 23 July 1970 at the Defence Research Establishment Suffield (DRES)- an isolated, 1000 square mile area in Alberta, Canada consisting entirely of barren prairie. It was a completely spherical ball of 32.6 pound blocks of cast TNT. The sphere was nearly 27 feet in diameter or almost as tall as a four story building. The lower third was encased in styrofoam to support it.
A modified section of an underground communication building was constructed at the Defence Research Establishment, Suffield, and experiments were conducted to determine blast-valve performance, overpressures in the air shaft and down-stream plenums, and overpressure damage to air ducts. The air ducts were installed in order to give an indication of the expected damage to air-conditioning equipment which would be caused by overpressure pulses. The experiments were conducted in the PRAIRIE FLAT and DIAL PACK Events. Both experiments employed 500 tons of TNT to produce the blast effects.
In the DIAL PACK event, the test structure was engulfed by a 12-psi blast overpressure. A louver blast valve and a lighter weight blast shutter were both blast closed. Air ducts behind the louver valve were only slightly indented, and those behind the blast shutter were undamaged.
The DIAL PACK Event of the MIDDLE NORTH Series, Bell Laboratories Project LN-318, involved the evaluation of the blast-induced response of the SA Manhole. The SA Manhole was a full-size, segmented, precast-concrete hardened structure, to be used by the Long Lines Department of American Telephone and Telegraph Company, to house electronic repeater equipment. Testing was designed to determine the extent of cracking, equipment environments, and overall structural response.
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