Blast tests of expedient shelters

Oak Ridge National Laboratory field tests of expedient shelters during the past three years have resulted in the selection and development of six types of expedient shelters. These were demonstrated by construction exercises to be the most practical for average rural and small-town Americans to build in the principal environmental regions of the United States. Each type of shelter is designed to be built within 48 hours by average family groups of such Americans, using only widely available materials such as trees, to provide all members with high-protection-factor shelter. To evaluate the blast protection afforded by these six types of expedient shelters, they were blast tested as a part of Defense Nuclear Agency's Mixed bompany Event, in the blast area of a 500-ton TNT detonationequivalent in air blast effects to a 1.0 to 1.8 kiloton nuclear detonation. A total of twelve shelters, representing six expedient types, were subjected to blast effecta at surface overpressures ranging from 29 to 3 psi. All except the two Door-Covered Trench Shelters were tested as closed shelters. Only one shelter was damaged: the Door-Covered Trench Shelter that was tested as an open shelter at 5 psi. The six types of shelters. tested at the following measured surface overpressures, were: Two Small-Pole Shelters, at 29 psi; Three Wire-Catenary-Roofed Shelters, at 29 psi and 13 psi; One aboveground A-Frame Pole Shelter, at 17 psi; One Shored-Trench Stoop-in Shelter, at 13 psi; Two Log- Covered Trench Shelters, at 13 psi; and Two Door-Covered Trench Shelters, at 5 psi and 3 psi. Earth arching increased the strength of the shelters that had an adequate depth of earth cover relative to the roof span. A new design of quickly closable, expedient blast door was tested at 29, 17 and 13 psi surface overpressure ranges. Only the blast door at 17 psi was damaged, snd even it remained intact and securely closed. Also tested were two new designs of blast valves, both of which can protect against 100 psi overpressures and are closed in 1 to 2 milliseconds. One of these valves, the Overlapping-Flaps Blast Valve, requires only widely available materials and can be made in a few hours with common tools. (auth