Effects of Closing Blocks on Hazard Areas

A series of tests were conducted with reduced scale magazines to study the blast reduction effectiveness of closing blocks placed at the entrances of storage chambers of underground ammunition storage magazines. Five small-scale magazines were made of reinforced concrete to investigate design features affecting the effectiveness of closing blocks. Three intermediate-scale magazines were constructed in hard rock to know the effectiveness of the blocks in magazines larger than the small-scale ones in real rock. Pressure-time histories measured in the free field were analyzed, and the blast-hazard area of each magazine was calculated according to the procedures of DoD explosive safety regulation. In our small-scale tests, the relative hazard area was strongly dependent on the chamber loading density and the areal density of the closing blocks, showing that the relative hazard area decreases with increasing chamber loading density and with decreasing areal density. We made some assumptions on the motion of closing blocks of our small-scale tests. It was shown that the relative hazard area was reduced by the increase in the initial acceleration, which was inversely proportional to the closing time. We obtained the equation representing the relative hazard area as a function of initial acceleration. All three of the intermediate-scale magazines worked effectively: The hazard area for each magazine was reduced to about 10% of that calculated according to the procedures of the DoD safety regulation. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE AUG 1994 2. REPORT TYPE 3. DATES COVERED 00-00-1994 to 00-00-1994 4. TITLE AND SUBTITLE Effects of Closing Blocks on Hazard Areas 5a. CONTRACT NUMBER