Ground Acceleration Measurements

Maximum vertical, radial, and transverse ground accelerations induced by air blast as measured at various distances on Operation TUMBLER are reported. Self-recording accelerometers were used as a secondary measuring instrument to back up the electronically operated system. The gages were mounted at a 5 ft depth on a cube of concrete grouted into the undisturbed soil. Results indicate that a considerable part of the energy entering the ground was absorbed within the first 5 ft. In Shots 1, 2, and 3, the beginning of the Mach region was clearly defined by the difference in vertical acceleration readings between two adjacent stations. No indication of the formation of the Mach region was evident on Shot 4 as the Mach was formed before reaching the first station. Agreement between results obtained with the self-recording gages and the electronic accelerometers is within the 30% limit of error reported. Report on Operation Tumbler, Nevada Proving Grounds, April-June, 1952, Project 1.6.