PLACEMENT EFFECTS ON GROUND SHOCK INSTRUMENTATION.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MISS
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During the past decade, numerous explosive field tests have been conducted using a variety of instruments to record ground shock due to dynamic loadings. These instruments have generally been placed sequentially in boreholes which were backfilled using various materials and placement techniques. To assess the influences these techniques can exert on embedded gages, a series of wave propagation tests were conducted as the U. S. Army Engineer Waterways Experiment Station in the Small Blast Load Generator. Four placement techniques were studied to cover a range of placement conditions used in field practice. The first, gage placement concurrent with specimen construction, is applicable only to laboratory or small-scale tests and was used primarily as a reference for the other placement methods. The other methods involved the placement of gages in boreholes and backfilling with the following materials the excavated in situ material, a property-matching artificial soil, and a dense, rained sand. Because of their sensitivity to placement, primary emphasis was put on soil stress gages. A limited number of motion gages were also used. The results of the study indicated that the borehole material properties must reasonably match those of the local in situ material to ensure that the measurements are truly representative of the actual free-field ground shock. As a result of this study, the artificial soil backfill technique was used for instrument placement in deep field holes on the HEST Test V experiment.Author
- Test Facilities, Equipment and Methods