FREQUENCY SPECTRUM METHOD FOR ANALYZING GROUND-MOTION DATA PRODUCED BY SINGLE AND MULTIPLE VIBRATORY SOURCES
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS
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Tests were conducted to investigate controlled single and multiple source vibrations induced in an earth media with the primary objective of evaluating the benefits afforded by two data reduction techniques in identifying the frequency and amplitude composition of the ground motion at selected locations. Single signals of known frequency and force level were induced to the ground surface by three types of vibrators mounted on a 10-ft-diameter concrete base. The resultant particle velocities were measured triaxially at each of four locations on the base and 15, 35, and 90 ft from the base. After the single source tests, the vibrators were operated simultaneously as a multiple signal source input. Data were again recorded at the same locations. Special tests were then performed with two electrodynamic vibrators on the ground surface operating both singly and simultaneously. Results indicate conclusively that highly accurate correlations can be made. The test results also showed that correlations between known input signals from single sources can be directly compared with multiple signals at corresponding frequencies and force levels.
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