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Because vibration techniques are commonly used for the preparation of laboratory test specimens, this study was carried out to examine some of the factors which affect the densities obtained. A simple, one-degree-of-freedom vibrating table device, equipped for control of both amplitude and frequency, was used to give a sinusoidal wave form of vibration. Tests were carried out with four size ranges of sand and with single size glass balls, and observations were made on the effects of time of vibration, intensity of vibration, and container size.
Maximum relative densities were achieved at a single value of the maximum acceleration in each case, these densities increasing with time of vibration up to about 30 min. Only low states of compaction were obtained for some of the vibrated specimens, and in no case was 100 percent relative density achieved.
By far the most significant experimental results related to the variation of density throughout the vibrated soil specimens. This was investigated using a split cylinder, with four equal parts, which could be dismantled after vibration enabling separate density measurements to be made. Considerable density variations existed throughout the specimens at vibration intensities below the optimum value. Only where the average relative density was high was an approximately homogeneous specimen obtained. This fact is important to those concerned with the preparation of test sections in the laboratory.
vibration, compacting, tests, sands, density (mass/volume), porosity, cohesionless soils
Associate professor, Geotechnical Engineering, Asian Institute of Technology, Bangkok,