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The state of packing of a mass of sand grains is described by its relative porosity nr which defines the packing relative to maximum and minimum porosities of the material. These limiting porosities depend in turn upon the physical characteristics of the grains themselves. In the research described herein, the influence of grain shape and size upon the limiting porosities of quartz sands and glass ballotini was studied.
The maximum porosities were determined by deposition of the sample through water as suggested by Kolbuszewski (1948) while minimum porosities were obtained by vibration under water. Shape parameters for the sands were determined from a correlation between the time of flow of a 0.5-kg specimen and the sphericity measured by examination of individual grains.
Both maximum and minimum porosities decreased with increasing sphericity while tests on glass ballotini indicated that the effect of grain size was negligible. The porosity interval was approximately 12.5 percent for all the sands and 11 percent for spherical ballotini. Mixtures of sand and ballotini gave reasonable agreement with the trend shown by the separate materials.
cohesionless soils, density (mass/volume), vibration, measurement, classifications, sands
Lecturer in Civil Engineering, The University of Liverpool,