Mineral dust resuspension under vibration: Onset conditions and the role of humidity

Abstract

he vibration of dusty surfaces inevitably causes re-entrainment of particles into the atmosphere. Given that movement of mineral dust particles deposited on a surface begins at a critical frequency (fc) and amplitude, an experimental laboratory study was conducted to determine the onset conditions for resuspension of a vibrated granular soil. We determined the resuspension state diagram as a function of frequency and amplitude of a sinusoidal vibration, the granulometry of the dust and the thickness of the soil bed. The mitigation effect of humidity was also evaluated. Critical frequencies ranged between 2.5 and 23 Hz when amplitudes were less than 12 mm. These results were independent of bed thickness and perturbation type. For all particle sizes observed, fc decreased monotonically with A, contrasting with behavior observed for individual particles. In dry samples, fc for large size classes was markedly less when A was greater than 6 mm; while the fc for fine fractions only decreased once amplitudes reached 10 mm. Experiments with wet granular soils demonstrated that wetting above an optimum humidity did not necessarily impede movement and caused agglomeration. This study provides guidelines for managing resuspension of granular soils subjected to vibrations.