Vibrocompaction properties of dry sand

The fundamental understanding of the behavior of dry sand as it is being vibrated is necessary to properly address a number of engineering issues such as the vibrocompaction process. The present paper first summarizes experimental works focusing on the effects of vibrations on the volume change of dry cohesionless soils. Original experiments characterizing the behavior of dry sand subjected to vertical vibration are then presented. The volume change and the motion pattern displayed by vertically vibrated sand particles are discussed. When cohesionless soil, placed in a cylindrical container, is vertically vibrated under the gravitational field (g), experiments performed on dry Fontainebleau sand allow to distinguish three types of dynamic behaviors, depending on the acceleration amplitude (a): the densification behavior (a/g 1). In the densification range, the sand simply settles. When the acceleration amplitude is increased beyond 1g, granular convection is observed and there is an instability in the sand mass leading to the emergence of an inclined free surface. If the acceleration amplitude is further increased, the free surface progressively flattens. There is an impressive dilatation of the whole sample and grain saltation is observed. The sand becomes fully vibro-fluidized. The efficiency of the vibrocompaction process is finally discussed especially with regard to these dynamic behaviors.