Vibrocompaction properties of dry sand

Abstract

International audienceThe fundamental understanding of the behaviour 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 behaviour 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 the distinction between three types of dynamic behaviours depending on the acceleration amplitude (a): the densification behaviour (a/g < 1), the instability surface behaviour (a/g ≈ 1), and the vibrofluid behaviour (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 vibrofluidized. The efficiency of the vibrocompaction process is finally discussed especially with regard to these dynamic behaviours

Arbeitsintegrierte Verdichtungskontrolle während der Rütteldruckverdichtung

“…Weitere wissenschaftliche Arbeiten befassen sich mit den bodenmechanischen Prozessen im zu verdichtenden Boden. Insbesondere sind die Arbeiten von Rodger und Littlejohn sowie Denies et al hervorzuheben.…”

Ultrasonic compaction of granular geological materials

“…In the case of horizontal vibrations, the rate of compaction increases with respect to ultrasonic vibration acceleration amplitude, however it was reported that these parameters are independent for vertical vibrations [19]. Therefore, horizontal vibrations appear to generate a higher level of compaction than vertical vibrations.…”

“…The influence of the direction in which the vibrations are applied to the substrate has also been reported [9,14,19]. In one study, a test setup was manufactured to generate vibrations in the plane of the face of a cylindrical sample (horizontal) and in the axial (vertical) direction [9].…”

“…Therefore, horizontal vibrations appear to generate a higher level of compaction than vertical vibrations. In addition, it is known that for horizontal vibrations, the effect of acceleration amplitude decreases as the void ratio, which is a measure of the porosity in the sample, is reduced [19]. Applying ultrasonic vibrations has been found to be successful in reducing the number of voids in the production of white mineral trioxide aggregate (an endodontic cement), and also increases the density [15,16].…”