Analysis of the densification of a vibrated sand packing.

International audienceTwo techniques have been used to analyze the densification of silica sand by horizontal sinusoidal vibrations of frequency f = 50 Hz for relative accelerations between 0 and 6: the quantitative analysis of motion observed through the transparent wall, and the altitude map of the free top surface of the sample. The first technique was used to analyze the transient regime: during the fust 10 s, slight densification occurs at the bottom of the powder bed, while the upper part enters convective notion and the intermediate part reaches densities higher than 66%. The second technique allowed to quantify the evolution of the overall density vs. acceleration f during the steady regime (dynamic density) and after the vibrations (relaxed density): a maximum density is observed in both cases for an optimal acceleration which depends on the initial height of the powder bed. These results are analyzed and discussed

Parametric study of horizontally vibrated grain packings Comparison between Discrete Element Method and experimental results

International audienceNumerical and experimental studies have been undertaken to analyze three parameters controlling the compaction of granular media submitted to sinusoidal horizontal vibrations. We have characterized the influence of the dimensionless acceleration Gamma, the geometry of the container and the friction coefficients on the grain velocities and on the packing densities. Above a critical acceleration Gamma(crit), the velocities increases with Gamma. For low values of Gamma, the surface layers are compacted, whereas the bottom layers remain at their initial density. For high values of Gamma, the bottom layers get compacted, the surface layers are fluidized so that the bulk dynamic and relaxed densities decreased. In the same way, the effect of the dimensions of the container and of the friction coefficients on the packing properties has been studied for given heights of sand, acceleration and frequency. It has been shown that the influence of the two last parameters is similar to that of acceleration. The numerical results given by the Discrete Element Method appear to be in good agreement with experimental results

Densification of a 3D granular bed by horizontal vibrations

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