  This paper deals with the vibration of granular materials due to cyclic
external excitation. It highlights the effect of the acceleration on the
settlement speed and proves the existence of a relationship between settlement
and loss of contacts in partially confined granular materials under vibration.
The numerical simulations are carried out using the Molecular Dynamics method,
where the discrete elements consist of polygonal grains. The data analyses are
conducted based on multivariate autoregressive models to describe the
settlement and permanent contacts number with respect to the number of loading
cycles.
