Cellular sandwich structures constitute efficient technological solutions to protect elements at risk from rockfall hazard. The design of these structures is for the most part empirically based which does not allow optimization. The mechanical behaviour of a cellular structure is investigated using a multi-scale approach: from the individual layers of the structure made up of rocky particles contained in wire netting cages, fine granular material and reinforced embankment, to the entire structure which is an assembly of these different layers. A computational tool based on discrete modelling of the structure is developed for design purposes. Information is gathered from experiments at the layer scale to calibrate the parameters of the structure model. These experimental results are also used to evaluate the capability of the model to provide relevant results for the impact of falling rocks on the structure.