The paper presents a comparison between numerical simulations and experimental results for a biaxial compression test of a 2D disks assembly. The numerical method is based on "contact dynamics" (CD) which is briefly described. Two numerical samples are considered: the first one uses as data the measured positions of gains in an experimental apparatus, the second one is derived from the first one by numerical changes. The obtained results show that the numerical macroscopic behavior of the sample depends strongly on the chosen initial state (sample preparation). As far as local mechanisms of deformation are concerned, "CD" proves its ability to capture the experimentally observed localization of deformation in shear banding.