A model for the design of rockfall protection sandwich structures is presented and evaluated using results from real-scale experiments. The experiments consist of the impact by a 260 kg spherical projectile on a structure composed of gabion cages filled with coarse materials in the front part and fine granular material in the kernel part. This structure stands against a rigid concrete wall. The model allows accounting for the mechanisms occurring in the individual layers of the structure. The comparison between the simulations and the experiments shows that the model correctly predicts the time evolution of the force on the projectile. However, the model partially accounts for the time evolution of the stress on the rigid concrete wall due to the simplicity of the formulation of the constitutive model used to characterize the kernel layer.