Mechanical properties of inclined frictional granular layers

We investigate the mechanical properties of inclined frictional granular layers prepared with different protocols by means of DEM numerical simulations. We perform an orthotropic elastic analysis of the stress response to a localized overload at the layer surface for several substrate tilt angles. The distance to the unjamming transition is controlled by the tilt angle $\alpha$ with respect to the critical angle $\alpha_c$. We find that the shear modulus of the system decreases with $\alpha$, but tends to a finite value as $\alpha \to \alpha_c$. We also study the behaviour of various microscopic quantities with $\alpha$, and show in particular the evolution of the contact orientation with respect to the orthotropic axes and that of the distribution of the friction mobilisation at contact.