  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.
