  We numerically investigate the problem of the propagation of a shock in an
horizontal non-loaded granular chain with a bead interaction force exponent
varying from unity to large values. When $\alpha$ is close to unity we observed
a cross-over between a nonlinearity-dominated regime and a solitonic one, the
latest being the final steady state of the propagating wave. In the case of
large values of $\alpha$ the deformation field given by the numerical
simulations is completely different from the one obtained by analytical
calculation. In the following we studied the interaction of these shock waves
with a mass impurity placed in the bead chain. Two different physical pictures
emerge whether we consider a light or a heavy impurity mass. The scatter of the
shock wave with a light impurity yields damped oscillations of the impurity
which then behave as a solitary wave source. Differently an heavy impurity is
just shifted by the shock and the transmitted wave loses its solitonic
character being fragmented into waves of decreasing amplitudes.
