  In this work, we thoroughly investigate the impact process on the granular
media in the limit when the ratio of the impact velocity to the acoustic speed
becomes of the order of 0.01-1, which is far greater than the existing
literature (0.0001-0.001). We show that the energy dissipation is largely due
to the energy cost associated with the exploration between different metastable
states via large scale reorganization of the force chain network. In this
regime, the conventional drag force models break down, and the drag force can
not be decomposed into a depth dependent static pressure and a depth
independent inertial drag as proposed in the existing literature. The high
dynamical stress generates acoustic pulses, which propagate longer distances
rather than decaying exponentially, as observed in the previous works. In the
latter stage of the impact process, the boundary also plays an essential role
in the reorganization of the force chains as the reflected acoustic pulses
interact with the original impact pulses. Furthermore, we study the scaling of
the early stage peak forces with the impact velocity and find that spatial
dimensionality strongly influences the scaling.
