the 2006 Doctor Who episode The
Impossible Planet (which I've been watching
again on DVD), an entire section of the Sanctuary Base collapses,
causing the TARDIS to fall down a crevasse into the heart
of the planet, apparently stranding the Doctor and Rose.
However, when the Doctor finds the TARDIS in the pit in the
next episode, The Satan Pit, there is no sign of debris
from the base, which should have fallen down there with it.
In any case, as the pit was until recently closed, there is
no way that the TARDIS could have ended up down there.
it is an impossible planet, after all!
Seriously, though, it's possible that the TARDIS was carried
down a narrow shaft branching off from the crevasse - an access
point that was either hitherto unknown or didn't exist prior
to the shockwave.
More likely, the HADS (Hostile Action Displacement System
- as seen in The Krotons) was activated. This system
enables the TARDIS to react to external threats and dangerous
local conditions by dematerialising and relocating to a safer
site nearby. This would also explain the ship's upright position
and the lack of wreckage from storage bays 5-8 of the base.
As an intelligent and four-dimensional entity, the TARDIS
might even have chosen its landing spot, to help the Doctor
out of a devil of a stew.