In the Stargate series, now and again members of SG-1 comment that other worlds can bury their Stargate in order to deter the Goa'uld attack from the gate.
In the Stargate Movie Continuum, when one of Ba'al's clones activate the Stargate that was on the Ship, we see it dematerialize the side of the ship as a result from the wormhole opening. This would suggest that even if a Stargate was buried, if it was activated, it could dematerialize the ground.
So how deep would one need to bury the Stargate to deter an attack from the gate? Not just Goa'uld attacks, but any other antagonistic race including humans (on the assumption that some humans start thinking of themselves as gods and try to subjugate lesser races which one SG Team did try in season 1 (assuming the role of a god, forcing the locals into servitude)).