The types of barriers that characters may have to {dig} out of the
way include those that they can move with their bare hands, such
as piles of stone, earth, and other debris, as well as those that
require tools to move, such as solid walls of dirt && rocks.

Rubble

Loose rocks are a common enough obstacle in caves and
dungeons, especially older ones. The natural erosion that occurs
gradually causes material to fall from the ceiling to the floor. Also,
previous inhabitants may have pushed rubble into an area purposely,
using it as a dump.

If the rubble is loosely packed--i.e., there are individual
chunks of small rocks rather than one or two huge slabs, characters
should be able to clear their way through. Of course, there is
often no way to tell how much of the corridor may be blocked by
such debris.

In one turn of excavation, a character can clear 1d4 feet of
passageway to a width equal to the minimum passageway size
listed in Table 7. If the passage is only partially blocked, the distance
that can be cleared in a turn is increased to 2d4 feet.

Solid Barriers

Characters excavate solid barriers at the rates listed in Table 27: Mining Rates (on page 49).
These rates assume that the characters are using pickaxes to aid in the excavation. If other
metal tools, such as shovels or swords, are substituted, the rate
of excavation is only 1/4 of the rate listed.