a. Boreholes that are loaded and fired for the purpose of relieving or
removing part of the burden of the charge to be fired in the main blast.
b. Holes drilled closely along a line, that are not loaded, and that serve
to weaken the rock so that it will break along that line.
Syn: trim holes
c. Singular. A port or passageway through which the core, as it advances
into the inner tube of a double-tube core barrel, forces water out of the
inner tube to the outside of the barrel through the innertube head.
d. Singular. A borehole drilled ahead of underground openings to tap and
drain a water-bearing formation. Also called cover hole; pilot hole.
Dictionary of Mining, Mineral, and Related Terms