It is a common occurrence to hear miners talk of gas cutting the roof and
causing it to weaken; however, this condition is seldom encountered. There
are some seams where gas does cut the roof, generally where top coal is
left in gassy seams. The most common cause of roof cutting is its exposure
to air. Gunite or painting of the top helps a condition of this kind.
Kentucky
Various hydraulically operated mechanized machines designed to install
roof bolts. Two workers can install up to 200 bolts per shift. Units are
available in both standard and special design to satisfy requirements in
different mines. Best, 1
A roof that is tenacious and when allowed to fall breaks down in large
blocks or frames of stone. Peel
The wedging of a loaded wagon or horse against the top of an underground
passage. Fay
In West Wales, a small, steeply inclined stone drivage from a lower to an
upper coal seam or for exploration in disturbed ground. Syn:roof-up
Nelson
A screw- or pump-type extension post used as a temporary roof support.
BCI
a. Uniformly thick layer of rock supported or clamped at the edges by
pillars. Obert
b. A layer of combustible gas under the roof of mine workings.
BS, 8
See:romometer
A downward projection of country rock into an igneous intrusion.
CF:cupola
The pressure that the overlying rocks exert on the support of mine
workings. See also:ground pressure
Rock forming the ceiling of a cave passage, underground chamber, mine
opening, etc. AGI
The layer or seam of shale occurring immediately above the Pittsburgh coal
seam. Because of its friable nature, this shale or slate is taken down in
most mining operations. Rice, 2
A survey station fixed in the roof of a mine roadway or working face.
BS, 7
Scot. The stone immediately above a coal seam. See also:roof
Fay
Used in a weak or scaly top in narrow rooms or entries that have short
life. It is done by placing lagging bars running parallel with the working
place above the header. It has limited uses because of necessary
additional height and because its weight rests on the center of the
header. See also:stringer
In the simple testing of the roof, it is struck by a hammer or a heavy
object. A loose roof will give off a dull or hollow sound compared with a
solid top, which has a clear ring. Good roof that has a clear ringing
sound is called "bell top." Also known as sounding, sounding the roof,
sounding the top, and jowling. Syn:top testing
Usually a wooden pole with a metallic ball at the upper end.
The deformation of the coal or ore pillars is estimated by monitoring the
closure of the entry. This roof-to-floor convergence is generally measured
with a tube extensometer, to an accuracy of 0.001 in (25.4 mu m), or a
tape measure, to an accuracy of 0.01 ft (3.048 mm). Measurements are
repeatedly taken as the mining geometry changes. SME, 1
See:roofing hole
A term applied to a vein worked overhead.
a. A place abutting an entry or airway where coal or ore has been mined
and extending from the entry or airway to a face.
b. A wide working place in a flat mine corresponding to a stope in a steep
vein. A chamber. CF:stope
c. A heading or short stall.