Scot. A passage in a mine crosscut toward the dip of the strata.
Standard, 2
The firing of small explosive charges for releasing stuck drilling tools
in a borehole. The shock of detonation causes the joint to expand and
unscrew slightly. All rods above the joint can then be removed from the
hole. Nelson
The portion of a lode lying between a level driven in a lode and the
surface. See also:back
The ore between two levels which has to be worked from the lower level.
See also:back
a. Resistance transferred from rock into drill stem when bit is being fed
at a faster rate than the bit can cut. Long
b. Pressure applied to the underside of the piston in the hydraulic-feed
cylinder to partially support the weight of the drill rods and hence
reduce pressure on the bit. Long
c. Rock pressures affecting the uppermost portion or roof in an
underground mine opening. Long
The name given to the raking strut that transfers the load from the
timbering of a deep trench to the ground. These struts are provided under
every second or third frame according to the type of ground being
excavated. Hammond
See:back brusher
The taking down of a thickness of roof beds in roadways some distance back
from the face. The thickness of roof excavated may vary from 1 ft (0.3 m)
or so to 6 ft (1.8 m) and more. This work is necessary where there has
been a gradual reduction in height, as a result of roof sag, and opening
height must be maintained. See also:second ripping
The seaward return of the water following the uprush of waves. For any
given tide stage, the point of farthest return seaward of the backrush is
known as the limit of backrush or limit of backwash. See also:backwash
AGI
a. The height of ore available above a given working level. If the orebody
has been proved by shaft sinking to a depth of 300 ft (91 m) from the
surface, the orebody is said to have 300 ft (91 m) of backs.
See also:back
b. A quarryman's term for one set of joints traversing the rock, the other
set being known as cutters. Nelson
c. A system of joints in coal or stratified mineral oblique to the bedding
at an angle of 35 degrees to 75 degrees . See also:slips
BS, 11
d. Slips; used to denote a slip met with first at floor level.
Syn:hugger
Jointed rock structures, the backs (joints) of which run in lines parallel
to the strike of the strata, the cutters (cross joints) crossing them at
about right angles. Standard, 2
The emergence of radiation from that surface of a material through which
it entered. Also used to denote the actual backscattered radiation.
NCB
a. The afternoon or night shift; any shift that does not fill coal or is
not the main coal-production shift. Mason
b. N. of Eng. The second or middle shift of the day; varies from 9 to
10:30 a.m. until 4:30 to 6 p.m. in different pits. Trist
A shot used for widening an entry; it is placed at some distance from the
head of an entry. Fay
a. A sight or bearing on a previously established survey point (other than
a closing or check point), taken in a backward direction. AGI
b. A reading taken on a level rod held in its unchanged position on a
survey point of previously determined elevation when the leveling
instrument has been moved to a new position. It is used to determine the
height of the instrument prior to making a foresight. Syn:plus sight
Abbrev: BS. Ant: foresight. AGI
A mark or stake placed at some distance behind the position a drill will
occupy in a specific compass direction from the borehole marker for an
incline hole to enable the driller to set the drill and drill the borehole
in the intended direction. Also called back hub; backsight.
See also:picket
Newc. A leather covering worn by workers in wet workings.
A joint in a coal seam that is inclined away from the observer from floor
to roof. It would be a face slip from the opposite direction.
CF:face slip
a. S. Wales. A slope with the stalls branching off and working the seam
with back slips along the face. Nelson
b. In geology, the less sloping side of a ridge. Contrasted with
escarpment, or steeper slope; esp., the slope more nearly parallel with
the strata. Also called structural plain. Standard, 2
c. The term is used where the angle of dip of the underlying rocks is
somewhat divergent from the angle of the land surface. The slope at the
back of a scarp; e.g., the gentler slope of a cuesta or of a fault block.
It may be unrelated to the dip of the underlying rocks. Also spelled:
backslope. AGI
d. Syn:dip slope
The working of the top portion of a thick seam that was left as a roof
when the bottom portion was worked. The top coal is recovered by working
over the goaf or packs of the first working. See also:back work
Nelson