a. See:swelled coupling
b. Sometimes used in Canada as a synonym for reaming shell. Long
A borehole the diameter of which is excessive because of the whipping
action or eccentric rotation of the drill string and bit. Long
See:drill collar; guide rod.
See:springing
In strata control, describes an area where the force is concentrated on
pillars. This type of area is said to be overstressed or superstressed.
This superstressing is limited by the strength of the seam or pillar.
CF:destressed area
Similar to a Wilfley table but of diamond shape (rhomboid), thus
eliminating the waste corners. Liddell
Hauling over public highways, usually by a dump truck. Various
restrictions, such as weight, width of vehicle, safety features, guard
against spillage, etc. must be considered in the type equipment used.
CF:off-the-road hauling
A low-angle thrust fault of large scale, with displacement generally
measured in kilometers. CF:underthrust
AGI
See:overthrust nappe
See:overthrust
The body of rock that forms the hanging wall of a large-scale overthrust;
a thrust nappe. Syn:overthrust block; overthrust sheet;
overthrust slice. AGI
See:thrust plane
See:overthrust nappe
See:overthrust nappe
The period beyond the normal shift time when a worker, on request by the
management, performs emergency tasks that are necessary for safety or
efficient operation of the oncoming shift. Nelson
Flow of water over the top of a dam or embankment. Nichols, 1
See:overwind
An endless-rope system in which the rope runs over the tubs or cars in the
center of the rails. This system is generally adopted on undulating roads,
where the tension in a heavily loaded rope would cause the rope to lift in
swilleys and derail tubs. It is also generally adopted in highly inclined
roads, as the lashing chain, often adopted with this method of haulage,
obtains a good positive grip on the rope and is easier to detach than a
clip. The rope is kept from rubbing on roof supports by holding-down
pulleys: six or eight small pulleys are mounted in circular cheeks,
allowing chains or clips to be accommodated in the spaces between the
pulleys; or large diameter pulleys may be used, of the hat or mushroom
shape, often starred to provide recesses for chains and clips. Similar
large pulleys direct the rope around curves. CF:undertub system
Sinclair, 5
Said of a fold, or the limb of a fold, that has tilted beyond the
perpendicular. The sequence of strata thus appears reversed.
Syn:inverted; inverted fold; reversed. AGI
A type of skip commonly used at metal mines, but not as often at coal
mines, because of increased breakage. This skip consists of a rectangular
receptacle for the material and a suspending frame of bail to an upper
crosspiece of which is attached a suspension gear connecting the rope to
the skip. Three guide shoes are generally provided at each side of the
bail to keep it vertical. The skip body turns about a horizontal shaft at
the lower end of the bail. Two rollers on the upper part are mounted on a
shaft and cause the skip to tilt at an angle of 35 degrees at the tipping
point in the headgear, where rollers run onto the curved guides. To
prevent shocks in the case of an overwind the skips are fitted with
overwind guides which glide along rollers fitted to the headgear above the
tipping point. Sinclair, 5
Too much air in the mine workings. Fay