A raise borer is a machine used in
underground mining
Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic vi ...
, to excavate a circular hole between two levels of a
mine
Mine, mines, miners or mining may refer to:
Extraction or digging
* Miner, a person engaged in mining or digging
*Mining, extraction of mineral resources from the ground through a mine
Grammar
*Mine, a first-person English possessive pronoun
...
without the use of
explosives.
The raise borer is set up on the upper level of the two levels to be connected, on an evenly laid platform (typically a concrete pad). A small-diameter hole (
pilot hole
In construction, a pilot hole is a small hole drilled into a piece of construction material. Its purpose may be:
#to guide a larger drill to the appropriate location and ease the job of the larger drill
#allow for the insertion of another hole-m ...
) is drilled to the level required; the diameter of this hole is typically 230mm - 445mm (9" - 17.5"), large enough to accommodate the
drill string. Once the drill has broken into the opening on the target level, the bit is removed and a
reamer
A reamer is a type of rotary cutting tool used in metalworking. Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides. There are also non-precisio ...
head, of the required diameter of the excavation, is attached to the drill string and raised back towards the machine. The drill cuttings from the reamer head fall to the floor of the lower level. The finished raise has smooth walls and may not require
rock bolt
A rock bolt is a long anchor bolt, for stabilizing rock excavations, which may be used in tunnels or rock cuts. It transfers load from the unstable exterior to the confined (and much stronger) interior of the rock mass.
Rock bolts were first use ...
ing or other forms of ground support. One impressive use of raise boring is the 7.1 m diameter shafts for Sasol's Middelbult and Bosjesspruit Mines in South Africa.
The ''boxhole borer'' (or machine roger) is a variant of a raise borer that is used when there is not enough space on the higher of the two levels to be connected. The boxhole borer is set up on the lower level, drills a pilot hole as a guide, then drives the reamer bit along the pilot hole from the lower level to the upper. Precautions have to be taken to redirect falling drill cuttings away from the machine, and to reinforce the drill string.
See also
*
2010 Copiapó mining accident - Rescue
References
External links
Dictionary of Mining, Mineral, and Related Terms Mining equipment
Underground mining
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