underground hard-rock mining


  • This method is similar to cut and fill mining with the exception that after being blasted, broken ore is left in the stope where it is used to support the surrounding rock
    and as a platform from which to work.

  • Declines are often started from the side of the high wall of an open cut mine when the ore body is of a payable grade sufficient to support an underground mining operation,
    but the strip ratio has become too great to support open cast extraction methods.

  • Typically, long hole mining requires two excavations within the ore at different elevations below surface, (15 m – 30 m apart).

  • [4] • Drift and fill is similar to cut and fill, except that it is used in ore zones, which are wider than the method of drifting will allow to be mined.

  • Selective mining methods[edit] • Cut and fill mining is a method of short-hole mining used in steeply dipping or irregular ore zones, in particular where the hanging wall
    limits the use of long-hole methods.

  • [4] • VRM/ VCR: Vertical retreat mining (VRM) also known as Vertical crater retreat (VCR) is a method where mine is divided in vertical zones[clarification needed] with depth
    of about 50 meters using open stoping, bottom-up mining.

  • [8][better source needed] Where caving does continue, the ground surface may collapse into a surface depression such as those at the Climax and Henderson molybdenum mines
    in Colorado.

  • There are six steps in development mining: remove previously blasted material (muck out round), scaling (removing any unstable slabs of rock hanging from the roof and sidewalls
    to protect workers and equipment from damage), installing support or/and reinforcement using shotcrete etceteras, drill face rock, load explosives, and blast explosives.

  • An orebody hosted in strong self-supporting rock may be mined by an open stoping method and an orebody hosted in poor rock may need to be mined by a cut and fill method where
    the void is continuously filled as the ore is removed.

  • [2] Production mining is further broken down into two methods, long hole and short hole.

  • As ore is removed from the drawbells the orebody caves in, providing a steady stream of ore.[4] If caving stops and removal of ore from the drawbells continues, a large void
    may form, resulting in the potential for a sudden and massive collapse and potentially catastrophic windblast throughout the mine.

  • Further consideration is needed for the strength of the ore as well as the surrounding rock.

  • They are also often built and maintained as an emergency safety access from the underground workings and a means of moving large equipment to the workings.

  • Using this method, mining is planned to extract rock from the stopes without filling the voids; this allows the wall rocks to cave in to the extracted stope after all the
    ore has been removed.

  • [6] [7] Bulk mining methods [edit] • Block caving is used to mine massive steeply dipping orebodies (typically low grade) with high friability.

  • There are several different methods of long hole mining.

  • This allows for greater recovery as less ore is left behind in pillars.

  • In many room and pillar mines, the pillars are taken out starting at the farthest point from the stope access, allowing the roof to collapse and fill in the stope.

  • A system of primary and secondary stopes is often used in VCR mining, where primary stopes are mined in the first stage and then backfilled with cemented fill to provide wall
    support for the blasting of successive stopes.

  • The primary sources of heat in underground hard rock mines are virgin rock temperature, machinery, auto compression, and fissure water.

  • In this case, the first drift is developed in the ore, and is backfilled using consolidated fill.

  • [3] Local ground support[edit] Local ground support is used to prevent smaller rocks from falling from the back and ribs.

  • This carries on until the ore zone is mined out to its full width, at which time the second cut is started atop of the first cut.

  • At the maximum depth of 9,889 feet (3,014 m) this mine is the deepest base metal mine in the world, and its low surface elevation means that the bottom of the mine is the
    deepest accessible non-marine point on earth.

  • Development mining is composed of excavation almost entirely in (non-valuable) waste rock in order to gain access to the orebody.

  • Short hole mining is similar to development mining, except that it occurs in ore.

  • Long-hole large-diameter holes are drilled vertically into the ore body from the top using in-the-hole (ITH)[5][clarification needed] drills, and then blasting horizontal
    slices of the ore body into an undercut.

  • Ventilation One of the most important aspects of underground hard rock mining is ventilation.

  • In deeper mines, the ore is dumped down an ore pass (a vertical or near vertical excavation) where it falls to a collection level.

  • Cable bolts are much larger than standard rock bolts and rebar, usually between 10 and 25 metres long.

  • [3] • Cable bolts are used to bind large masses of rock in the hanging wall and around large excavations.

  • Area ground support[edit] Area ground support is used to prevent major ground failure.

  • [3] They are: Mechanical bolts[edit] • Point anchor bolts (or expansion shell bolts) are a common style of area ground support.

  • Such a configuration is one of several to which miners apply the term “glory hole”.

  • They may also be started into the wall of an open cut mine 3.

  • In deep, hot mines ventilation is used to cool the workplace; however, in very cold locations the air is heated to just above freezing before it enters the mine.

  • High pressure water is injected into the bolt to expand the bolt diameter to hold the rock together.

  • Ore removal In mines which use rubber tired equipment for coarse ore removal, the ore (or “muck”) is removed from the stope (referred to as “mucked out” or “bogged”) using
    center articulated vehicles (referred to as boggers or LHD (Load, Haul, Dump machine)).

  • Only enough ore is removed from the stope to allow for drilling and blasting the next slice.

  • The dip of the orebody also has an influence on the mining method for example a narrow horizontal vein orebody will be mined by room and pillar or a longwall method whereas
    a vertical narrow vein orebody will be mined by an open stoping or cut and fill method.

  • Depending on the amount of overburden and quality of bedrock, a galvanized steel culvert may be required for safety purposes.

  • Ventilation is also used to manage underground temperatures for the workers.

  • The rebar used is of similar size as a point anchor bolt but does not have an expansion shell.

  • However, massive refrigeration plants are used to bring the temperature down to around 28 °C (82 °F).

  • Ore access[edit] Levels are excavated horizontally off the decline or shaft to access the ore body.


Works Cited

[‘o de la Vergne, Jack (2003). Hard Rock Miner’s Handbook. Tempe/North Bay: McIntosh Engineering. p. 2. ISBN 0-9687006-1-6.
o ^ Brazil, M. “Decline design in underground mines using constrained path optimisation” (PDF). math.uwaterloo.ca. Archived
from the original (PDF) on 2010-11-24. Retrieved 19 Jun 2023.
o ^ Jump up to:a b c d e f Puhakka, Tulla (1997). Underground Drilling and Loading Handbook. Finland: Tamrock Corporation. pp. 153–170.
o ^ Jump up to:a b c Puhakka, Tulla (1997). Underground
Drilling and Loading Handbook. Finland: Tamrock Corporation. pp. 98–130.
o ^ “Archived copy”. Archived from the original on 2017-02-02. Retrieved 2017-01-29.
o ^ “Vale Inco’s Creighton mine: Digging deeper by the day”. Viewpoint (3): 2. 2008.
Archived from the original on 2015-06-21. Vertical retreat mining (VRM) was introduced in the mid-1980s to replace the cut-and-fill mining method. The slot-slash mining method, a modified VRM, was introduced in the late 1990s and replaced the VRM
o ^ “Mining & Metallurgy 101”. www.miningbasics.com. Archived from the original on 2011-12-06. Retrieved 2017-01-27.
o ^ Fowler, J. C. W.; Hebblewhite, B. K. (2003). “Mining publication” (PDF). New South Wales. Archived (PDF) from the
original on 2006-09-20. Retrieved 2007-05-30.
o ^ http://www.mineweb.com/archive/greGreener underground mining[dead link]
o ^ “TauTona, Anglo Gold, South Africa”. 2009. Archived from the original on 2019-05-12. Retrieved 2009-05-01.
o ^ Godkin,
David (1 February 2014). “Being safe is no accident”. Canadian Mining Journal. Archived from the original on 19 July 2019. Retrieved 19 February 2020.
o ^ “Home | Kidd Operations”. Archived from the original on 2020-03-02. Retrieved 2020-02-19.
o ^
“Agnico Eagle Mines Limited – Operations – Operations – LaRonde Complex”. www.agnicoeagle.com. Archived from the original on 2022-02-01. Retrieved 2022-02-01.
o ^ “Skalisty mine reaches design depth of 2,056 m below surface – Nornickel”.
o ^ “Mineral
deposits: from their origin to their environmental impacts”. Taylor & Francis. 1995. ISBN 978-9054105503.
Photo credit: https://www.flickr.com/photos/phalaenopsisaphrodite523/15275199229/’]