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Encyclopedia > Underground mining (hard rock)

Underground hard rock mining refers to various underground mining techniques used to excavate hard minerals such as those containing metals like gold, copper, zinc, nickel and lead or gems such as diamonds. In contrast soft rock mining refers to excavation of softer minerals such as coal, or oil sands. This article is about mineral extraction. ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Atomic mass 63. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... General Name, Symbol, Number nickel, Ni, 28 Chemical series transition metals Group, Period, Block 10, 4, d Appearance lustrous, metallic and silvery with a gold tinge Atomic mass 58. ... For PB or pb as an abbreviation, see PB. General Name, Symbol, Number lead, Pb, 82 Chemical series poor metals Group, Period, Block 14, 6, p Appearance bluish white Atomic mass 207. ... This article is about the gemstone. ... Coal Coal (IPA: ) is a fossil fuel extracted from the ground by coal mining, either underground mining or open-pit mining (surface mining). ... Athabasca Oil Sands Oil sands, also referred to as tar sands or bituminous sands, are a combination of clay, sand, water, and bitumen. ...

Contents

Mine Access

Underground Access

Accessing underground ore can be achieved via a decline (ramp) or vertical shaft. Iron ore (Banded iron formation) Manganese ore Lead ore Gold ore An ore is a volume of rock containing components or minerals in a mode of occurrence which renders it valuable for mining. ... Shaft mining is a type of underground mining done by use of a mine shaft. ...

  • Declines can be a spiral tunnel which circles either the flank of the deposit or circles around the deposit. The decline begins with a box cut, which is the portal to the surface. Depending in the amount of overburden, and quality of bedrock a galvanized steel culvert may be required for safety purposes.
  • Shafts are vertical excavations sunk adjacent to ore an ore body. Shafts are sunk for ore bodies where haulage to surface via truck is not economical. Shaft haulage is more economical than truck haulage at depth, and a mine may have both a decline and a ramp.

A box cut is a small open cut created to provide a secure and safe portal as access to a decline to an underground mine. ... Overburden is the term used in mining to describe material that lies above the area of economic interest. ... Bedrock is the native consolidated rock underlying the Earths surface. ... Hot-dip galvanizing is a form of galvanization. ... A culvert is a flowing body of water which passes underneath a road, railway, or embankment, or the part thereof that does so. ...

Ore Access

Levels are excavated horizontally off the decline or shaft to access the ore body. Stopes are then excavated perpinducular (or near perpindicular) to the level into the ore.


Development Mining vs. Production Mining

There are two principle types of mining, development mining and production mining.


Development mining is composed of excavation almost entirely in (non-valueble) waste rock. There are five steps in development mining, remove previously blasted material (muck out round), drill rock face, load explosives, blast explosives, support excavation.


Production mining is further broken down into two methods, long hole and short hole. Short hole mining is similar to development mining, except that it occurs in ore. There are several different methods of long hole mining. Typically long hole mining requires two excavations within the ore at different elevations below surface, (15m-30m apart). Holes are drilled between the two excavations and loaded with explosives. The holes are blasted and the ore is removed from the bottom excavation.


Ventilation

One of the most important aspects of underground hard rock mining is ventilation. Ventilation is required to clear toxic fumes from blasting and removing exhaust fumes from diesel equipment. In deep hot mines ventilation is also required for cooling the workplace for miners. Ventilation raises are excavated to provide ventilation for the workplaces, and can be modified to be used as escape routes in case of emergency. Return inlet (left)Supply outlet (right). ...


Ground Support

Some means of support is required in order to maintain the stability of the openings that are excavated. This support comes in two forms, local support and area support.


Area Ground Support

Area ground support is used to prevent major ground failure. Holes is drilled into the back (ceiling) and walls and a long metal bar is installed to hold the ground togeather. There are several different styles of area ground support.

  • Point Anchor Bolts are a common style of area ground support. A point anchor bolt is a metal bar between 20mm-25mm in diameter, and between 1m-4m in length (the size is determined by the Mine's engineering department). There is an expansion shell at the end of the bolt which is inserted into the hole. As the bolt is tightened by the installation drill the expansion shell expands and the bolt tightens holding the rock together.
  • Resin Grouted Rebar is used in areas which require more support than a point anchor bolt can give. The rebar used is of similar size as a point anchor bolt but does not have an expansion shell. Once the hole for the rebar is drilled, cartrdges of epoxy resin are installed in the hole. The rebar bolt is installed after the resin and spun by the installation drill. This opens the resin cartridge and mixes it. Once the resin hardens the drill spinning tightens the rebar bolt holding the rock together.

Mining Engineering is a field that involves many of the other engineering disciplines as applied to extracting and processing minerals from a naturally occurring environment. ... Rebar is common steel reinforcing bar, an important component of reinforced concrete and reinforced masonry structures. ... Epoxy or polyepoxide is a thermosetting epoxide polymer that cures (polymerizes and crosslinks) when mixed with a catalyzing agent or hardener. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A. The first commercial attempts to prepare resins from epichlorohydrin occurred in 1927 in the United...

Local Ground Support

Local ground support is used to prevent smaller rocks from falling from the back and walls. Not all excavations require local ground support. Look up Prevention in Wiktionary, the free dictionary. ...

  • Welded Wire Mesh is a metal screen with 10cm x 10cm openings. It is held to the back using point anchor bolts or resin grouted rebar.
  • Shotcrete is a spray on concrete which coats the back and walls preventing smaller rocks from falling. Shotcrete thickness can be between 50mm-100mm.
  • Latex Membranes can be sprayed on the back and walls similar to shotcrete, but in smaller ammounts.

Stope and Retreat vs. Stope and Fill

Stope and Retreat

Sub-Level Caving Subsidence reaches surface at the Ridgeway underground mine.

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. The stope is then sealed to prevent access.

Stope and Fill

Where large bulk ore bodies are to be mined at great depth, or where leaving pillars of ore is uneconomical, the open stope can be filled with backfill, which can be cement and rock mixture, acement and sand mixture or a cement and tailings mixture. This method is popular as the refilled stopes provide support for the adjacent stopes, allowing total extraction of economic resources. In the most general sense of the word, cement is a binder, a substance which sets and hardens independently, and can bind other materials together. ... Patterns in the sand Sand is a granular material made up of fine rock particles. ... Tailings (also known as slickens[1]) are the waste left over[2] after removing the gangue from ore. ...


Mining Methods

  • Cut and Fill mining is a method of short hole mining used in narrow ore zones. An access ramp is driven off the main level to the bottom of the ore zone to be accessed. Using development mining techniques a drift is driven through the ore to the defined limit of mining. Upon completion the drift (or "cut") is filled back to the access ramp with the defined type of backfill, which may be either consolidated or unconsolidated. Another drift is driven on top of filled cut. This process continues until the top of the stope is reached.
  • Drift and Fill is similar to cut and fill, except it is used in ore zones which are wider than the method of drifting will allow to be mined. In this case the first drift is developed in the ore, is backfilled using consolidated fill. The second drift is driven adjacent to the first drift. 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.
  • Room and Pillar mining : Room and pillar mining is commonly done in flat or gently dipping bedded ore bodies. Pillars are left in place in a regular pattern while the rooms are mined out. In many room and pillar mines, the pillars are taken out starting at the farthest point from the stope access, allowing the roof collapes and fill in the stope. This allows a greater recover as less ore is left behind in pillars.
  • Block Caving is a form of stope and retreat, used to effect with large sized orebodies which are composed of hard, stable rock. The method works best with cylindrical, vertical orebodies, where the orebody can be dropped down into the stope, which is filled with waste, the whole process removing the ore from base upwards. The roof pillar, the rock which sits above the orebody, is either left in place or removed, depending on whether the deposit outcrops at surface.

Loose, unattached, unstratified particles of earth material such as gravel, sand, sediment or dust, without combined rigidity or cohesiveness due to a lack of binding or natural mineral cement (such as gypsum or limestone) to hold it together; as opposed to consolidated. ...

Ore Removal

In mines which use rubber tired equipment for coarse ore removal, the ore is removed from the stope (refered to as "mucked out") using center articulated vehicles (refered to as boggers or LHD[short for Load, Haul, Dump]). These pieces of equipment may operate using diesel or electric engines and resemble a low-profile front end loader. Iron ore (Banded iron formation) Manganese ore Lead ore Gold ore An ore is a volume of rock containing components or minerals in a mode of occurrence which renders it valuable for mining. ... (See also trailer, semi-trailer, articulated bus) Any vehicle towing a trailer can be described as an articulated vehicle. ... Rudolf Christian Karl Diesel (1858-1913), inventor of the Diesel engine. ... A Volvo L120E front loader. ...


The ore is then dumped into a truck to be hauled to surface (in shallower mines). In deeper mines the ore is dumped down an ore pass (a vertical or near vertical excavation) where it falls to a collection level. On the collection level it is moved by Conveyor belts, trucks or occasionaly trains to the shaft to be hoisted to surface in buckets or skips and emptied into bins beneath surface headframe for transport to the mill. A conveyor belt or belt conveyor consists of two end pulleys, with a continuous loop of material that rotates about them. ... Trucks can refer to several things: The plural of: Truck, the motorized vehicle Truck, other uses of the singular As a name: Trucks was a rock band Trucks is a short story by Stephen King Trucks is a movie based on the Stephen King short story Trucks! is a television... This article is about trains in rail transport. ... Shaft mining is a type of underground mining done by use of a mine shaft. ...


Trivia

  • The deepest mines in the world are the TauTona (Western Deep Levels) and Savuka gold mines in the Witwatersrand region of South Africa, which are currently working at depths exceeding 3,700 meters. AngloGold plans to increase the maximum depth of these mines to 3,910m by 2009.
  • The deepest hard rock mine in North America is Xstrata's Kidd Mine, which mines copper and zinc ore in Timmins, Ontario. Mining is actively occurring 8800 feet below surface. The shaft bottoms out at over 9600 feet down.
  • The nickel ore at Sudbury is thought to have formed from a meteorite impact.
  • The deepest hard rock mines in Australia are the copper and zinc lead mines in Mount Isa, Queensland at 1,800 m.
  • The deepest platinum-palladium mine in the world is the Merensky Reef, in South Africa, with a resource of 203 million Troy ounces, currently worked to approximately 2,200 m depth.
  • The harshest conditions for hard rock mining is in the Witwatersrand area of South Africa, where workers toil in temperatures of up to 45 °C (113 °F).

TauTona is a gold mine in South Africa. ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ... Witwatersrand is a low mountain range which runs through Gauteng in South Africa. ... AngloGold was a gold mining company based in South Africa and majority-owned by the Anglo American group. ... World map showing North America A satellite composite image of North America. ... Xstrata plc is an international mining company. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Atomic mass 63. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... Iron ore (Banded iron formation) Manganese ore Lead ore Gold ore An ore is a volume of rock containing components or minerals in a mode of occurrence which renders it valuable for mining. ... Timmins, with a population of 43,686 (2001), is a city in northeastern Ontario, Canada on the Mattagami River. ... Motto: Ut Incepit Fidelis Sic Permanet (Latin: Loyal she began, loyal she remains) Official languages English (de facto) Flower White Trillium Tree Eastern White Pine Bird Common Loon Capital Toronto Largest city Toronto Lieutenant-Governor James K. Bartleman Premier Dalton McGuinty (Liberal) Parliamentary representation  - House seats  - Senate seats 106 24... Willamette Meteorite A meteorite is a natural object originating in outer space that survives an impact with the Earths surface without being destroyed. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Atomic mass 63. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... For PB or pb as an abbreviation, see PB. General Name, Symbol, Number lead, Pb, 82 Chemical series poor metals Group, Period, Block 14, 6, p Appearance bluish white Atomic mass 207. ... Mount Isa, Queensland, Australia Mount Isa is a city and Local Government Area located in north-western Queensland, Australia. ... Capital Brisbane Government Const. ... General Name, Symbol, Number platinum, Pt, 78 Chemical series transition metals Group, Period, Block 10, 6, d Appearance grayish white Atomic mass 195. ... General Name, Symbol, Number palladium, Pd, 46 Chemical series transition metals Group, Period, Block 10, 5, d Appearance silvery white metallic Atomic mass 106. ... Troy weight is a system of units of mass customarily used for precious metals and gemstones. ...

Hardrock mining terms

  • stope and pillar
  • room and pillar
  • longhole stoping
  • benching
  • breasting
  • vertical crater retreat
  • block caving
  • sub level caving
  • shrinkage stoping
  • cut & fill
  • panel mining

See also


 
 

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