Underground hard-rock mining refers to various underground mining techniques used to excavate "hard" minerals, usually those containing metals, [1] such as ore containing gold, silver, iron, copper, zinc, nickel, tin, and lead. It also involves the same techniques used to excavate ores of gems, such as diamonds and rubies. Soft-rock mining refers to the excavation of softer minerals, such as salt, coal, and oil sands.
Accessing underground ore can be achieved via a decline (ramp), inclined vertical shaft or adit.
Planning and preparation are crucial initial steps in the core drilling process. This stage involves conducting a comprehensive assessment of the site and establishing the necessary groundwork for a successful drilling operation. Here's a breakdown of the key aspects involved:
Before drilling can begin, a thorough site assessment is conducted to determine the optimal drilling locations. This assessment involves evaluating factors such as the type of material to be drilled, subsurface conditions, potential obstacles (e.g., underground utilities), and structural integrity. This information helps identify suitable areas for drilling that minimize risks and ensure accurate results.
Depending on the location and regulations governing the site, it may be necessary to obtain permits and permissions before commencing drilling activities. This involves understanding and complying with local regulations, environmental guidelines, and any specific requirements for drilling in certain areas.
Safety is paramount in any drilling operation. During the planning stage, safety protocols and measures are established to protect personnel, equipment, and the surrounding environment. This includes assessing potential hazards, developing emergency response plans, and ensuring the availability of necessary safety equipment.
Planning also involves determining the equipment and resources required for the core drilling operation. This includes selecting the appropriate drilling rig, drill bits, and accessories based on factors such as the material being drilled, desired core diameter, and drilling depth. Adequate resources such as water supply, drilling mud, and coolants are also considered to ensure smooth drilling operations.
Establishing a timeline for the core drilling project is essential for effective project management. This includes setting deadlines, scheduling equipment and personnel, and coordinating with other stakeholders involved in the project. Logistics, such as transportation of equipment and materials to the site, are also planned during this stage.
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. 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.
Levels are excavated horizontally off the decline or shaft to access the ore body. Stopes are then excavated perpendicular (or near perpendicular) to the level into the ore.
There are two principal phases of underground mining: development mining and production mining.
Development mining is composed of excavation almost entirely in (non-valuable) waste rock in order to gain access to the orebody. 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. To start the mining, the first step is to make the path to go down. The path is defined as 'Decline' as describe above. Before the start of a decline, all pre-planning of the power facility, drilling arrangement, de-watering, ventilation and, muck withdrawal facilities are required. [2]
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, (15 m – 30 m 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.
One of the most important aspects of underground hard rock mining is ventilation. Ventilation is the primary method of clearing hazardous gases and/or dust which are created from drilling and blasting activity (e.g., silica dust, NOx), diesel equipment (e.g., diesel particulate, carbon monoxide), or to protect against gases that are naturally emanating from the rock (e.g., radon gas). Ventilation is also used to manage underground temperatures for the workers. 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. Ventilation raises are typically used to transfer ventilation from surface to the workplaces, and can be modified for use as emergency escape routes. The primary sources of heat in underground hard rock mines are virgin rock temperature, machinery, auto compression, and fissure water. Other small contributing factors are human body heat and blasting.
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 is used to prevent major ground failure. Holes are drilled into the back (ceiling) and walls and a long steel rod (or rock bolt) is installed to hold the ground together. There are three categories of rock bolt, differentiated by how they engage the host rock. [3] They are:
Local ground support is used to prevent smaller rocks from falling from the back and ribs. Not all excavations require local ground support.
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.
Where large bulk ore bodies are to be mined at great depth, or where leaving pillars of ore is uneconomical, the open stope is filled with backfill, which can be a cement and rock mixture, a cement 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.
The mining method selected is determined by the size, shape, orientation and type of orebody to be mined. The orebody can be narrow vein such as a gold mine in the Witwatersrand, the orebody can be massive similar to the Olympic Dam mine, South Australia, or Cadia-Ridgeway Mine, New South Wales. The width or size of the orebody is determined by the grade as well as the distribution of the ore. 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. Further consideration is needed for the strength of the ore as well as the surrounding rock. 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.
Orebodies that do not cave readily are sometimes preconditioned by hydraulic fracturing, blasting, or by a combination of both. Hydraulic fracturing has been applied to preconditioning strong roof rock over coal longwall panels, and to inducing caving in both coal and hard rock mines.
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)). These pieces of equipment may operate using diesel engines or electric motors, and resemble a low-profile front end loader. LHD operated through electricity utilize trailing cables which are flexible and can be extended or retracted on a reel. [9]
The ore is then dumped into a truck to be hauled to the 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 may receive primary crushing via jaw or cone crusher, or via a rockbreaker. The ore is then moved by conveyor belts, trucks or occasionally trains to the shaft to be hoisted to the surface in buckets or skips and emptied into bins beneath the surface headframe for transport to the mill.
In some cases the underground primary crusher feeds an inclined conveyor belt which delivers ore via an incline shaft direct to the surface. The ore is fed down ore passes, with mining equipment accessing the ore body via a decline from surface.
Mining is the extraction of valuable geological materials from the Earth and other astronomical objects. Mining is required to obtain most materials that cannot be grown through agricultural processes, or feasibly created artificially in a laboratory or factory. Ores recovered by mining include metals, coal, oil shale, gemstones, limestone, chalk, dimension stone, rock salt, potash, gravel, and clay. The ore must be a rock or mineral that contains valuable constituent, can be extracted or mined and sold for profit. Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water.
A gunnies, gunnis, or gunniss is the space left in a mine after the extraction by stoping of a vertical or near vertical ore-bearing lode. The term is also used when this space breaks the surface of the ground, but it can then be known as a coffin or goffen. It can also be used to describe the deep trenches that were dug by early miners in following the ore-bearing lode downwards from the surface – in this case they are often called open-works; their existence can provide the earliest evidence of mining in an area. William Pryce, writing in 1778, also used the term as a measure of width, a single gunnies being equal to three feet.
Open-pit mining, also known as open-cast or open-cut mining and in larger contexts mega-mining, is a surface mining technique of extracting rock or minerals from the earth from an open-air pit, sometimes known as a borrow.
Shaft mining or shaft sinking is the action of excavating a mine shaft from the top down, where there is initially no access to the bottom. Shallow shafts, typically sunk for civil engineering projects, differ greatly in execution method from deep shafts, typically sunk for mining projects.
Drilling and blasting is the controlled use of explosives and other methods, such as gas pressure blasting pyrotechnics, to break rock for excavation. It is practiced most often in mining, quarrying and civil engineering such as dam, tunnel or road construction. The result of rock blasting is often known as a rock cut.
Harmony Gold is the largest gold mining company in South Africa. Harmony operates in South Africa and in Papua New Guinea. The company has nine underground mines, one open-pit mine and several surface operations in South Africa. In Papua New Guinea, it has Hidden Valley, an open-pit gold and silver mine and a 50% interest in the Morobe Mining Joint Venture, which includes the Wafi-Golpu project and extensive exploration tenements. Outside the joint venture, Harmony's own exploration portfolio focuses principally on highly prospective areas in Papua New Guinea.
A raise borer is a machine used in underground mining, to excavate a circular hole between two levels of a mine without the use of explosives.
Mine exploration is a hobby in which people visit abandoned mines, quarries, and sometimes operational mines. Enthusiasts usually engage in such activities for the purpose of exploration and documentation, sometimes through the use of surveying and photography. In this respect, mine exploration might be considered a type of amateur industrial archaeology. In many ways, however, it is closer to caving, with many participants actively interested in exploring both mines and caves. Mine exploration typically requires equipment such as helmets, head lamps, Wellington boots, and climbing gear.
The Challenger mine is a gold mine in the Far North of South Australia, 165 km west of the Stuart Highway and 740 km north-west of Adelaide. It was operated by Dominion, Kingsgate and then WPG Resources. The mine is now on Care and Maintenance. The deposit was named by the geologist who discovered it, after his dog.
Creighton Mine is an underground nickel, copper, and platinum-group elements (PGE) mine. It is presently owned and operated by Vale Limited in the city of Greater Sudbury, Ontario, Canada. Open pit mining began in 1901, and underground mining began in 1906. The mine is situated in the Sudbury Igneous Complex (SIC) in its South Range geologic unit. The mine is the source of many excavation-related seismic events, such as earthquakes and rock burst events. It is home to SNOLAB, and is currently the deepest nickel mine in Canada. Expansion projects to deepen the Creighton Mine are currently underway.
The following outline is provided as an overview of and topical guide to mining:
Stoping is the process of extracting the desired ore or other mineral from an underground mine, leaving behind an open space known as a stope. Stoping is used when the country rock is sufficiently strong not to collapse into the stope, although in most cases artificial support is also provided.
Boring is drilling a hole, tunnel, or well in the Earth. It is used for various applications in geology, agriculture, hydrology, civil engineering, and mineral exploration. Today, most Earth drilling serves one of the following purposes:
Mining in the Upper Harz region of central Germany was a major industry for several centuries, especially for the production of silver, lead, copper, and, latterly, zinc as well. Great wealth was accumulated from the mining of silver from the 16th to the 19th centuries, as well as from important technical inventions. The centre of the mining industry was the group of seven Upper Harz mining towns of Clausthal, Zellerfeld, Sankt Andreasberg, Wildemann, Grund, Lautenthal und Altenau.
The Kemi Mine is owned by Outokumpu Chrome Oy, a subsidiary of Outokumpu Oyj. It is located in Elijärvi, in the municipality of Keminmaa, to the north of Kemi. The Kemi Mine is the largest underground mine in Finland, with an annual production capacity of 2.7 million tonnes of ore. It is also part of the integrated ferrochrome and stainless steel manufacturing chain owned by Outokumpu in the Kemi-Tornio region. The Kemi Mine has approximately 400 employees every day, both employees of Outokumpu and contractors.
Steep Rock Lake is a body of water near the township of Atikokan, northern Ontario, Canada. It was originally fed by the Seine River.
A Pinge or Binge ("binger") is the name given in German-speaking Europe to a wedge-, ditch- or funnel-shaped depression in the terrain caused by mining activity. This depression or sink-hole is frequently caused by the collapse of old underground mine workings that are close to the Earth's surface. Unlike natural landforms, a Pinge is a direct result of human activity. The term has no direct equivalent in English, but may be translated as "mining sink-hole", "mine slump" or, in some cases, as "glory hole".
LHD loaders are similar to conventional front end loaders but developed for the toughest of hard rock mining applications, keeping overall production economy, safety, and reliability in consideration. They are extremely rugged, highly maneuverable, and exceptionally productive. More than 75% of the world's underground metal mines use LHD for handling the muck of their excavations.
Deep level underground is construction that is 20 m (66 ft) or more below ground and not using the cut-and-cover method, especially train stations, air raid shelters and bunkers, and some tunnels and mines. Cut-and-cover is a simple method of construction for shallow tunnels where a trench is excavated and roofed over with an overhead support structure that is strong enough to carry the load of what is to be built above the tunnel.
The Rajpura Dariba Mine VRM disaster took place in Dariba, Udaipur, India on 28 August 1994 at a mine operated by Hindustan Zinc Ltd.
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: CS1 maint: archived copy as title (link)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 mining.