Module 6

Underground mining

- more expensive than surface operations. the overall cost of underground mining can be up to four times the costs of surface mining - When it is clear that an underground mining method is more economically viable, a change from surface to underground mining methods is made. • naturally supported • artificially supported • caving methods

Open pit mining (surface mining)

- the most prevalent surface mechanical mining method used to excavate metals and industrial minerals from hard rock - also used in some circumstances for extraction of coal seams from hard rock environments - looks simple compared to underground mines but every open pit is tailor-made for its mineral deposit The slope angle of the walls in an open pit is critical, since the walls must stay up for the duration of the pit's life. Consequently, there is much planning and expertise used when designing the pit's slopes. Both the waste rock and the ore are removed in a series of horizontal benches. There is a delicate economic balance when determining how much waste rock can be removed in order to access the commodity of value, since this determines how deep the pit can go. The amount of waste rock mined relative to the ore mined is known as the stripping ratio. A stripping ratio of 3:1 means that during mining three times as much waste rock as ore is removed from the pit. To be profitable, a pit must be designed so that the cost of removing the waste is more than covered by the value received from the mined ore. The first few benches (steps down) in an open pit are generally used to remove the waste overburden above the ore body. The overburden depth can vary from a few meters in depth to several tens of metres depending on the geology of the area. Benches are developed in heights of up to 15m. Bench height is determined by the slope of the pit walls and the size and type of drilling and excavation equipment working in the pit. The horizontal part of the bench provides adequate space for the equipment to work safely and productively. Ramps are developed from bench to bench as the pit progresses downwards. These are used by the equipment to access each bench and by the haul trucks to remove the mine's ore and waste. Most open pit mining equipment is very large. This is because the cost per tonne mined drops with larger equipment. Some of the major equipment manufacturers are Caterpillar and Komatsu.

Mining activities can be divided into two groups:

1. Activities carried out at the surface in the form of open pit or open cast mines. -> Used when the ore body is situated close to the surface, is of sufficient size and does not have excessive overburden cover. 2. Activities that are carried out below the surface in underground mines. -> Used when the ore body depth or shape make it unsuitable or uneconomic for surface mining methods.

Selecting a Mining Method: Other Factors. Other determining factors in the selection of mining methods

1. Geologic and geotechnical characteristics These affect the choice between selective and bulk mining methods as well as the mine's layout. The main geologic and geotechnical characteristics are: • Mineralogy - is the ore sulphide, oxide or mixed and does it require separation? • Deposit structure - are there folds, faults, planes of weakness and discontinuities? • Alteration - are there zones of altered or changed mineralization? • Grade uniformity - is the grade uniform over the deposit or variable? • Rock strength - can the rock stand unsupported or is support required? • Rock characteristics - is the rock porous or permeable and are there voids in rock? 2. Technological factors Selecting a mining method depends on the most appropriate technological match between the natural conditions and the method in question. Some methods might be excluded because they adversely affect downstream operations (e.g., ore processing). The main technological factors to consider are: • Recovery - what portion of the ore can be recovered by mining? • Dilution - what is the amount of unwanted rock (waste) that will mix with the ore? • Selectivity - how can one maximise ore extraction and minimise waste mixture? • Flexibility - how adaptable is the method to changing geologic/geotechnical conditions? • Mechanization - is the method readily mechanized and automated? 3. Economic factors In the end, economics is the deciding factor in terms of choosing a mining method. This is because a mining method can affect a mine's cash flow and profitability level. The main economic factors to be considered are: • Reserves - how do the tonnage and grade affect the rate of mining and the life of the mine? • Production rate - how does the mining rate affect the unit costs of mining? • Costs of method - what are the comparative mining costs for different methods? 4. Environmental factors The physical, social, and overall economic climate of the location of the mineral deposit must be considered and may, on occasion, require that an otherwise appropriate method be rejected. The main environmental factors to be considered are: • Ground subsidence - can the surface be allowed to subside or not? • Atmospheric control - what are the requirements for air quality and noise abatement? • Waste disposal - are there available sites for waste disposal from the mine? • Workforce - what is the availability of trained personnel and training facilities? • Safety - what are the comparative safety methods of suitable mining methods? The mine designer's level of experience with numerous mining methods often plays a major role in the selection of the method. Because not all of the above-mentioned factors can be easily quantified, good judgment is essential in the selection process. Along with personal experience, a mine designer relies on the use of quantitative engineering evaluation, including the following: • computerized data gathering • 3-D computer modelling of mineral deposits • 3-D computer modelling of mine design layouts The mining method selected is usually most successful when the quantitative analysis and the designer's experienced evaluation are in total agreement. Incorrect selection may result in poor operating efficiency, excessive costs, unsafe working environments and inability to extract the full potential of the deposit.

The optimum gradient for developing a ramp access into an underground mine is:

15-17%

In the United States, surface mining methods account for what percentage of production of minerals and fossil fuels?

85%

Underground Mining: Layout Mine Access

Access points and workings are two major features of a mine. Access points allow entry and exit for people, materials, ventilation air and equipment into the mine and provide a way for ore and waste to be brought out of the mine. In many cases a mine will have more than one type of access and each may serve a different function (see below). The three types of access points are: 1. Shafts 2. Declines and ramps 3. -Adits

Artificially supported methods

Artificially supported mining methods are used to mine both flat-lying and steeply dipping deposits. They are used when the structure of the rocks surrounding the ore is so weak that they will not stand up over large open areas and require some kind of introduced support system while mining takes place in the ore zones. As with the naturally supported methods, it will help to increase your understanding through a comparison of the workings and characteristics of the various methods (see Table). You will notice that longwall mining can be further sub-divided depending on whether the mineral deposit is hard rock or soft rock (potash, coal).

Shift(s)

As with open pits, most large underground mines run 24 hours a day, seven days a week. Consequently, the work time is split up into shifts with mine crews allocated to different shifts depending on their jobs. For example, production and development crews may be on all shifts while service crews may only work on a day shift. In underground operations, the three shifts, eight hours per shift system is most common, although some mines are now working two extended shifts of up to ten hours each. Some mines may not operate seven days a week but only five or six with the spare day used for maintenance of the facilities and plant (e.g., the hoists and crushers).

Hauling

Broken ore and waste is loaded into large off-highway rear dump trucks. Ore is taken to a crusher for processing, whereas waste rock is dumped in a pile that would be out of the way of mine operations.

Mine Development and Production: Introduction

Choosing the appropriate mining method has two important consequences: 1. the productive capacity of the mine (i.e., the level of output) 2. the development of the mine

Production rate and mine life

Different mining methods are capable of quite different production rates. For example, cut and fill mining, while a selective method, is a low production method with output in the low 1000s of tonnes per day. In comparison, block caving, a bulk mining method with no selectivity, is a high production method with outputs ranging from around 30,000 tonnes to well over 100,000 tonnes per day. The production rate is based on geologic conditions as well as the desired rate of return. These in turn affect the mine life. In the past, production planning tried to maximise mine life by continuing operation for decades or even centuries. However, with high costs of borrowing money and increased investment risks, mine lives are now much shorter in order to make a quicker return on investment. It is now not unusual to have mines with an expected mine life of only three to five years.

Placer mining - dredging Two Views of Tin DredgingTin Mining (Malaysia)Tin Mining (Malaysia)Click on the thumbnails to view the full versions.

Dredges are floating excavation plants that recover placer deposits from underwater. Dredges can work in relatively shallow, fabricated ponds, such as those that mined tin in Malaysia and gold in the Yukon and Alaska . Dredges can also work in the deeper open ocean, such as those used for diamond mining off the shores of Namibia . Dredges recover the loose mineral bearing strata using a number of methods. The two most common are a mechanical bucket-line dredge and a suction cutter-head dredge. The first type uses a series of buckets in a continuous chain to dig up the placer deposits from the bank of the pond. The material is treated directly on the dredge and the waste is deposited back in the water behind the dredge. This type of dredge has been used for mining gold and tin placer deposits. The suction cutter-head dredge, uses a rotary cutting head to dig up the bank and material and lift it to the surface through a large suction tube. Material is then pumped to shore for treatment. These dredges are used for mining sands and industrial minerals and for mining diamonds in the shallower offshore waters of Namibia.

Mining cycle and equipment used in open pit mining operations

During the development and excavation stages of an open pit, the main tasks of removing ore and waste are generally carried out in unit operations . Unit operations are basic steps required for extracting minerals from the deposit (e.g., drilling the ore, breaking the ore, excavating the ore, etc.). They are usually grouped into what is known as the production cycle and auxiliary operations . The production cycle is the sequential steps directly involved in mineral extraction. Auxiliary operations are those activities that support the production cycle.

Underground plant

In addition to the primary and secondary underground development to access the mineral deposits, a number of specialized openings and equipment are required. These are usually grouped around the shaft. The first is the shaft station. This is where the vertical shaft intersects with horizontal openings. It is here that workers and materials are off-loaded from the cage for transport to the working areas. Facilities such as electrical transformer stations, explosive magazines, and storage for fuels and oils are also housed here. In addition, the underground plant includes the materials handling systems of crushers, storage bins, loading pockets as well as the mine dewatering system of sumps and pump rooms and other installations that provide auxiliary services to the underground operation. In trackless mines, one special facility is the underground maintenance shop. In deep mines, and especially those that do not have a ramp to the surface, it is not practical to take mining equipment such as jumbo drills and scoop trams to the surface for servicing and repairs. In many mines, once a piece of mining equipment is taken underground it will never again see the light of day. Instead, it will spend its working life in the mine, and will be left there at the end of the mine's life.

Mine plant and services

In order to support the operations of mine development and production, a mine needs three groups of physical plants to provide services to the mining areas: surface plant shaft plant and underground plant

Underground Mining: Introduction to Layout and Methods

Mineral excavation that is carried out beneath the earth's surface is known as underground mining. It is used when the depth of the deposit, strip ratio of overburden to mineral, or both become so excessive that surface mining is no longer viable. Once economic analysis indicates underground mining must be used, one must choose between a number of very different methods of underground mining. The choice of mining method primarily hinges on: • designing the openings and sequence of extraction according to the spatial characteristics of the mineral deposit • determining the appropriate form of ground support that is required to keep the mine open and safe The three classes of underground methods are differentiated by the nature and amount of ground support required: • Naturally supported methods are essentially self-supporting, relying on pillars and localized means of support (roof bolts, timber, etc.) to maintain the mine openings. • Artificially supported methods require substantial amounts of support (such as waste rock or hydraulic backfill) to supplement local means of support and maintain the mine openings. • Caving requires no support and is based on allowing both the ore and surrounding wall rock to cave as a means of extracting the ore from the workings.

Naturally supported methods

Naturally supported mining (stoping) methods are used for mining tabular and vein type deposits that are either flat (horizontal) or steeply dipping (see the table below). Because there is very little or no artificial support, they are used in ore bodies that have strong ore and strong surrounding rock. Even so, there is always local support used in the form of rockbolting and timber sets to maintain the mine openings. This is to ensure that areas where people are working are safe. There are three main types of naturally supported mining methods: 1) Room and Pillar - Large horizonal areas are excavated and pillars of rock are left to support the hanging wall (roof). 2) Shrinkage stoping - Ore is cut out in horizontal slices and progresses upwards. Ore is removed from beneath the ore pile, but some of the ore is left to support the working area. This method is effective because rock blasting increases the volume of material by about 50%. 3) Sub level stoping - Just like shrinkage, this method is used on steeply dipping (vertical or near vertical) ore bodies. Instead of working upwards like in shrinkage, this method works horizontally from a number of parallel access drifts.

Blasting

Once the holes have been drilled explosive charges are poured into the holes and connected so they will detonate and break the rock into a size suitable for excavation. Explosives are delivered and loaded into the holes using various forms of bulk supply trucks. The choice of explosives depends on how wet the holes are the strength of the rock. Generally ANFO (ammonium nitrate/fuel oil) is preferred for its low cost. The "blast" is detonated in a sequence that optimizes the breakage of the rock while minimizing damage to surrounding areas and reducing the noise or "air blast" caused by the explosion.

Mine development

Once the mining method is chosen and the production rate decided on, development of the mine can proceed. The mining method largely governs the type and placement of the primary development opening such as the shaft, ramp, adit or whatever combination is decided upon. If a disturbance to the surface due to subsidence is expected as in the case of block caving and other bulk mining methods, then all access must be placed well outside any possible zone of subsidence. This is less critical in supported methods of mining but it is still important to make sure that long term development infrastructure will not be affected by mining.

Levels

Once the orebody has been reached a series of horizontal levels are typically developed. These levels alow miners to reach the orebody at different elevations. Mining may be occur on several levels at the same time.

Open cast (strip) mining (surface mining)

Open cast mining is a surface method mainly used to mine coal seams and other bedded deposits at or close to the surface. It is similar to open pit mining except that instead of transporting the overburden (or spoil) on top of the seam to dumps, it is disposed of in adjacent mined-out panels. Consequently, the method gets its dual names from the fact that the overburden is first stripped off the seam and cast aside into worked-out areas to expose the coal seam that is then mined in strips. After the coal or bedded deposit is removed, the strip is filled with overburden from the adjacent new strip and the area is re-vegetated using previously removed topsoil. Open cast mining is carried out on a large scale and, in the U.S. more than 50% of all coal production is obtained this way. It is economical due to the replacement of waste haulage by casting and the depositing of the soil in mined out areas. The latter concentrates the mining activity in a relatively small area thereby allowing reclamation to directly follow the mining of a strip of seam. Thus the mine can progress along many kilometres of coal seam while disturbing relatively small areas of land at any one time. The key to productivity and low cost in open cast mining is the output of the equipment doing the stripping. Gigantic machines known as walking draglines, stripping shovels, and bucket wheel excavators are used to strip the overburden and cast it into the adjacent worked out areas in one single operation. The coal is then mined using smaller power shovels, excavators or large front-end rubber tired loaders. In most cases, some drilling and blasting is required to loosen hard bands of overburden material, but it is unusual to have to extensively blast either the overburden or coal seams.

Placer mining - sluice-box (surface mining)

Placer deposits are made up of heavy minerals (e.g., platinum, gold, tin ores, and diamonds) that were eroded from bedrock by weathering, and then transported by the action of running water in streams, rivers and beaches. Eventually the heavy minerals were are concentrated and re-deposited as alluvium at slow spots in the river or beach. These concentrations are usually found in an unconsolidated form in depressions above or in the bedrock and are covered by layers of sand, gravel, and colluviums. Sluice box mining is a surface method whereby loosely consolidated placer deposits containing heavy metals (e.g., gold, tin, diamonds, and other alluvial depositions) are excavated using mechanical equipment and transported to an onsite treatment plant called a sluice box. At the plant, water and gravity are used to separate and recover valuable commodities from waste material.

Shifts

Since most large mining operations run 24 hours a day and usually run seven days a week, operating time is divided up into shifts. Each shift has a full crew to operate mining equipment for the production cycle and most of the auxiliary operations. Consequently, in a 24-hour-a-day operation there might be three shifts, each eight hours long or, as is more common now, two shifts, a day and a night shift, each 12 hours long. Some mine service jobs only require a single shift of work per day, usually the day shift. Each shift has its own foreman. There is often a separate foreman for drilling and blasting operations. Technical staff normally only work the day shift and five days-per-week.

Miners

Small workforces of equipment operators and service personnel organized into crews

Solution mining

Solution mining includes both borehole mining techniques for extracting minerals (e.g., salt, potash, and sulphur) and in situ leaching techniques to extract minerals (e.g., gold and copper). In borehole mining of salt, hot water is pumped underground though boreholes to dissolve the salt. The resulting salt solution is recovered through other boreholes and pumped to the surface for treatment. A similar method known as the Frasch process uses hot water to melt and transport sulphur to the surface. In situ leaching (ISL) of metals (e.g., copper, gold, and more recently uranium) uses a series of boreholes (or wells) to inject the mineral deposit with chemical solutions (known as lixiviants) such as dilute acids, alkalis or sodium cyanide (for gold). These solutions leach the metals out of their host material with the resultant solution transported to surface and the metals recovered in a processing plant.

Mine production methods

Surface mining's appeal lies in its mass production and minimal cost capabilities. Most metal, coal, and industrial minerals are produced using surface methods. Underground mining, however, plays a vital role in many nations' mining economies as it can be used to mine a variety of mineral deposits that cannot be approached using surface mining. In the United States, surface mining is the predominant method, producing about 85% of all minerals and fossil fuel. Almost 98% of metallic ores, 97% of non-metallic ores, and 61% of coal are mined using surface methods (mostly open pit and open cast methods).

Drilling

The first unit operation in the production cycle is the drilling of blast holes in the rock for placement of explosives. In modern surface mines these holes can be anywhere from 75mm to 380mm in diameter. Large rotary drills are used to make these holes.

Mining cycles and equipment used in underground mining operations

The main unit operations in underground mining cycles are similar to those found in a surface mine and generally the same sequence. The size of the equipment used, however, is considerably smaller. In underground mining, unit operations can be grouped into two types of mining cycles: development cycles and production cycles. Mine services are also required to support development and production cycles. These auxiliary operations consist of ventilation of the mine, mine dewatering, equipment maintenance, and delivery of compressed air, water, and power into the mine. The development cycle Development cycles are used in the excavation of horizontal and vertical mine openings such as drifts, crosscuts, raises and ramps. Shaft sinking employs a special type of development cycle. In underground mining, additional unit processes are required that are not necessary in open pits. These include: - ventilating the underground working area before miners return to the workplace - supporting the roof (or back) so it is safe for miners to work The production cycle Production cycles are used for breaking and removing ore from the mine in the stoping operations. Unit operations are much the same as for open pit mining except that the equipment used is much smaller and adapted for the underground environment. In addition, the single unit operation of hauling used in an open pit to transport broken ore to the processing plant is replaced with the dual operations underground of tramming and hoisting or hauling (if using a ramp).

Selecting a mining method

The selection of a mining method must take into account many factors and the method of extraction may change over time. For example, a large copper deposit may initially be extracted using a surface open pit method, then extracted using a high production underground method, and, finally, extracted using a solution mining method. Overall, mines range in size from small underground operations that produce a few hundred tonnes each day to large surface mines that produce tens of thousands of tonnes of ore per day. Despite the wide variety of excavation methods, the selection is usually dependent on the shape, location, size, and orientation of the ore body that is to be extracted. - Small underground mine - 100s tons/day - medium size open pit gold mine - 1000s tonnes/day - Large open pit mine - 10,000s tonnes/day

Shaft Plant

The shaft plant consists of the physical plant installed for handling the ore, coal, or mineral out of the mine and miners and materials into the mine. It also includes the systems for ventilating the mine, drainage of water from the mine and supply of power, compressed air, water and communications into the mine. All service lines must be fed down the shafts or declines into the mine's working areas. Ventilation air is of particular importance. For safety reasons, all mines have more than one way of entering, in case there should be an accident or failure in one of the routes. Consequently, there are often two or more shafts or declines at an operating mine. These are used to set up a ventilation flow with fresh air entering down one entry point and foul (or return air) exiting up the other one.

Surface plant

The surface plant consists of a variety of facilities to provide the mine with necessary services. These include access roads, power supply, water supply, offices, workshops for equipment repair, ore storage bins and disposal areas for waste rock and water from the mine. Most of these buildings are clustered around the entrance to the mine be it a shaft, decline or adit. In the case of a shaft entrance, there are the additional facilities of a shaft collar, head frame with bins and a hoist house. In many mines the head frame is the most prominent structure representing the centre of the mine and seen by all from many miles around. When a decline or adit is the means of access, the surface plant is simplified as the head frame and hoisting facilities are dispensed with.

Stoping

The terms stopes and stoping methods apply to hard rock mining operations and are generally not used when referring to coal or other soft rock mines. In hard rock mines, a stope is the production centre where the major portion of the ore is broken for removal from the mine (Also known as the working face). Hard rock mines are divided up into stoping areas where a number of individual stopes form a stoping panel or line of stopes. Often, there will be a pillar of ore left between stopes at both the side and above the stope. Depending on the method, this pillar may be left in place or removed at a later date. Thus, the term "stoping method" is interchangeable with the term "mining method". In soft rock mining, terms such as room, panel and opening are used to refer to the production centres of the mine. There are three main categories of mining methods: 1. Naturally supported mining methods 2. Artificially supported mining methods 3. Caving mining methods

Other openings

There are a great many other special openings in an underground mine: 1. ore passes used to move ore vertically down to the main collection point 2. winzes and raises that connect levels below and above each other 3. maintenance shops for equipment repair 4. sumps for collecting water draining down in the mine

What do they affect?

These spatial characteristics are the main factors that influence the choice between surface and underground mining. They not only affect the choice between selective and bulk mining methods and the determination of production rate but they also influence the mine's general layout.

Caving mining methods

This is a class of mining methods in which the extraction openings are designed to collapse. That is, mining is designed so that rock (including ore) caves in and the resulting rubble is then removed. Caving can be induced using two methods: 1. drilling and blasting to break the rock and start the caving process 2. massive, where once caving is started the stresses in the ore and surrounding rocks tend to perpetuate and progress the caving process All caving methods are bulk mining systems akin to the level of open pit mining. There is little or no opportunity for selective mining of parts of the ore body. Consequently, they are only used in very large tabular or massive deposits that have a large aerial extent and depth and a uniform (generally low) value to the ore.

Placer mining - hydraulicking

This method utilizes high-pressure jets of water directed at loosely consolidated alluvium to break them up and transport them to a central collection point for pumping to a treatment plant. This method was popular a number of years ago as a means of mining both gold and tin placer deposits since it was inexpensive provided that a plentiful supply of water existed. Hydraulicking and, to a lesser extent, sluice-box mining, are rarely practiced in North America today due to environmental problems and costs associated with these methods. They are still practiced in some areas of Africa and South America . This method is still employed in mining industrial deposits of china clays (kaolinite) in areas such as Cornwall, England. China clays are used in the ceramics and paper manufacturing industries. Here, environmental controls are extremely tight with all mining taking place within the confines of an open pit and plant discharges strictly controlled.

Selecting a Mining Method: Type of Deposit

Type of deposit: 1. Size - height, thickness, overall dimensions of the orebody 2. Shape - tabular, lenticular, massive, vein 3. Dip - steeply dipping or flat lying 4. Depth - how far below surface and how much overburden to remove?

Auxiliary operations and mine services

While the production cycle constitutes the major mining activity in an open pit, auxiliary operations and mine services are required to support main mining activity. Without them, the operation would fail. Auxiliary operations consist of such things as: - keeping bench workings areas around the major mining equipment in a good condition - keeping access ramps and roadways in the pit area in good condition for the haul trucks - keeping waste dumps in a stable and safe condition Mine services consist of such things as: - survey and engineering services for pit design and development - dewatering the bottom of the pit - supplying electric power to the mining equipment when required - ensuring pit walls are maintained in a safe condition - servicing of the fleet of mine equipment and vehicles

A copper porphyry deposit is an example of:

a massive type deposit

Quarrying (Surface method)

another type of mechanical surface method. The term generally applies only to the mining of industrial minerals used for construction purposes (e.g., crushed limestone and other aggregates). One specialized form of quarrying is the production of intact blocks of rock called dimension stone that are used for architectural and decorative use. Surface quarries for bulk building materials resemble open pits except that the size of the quarry is usually considerably smaller than a typical open pit and the equipment used is also scaled down in size, as shown in the image below. In dimension stone quarries, bench heights are generally lower than in open pits while the walls are frequently vertical and often hundreds of feet high. In addition, explosives are less frequently used to break the rock, which is often cut using large band saws, although low strength explosives might be used to free large blocks of stone for removal by cranes or other special handling equipment.

Cut and fill is a ____________ mining method.

artificially supported

Production crews (usually several miners, depending on the stoping method)

assigned to certain stoping areas and responsible for the drilling, blasting, mucking and tramming of ore from the stopes

Mine service crews

auxiliary operations (e.g., moving power cables, dewatering the pit and general work around the pit)

What is the name of the device used to transport miners in and out of a mine?

cage

Depth (Massive)

can outcrop at surface or be covered by deep layers of overburden material

Development crew (2 or 3 miners)

carry out the development of horizontal or vertical headings

Which of the following is not a spatial characteristic of a mineral deposit?

dilution

Dip (Vein type)

dip more steeply than bedded deposits

Foremen

direct day-to-day operations

In an open-cast coal mine the waste material is generally side-cast using:

draglines

In an open pit operation the production cycle consists of a number of unit operations. Which of the following is in the correct sequence?

drill-charge-blast-load-haul-dump

Equipment operators

driving haul trucks operating heavy equipment such as dozers, graders and loaders and eventually the large mining shovels or one of the rotary drills

Bedded type deposits are generally:

either flat or gently dipping

In a tracked underground mine tramming is performed by using:

electric locomotives and ore cars

Timber crews

erect timber support in the mine and build all sorts of structures from timber barricades and packs to ore chutes to installing ventilation barricades

Size (Massive)

extensive in area and depth

Dredge mining is an underground method of mining.

false

The block caving mining method is a naturally supported mining method.

false

The headframe for an underground mine is situated at the bottom of a ramp access.

false

Dip (Bedded or tabular)

flat or gently dipping deposits parallel to the sedimentary layers

Shift bosses (equivalent to foremen in open pit mines)

front line day-to-day supervision of the mining crews

Mine captains

have a set area of the mine to supervise

In an underground mine you might use an adit in preference to a shaft in:

in mountainous terrain

Surface mining

involves excavation of ore, coal or stone exclusively at the surface of the earth with essentially no exposure to the miners underground. Although mechanical methods and aqueous methods are both classified as surface mining, they use very different methods to extract the mineral of interest. Of the two, mechanical methods represent over 90% of North American surface mining.

Size (Bedded or tabular)

laterally extensive

Mechanics and electricians

maintenance and servicing of mine equipment

Mine manager

management and direction of the operation

Depth (Vein type)

may outcrop at the surface or be covered by an overburden layer

In an underground mine a scoop tram is used for:

mucking ore out of a draw point

Depth (bedded or tabular)

near to or on the surface or deep under the ground

Dip (lenticular)

occur as isolated pockets or lenses of ore may be offshoots of other ore bodies

Size (Lenticular)_

of limited extent

Other ( Vein type)

often associated with zones of weakness such as faults, joints, etc.

Other ( Lenticular)

often quite rich in grade

Loading

once the rock has been blasted the operation of loading the broken rock begins. In most surface mines loading is done by shovels or wheel loaders depending on the size of operation and flexibility required. There are two types of shovels, a cable or rope shovel operated using winches and ropes or hydraulic shovels or excavators operated using a series of hydraulic cylinders.

Service personnel

operate the underground crushers, the pumps and sumps, and the hoisting system for ore, miners, materials and the mechanics and electricians who work in the underground shop repairing the equipment

Excavation or mining activities

part of the fourth stage in the life cycle of a mine. At this stage, minerals are recovered from the earth's crust in economic quantities and delivered to shipping or processing facilities.

Geologists, mine engineers, mining technologists and surveyors

planning and monitoring of the mining operation

In open pit mining ___________ are used for hauling ore and waste out of an open pit.

ramps

Size (Vein type)

ranging in thicknesses from less than 0.5 m or to 3.0 m or even greater

Which of the following is not a method used for mining placer deposits?

room and pillar

Which of the following underground mining methods is applicable for mining a flat lying tubular deposit?

room and pillar

Blasters

safe handling of explosives

Which of the following are primary methods of accessing an underground mine? (note: more than one correct answer).

shafts adits

In situ leaching of copper is a ________________ mining method.

solution

Dip (massive)

some are vertical while others dip at an angle

Mine manager (or mine superintendent

supervises the general operations of the mine

Surveyors and assistants

take care of surveying tasks (generally more complicated than open pit mining)

Geologists, mining engineers, and technologists

take care of the technical aspects of mine development and production

Surface mining advantage

that economies of scale can be employed since the size of equipment is much greater than that found in underground mines while very high production rates (over one hundred thousand tonnes of ore and waste per day) can be attained. many advantages over underground mining for relatively shallow to moderately deep deposits but these quickly disappear as deposit depth increases. - less expensive than underground mining Surface mining is used for: • mechanical excavation methods (e.g., quarrying, open pit, open cast mining) • aqueous methods (e.g., placer and solution mining).

Which one of the following factors is not a major consideration when deciding between mining a deposit by surface or underground methods?

the proximity of the deposit to an area of population

In open pit mining, the ratio of waste rock to ore is known as:

the stripping ratio

Which of the following considerations do you rate as the most important when selecting a mining method?

to mine in a safe working manner

A vein type deposit is a band of mineralization often associated with zones of weakness such as faults and joints.

true

In an underground mine a raise is developed __________ from one level to the next.

upwards

Other (Massive)

usually of relatively uniform but low ore grade but can have zones of enrichment that increase the ore's grade