ISO 21557:2025
(Main)Mining — Mining methods — Classification and specification
Mining — Mining methods — Classification and specification
This document establishes a classification of mining methods based on specification such as ore grade and recovery, cost of infrastructure, ore extraction, labour and machine costs, underground support costs and geotechnical factors.
Exploitation minière — Méthodes d'exploitation minière — Classification et spécifications
General Information
Standards Content (Sample)
International
Standard
ISO 21557
First edition
Mining — Mining methods —
2025-12
Classification and specification
Exploitation minière — Méthodes d'exploitation minière —
Classification et spécifications
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General . 1
5 Classification of mining method based on depth of deposit . 2
5.1 Surface mining methods .2
5.1.1 Description .2
5.1.2 Evaluation of surface deposits .2
5.1.3 Steps of surface mining operation .3
5.1.4 Strength and consolidate ore or rock -based mining methods .4
5.1.5 Unconsolidated and permeable ore or rock -based mining methods. 12
5.2 Underground mining methods . 23
5.2.1 Strong to moderate competent ore and rock based mining methods . 23
5.2.2 Moderate to weak incompetent ore and rock -based mining methods .32
5.2.3 Moderate to weak, cavable-based mining methods . . 36
Bibliography .44
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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iv
Introduction
A proper data classification allows the organisations to apply appropriate controls based on that
predetermined category data. The controls often come with a cost. It does not necessarily need to have the
same kinds of controls for all kinds of data.
Classifying your data can save your time and money because you are able to focus on what’s important, and
not waste your time putting unnecessary controls in place.
The primary purpose of this document on classification of mining methods is to promote uniformity and
comparability of mining information and it will be easier to be found when needed.
There are four main reasons why Information classification is important:
a) efficiency;
b) security;
c) culture of safety;
d) conformity.
v
International Standard ISO 21557:2025(en)
Mining — Mining methods — Classification and specification
1 Scope
This document establishes a classification of mining methods based on specification such as ore grade and
recovery, cost of infrastructure, ore extraction, labour and machine costs, underground support costs and
geotechnical factors.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 22932 (all parts), Mining — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 22932 series apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 General
The purpose of a classification system for mining methods is to provide an initial guideline for the
preliminary selection of a suitable method or methods. Its significance is great as this choice impinges on all
future mine design decisions and, in turn, on safety, economy, and the environment.
The choice of a mining method assumes a previous but cursory knowledge of the methods themselves.
It also assumes a brief understanding of ground control and of excavating and bulk handling equipment.
In the formal mine design procedure, the choice of mining methods immediately follows geological and
geotechnical studies, and feeds directly into the crucial milestone diagram where regions of the property
are delineated as to prospective mining methods. This step in turn just precedes the subjective, complex,
and critical layout and sequencing study.
The choice of mining method is an extremely important decision affecting the entire mining project;
The definition of the method permits to
a) establish the configuration of the mine,
b) choose mining equipment, and
c) perform an economic evaluation of the project.
Examples of factors in the choice of mining method are:
a) form of deposit;
b) dimensions of deposit;
c) strength of the ore and host rocks depth;
d) geological conditioning;
e) content and distribution of the ore deposit.
This document defines two following major mutually exclusive categories to classify mining methods based
on the geometry of the deposit and the ground conditions of the hanging wall, footwall and ore zone.
One category is the surface mining and the second one is the underground mining. In this regard, all mining
methods can be placed into the following categories:
— surface mining (see 5.1);
— underground mining (see 5.2).
5 Classification of mining method based on depth of deposit
5.1 Surface mining methods
5.1.1 Description
Surface mining is a form of mining in which the soil and the rock covering the mineral deposits are removed.
It is the other way of underground mining, in which the overlying rock is left behind, and the required
mineral deposits are removed through shafts or tunnels.
The traditional cone-shaped excavation (although it can be any shape, depending on the size and shape of
the ore body) that is used when the ore body is typically pipe-shaped, vein-type, steeply dipping stratified or
irregular.
Although it is most often associated with metallic ore bodies, it can be used for any deposit that suits the
geometry – most typically diamond pipes.
5.1.2 Evaluation of surface deposits
The following outline lists the basic factors which must be taken into account for evaluation of a prospective
surface mine:
a) geography;
b) legal status of land and mining rights;
c) historical, political, and sociological factors;
d) geology;
e) mining conditions;
f) ore treatment requirements;
g) economic analysis.
5.1.2.1 Geography
Topography, a function of location, affects cost of development and operation of a surface mine. Geographic
location establishes climate.
Location establishes the condition of remoteness from or proximity to civilization and its developed
facilities such as transportation systems, power supply, labour pool, manufacturing and supply services, and
specialty repair shops.
Location establishes the condition of remoteness from or proximity to civilization and its developed
facilities such as transportation systems, power supply, labour pool, manufacturing and supply services, and
specialty repair shops.
5.1.2.2 Legal status of land and mining rights
Land and other necessary rights should be checked, such as water use rights and the ability to acquire
auxiliary land for plant site, roads, tailings disposal ground.
5.1.2.3 Historical, political, and sociological factors
It is important to determine the extent and nature of national and local laws and regulations in regard to
conservation, water use, water and air pollution, tailings disposal, reclamation, handling of explosives, taxes,
royalties, import duties, mining safety and health codes, wage and labour conditions, pension requirements,
and unions.
5.1.2.4 Geology
Geological evaluation may include wide-spaced drilling, drill-sample logging, testing and processing,
plotting of the data on maps and cross-sections, preparation of specialized interpretive maps, calculation of
reserves by grades, calculation of stripping requirements, groundwater studies, and economic analysis.
5.1.2.5 Mining conditions
The geometry of an ore body and the topography of the land surface beneath which the ore body exists
will affect the kind and cost of a surface mine. The depth and character of overlying rock and the physical
characteristics of the wall rock also affect the configuration and cost of a surface mine.
5.1.2.6 Ore treatment requirements
Almost every potential surface mine must consider some phase of product upgrading (beneficiation).
This may vary from a simple crushing and sizing operation to a complex operation including multiple stages
of size reduction, concentration and agglomeration. In many cases, pilot-scale testing is deemed advisable.
5.1.2.7 Economic analysis
In the broadest sense, economic analysis for a surface mine involves the determination of market value of
the product and all the elements of cost of production.
By subtraction, a margin of profit (or loss) can be calculated.
Many new surface mines require very high capital investments. There are three commonly used yardsticks
to value investment worth:
a) degree of necessity;
b) payback period;
c) rate of return.
5.1.3 Steps of surface mining operation
a) strip out overburden (becomes spoils);
b) traditional surface mining methods fall into two broad categories based on locale as follow:
a) mechanical excavation methods;
b) aqueous methods;
c) clean up (reclamation).
5.1.4 Strength and consolidate ore or rock -based mining methods
This category comprises the four following mutually exclusive sub-categories that will be done mechanically:
a) open pit mining;
b) quarrying or quarry mining;
c) strip mining;
d) Auger mining.
5.1.4.1 Open pit mining
5.1.4.1.1 Description
Open-pit mining is surface mining in which huge portions of earth are dug from the surface to extract the
desired mineral within them. During the mining process, the land face is scraped away by explosives and
digging creating a deeper and deeper pit until the mining is complete. The final shape of the open pit is
decided before excavation begins. To most profitable mining pits are the ones where the entire mining area
is divided into 3-D blocks. Using geological information from drilled holes, the value of the desired mineral
in each block is estimated. The cost of mining each particular block is also determined; therefore, you can
designate a profit value for each block in the mine.
Open-pit mining has several levels of excavation in which we see varying visual displays. In the first steps
there is strip mining techniques that used from explosives, to surface scraping and bulldozing resulting in
quite bland rock formations. As the miners dig furthermore specific and detailed work done will be done.
Open-pit miners will work around the ore and get rid of all the surrounding material providing near cave-
like features. 3-D block miners create a puzzle-like display.
5.1.4.1.2 How it works
5.1.4.1.2.1 Step 1: designing the mining layout and blasts
The mine engineers, geologists, blasters, drillers and void officers all work together to make a safe,
profitable and efficient plan to which they all agree to. Until all these parties concur the mining cannot begin.
Throughout their planning the size, shape and depth of the mine are decided upon along with a sufficient
blast outline.
5.1.4.1.2.2 Step 2: probe drilling
Special machines are used for this process. These drills are used to create 16 m to 25 m probe holes into
potentially unstable ground. Using this equipment minimizes injury and costs. Through this step miners
find possible hot spots, unsafe areas and useful bench locations.
5.1.4.1.2.3 Step 3: grade control drilling
Once probe drilling is complete, geologists begin work to finalize the location of ore blocks by drilling grade
control holes. A sample is take at regular depth intervals and sent to the lab for assessment of value. Through
this step engineers know where valuable deposits, waste material and marginal deposits lay, furthering the
detail of the production plan. Once all probes are complete the surface is smoothed over in preparation of
production drilling.
5.1.4.1.2.4 Step 4: production drilling
During this stage drillers find specific areas in which blasters can optimize their clearing ability. As little
explosives as possible are used.
5.1.4.1.2.5 Step 5: charging
As soon as the drilling pattern is complete quality control is assessed in the holes. Checks for water, poor
drilling and overall safety are made. If there is water present during blasting irregular clearing occurs
resulting in either toe or over-sized holes. After checks are finished, the holes are filled with the proper
amount of explosives.
A detonator and a primer are lowered to about 1 m above the explosives. The hole is topped off by a minimum
of 3 m of gravel in order to plug the blast.
5.1.4.1.2.6 Step 6: blasting
Blasting varies from mine to mine and company to company. Regulations in certain countries and cities
result in several methods of blasting. If the mine is relatively close to an urban area, the wind is taken into
serious consideration. The dust produced by open mine blasting is quite abundant and harmful, so if the
wind is blowing towards residents blasting may be delayed. When blasting does commence, it is done hole
by hole, never simultaneously to avoid harmful vibration and excessive noise. After workers are cleared the
explosives are detonated.
5.1.4.1.2.7 Step 7: clearing the blast and marking the ore
Depending on company regulations a certain number of hours are passed before any crew goes to the blast
site. First to the site are the blasters to ensure that there are no undetonated explosives present. When
satisfied he/she allows the crew to proceed. Geologists then mark where ore blocks are present and create
a “dig plan.”
5.1.4.1.2.8 Step 8: digging
In this stage in the operation is where we see the heavy lifting and excavation of the desired ore. Bulldozers,
shovels, lifters and water machines are the main components of the crew. Shovels are enormous machines
which dig out from the markings and pull out the blocks of material to the surface. Lifters take the blocks
from the shovels and put it into either the valuable, marginal or waste dumps. The water machines are used
to spray the mine floor constantly to keep the dust down for the miners. They also help reduce the overall
dust production of the operation.
5.1.4.1.2.9 Step 9: drop off
When a lifter possesses a valuable or marginal load, it takes it to a primary crusher or a blend finger. The
blocks which need more work go to the crusher where they are obviously crushed and hashed. The pieces
which travel to the blend finger are usually quite developed and valuable. They need less destruction work
and more detailed mining. Through the finger the ore is found and stockpiled and the waste is then picked
up by dumpers.
5.1.4.1.2.10 Step 10: clean-up
Once the current level of mining is complete shovels and lifters are removed from the site. The level is
cleaned off and smoothed over to allow the process to start all over again.
5.1.4.1.3 Significant design issues
5.1.4.1.3.1 Biosphere
a) Clearing.
Site clearing for mining necessarily removes most if not all existing flora and displaces native fauna species
from the site. Clearing should be tailored as much as possible to minimize such effects. Local jurisdiction(s)’
regulations should be consulted and complied with.
b) Mining.
Mining processes can create significant amounts of air, ground, and water contamination. Environmental
factors such as wind and rain can disperse such contaminants and can lead to chemical changes to the
contaminants that increase or decrease their harmful effects on local flora, fauna, and human inhabitants,
as well as mine site workers. Processes should be tailored to minimize such effects. Local jurisdiction(s)’
regulations should be consulted and complied with.
c) Chemical and toxic pollution.
Chemicals used in mining processes and other contaminants resulting from mining processes can create
varying levels of potentially very toxic pollution. This pollution can be easily spread by environmental
conditions and mining practices, thus causing harmful effects on local flora, fauna, and human inhabitants,
as well as mine site workers. Effects can be more significant in close proximity to large bodies of water.
Processes should be tailored to minimize such effects. Local jurisdiction(s)’ regulations should be consulted
and complied with.
5.1.4.1.3.2 Lithosphere
a) Soil degradation.
Mining necessarily changes the soil. Chemical changes and degradation typically occurs during open
pit mining. Strong acidic or alkaline deposits can seep into the soil surrounding the mine. Remediation,
reclamation, and restoration can and should be conducted. Local jurisdiction(s)’ regulations should be
consulted and complied with.
b) Exposure.
Open pit mining exposes levels of ground which would never naturally be exposed. This creates problems for
the soil; the exposure to weathering erodes the soil much quicker. The chemical altering involved in mining
especially with nitrogen is quite harmful and the soils endure mass compaction.
c) Scree.
At times mining operations are found on mountain sides or directly on the mountain. When the miners start
to cut into the earth, the mountain’s shape is disturbed creating a scree drop effect
5.1.4.1.3.3 Atmosphere/Hydrosphere
a) Dust.
Open-pit mining is known for its dust complications. Especially during the blasting stage, dust becomes a
major problem for the atmosphere and hydrosphere. Gravel and sand are usually used to plug holes full
of explosives, when these explosives disintegrate these substances to dust it is released into the air. Dust
particles contribute to ground level ozone as well.
b) Chemical pollution.
The quantity and size of machinery typically used in mining processes can contribute significant levels of
potentially very toxic pollution to the mine site and local area. Mining processes often continue with minimal
downtime, increasing the rate of pollution exposure. Processes should be tailored to minimize such effects.
Local jurisdiction(s)’ regulations should be consulted and complied with.
c) Clearing of plants and trees.
Site clearing for mining necessarily removes most if not all existing flora. This changes the local
environmental processes significantly, such as conversion of carbon dioxide to oxygen. Clearing should be
tailored as much as possible to minimize such effects. Local jurisdiction(s)’ regulations should be consulted
and complied with.
5.1.4.1.4 Pros and cons
The advantages and disadvantages of one type of surface mining versus another are often related to the
types of equipment used and the associated costs and benefits derived from their use.
The advantages of open-pit mining in relation to underground mining are lower costs, greater safety, and
mechanically easier operations.
It is often agreed upon that surface mining is more sufficient than underground mining in terms of recovery,
grade control, economy, and flexibility of operation.
However, there are many deposits, that are too small or irregular, and or deeply buried to be extracted
cost-efficiently by surface mining methods. When the minerals extend deep in the ground, the removal of
the valueless rock becomes too expensive and the mine must be converted to underground operations or
abandoned.
Ecological degradation is often associated with open-pit mining.
5.1.4.1.5 Geometry of the deposit
The geometry of the deposit can be any shape, any dip, thick and large size.
5.1.4.2 Quarrying or quarry mining
5.1.4.2.1 Description
Quarrying or quarry mining is usually restricted to mining dimension stone-prismatic blocks of marble,
granite, limestone, sandstone, slate that are used for primary construction of buildings or decorative facing
materials for exterior and interior portions of buildings.
Quarries generally have benches with vertical faces from a few centimetres to 66 m in height. Blocks are
drilled and wedged free in a highly selective manner using time consuming and expensive methods.
Planning of the excavation is based primarily on geological factors such as the direction and attitude of
bedding and joint systems.
5.1.4.2.2 How it works
5.1.4.2.2.1 General
Quarrying of stones is the art of extracting stones from the rock beds. The place from which the stones are
obtained (by digging or blasting) is known as ‘quarry’.
Quarrying differs from mining in which various operations are carried out for exploring minerals, such as
coal, quartzite from a mine under the ground.
The different methods of quarrying are as follow:
a) by digging;
b) by heating;
c) by wedging;
d) by blasting.
5.1.4.2.2.2 Hand digging method
Digging or excavation of stones is carried out with the help of tools such as crowbars and pickaxes.
Only those stones which occur in the form of detached nodules buried in earth can be recovered by this
method.
5.1.4.2.2.3 Surface heating method
The use of this method is resorted to only in case of those stones which are required in small pieces to be
employed for road metal, railway ballast and aggregates.
In this method, fuel is collected on the exposed surface of the portion of the rock to be removed and the fire
is burnt for several hours continuously (ordinary bundle wood is employed for burning).
The detached portion is then removed with the quarrying tools and then broken into small pieces as per
requirements.
5.1.4.2.2.4 Wedging method
This method of quarrying is employed for the rocks which are in the form of layers along which it can be
easily split (e.g. sedimentary and soft rocks like limestone, marble, slate and laterite), and the stone is
required in blocks for building purposes.
Soft stratified rock can be removed with the help of pick-axes and crowbars but in case of hard rocks the
holes are made and grooves are cut at shorter intervals.
Blunt wedges are then inserted in the grooves or conical pins of steel are driven into the holes with a hammer.
In place of conical pins sometimes plug and feathers are used. The plug is a conical wedge and feathers are
flat wedges with upper ends slightly bent.
The plug along with the feathers is applied into the holes and is subjected to hammer blows.
If the plugs and feathers are arranged a few centimetres apart and all driven at the same time, the stone will
get cracked.
In the case of harder stone, the holes are originated from a pneumatic drill.
5.1.4.2.2.5 Blasting method
a) General.
This method is employed for quarrying hard and compact stones.
The various stages involved in the method of quarrying by blasting are as follows:
b) Boring hole in the rock.
The holes are usually made (of desired depth, from 1,25 m to 2,5 m deep, and 20 mm to 40 mm diameter)
with a steel bar with knife-edged ends called jumper. When a large quantity of stones is required, holes may
be drilled by a drilling machine.
During the drilling operation, water is used to facilitate the operation. The mud and rock powder produced
as a result of drilling are removed by a scraper, or a spoon or by a compressed air blast.
c) charging with explosive.
The drilling of the hole is followed by charging it with an explosive. It should be ensured that the hole is
thoroughly dry before being filled with explosives.
d) tamping.
Tamping is of paramount importance to prevent the reaction of the explosive along the blasting hole itself.
While charging the hole with explosive and prior to tamping a fuse of sufficient length is inserted.
Tamping consists in filling the hole with stiff sandy clay by a brass rod called the tamping bar.
e) Firing.
The fuse is kept of a sufficient length as to enable the person firing it enough time to retire to a safe place
before the explosion of the charge occurs.
The use of electrically firing devices is also made to create the spark needed for the explosion. When the
explosion occurs masses of stones around the hole are removed.
For preventing any misfire, the following precautions shall be taken:
a) The boreholes should be charged with explosives only after these are thoroughly cleaned.
b) As far as practicable, a maximum of ten holes may be loaded and fired at one time successively and not
simultaneously.
c) The lighting end of the safety fuse should be cut (with a knife) in an oblique direction.
d) After the insertion of the fuse in the detonator, it should be fixed by nippers.
e) When water is present or hole is damp, the junction of the fuse and detonator must be made watertight
by using tough grease, white lead or tar.
Firing of the fuse by electricity entails the following advantages:
a) ensure safety;
b) saving in labour and time;
c) the efficiency of explosive greatly increases (due to simultaneous firing), eventually making operation
economical;
d) useful for firing fuse underwater or in wet places;
e) no danger of misfire;
f) proper signalling can be arranged to avoid the occurrence of accidents.
5.1.4.2.3 Significant design issues
A good location of a quarry should fulfil the following requirements:
a) A large quantity of good quality stone must be available about the earth’s surface.
b) It should be located near roads and railway lines.
c) Ample space for the installation of crushers, storage of stones and other materials should be available.
d) In case the quarrying is to be done by ‘blasting’; the site of quarry should be away from any permanent
structure.
e) There should be proper provision for drainage of rainwater.
5.1.4.2.4 Pros and cons
The introduction of infrastructure necessary for mining can be a benefit to a local community if available
for their use especially in improving access. Job creation for mine workers and supporting services can
economically benefit a local community. Quarry mine sites which are properly reclaimed can become sites
for recreation and tourist activities.
Pollution, habitat destruction, and environmental degradation can negatively impact the local ecology and
human community. Introduction of non-native flora and fauna can negatively affect the local environment.
5.1.4.2.5 Geometry of the deposit
The geometry of the deposit can be tabular or massive, any dip, thick and moderate size.
5.1.4.3 Strip mining
5.1.4.3.1 Description
Strip mining describes a particular type of surface mining method that relies heavily on the progressive and
sequential disposal of overburden spoil into a previously mined void. Coal mining often falls in this category,
although bauxite miners often adopt a variant of strip mining.
Dragline equipment, supplemented by truck and shovel systems, are often observed in strip mines. Strip
ratios can be relatively high, and slope angles can be relatively steep, largely due to the relatively low overall
height of these slopes.
5.1.4.3.2 How it works
5.1.4.3.2.1 General
Strip mining is a mineral-extraction process in which a layer or seam of undesired material (called
“overburden”) is removed from the surface of an area to allow efficient access to a desired material existing
underneath the layer being stripped. As the process suggests, it is a form of surface mining, and it is primarily
used to extract material that lies relatively close to the surface.
There are two forms of strip mining as follow:
a) Area stripping;
b) Contour stripping;
5.1.4.3.2.2 Area stripping
The first and most common approach is referred to as area mining; it is used on fairly flat terrain over a large
area and involves the removal of long strips (potentially 100 m) at once. In this approach, the overburden
removed from each new strip is deposited into the excavated area left by the previous strip.
5.1.4.3.2.3 Contour stripping
The second approach, called contour mining, is used on hilly terrain and involves removing the overburden
above the mineral seam near the outcrop in hilly terrain in a manner that mirrors its topography, where the
mineral outcrop usually follows the contour of the land. Contour stripping is often followed by auger mining
into the hillside, to remove more of the mineral. This method commonly leaves behind terraces in mountain
sides.
5.1.4.3.3 Significant design issues
Strip mining encompasses a number of different mining strategies, each a unique combination of pit
configuration, equipment selection, and operating methodology and what drives the selection of one strip
mining strategy over another.
5.1.4.3.4 Pros and cons
5.1.4.3.4.1 List of pros of strip mining
a) It is much more efficient compared to underground mining techniques.
Supporters of strip mining are lauding the efficiency of the process compared to the more traditional
underground mining. For them, the cost and safety for this kind of method is so much better than the
traditional one.
With strip mining, tunnels no longer need to be dug and supported. The lifting of minerals is not done on
long routes just to get to the surface either. That said, retrieval and transport are more convenient using
surface mining techniques.
b) It costs lower.
Lower processing costs often mean production costs will not be that high either As a result, the final cost of
the material won’t be that much as well.
c) It is safer.
Underground mining poses several threats to workers because tunnels can collapse or they can breathe
toxic air. Companies that engage in strip mining are required to reclaim the land they used by filling the
areas they removed and covering them with topsoil and replanted vegetation.
5.1.4.3.4.2 List of cons of strip mining
a) It has a negative impact on the environment.
The effect of strip mining on the environment has always been raised. This method not only introduces
pollutants to the environment, it also destroys the natural ecosystem.
Companies are required by law to reclaim the land they strip mined but it takes years to get the land back to
what it once was.
Also, fragile ecosystems may take years to recover (or regain equilibrium) once they have been disturbed.
This leads to the loss of plant and animal life. Plus, there’s a risk of reclamation jobs not being done properly
resulting in the land becoming prone to erosion and flooding which just spells more destruction.
b) It can lead to water sources being contaminated.
Extraction solvents are used in strip mining and this can lead to water sources being contaminated. Not
only that, excavated material are also dumped which can also affect water supply. Toxins and dust are also
released into the air when strip mining is performed which results in poorly controlled contamination.
Although efforts are being done to prevent this from happening, it’s not always a guarantee. For example,
sealed tailing ponds are meant to hold liquid contaminants until they are solid and can safely be removed.
However, it has been shown that leaks do occur and can contaminate areas located nearby.
5.1.4.3.5 Geometry of the deposit
The geometry of the deposit can be tabular, low dip, thin and large size.
5.1.4.4 Auger mining
5.1.4.4.1 Description
Auger mining refers to a method of removing coal, clay, phosphate, oil-shale from thin seams exposed in
deep trenches or high-walls in strip mines.
5.1.4.4.2 How it works
A mining method often used by strip mine operators where the overburden is too thick to be removed
economically. Large-diameter, spaced holes are drilled up to 61 m into the coalbed by an auger. Like a bit
used for boring holes in wood, this consists of a cutting head with screw like extensions. As the auger turns,
the head breaks the coal and the screw carries it back into the open and dumps it on an elevating conveyor;
this, in turn, carries the coal to an overhead bin or loads it directly into a truck. Auger mining is relatively
inexpensive, and it is reported to recover 60 % to 65 % of the coal in the part of the bed where it is used.
The auger consists of two principal pieces. The first is a cutting head, generally from 45 cm to 245 cm
in diameter. It may be single or multiple. The second is a prime mover, usually a skid mounted carriage,
providing a mounting for the engine, drive head, and controls. As coal arrives at the surface it is transported
via a conveyor belt or a front-end loader to a waiting truck.
5.1.4.4.3 Significant design issues
The design concept of auger mining consists of three categories as the single pass, double passes and multiple
passes. The single pass is confirmed to have only one row of hole. Secondarily, the double passes are the
technique of application two rows of auger holes, which has the lower first hole and the upper second holes.
The last one is multiple passes which is the application of auger miner into different coal seams. However,
this research is mainly studied exclusively on the operation of auger mining on the single pass.
Auger mining shall be planned and conducted by the operator to insure against any hazard to underground
workings located at or near such auger operations and all auger holes shall be located so as to prevent:
a) the disruption of the ventilation system of any active underground mine;
b) inundation hazards from surface water entering any active underground mine;
c) damage to the roof and ribs of active underground workings;
d) intersection of auger holes with underground mine workings known to contain dangerous quantities of
impounded water.
Auger mining service is including pit preparation and haulage to ROM stockpile, site assessment, auger
reserve estimation, geotechnical design and operational planning support.
5.1.4.4.4 Pros and cons
This operation is usually low-cost and highly productive, but recovery ranges from 40 % to 60 %. It can be
implemented with relatively low capital costs.
In this method parts of the reserve remains in place, but it has been sterilized, i.e. left in a condition where
it will be essentially impossible for anyone to recover them in the future. The holes into the side of the hill
create drainage holes for acid-laden water, and that is a big problem. Surface subsidence and spontaneous
combustion in the auger holes are additional concerns.
Auger mining is used for recovering coal by boring into a coal seam at the base of strata exposed by
excavation. Normally one of the lowest-cost techniques of mining, it is limited to horizontal or slightly
pitched seams that have been exposed by geologic erosion. Augering is usually associated with contour
strip-mining, recovering coal for a limited depth beyond the point where stripping becomes uneconomical
because the seam of coal lies so far beneath the surface.
5.1.4.4.5 Geometry of the deposit
The geometry of the deposit can be tabular, flat, thin and remnant.
5.1.5 Unconsolidated and permeable ore or rock -based mining methods
5.1.5.1 General
This category comprises the four following mutually exclusive sub-categories that will be done under title of
aqueous methods.
Aqueous surface mining methods, uniquely involving the use of water for extraction, can be used in
special circumstances. The mining of placer-type deposits that contain concentrations of heavy metals in
unconsolidated overburden are particularly suitable to dredging and hydraulic mining if an adequate water
supply is available and the mining operation can comply with the applicable environmental regulations:
a) placer mining:
1) hydraulic mining;
2) dredging mining;
b) borehole mining;
c) leaching mining:
1) in situ leaching;
2) heap leaching;
d) undersea mining.
5.1.5.2 Placer mining
5.1.5.2.1 General
a) The extraction of heavy mineral from a placer deposit by concentration in running water. It includes
ground sluicing, panning, shovelling gravel into a sluice, scraping by power scraper and excavation by
dragline, dredge or other mechanized equipment.
b) Extracting the gold or other mineral from placers, wherever situated-in dry channels and in channels
temporarily filled with water. The mineral may be found in deep channels, in navigable streams, or in
estuaries or creeks and rivers where the sea ebbs and flows.
c) That form of mining in which the superficial detritus is washed for gold or other valuable minerals. When
water under pressure is employed to break down the gravel, the term hydraulic mining is generally
employed. There are deposits of detrital material containing gold which lie too deep to be profitably
extracted by surface mining, and which must be worked by drifting beneath the overlying barren
material. The term "drift mining" is applied to the operations necessary to extract such auriferous
material.
d) The extraction and concentration of heavy metals or minerals from placer deposits by various methods,
generally using running water.
Because large placer deposits can be thoroughly explored before floating a dredge, such operations can lend
themselves to thorough planning, and it is possible to carry out reclamation as mining progresses at only a
slight increase in operating costs.
There are two types of placer mining:
5.1.5.2.2 Hydraulic mining
5.1.5.2.2.1 Description
Hydraulic mining uses high-pressure water cannons, known as monitors, to dislodge relatively
unconsolidated material.
Hydraulicking, now often termed hydraulic mining, ideally requires the presence of a natural gradient
away from the deposit to facilitate hydraulic transport of the resultant ore or waste slurry to the process or
disposal area.
One of the earliest applications of hydraulic mining was to break down banks of alluvium containing gold
and silver. These alluvial deposits are firm, but break down quickly upon the application of the water
cannons. Of course, if digging the banks of alluvium were the goal, we could use wheeled front loaders or
other traditional digging and loading equipment.
The goal is not only to excavate the banks but to separate the gold, silver, or other metals from the sediments
in these alluvial deposits. Towar
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