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349
CHAPTER 6.2
Mining Methods 
Classification System
L. Adler and S.D. Thompson
INTRODUCTION
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 proce-
dure, the choice of mining methods immediately follows geo-
logical and geotechnical studies, and feeds directly into the 
crucial milestone diagram where regions of the property are 
delineated as to prospective mining methods (Lineberry and 
Adler 1987). This step in turn just precedes the subjective, 
complex, and critical layout and sequencing study.
To develop the proposed classification system adopted 
here, many existing ones (both domestic United States and 
foreign) were examined and incorporated to varying degrees. 
The result is deemed more systematic, inclusive, and under-
standable than its predecessors (i.e., Stoces 1966).
Subsequent parts of this handbook elaborate on the selec-
tion and comparison of mining methods.
INPUT STATEMENT
A comprehensive statement has been developed to provide a 
rapid checklist of the many important input parameters (Adler 
and Thompson 1987). The three major areas are (1) natural 
conditions, (2) company capabilities, and (3) public policy 
(Table 6.2-1). Those parameters appearing early are gener-
ally the most important. Natural conditions require that a dual 
thrust be maintained concerning resource potentials and engi-
neering capabilities. An additional basic distinction occurs 
between geography and geology. For company capabilities, 
fiscal, engineering, and management resources must be recog-
nized. This includes the scale of investment, profitability, and 
personnel skills and experience. Public policy must be consid-
ered, particularly as to governmental regulations (especially 
safety, health, and environmental), tax laws, and contract 
status. Some of the latter input factors are held in abeyance 
until near the end of the investigation, and then considered as 
modifying factors. This organization duplicates but tightens 
others (Hartman 1987).
SPATIAL DESCRIPTION
Most mineral deposits have been geometrically characterized 
as to an idealized shape, inclination, size, and depth. Complex 
or composite bodies are then composed of these elements.
Ideal shapes are either tabular or massive, with chim-
neys (or pipes) being subordinated. Tabular deposits extend 
at least hundreds of meters (feet) along two dimensions, and 
substantially less along a minor dimension. Massive bodies 
are approximately unidimensional (cubic or spherical), being 
at least hundreds of meters (feet) in three dimensions. A modi-
fication is recommended later to achieve closure with tabular 
deposits. For tabular deposits, the inclination (attitude or dip) 
and thickness are crucial. Inclinations range from flat to steep 
(Table 6.2-2) (Hamrin 1980; Popov 1971).
L. Adler, Professor, West Virginia University, Morgantown, West Virginia, USA 
S.D. Thompson, Assistant Professor, University of Illinois at Urbana–Champaign, Illinois, USA
Table 6.2-1 Input statement categories
Primary Categories 
(Dependency) Secondary Categories
Natural conditions 
(invariant)
Geography
Geology
 Economic engineering
Company capabilities 
(variant)
Business administration
Monetary aspects
Management aspects
Public policy 
(semivariant)
Regulations
Taxes
Contracts
Incentives
State of the art 
(mining engineering)
Salient distinctions
 Total systems (design/control)
 Encumbered (and regulated) space
 Full-spectrum practice (manage/evaluate)
 Professionalism
350 SME Mining Engineering Handbook
In surface mining, the inclination limits the advanta-
geous possibility of being able to cast waste material nearby, 
as opposed to hauling it a distance and then storing it. For flat 
deposits, especially when fairly shallow, an area can be suc-
cessively opened up and the waste can then be cast into the 
previously mined-out strips, a substantial economic advan-
tage. Casting, in its normal sense, is not restricted to the use of 
rotating excavators; broadly, it means relatively short-distance 
hauling of waste, which can also be done with mobile loaders 
and/or trucks or with mobile bridge conveyors. For steeper 
(and deeper) deposits, stable pit slopes become important 
(Table 6.2-3) (Hartman 1987; Popov 1971). Where the deposit 
inclination exceeds that of the stable slope, both the hanging 
wall and footwall must be excavated and the increased waste 
then handled and placed.
For both surface and underground mining methods, the 
inclination cutoff values nearly coincide (one for pit slopes, the 
other for face bulk handling mechanisms, whether mechanical 
or by gravity). While not identical, they are close enough to 
use similar values (20° and 45°; see Table 6.2-2).
The thickness of a tabular deposit is also important 
(Table 6.2-4), with reference primarily to underground work 
(Popov 1971). When three or more benches are required, the 
deposit tends to be treated as massive. Primarily in flat under-
ground deposits, thickness governs the possible equipment 
height (low profile), and in steep ones its narrowness. Also, 
in underground mining, the deposit thickness becomes a sup-
port problem, especially if effective pillars become so massive 
that recovery is compromised. When the upper limit of any 
of these concerns is reached (e.g., benching, equipment size, 
and pillar bulk), closure with massive deposits occurs for all 
practical purposes. Pillar size vs. recovery can dictate caving 
except where pillar sizes may be decreased because backfill-
ing is used, such as in postpillar cut-and-fill.
Finally, the depth below the ground surface is impor-
tant (Table 6.2-5) (Popov 1971; Stefanko 1983). For surface 
deposits, even flat ones, this can obviate casting and require 
increased waste haulage and expanded dump sites. For under-
ground mining, earth pressures usually increase with depth, 
consequently raising the support needs. The ground surface 
location above a deposit must be clearly identified to evaluate 
other parameters (see “Input Statement” section previously).
CORRELATING DEPOSIT TYPES
The inclination (dip) can be roughly related to the deposit 
type (Table 6.2-6). Rocks can also be related to strength 
(Table 6.2-7) (Hartman 1987). The strength of the deposit and 
its envelope of country rock can then be related to its type 
(Table 6.2-8). For determining pit slopes, (surface mining) 
and support requirements (underground mining), these rela-
tionships become important. Some variations are noted, espe-
cially for veins and disseminated deposits.
Table 6.2-2 Tabular deposits classified by attitude and related to 
bulk handling and rock strength
Class
Attitude 
or Dip Bulk Handling Mode Rock Strength
Flat ≤20° Use mobile equipment 
(and conveyors)
Weak rock (surficial)
Inclined 20–45° Use slashers (metal plate 
can also vibrate—as 
gravity slides)
Average rock
Steep ≥45° Gravity flow of bulk solids Strong rock (at depth)
Table 6.2-3 Surface pit slopes related to rock strength and time
Rock
Maximum Pit Slope
Short Term Long Term
Strong 41°–45°(–70°)* 18°–20°
Average 30°–40° 15°–18°
Weak (soils also) 15°–30° 10°–15°
*Infrequently up to 70°.
Table 6.2-4 Underground deposits classified by thickness
Class
Deposit Thickness
CommentsCoal Ore
Tabular
 Thin 0.9–1.2 m 
(3–4 ft)
0.9–1.8 m 
(3–6 ft)
Low profile or narrow 
mine equipment
 Medium 1.2–2.4 m 
(4–8 ft)
1.8–4.6 m 
(6–15 ft)
Post and stulls 
≤3.1 m (10 ft)
 Thick 2.4–4.6 m 
(8–15 ft) pillar 
problems
4.6–15.3 m 
(15–50 ft) can 
cave (steep dip)
Small surfaceequipment; crib 
problems
Massive ≥4.6 m 
(15 ft)
≥5.3 m 
(50 ft)
Pillar problems 
or poor recovery; 
benching necessary; 
caving considered
Table 6.2-5 Deposits classified by depth
Class
Deposit Depth
Underground 
(a measure of overburden pressure)
SurfaceCoal Ore
Shallow ≤61 m 
(200 ft) slope 
entries possible
≤305 m 
(1,000 ft)
≤61 m
(200 ft)
Moderate 122–244 m 
(400–800 ft) 
pillar problems
305–457 m 
(1,000–1,500 ft)
61–305 m
(200–1,000 ft)
Deep ≥915 m 
(3,000 ft) bumps, 
burst, closure
≥1,830 m 
(6,000 ft)
≥305–915 m 
(1,000–3,000 ft) 
open pit
Table 6.2-6 Deposit classified by geometry and type
Geometric Class Deposit Type Comments
Tabular Alluvium (placer) Near surface—weak
 Flat and 
inclined
Coal (folded too) Weak country rock—an 
erosion surface
Evaporites (domes too)
Sedimentary Good country rock, thicker
Metamorphic (folded too)
 Steep Veins Can be weakened or 
rehealed (gouge and 
alteration)
Massive Igneous (magmatic) Strong
Disseminated ores Can be weakened
 Mining Methods Classification System 351
CLASSIFYING SURFACE MINING METHODS
Depth Related to Inclination
The surface mining classification, although based on the cru-
cial ability to cast waste material rather than to haul it, has 
other features. These are primarily based on the depth of the 
deposit being a function of its inclination. Flat seams tend to 
be shallow, and casting is possible; steep and massive deposits 
trend to depth. From this, a number of relationships result.
Depth Related to Excavating Technique and Stripping 
Ratio
Because of the effects of weathering and stress release, exca-
vating becomes more difficult and expensive with depth, 
following a continuum from hydraulic action and scooping 
through to blasting (Hartman 1987).
As a matter of definition, the stripping ratio (ratio of 
waste to mineral) usually increases with depth. However, 
the relatively inexpensive handling of waste near the surface 
by casting tends to mitigate this increase, permitting higher 
ratios. The use of mobile, cross-pit, high-angle conveying 
allows greater pit depths and, along with the mineral value, 
also influences this ratio.
Surface Mining Classification System
Based on the foregoing factors, a surface mining classification 
has been developed (Table 6.2-9). The classification incorpo-
rates information dependent on the intrinsic characteristics of 
the geometry of the deposit. Quarrying appears to be anoma-
lous because of (1) relatively steeper pit slopes, (2) special-
ized means of excavating and handling, and (3) less critical 
amount of overburden. “Glory hole” mining or its equivalent 
is making a comeback in very deep open pits using inclined 
Table 6.2-7 Rocks classified by strength
Class Compressive Strength Examples
Weak ≤41.3 MPa (6,000 psi) Coal, weathered rock, 
alluvium
Moderate 41.3–137.9 MPa 
(6,000–20,000 psi)
Shale, sandstone, limestone, 
schist
Evaporites, disseminated 
deposit
Strong 137.9–206.8 MPa 
(20,000–30,000 psi)
Metamorphic, igneous, veins, 
marble, slate
Very strong ≥206.8 MPa (30,000 psi) Quartzite, basalt, diabase
Table 6.2-8 Deposits related to geometry, genesis, and strength (in order of induration)
Deposits Type Geometry Genesis
Strength and Stiffness, 
Deposit/Country Rock Examples
Alluvium (placers) Tabular-flat Surface-stream action deposition 
(fans, deltas, meanders, braids)
Poor/poor Sand and gravel; precious metals 
and stones (tin)
Erosion surface (swamps) Tabular-flat and thin 
(possible folding)
Swamps (possible dynamic 
metamorphism)
Poor/poor to good Coal
Disseminated Massive Underground channels and 
multifaceted advance
Poor/poor Hydrothermal ores (porphyry 
coppers and sulfides)
Vein (can be rehealed) Tabular-inclined (pipes, 
chimney shoots)
Major underground channels 
(fissures), gouge, alteration (reheal)
Poor to good/good Hydrothermal ores (porphyry 
coppers and sulfides)
Evaporites Tabular-flat-thick Interior drainage Good/good Salt, phosphates
Sedimentary (bedded) Tabular-flat-thick Shallow seas Good/good Limestone, sandstone
Metamorphic Tabular-flat-thick Dynamic and/or thermal Good/good Marble, slate
Igneous (magnetic) Massive Plutonic emplacement Good/good Granite, basalt, diabase
Table 6.2-9 Classification of surface mining methods
Shape, 
Attitude (dip)
Deposit 
Characteristics Stripping Ratio
Excavation
Mining MethodWaste Handling Excavation
Tabular
 Flat Near surface Low Onsite Hydraulic, scoop, dig Placers—hydrosluicing, dredging, 
solution—at depth
Shallow Moderate Cast Scoop, dig, light blast Open cast (strip)—area, contour, 
mountain top
 Inclined Moderate Moderate (remove 
hanging wall)
Need highwall Auger Auger
Haul (to waste dump) Blast Open pit
Deep High (remove both 
hanging wall and 
footwalls)
Haul (to waste dump) — Open pit
Saw, jet pierce (joints) Quarry
Massive Full range Depends on depth Haul (to waste dump) — Open pit; glory hole
Note: In-situ mining is always possible.
352 SME Mining Engineering Handbook
hoisting. Glory hole mining utilizes a single large-diameter 
raise located in the lowest point of the pit, down which all 
blasted material is dumped. The bottom of the hole feeds 
into crushers and a conveying system, which transports the 
material to the surface through a horizontal or inclined drift 
(Darling 1989).
In contrast to the underground classification, the surface 
one is not formed into a matrix. This is because depth and 
therefore the excavating technique, waste handling, and strip-
ping ratio are all functionally related to the deposit geometry, 
particularly the seam inclination. No preceding classification 
recognizes this relationship (Hartman 1987; Lewis and Clark 
1964; Morrison and Russell 1973; Stout 1980; Thomas 1973).
CLASSIFYING UNDERGROUND MINING METHODS
Normally, two major independent parameters will be consid-
ered that form a matrix, unlike for surface methods. These two 
parameters are (1) the basic deposit geometry, as for surface 
methods, and (2) the support requirement necessary to mine 
stable stopes, or to produce caving, a ground control prob-
lem (Boshkov and Wright 1973; Hamrin 1980; Hartman 1987; 
Lewis and Clark 1964; Thomas 1973).
Deposit Geometry
Deposit geometry employs the same cutoff points for tabular 
deposits as in the surface classification, but for different rea-
sons. Flat deposits require machine handling of the bulk solid 
at or near the face; steep ones can exploit gravity (Table 6.2-2), 
with an intermediate inclination recognized. If stopes are 
developed on-strike in steep seams as “large tunnel sections” 
or “step rooms” (Hamrin 1980), machine handling can still be 
used. The resulting stepped configuration causes either dilu-
tion or decreased recovery, or both. Because this face can also 
be benched, stope mining simply reproduces tunneling.
Ground Control
Ground control requires knowledge of the structure (opening), 
material (rock), and loads (pressures). Structural components 
are detailed in Table 6.2-10. Earlier tables detailed the deposit 
by its depth and detailed rocks by strength (Tables 6.2-5 and 
6.2-7, respectively). From the point of view of support, the 
roof, pillars, and fill are of primary concern.
Main Roof
The main roof (sometimes the hanging wall) is distinguished 
from the immediate roof by being the critical load transferring 
element between the overburden and pillars. The immediate 
roof can be removed (mined out) or supported artificially and 
lightly. The main roof is defined as the first close-in, compe-
tent (strong) seam. If it is only marginally competent, heavy 
artificial support may keep it stable; if not, then caving can be 
expected. For a flat seam, the vertical (perpendicular) loads on 
the main roof are largely due to the overburden and its own 
body load. Horizontal (tangential) loads or pressures will tend 
to be uniformly distributed, resulting in a low stress concentra-
tion. If bed separation occurs above the main roof, this stress 
uniformity is enhanced;but at depth, overburden loading tends 
to decrease separation. Body loads are invariant, whereas 
edge loads—particularly those due to the overburden— 
can be shifted (pressure arching). The main roof is often suf-
ficiently thick so that it can be arched below 1/5 (i.e., at less 
than 1 horizontally and 5 vertically) to increase stability. A 
guideline for coal is that stable spans are usually less than 
3 m (10 ft), whereas for hard rock they are generally less than 
30 m (98 ft).
For an inclined seam, the main roof is the hanging wall, 
and the results are similar to a flat seam. Pressures perpen-
dicular to it are more significant then tangential ones, and bed 
separation due to gravity is less likely.
Table 6.2-10 Structural components located and described for underground mining
Component (time dependent) Location/(Material) Loaded by Supported by Comments
Roof (can deteriorate, slough, 
slake—dry and crumble)
Back and hanging wall 
(envelope)
Main roof—all, especially 
overburden (cap rock)
Pillars and fill, also arched 
(1/5)
Spans ~3 m (10 ft) for coal to 
30.5 m (100 ft) for rock
Immediate roof—body Artificial supports can remove Spans ~3.1 m (10 ft) 
(stand-up time)
Pillars and walls (can 
deteriorate—slough, slake)
Sides, deposit and waste 
(horses mainly deposit)
All—especially overburden Floor Critical:
1. Stiffness: (slenderness ratio: 
approximately 10/1 [coal] to 
1/3 [rock])
2. Strength (material)
3. Percentage recovery
Floor (can settle and heave) Footwall (envelope) All—through pillar watch 
water
Country rock can be 
compacted, removed, drained
Critical:
1. Stiffness
2. Strength (bearing capacity 
especially if water)
3. Heave (deep-seated)
Fill (for permanent stability) Crushed waste, sand, water All—especially as pillars 
are removed
Footwall and floor Good mainly to support hanging 
wall. Requires greater than 
angle of slide and confinement.
Artificial support (limited time) External: Timber (props, sets, 
cribs, stulls, posts); concrete 
gunite (mesh)
Mainly immediate roof Floor Deterioration (chemical and 
stress)
Internal: Bolts (headers), 
trusses, cables, grout, 
cementation
Mainly immediate roof Anchorage in roof, etc. Anchorage a concern
 Mining Methods Classification System 353
Pillars
Pillars serve to support the main roof and its loads, primar-
ily the overburden acting over a tributary area. Pillar material 
consists mainly of the seam itself and sometimes waste incor-
porated within the seam. Pillars must not only be sufficiently 
strong but also must be sufficiently stiff, a frequently over-
looked requirement. If pillars are not adequately stiff, but still 
adequately strong, the roof will collapse about the still free-
standing pillars, especially when differential pillar (and floor) 
deflection occurs. The minimum slenderness ratio for pillars to 
avoid this crippling is inversely proportional to the recovery. 
The mining of flat, thick seams of coal dramatically reflects 
this relationship and is a factor in classifying seam thicknesses 
(Table 6.2-4). For massive deposits, even in strong rock, this 
makes freestanding pillars of doubtful value. Upper slender-
ness ratios range from about 10/1 for coal to 1/3 for rock. 
Continuous vertical pillars are used to separate vertical stopes 
in hard rock that employ steep, tabular stoping methods. Even 
with stable ground, these are usually filled soon after mining 
for long-term stability. When massive deposits along with 
their cap rock are weak, caving is necessitated, usually per-
formed as horizontal lifts or as block caving. Caving always 
requires a sufficient span 9 m (30 ft), good draw control, and 
also risks dilution and/or poor recovery. Soft or nonuniform 
floors (footwalls) act the same as do soft and irregular pillars.
Fill
Fill, often a sandy slurry consisting of crushed waste, cement, 
and water, can be readily introduced into confined (plugged), 
inclined, and steep tabular stopes. When drained and dried, 
this hardened slurry provides permanent resistance to ground 
movement, especially for the walls or pillars. It is widely used 
in all but the caving methods. It is either run in progressively 
as a stope is mined out or done all at once at the end of stope 
mining. Because of settlement and shrinkage away from a flat 
back, it is marginally useful for flat deposits.
When timbering is densely placed, especially with square 
sets, it rivals pillars. It, too, is usually filled as stoping pro-
gresses (overhand mining). These relationships are summa-
rized in Table 6.2-11 and lead into the formal classification.
Underground Mining Classification System
Based on an understanding of bulk handling and ground 
control, the underground classification system shown in 
Table 6.2-12 closely follows previous ones. The primary dif-
ference is that sometimes shrinkage stoping is considered 
self-supported rather than supported. However, although the 
broken mineral provides a working floor, it is still supporting 
the hanging wall (roof). On the other hand, when the stope 
is drawn empty, it remains substantially self-supported until 
fill is introduced. The disadvantages of the shrinkage method 
are unique: (1) an uncertain working floor, (2) dilution due 
to sloughing and falls of rock, (3) possibly adverse chemical 
effects, and (4) tying up about two-thirds of the mineral until 
the stope is drawn.
Vertical crater retreat mining is included in the classifica-
tion between sublevel and shrinkage stoping (Hamrin 1980).
OTHER FACTORS
While subordinated, there are additional factors that must be 
closely evaluated. These deal with the broad impacts on the 
environment, health and safety, costs, output rate, and oth-
ers. They are usually evaluated on a relative basis, although 
numbers may also be employed (Table 6.2-13) (Boshkov 
and Wright 1973; Hartman 1987). An example of where 
the environmental considerations on the surface are begin-
ning to affect mining methods is in the use of high-density 
paste backfilling in order to return most of the tailings back 
Table 6.2-11 Deposit and structural components related to underground mining methods
Deposit Geometry
Structural Main 
Roof and Floor
Components Rated 
(pillars, walls)* Underground Mining Methods Type
Tabular
 Flat (and inclined) Good Good Room-and-pillar (spans ≤6 m [20 ft]);
stope-and-pillar (spans ≤31 m [100 ft])
Self-supported
Good Poor Room-and-pillar; stope-and-pillar Supported
Poor (roof collapses about 
free-standing pillars)
Good Longwall; pillaring Caved
Poor Poor Immediately above Caved
 Steep Good Good Sublevel stoping (spans 6–31 m [20–100 ft]);
large tunnel section
Self-supported then filled
Good Poor Hydraulicking—coal (spans 6–21-m [20–70-ft] arch); 
shrinkage
Supported then filled
Poor Good Cut-and-fill
Poor Poor Sublevel caving and top slice spans ≥6 m (20 ft) 
(for gravity flow)
Caved
Massive Good Good Vertical slices† Self-supported
Good Poor Vertical slices Supported then filled
Poor (cap rock) Poor Block caving (spans ~34 m [110 ft] active—
end stope used)
*Rated as to strength (and stiffness of pillar).
†Horizontal slices can introduce the many problems associated with multiple-seam mining.
354 SME Mining Engineering Handbook
Table 6.2-12 Classification of underground mining methods based on deposit geometry and support
Deposit Shape, Attitude (dip)
Degree of Support
Unsupported (open stopes) Supported Caved
Tabular
 Flat (mobile bulk handling) Room-and-pillar; stope-and-pillar Some degree of artificial support for 
room-and-pillar and stope-and-pillar
Longwall (shortwall); pillaring (especially 
room-and-pillar)
 Inclined (mixed bulk handling) Above with scrapers Above with scrapers Longwall (difficult)
Large tunnel section (on-strike) Large tunnel section with artificial 
support
 Steep (gravity bulk handling) Coal hydraulicking Shrinkage stoping; cut-and-fill stoping Sublevel caving
Sublevel stoping Timbered stoping (square sets, stulls, 
gravity)
Top slicing(control dilution-and-recovery)
Vertical crater retreat Fill as needed
Shrinkage stoping Gravity fill as needed
Massive Immediately above mine in vertical slices.
Fill—gravity placement.
To remove pillars, can mine and then fill horizontal lifts.*
Immediately above in horizontal lifts 
block caving (bulk mining)
* For ground control problems, especially those associated with coal, treat as if they were to be extracted by thick-seam and/or multiple-seam mining. 
As pressure increases (especially with depth), or as rock strength decreases, shift right for suitable method (toward supported and caved).
Table 6.2-13 Secondary factors to be considered when selecting a mining method
Method
Relative 
Cost
Flexibility/ 
Selectivity
% Recovery/ 
% Dilution Environment Safety and Health
Output (t/h) and 
Productivity 
(t/employee) Miscellaneous
Surface Mining
Placers and 
dredging
0.05 Low/high High/low High impact, and water 
pollution
Fair Moderate Need water; impact of 
weather
Open-cast 0.10 Moderate/ 
moderate
High/low Blasting can lead to frequent 
claims and water pollution
Fair High Flat topography and 
impact of weather
Open-pit 0.10 Moderate/ 
moderate
High/low Ground disturbance, waste 
piles, and some water 
problems
Slope stability (slides) High Impact of weather
Quarry 1.00 Low/high High/high Ground disturbance and 
waste piles
Slope stability Very low Skilled workers and 
impact of weather
Underground Mining
Room-and-pillar 
(coal)
0.30 High/high 50–80/20 Subsidence and water 
pollution
Ground control and 
ventilation
High Pillaring common
Stope-and-pillar 0.30 High/high 75/15 Good Ground control and 
ventilation
High Benching common
Sublevel stope 0.40 Low/low 75/15 Fill to avoid subsidence Less, blast from long 
holes
Moderate Fill common
Shrinkage 0.50 Moderate/ 
moderate
80/10 
plucking 
during draw
Fill to avoid subsidence Poor floor (collapse) 
and stored broken 
mineral*
Low Tie up 2⁄3 of ore
Cut-and-fill 0.60 Moderate/ 
high
100/0 Fill to avoid subsidence Some Low Sort in stope
Timbered 
square set
1.00 Moderate/ 
high
100/0 Fill to avoid subsidence Smolder, and fall (of 
personnel)
Very low Sort in stope
Longwall 0.20 Low/low 80/10 Subsidence and water 
pollution
Good Very high High capital ≤12° dip 
≤2.4 m (8 ft) thick
Sublevel caving 
(top slicing)
0.50 Low/low 90/20 Severe subsidence disruption Fair and stored broken 
mineral*
High Cave width ≥9.2 m 
(30 ft)
Block caving 0.20 Low/low 90/20 Severe subsidence disruption Air blasts and stored 
broken mineral*
High Tie up mineral
*Can pack (cement), oxidize, and smolder.
 Mining Methods Classification System 355
underground (in order to obtain mining permits from environ-
mental agencies).
In addition, innovation is always occurring and some 
is currently of proven value. These include rapid excava-
tion, methane drainage, underground gasification, and retort-
ing (Hartman 1987). Many methods are now automated and 
robotized.
ACKNOWLEDGMENTS
This chapter has been revised from the corresponding chapter 
in the previous edition of this handbook.
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