OCTOBER TOPIC

11 MINING METHOD SELECTION

OCTOBER TOPIC

11 MINING METHOD SELECTION

Classification

North Antelope Rochelle Mine, WY

In some cases, the choice of surface or underground is obvious …

Input statement categories

Rocks classified by strength

Underground deposits classified by thickness

Tabular deposits classified by attitude and related to bulk handling

and rock strength

Underground deposits classified by depth

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Deposits related to geometry, genesis, and strength (in order of induration)

Structural components located and described for underground mining

Deposit and structural components related to underground mining methods

Secondary factors to be considered when selecting a mining method

INTRODUCTIONWhen choosing between surface andunderground methods, some of the factorsthat must be considered include: Size, shape, and depth of the deposit; Geologic structure and geomechanical

conditions; Productivities and machinery capacities; Availability of experienced work force; Capital requirements and operating costs;

INTRODUCTIONWhen choosing between surface andunderground methods, some of the factorsthat must be considered include: Ore recoveries and revenues; Safety and injuries; Environmental impacts, during and

after mining Societal and cultural expectations.

SURFACE TO U/G TRANSITION METHODS

Transition depth is dependent on manyfactors: the relative scale of the surfacemine and the underground mine, the lead time required to developthe underground mine, the optimum underground miningmethod.

CAPITAL COST vs OPERATING COST

CAPITAL COSTCapital Cost: are fixed, one-time expensesincurred on the purchase of land, buildings,construction, and equipment used in theproduction of goods or in the rendering ofservices. In other words, it is the total costneeded to bring a project to a commerciallyoperable status

OPERATING COSTOperating Cost: are the expenses whichare related to the operation of a business, orto the operation of a device, component,piece of equipment or facility. They are thecost of resources used by an organizationjust to maintain its existence.

Controlling Directorates

Çan Lignites Enterprise, Çanakkale

Ege Lignites Enterprise, Manisa

Garp Lignites Enterprise, Kütahya

SELECTION OF A MINING METHOD

Selection of the best mining method for anydeposit requires analysis of many factorsbesides the simple productivity in metric tonsof ore per worker-hour.

Location of the Deposit Geology of the Deposit Processing Requirements

Political and Social Conditions Work Force

LOCATION OF THE DEPOSITIn some cases, a mineral deposit may belocated in a place where a large surfacemine is simply unacceptable. Undergroundmining methods have adverse effects whenoperated under built-up areas.

Surface subsidence and mine water release must both be monitored and

controlled.

GEOLOGY OF THE DEPOSITThree aspects of a deposits geology relateto the choice of surface or undergroundmining: the intrinsic value or grade and thestructure.

Grade: A material with a higher grade will support amore expensive mining method.An unusual narrow vein gold deposit, where the goldoccurs in very high-grade but sporadic pockets, couldsupport a labor-intensive underground mining method.

GEOLOGY OF THE DEPOSITThree aspects of a deposits geology relateto the choice of surface or undergroundmining: the intrinsic value or grade and thestructure.

The geologic structure: It is more difficult to generalizeabout this factor, if the deposit is highly folded andfaulted, and required selective mining to extract the orein a manner that could only have been done byunderground methods, rather than surface.

PROCESSING REQUIREMENTSIt may be possible to mine a low-grade oreat very low cost using a surface method, butthe resulting dilution may make processingso expensive that the overall operation isnot profitable.

Locations of available processing facilitiesand the ease with which new facilities canbe permitted and built are also important.

POLITICAL AND SOCIAL CONDITIONS

Political and social conditions can determinenot only whether or not a mineral depositcan be mined, but also the method by whichit is to be mined.

WORK FORCE

More specialized work force in U/G thansurface methods.

Workers with experience in operating heavyequipment in agriculture or construction canoften transfer their skills for use in surfacemining operations, but underground miningequipment and processes are significantlydifferent.

CONCLUSIONSelection of the best mining method for a

given deposit, including the choice between surface and underground mining, is a

complex process involving the analysis of many interrelated variables.

These variables are not just technical; they include consideration of environmental, social, and

political conditions and constraints, and of the time and expense required to obtain the required

government permits.

OCTOBER TOPIC

11 MINING METHOD SELECTION

Selection Process for UndergroundSoft-Rock Mining

INTRODUCTIONThe soft rocks usually are part of thesedimentary minerals classification, which issubdivided into elastic, organic, andchemical.

Examples of the soft-rock ores include coal,metalliferous shales, oil shales, potash, salt,trona.

INTRODUCTIONCoal, potash, trona, and salt are theprincipal soft-rock ores and, within limits,share similar production methods that focuson economies of scale.

The most common mining techniques forsoft-rock ores are longwall, room-and-pillar.For water-soluble minerals, solution miningis an alternative.

ORE DEPOSIT CHARACTERISTICSSome of the considerations are based onore deposit characteristics favorable to themining method being considered:

Ore & host rock strength Deposit shape/dip/size Deposit thickness Deposit grade Ore uniformity Deposit depth

ORE DEPOSIT CHARACTERISTICS Other characteristics are a function ofmining method:

Operating cost Capital cost and development timing

Production rate Mechanization

Selectivity and flexibility Health and safety

Environmental effects

ORE STRENGTHThe material properties of the ore often

drive mine design decisions.

Although there are many mechanicalproperties, compressive strength is oftendiscussed as an indicative characteristicinferring structural performance andsuitability for mechanical cutting.

ORE STRENGTH

ORE STRENGTHIt is important to note that the strength andmechanical properties of a rock are significantlyaffected by fracturing and planes of weakness inthe deposit.

Cleat is a fracture system ordinarily observed incoal. During exploration, the degree of fracturingshould be quantified and utilized to reduce orestructural properties, potentially leading to smalleropenings, larger pillars, and increased groundcontrol costs.

ORE STRENGTHIt is important to note that the strength andmechanical properties of a rock are significantlyaffected by fracturing and planes of weakness inthe deposit.

Limited fracturing may be a positive factor forsome mining methods, because it promotescaving, lowers blasting requirements, and aidsmechanical cutting. However, excessive fracturingcan have a negative influence on ground control,water, and gas inflows.

HOST ROCK STRENGTHThe strength of the rock enclosing the ore is alsoan important driver in mining method selection.

Temporary and permanent openings must bedeveloped either in the host rock, in order toaccess the ore, or with the host rock as roof (backor hanging wall) or floor (footwall) for the oreopenings (entries or crosscuts). To execute anappropriate design, the material properties mustbe understood.

HOST ROCK STRENGTHThe strength of the rock enclosing the ore is alsoan important driver in mining method selection.

It is inaccurate to assume that the ore and hostmaterial will have the same characteristics, soeach must be independently characterized bygeomechanical testing.

DEPOSIT SHAPEOre deposits are classified into two broad

categories: tabular and massive.

The difference between ore and waste may be a function of grade rather than rock type.

Massive deposits may be unpredictable and require a considerable exploration investment in order to document and fully understand the

resource.

DEPOSIT SHAPE

Deposit shape definitions

DEPOSIT DIPDip is defined as the angle of inclination of aplane measure downward, perpendicular tothe strike direction.

Both flat-lying soft-rock ore beds and near-vertical ore veins may be classified astabular, but the mining methods used toexploit them are dramatically different.Several methods are highly dependent ongravity for material

DEPOSIT DIP

Deposit orientation definitions

DEPOSIT SIZEThe volumetric size of an ore body mustalso be considered.

Deposit size is characterized subjectively bythe terms small, medium, and large.

As a generalization, large ore deposits havetens to hundreds of million cubic yards ofore and suggest mine lives in the 10 to 50year range.

DEPOSIT THICKNESSDeposit thickness refers to the ore thickness oftabular deposits.

Thickness plays an important role in openingstability and may prevent certain equipment fromfunctioning efficiently or mining methods frombeing effective.

These definitions are most relevant to mechanicalcutting and loading applications, such as longwallor continuous miner room and pillar mining.

DEPOSIT THICKNESS

Tabular deposit thickness definitions

DEPOSIT GRADEGrade is discussed in terms of theamount/value of recoverable/salablematerial in a unit weight or volume of in-place mineral resource

A gold ore may contain as low as 0.1 ppm and stillbe economic, whereas iron ore grades mayapproach 60% by weight. Coal is generallycharacterized by its attributes-that is, energycontent (kcal/kg); percentage of ash, moisture, andsulfur

DEPOSIT GRADESome mining methods with high operatingcosts necessitate high-grade ores in order tobe economic.

Large-scale methods may be suitable forlarge, low-grade deposits, such as lignite.

DEPOSIT GRADE

Ore grade definitions

ORE UNIFORMITYIt is undesirable to excavate sub-economicmaterial, unless it is necessary to reach oreor create necessary infrastructure, such asbelt-conveyor galleries.

A mineral deposit may be segmented byfaults, sub-economic mineral occurrence, orlegal/environmental issues.

ORE UNIFORMITYSome mining methods are well suited toflexibility because they can selectivelyextract specific sections of a deposit withoutdisrupting the overall operation.

In some areas, igneous or sedimentarymaterials may be injected into tabulardeposits, such as dolerite dykes in coalseams, and create impediments tomechanized cutting and loading.

ORE UNIFORMITYAn inconsistent feed of material may disruptprocessing plant performance or requireblending, rehandling, or disposal of minedmaterial

DEPOSIT DEPTHShallow deposits are generally more suitedfor surface mining. Deeper deposits mayrequire progressively greater ground controlmeasures (increased costs), larger pillarsizes (lower recovery), or decreasedapplicability of some mining methods inorder to ensure safety and sustainability.

MINING METHOD CHARACTERISTICS

Every mining method has characteristicsthat will produce different outcomes basedon the ore deposit to be mined.

Operating cost Capital cost and development timing

Production rate Mechanization

Selectivity and flexibility Health and safety

Environmental effects

OPERATING COSTThe operating cost of a mine is the costassociated with the production of ore fromthe primary mining method

In mining, the operating cost is composed offixed and variable expenses.

OPERATING COSTVariable expense totals change inproportion with activity, such as roof-controlcost ($/ft) that typically accumulates with theamount of entry development.

In comparison, fixed costs, such as labor andventilation, stay relatively constant over amoderate range of activity variation. Somemethods are labor intensive or may require alarge quantity of materials in order to operate

CAPITAL COST AND DEVELOPMENT TIMING

Initial capital cost is defined as the amountof investment needed before the minebegins to generate revenue.

Higher capital costs are frequentlyassociated with development or start-uptimes. Equipment manufacturers often havewait times of months or even years beforeassembly and delivery of new equipment.

PRODUCTION RATEA high production rate can accommodate alarge market and may overcome low-valueore if operating costs are low.

The ability to stockpile and blend ores ofvarying grade in order to maintain aconsistent feed to the mill is typicallyadvantageous.

MECHANIZATIONMechanization is a critical element of amodern mine. To justify a large capitalinvestment in equipment, it is common toneed a longer mine life and thus a larger orebody.

Highly mechanized mining is safer than lessmechanized methods because fewerworkers will be needed and thus the overallhazard exposure will be lower.

SELECTIVITY AND FLEXIBILITYIt is generally valid to assume that miningconditions, market prices, and technologywill change over the course of a mine's life,so the mining method must be adaptable tothese fluctuations.

If commodity prices were to dropsubstantially, a portion of the ore in amassive deposit may become uneconomicto mine.

MINING HEALTH AND SAFETY CHARACTERISTICS

The safety and health of a mine's workers should be the top priority of every operator.

Longwall mining is recognized as the safestmethod of mining applied to soft-rockdeposits

ENVIRONMENTAL EFFECTSThe largest environmental impacts of anunderground mine typically fall into threecategories:

subsidence,groundwater,

atmospheric emissions.

ENVIRONMENTAL EFFECTSSubsidence is defined as the sinking of thesurface above mine workings as a result ofmaterial settling into the voids created bymineral extraction. It is contentious in urbanor suburban areas where it can affecthomes, schools, and roads etc.

The surface subsidence created by modern longwall minesis largely predictable in its timing and magnitude, incontrast to the unpredictable outcomes associated withsome room and pillar mines.

ENVIRONMENTAL EFFECTSWater impacts may arise by accidentalcauses. Acid generating rock of multipletypes in excavated ore, waste, or overlyingstrata may produce acid mine drainage.

ENVIRONMENTAL EFFECTSAir quality in underground mines is typically

affected by the natural liberation of mine gases.

MAD 345 – MINING II (PART 2)w/Prof Gulsev AKSOY

ENVIRONMENTAL EFFECTS Zero harm is a sustainability principle

applied by the foremost mining enterprisesin the context of health, safety,environment, and communities wheremines in their portfolios actively operate. Itis an acknowledged goal that communitieswill be forever improved because of theglobal and local activities of these miningenterprises.

OCTOBER TOPIC

11 MINING METHOD SELECTION

Coal – Room and Pillar –Longwall Mining

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ROOM-AND-PILLAR MINING METHOD

ROOM-AND-PILLAR MINING METHOD

LONGWALL MINING METHOD

LONGWALL MINING METHOD

The difference between coal and noncoalproduction methods are four main factors:

Strength: Higher strength generallycorrelates with higher specific energy ofcutting and lower productivity in cuttingapplications.

Scale: Coal mines are usually larger inthroughput than other soft-rock mines

The difference between coal and noncoalproduction methods are four main factors:

Methane (CH4): Where most coal mines are"gassy," many noncoal mines are free ofthat hazard. In most countries coal minesand their related equipment are governedby strict regulations designed to preventmethane or coal dust explosions.

The difference between coal and noncoalproduction methods are four main factors:

Coal workers’ pneumoconiosis, morecommonly known as black lung. Thischronic, debilitating disease is related toexcessive exposure to respirable coal dust,usually during employment in coal mining.

U/G MINING METHODSCan be divided into three broad classes;caving, stoping, and other methods.

“Caving” implies the controlled collapse ofthe rock mass under the force of gravity,

“Stoping” implies the excavation of astable opening of small or large dimensions.