Mine Planning and Scheduling42
September 23, 2022 | Author: Anonymous | Category: N/A
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MINE PLANNING AND SCHEDULING
HOW DO MANAGERS USE THE PLANNING PL ANNING • PLANNING IS ONE OFPROCESS? THE FOUR FUNCTIONS OF MANAGEMENT
• PLANNING IMPROVES COORDINATION AND CONTROL
• IN A HIERARCHY OF OBJECTIVES, LOWER-OBJECTIVES HELP ACHIEVE HIGHER-LEVEL ONES • PLANNING IMPROVES TIME MANAGEMENT
• GOAL SETTING HELPS ALIGN PLANS AND ACTIVITIES THROUGHOUT AN ORGANIZATION ORGANIZATION STRETCH
GOALS ARE PERFORMANCE PERF ORMANCE TARGETS THAT WE HAVE TO WORK EXTRA HARD AND STRE HAVE STRETCH TCH TO REACH
• CONTROL BEGINS WITH OBJECTIVES AND STANDARDS
Mine Planning The classic procedure for designing a mine starts by determining the mining method(s) and probable optimum mining rate . This unit is principally devoted to the next step – determining initial mine layout or "conceptual mine design." The procedure is also considered initial mine planning.
Mine Layout - Surface If the mining method is open pit, the layout starts with the basic design of the open pit itself. This includes pit layouts in intervals up to the final design (ultimate pit). With the pit established, the infrastructure is planned, including surface haul roads, stockpiles, dumps, tailings impoundment, utility corridors, and surface plant layout.
The mine layout for an open pit mine might have to be modified if underground mining is contemplated when the pit is exhausted.
Mine Layout - Underground Underground If the plan includes underground mining, planning starts with locating and sizing pre-production and ongoing development requirements. The initial planning includes determining level intervals, haulage ways, primary access (shaft, ramp or adit), and other major entries. The design of major entries requires considering the requirements for ore handling, waste rock handling, primary ventilation circuit, backfill, transfer, materials handling, access for personnel, refuge stations, and escape route(s).
Once the underground mine concept is established, the surface infrastructure is designed, including access roads, dumps, tailings impoundment, utility corridors, maintenance facilities, explosives storage, and surface plant layout.
Underground Mine Planning The planning process will, in general move through four steps, irrespective of the design phase: · baseline assessment, ·
reserve determination,
·
premine planning and
·
subsystem design.
Phase I - BASELINE ASSESSME ASSESSMENT NT Baseline assessment of all available data precedes any planning efforts. It is a comprehensive initial review of all available information on the potential reserve or mine from geographic, geologic, environmental, technical, and economic standpoints.
1) Baseline Assessment Geologic Factors The geologic model is only an interpretation of the actual act ual conditions based on thethorough skill of geologists and the t he economic backing available to do testing . Constant testing and drilling is done as the project moves through the design phases. The data collected dictates the changes that effect the geologic model.
2) Baseline Assessment Environmental Factors Today designing a mine requires planning for environmental protection and reclamation from the very beginning.
RESERVE DETERMINATION The characteristics of a reserve are as crucial as the reserve magnitude or grade: the depth, inclination, geometry, type and properties of host and deposit rocks, quality quality,, and etc. play a key role in the design. Criteria A mineral deposit or resource can only be classified as an ore body only when it can be mined at a profit. The planning and design attempts to identify the method to make this possible. Demand of the ore body and mining technology can affect the future of a project.
PREMISE PLANNING The mine plan constantly evolves as the mine process changes physical characteristics. scienceinto andthe technology constantly evolving whileEngineering the mine is locked physical are framework. An interesting fact is that equipment changes with time but the basic design of the mine remains the same. sa me. This is most obvious in comparing existing and newer mines. mines.
Following is a list of concerns for underground mining: mining: 1) Regulatory and Legal Factors Permits and approvals may be at the federal, state, local, or regional. These are subject to continual revision or reinterpretation requiring ongoing review of the mine plan.
Compliance plans include: 1) mine mine layout layout with with proj project ection ions s 2) str strat ata/ a/ro roof of con contr trol ol pla plan n
5) dust dust cont control rol plan plan
6) med medic ical al / eme emerg rgen ency cy eva evacu cuat atio ion n plan plan
3) ve ventilatio tion plan
7) ffiire control/mine evacuation plan
4) ffa an st stoppage pl plan
8) es escapee ma map/plan.
2) Geologic/ Geotechnical Factors Depending on the mining methods under consideration, many geologic and geotechnical factors must be considered. The economics usually favor extraction of the best grade materials or the lowest mining cost areas to maximize the return on investments and shorten payback period. While the immediate extraction of the best grade materials enhances immediate finances it can compromise designs.
3) Environmental Factors The impact on the environment must be considered from the beginning of the plan design. The impacts to the environments can include; noise, aesthetics, aesthetics , air quality quality,, water discharge and run off. The environment must remain within regulation during the initial data gathering to the reclamation process. Reclamation plans include; drainage control, segregation of waste material, erosion and sediment control, solid waste disposal, restoration of waste mine areas. The regrading plan mustand include the effects of theand mine subsidence, vibration ( induced by transportation, mining, processing or subsidence) and impact on surface water. The environmental items often dictate the economics and viability of the mine.
4) Technical Factors The technical areas of the plan is the most extensive. It takes in consideration the regulations, geologic, and and environmental factors to develop each part of the plan. The layout of the mine is determined by the size and shape of the reserve. After the ore deposit is mapped, access acce ss development for the reserve area is figured into the plan. The size of the reserves determines the kinds of access and the number of access portals needed. Access can be vertical shafts, inclined slopes, and drifts or horizontal entries. The larger the reserve, the more complicated c omplicated the plan becomes. becomes.
Surface Facilities The productivity and the reserve size determine the size and placement of facilities. Consideration mustremoval, be madeand for access, extraction, storage of the ore, the physical needs of the work force, and the operational needs of the t he facility. Land acquisition for disposal areas, dust, noise, safety, and layout are other design considerations.
Physical Factors Geological mapping is used to determine the reserve depth and develop the best mine layout. The plan lays out the number of benches and designates the portion of the reserve that will best meet the needs of the market. Economics drive the design to gain the most profit from the mine while still maintaining plans for reclamation. The sequence of the extraction can be important to maximize the reserve recovery. The mine may have multiple seams being extracted at once or only a single vein. The plan will take this into consideration and plan for the most efficient efficie nt method of recovery. Poor mining conditions must be factored into the analysis to account for changes in productivity rates and mine costs.
Equipment The equipment needed is determined by the dimensions and the hardness of the mineral deposit. Other factors that need to be considered are production rates, seam working height, and property extent.orVentilation, size constraints, regulations, and floor pressures may impact the choice of diesel-or electricpowered equipment. Schedules for equipment overhaul should be developed to assure productivity rates. New equipment purchase should consider the incorporation of new technology as it becomes available.
Support Systems/ Infrastructure As the development of the mine progresses the mine entries, drifts, and levels become part of the infrastructure. All parts of the system must be evaluated for capacity and availability . The systems are built in a series so that if one of the systems fails the whole system is halted until systems are corrected. A series system design is usually used to keep costs low as many systems are parallel or redundant. They are designed to be as maintenance free as possible.
Transportation Tr Transportation ansportation encompasses provisions for the movement of materials, personnel and equipment into and out of the mine. Supplies, workers, equipment must be transported in a timely manner to maintain the planned production. One of the main transportation plans include moving the mined material from the face to the processing facility. A successful mine design will have a smooth transportation flow.
Manpower Staffing of the system syste m is a function of the required production level. Typically the manpower level is inversely related to the relative level of capital spending but related to the reserve size. Adequate personnel must be provided to allow the system sy stem to function properly. properly. Personnel includes the supervisory work force as well. Consideration must be made for support staff levels such as administration, engineering, financial staff. The centralization of the the support personnel may be more effective if centrally located depending on particular circumstances. The physical location of the mine must be considered also.
Ventilation After most of the other factors are laid out the ventilation is designed to provide the mine's life support system. The first consideration is providing clean respirable air to the workers. The dilution of contaminants is next. In other cases air can used to cool also. Mine layout is dramatically impacted by the ventilation system. Proper airflow requires proper sizing , location and numbers of airways. Minimum and maximum velocities, and quantities are often specified by regulations and mine condition.
5) Mine Closing and Reclamation After the deposit has been completely mined, the mine area must be cleaned up and returned to approximately it original condition. Permits require bonds to be set for protection against not completing this reclamation. Funds are allocated to cover this process from the onset of the mine. Many of the reclamation process begin with the first breaking break ing of the ground. Openings are sealed, pits filled and revegetated, and the structures removed.
PROJECT PHASES
All project pass through fve distinct phases Conceptual Pre-easibility Feasibility Construction Operation O these the most important is the preeasibility stage, because this is where we do all the trade-os, separate the wheat rom the cha and select one option to take into the expensive
easibility study.
EVALUATION OF MINERAL MINER AL DEPOSIT DEPOSITS S PROJECT EVALUATION IS THE PROCESS OF IDENTIFYING THE ECONOMIC FEASIBILITY OF A PROJECT THAT REQUIRES A CAPITAL INVESTMENT AND MAKING THE INVESTMENT INVESTMENT DECISIONS DECISIONS
USERS OF PROJECT EVALUATION METHODS THERE ARE THREE GENERAL TYPES OF USERS OF PROJECT EVALUATION RESULTS:
• PRIVATE INVESTORS (INCLUDING PRIVATELY OWNED CORPORATIONS) • LENDERS • GOVERNMENTS
MINE PROJECT FINANCE STRUCTURES • PROJECT FUNDING CAN BE OBTAINED FROM THE THREE SOURCES. THE CHARTS CHARTS BELOW DEMONSTRATE THE DIFFERENCE BETWEEN PUBLIC, CORPORATE CORPORATE AND PROJECT FUNDING, USING AN EXAMPLE OF A TREATMENT PROJECT.
PUBLIC FINANCE
• FOR YEARS, MANY GOVERNMENTS, FUNDED PROJECTS BY • USING EXISTING SURPLUS FUNDS OR ISSUED DEBT (GOVERNMENT BONDS) TO BE B E REPAID OVER A SPECIFIC PERIOD. • HOWEVER, GOVERNMENTS HAVE INCREASINGLY FOUND THIS FUNDING TO BE LESS ATTRACTIVE, AS IT STRAINED THEIR OWN BALANCE SHEETS AND THEREFORE LIMITED THEIR ABILITY TO UNDERTAKE OTHER PROJECTS. • THIS CONCERN HAS STIMULA STIMULATED TED THE SEAR SEARCH CH FOR ALTERNATIVE SOURCES OF FUNDING
CHARACTERISTICS OF MINERAL PROJECT INVESTMENT DECISIONS • BEFORE SPECIFIC TYPES OF EVALUATION METHODS AND DECISION CRITERIA CAN BE ADDRESSED, IT IS IMPORTANT TO KNOW ABOUT THE CHARA CHARACTERISTICS CTERISTICS OF THE INVESTMENT DECISIONS AT HAND. THESE CHARACTERISTICS DETERMINE WHICH EVALUATION TECHNIQUE OUGHT TO BE USED. IT IS POSSIBLE TO APPLY AN INCORRECT TECHNIQUE OR DECISION CRITERION AND UNKNOWINGLY OBTAIN AN ANSWER THAT IS MATHEMATICALLY CONSISTENT AND MAY EVEN SEEM REASONABLE BUT IS STILL INCORRECT INCORRECT.. IT IS ALSO POSSIBLE TO DO EVERYTHING EVERYTHING CORRECTL CORRECTLY Y AND THEN MISINTERPRET THE RESULTS. RESULTS. EITHER OF THESE S SITUA ITUATIONS TIONS MA MAY Y WELL RESULT IN INCORRECT DECISION MAKING
POSITIVE POSITIV EE EV VALU ALUA ATION METHO METHODS DS 1 •
GEOLOGIC
• GEOLOGIC QUANTITIES OF MATERIAL CAN BE MEASURED USING GEOLOGIC INFERENCES AND ENGINEERING CALCULATIONS. • HOWEVER ORE AND RESER RESERVES VES ARE DEFINED AS MATERIAL THAT CAN BE REMOVED AT A PROFIT GIVEN EXISTING OR IMMEDIATELY ANTICIPATED TECHNOLOGIES TECHNOL OGIES AND PRICES.
• GEOLOGIC EVALUATIONS ARE ALWAYS OBTAINED THROUGH SAMPLING AND ARE BY BY DEFINITION S SUBJECT UBJECT TO SAMPLING ERRORS.
MINING GEOLOGY YA AND ND GEOLOG EXPLORATION
·
OW MUC
METAL IS AVAILABLE?
·
W AT IS A MINERAL? W AT IS ORE?
·
OW DO ORE DEPOSITS FORM?
·
MINING EXPLORATION MET ODS
·
ROLE OF EXPLORATION IN MINING
·
CASE
ISTORIES
EVALUATION OFDIFFEREN POTENTIAL OREBODY • ORE GRADE: LOTS OF DIFFERENT T UNITS, CUT-OFF GRADE, HOMOGENEITY
• BY-PRODUCTS: COMMONLY CRITICAL TO SUCCESS; AU, AG, W • COMMODITY PRICES: FORCASTING THE FUTURE • MINERALOGICAL MINERALOGICAL FORM: NA NATIVE TIVE VS SULFIDE VS OX OXIDE IDE VS SILICATE
RESOURCE • INFERRED: THAT PART OF A MINERAL RESOURCE FOR WHICH TONNAGE, GRADE AND MINERAL CONTENT CAN BE ESTIMATED WITH A LOW LEVEL OF CONFIDENCE. • INDICATED: THAT PART OF A MINERAL RESOURCE RESOUR CE FOR WHICH TONNAGE, DENSITIES, SHAPE, PHYSICAL CHARACTERISTICS, GRADE AND MINERAL CONTENT CAN BE ESTIMATED WITH A REASONABLE LEVEL OF CONFIDENCE. • MEASURED: THAT PART OF A MINERAL RESOURCE RESOUR CE FOR WHICH TONNAGE, DENSITIES, SHAPE, PHYSICAL CHARACTERISTICS, GRADE AND MINERAL CONTENT CAN BE ESTIMATED WITH A HIGH LEVEL OF CONFIDENCE
RESOURCE
•
PROBABLE:
•
PROVEN:
RESERVES
THE ECONOMICALLY MINEABLE PART OF AN INDICATED INDICA TED AND AND,, IN SOME CIRCUMST CIRCUMSTANCES, ANCES, MEASURED MINERAL RESOURCE. THE ECONOMICALLY MINEABLE PART OF A MEASURED MINERAL RESOURCE.
RESERVES
CASE STUDY
A PLATINUM MINE
This project project started started o in the normal way..................with boreholes that intersected a ree
Because the continuity o this ree is a would common actor,horizon the tendency be to accept this as act.
So much more ado, we without could lay out and construct a mine
However, someone decided to run a seismic survey..........
........ and ound a discontinuity!
This called or another borehole, which changed the whole picture
........and
prevented some very embarrassing questions
?
SO FAR, THEY HAVE GOT IT RIGHT!
POSITIVE POSITIV EE EV VALU ALUA ATION METHO METHODS DS 2 • TECHNOLOGICAL
TYPES OF TECHNOLOGIC TECHNOLOGIC EV EVAL ALUA UATIONS TIONS TECHNOLOGIC EVALUA EVALUATIONS TIONS CAN BE DIVIDED INTO FOUR MAIN TYPES:
• MINING • PROCESSING • TRANSPOR TRANSPORTING TING • MARKETING
MINING AND HIGH TECH: AN OXYMORON?
TECHNOLOG TECHNOL OGY Y MAKING A DIFFERENCE • UNIVERSAL DRAGLINE • 25% + PRODUCTIVITY IMPROVEMENT PRODUCTION BY • FOR BMA EQUIVALENT TO INCREASING 1 NEW MINE (10 MT/Y) AT 1/3RD CAPITAL COST OF MINE
BUYCRUS EERIE 2570W DRAGLINE
WHERE MINING TECHNOLOGY IS GOING • REAL OPPORTUNITIES FOR STEP-CHANGE IMPROVEMENTS • MINING SUFFERS FROM POOR PLANNING AND EXECUTION BECAUSE OF IMPRECISE KNOWLEDGE • POOR RELIABILITY AND UTILISATION OF EXPENSIVE CAPITAL FLEETS • HIGH LEVELS OF GEOLOGICAL UNCERTAINTY UNCERTAINTY
• WHEREAS • MANUFACTURING/ “JUST-IN-TIME” • RETAILING = “JUST-IN-TIME” • MINING = “JUST-IN-CASE”
• RESEARCH APPROACHES • SMART MINING SYSTEMS • SMART MINING MACHINES
• STEP-CHANGE MINING SYSTEMS
POSITIVE POSITIV EE EV VALU ALUA ATION METHO METHODS DS 3 • INVESTMENT
DETERMINERESERVE THE MINABLE ORE • ASSUME ECONOMICS ECONOMI CS FOR MA MATERIAL TERIAL REMOVAL • LOOK AT AT GEOLOG GEOLOGY Y FOR HOW STEEP THE PIT SLOPES CAN WITHOUT SLIDING IN • STAND HAVE HA VE THE COMPUTER ANA ANAL LYZE THE L LARGEST ARGEST SET OF BLOCKS THAT THAT CAN BE REMOVED WITHO WITHOUT UT T TAKING AKING STUF STUFF F THAT THA T LOOSES LOOSES MONEY MONEY SET MEASURES MEASURES THE SI SIZE ZE PIT THA THAT T CAN ULTIMA ULTIMATEL TELY Y BE • THIS MINED (CALLED THE ULTIMA UL TIMATE TE OF PIT)THE PIT
• TOO COMPLEX COMPLEX TO VISUALIZE VISUALIZE • DONE WITH EITHER A FLOATING CONE MINER OR LEARCHGROSSMAN COMPUTER ROUTINE (EASIL (EASILY Y AVAILABLE AVAILABLE IN MINESIGHT) MI NESIGHT)
COMPUTER VIEWS OF PITS
THE TIME VAL VALUE UE OF MONEY
• A REVIEW FOR THOSE WITH ENGINEERING ECON
• SOME NEW THOUGHTS FOR OTHERS • WOULD YOU RATHER GET $100 NOW OR $100 FIVE YEARS FROM NOW • MOST WOULD PICK NOW
• ONE REASON – IF YOU PUT MONEY IN CD AT 3% INTEREST IN 5 YEARS YOU WOULD HA HAVE VE $116 • YOU’D ONLY ONLY NEED $86 NOW TO EARN TO $100 IN FIVE YEARS SO HOW CAN $100 NOT DELIV DELIVERED ERED FOR FIVE YEARS BE WORTH MORE THAN $86?
HANDLING THE TIME VALUE OF MONEY
• MONEY CAN BE MULTIPLIED BY A DISCOUNT FACTOR TO ADJUST TO HOW MUCH RIGHT NOW MONEY IT IS EQUAL TO. • MINING COMMONLY LOOKS FOR INVESTMENTS TO EARN 15% • IF YOU GET $100 NOW ITS $100 • IF YOU GET $100 IN 1 YEAR ITS LIKE $87 • IF YOU GET $100 IN 5 YEARS ITS LIKE $50
• IF YOU GET $100 IN 10 YEARS ITS LIKE $25 • Y YOU OU SEE THE P PA ATTERN – THE LON LONGER GER THE MONEY MONEY TAKES TAKES TO GET HERE THE LESS IT IS WORTH
WHAT DOES TIME VALUE MONEY DOTHE TO MINE PLANS?OF $100,000,000
0
1
2
3 4
5
6
7
8
9
10
11 12
13
$100,000,000 Just adding up money gives $600,000,000 $600,000,000 Total
ut not all the money got here at the same time – i we apply discount actors and
en add we get $1,670,000 – almost even even money (at 15% interest) (A Total Ater Multiplying by Discount Factors is called a Net Present Value – The more a project is worth the hotter the item!)
SAME MONEY BUT SOME IS MOVED FORWARD IN TIME $150,000,000
$50,000,000 0
1
2
3 4
5
6
7
8
9
10
11 12
$100,000,000 Same money but I collect more money sooner and less later NPV is now now $57,100,000 instead o $1,670,000
13
Get more o your money aster = Better NPV!
PUT-OFF EXPENSES $150,000,000
$0 0
1
2
$50,000,000
3 4
5
6
7
8
9
10
$100,000,000 Same Money Again but now the NPV is $197,374,000
11 12
13
Getting money A WHOLE LOT!early and putting o expenses makes project values improve
HOW CAN I MAKEFIELD THAT HAPPEN IN THE • SUPPOSE I MINE MY BEST AND MOST VALUABLE ORE FIRST? • SUPPOSE I DELAY SPENDING MONEY STRIPPING WASTE MATERIAL • IF I MINE FROM THE TOP DOWN I WILL USUALLY MINE MOSTLY WASTE AT FIRST • AND WAIT A LONG TIME TO GET DOWN TO THE BEST ORE
• WHAT I WOULD LIKE ME TO THE DO FOR A ORE SEQUENCE IS TO ASK THE COMPUTER TO FIND BEST WITH THE LEAST STRIPPING FIRST • I WILL GET THE COMPUTER TO IDENTIFY A SERIES OF NESTED PITS THAT THA T HAVE HAVE THE MOST VAL VALUE UE AND USE THA THAT T AS MY DR DRAFT AFT
SEQUENCE
DEVELOPING A P PR RACTICAL LA LAY YOUT
• WITH A SERIES OF NESTED PIT SHELLS AS A GUIDE DESIGN A SET OF PITS THAT FOLLOWS THE GUIDES BUT HAS BENCHES, AND ROADS REQUIRED FOR PRACTICAL MINING. • MINESIGHT IS A 3D CAD PROGRAM SO I CAN DRAW IN MY ROADS AND BENCHES
• LOOK AT FURTHER BOOSTING EARNINGS BY RUNNING ARTIFICIALLY HIGH CUT-OFF GRADES AT FIRST AND SIZING MINE PRODUCTION • CAN BE DONE WITH VALP IN MINESIGHT
• SIZE UP YOURHAULAGE EQUIPMENT FLEETS ANDWEAK HAULAGE TIMES • MINESIGHTS PROGRAM IS STILL (WE WILL USE FPC)
• DEVELOP DETAILED LONG TERM SCHEDULES OF WHAT WILL BE MINED FROM WHERE • MINESIGHT STRATEGIC PLANNER CAN DO THIS
• IN FOR MAJOR REFINEMENT IN MARCH OR APRIL
• COLLECTIVELY THESE STEPS ARE CALLED LONG TERM MINE PLANNING
STAGES OF EVALUATION • EVALUA EVALUATION TION OF A MINERAL RESOURCE IS THE PROCESS OF DETERMINING IF THE RESOURCE WILL SUPPORT ECONOMIC EXPLOITATION
STAGES OF EVALUATION • FORMAL RESOURCE RE SOURCE PROJECT EV EVALUA ALUATION TION IIS S AN ITERATIVE PROCESS USUALLY ACCOMPLISHED VIA A SERIES OF • PROGRESSIVELY MORE DETAILED STUDIES THAT PUNCTUATE AND DRIVE ONGOING DATA COLLECTION PROGRAMS STAGES ARE
• SCOPING (CONCEPTUAL) • PREFEASIBILITY
• FEASIBILITY
STAGES OF EVALUATION • SCOPING TO IDENTIFY :
• TECHNICAL ISSUES REQUIRING FURTHER INVESTIGATION OR TESTWORK • FEATURES AND ORDER OF MAGNITUDE PARAMETERS OF PROJECT
• COSTS AND TIME REQUIRED TO UNDERTAKE FURTHER DEVELOPMENT.
• SCOPING STUDIES ARE CONCEPTUAL STUDIES AND • ARE NOT SUFFICIENTLY ACCURATE TO CARRY OUT A MEANINGFUL ASSESSMENT OF THE ECONOMIC VIABILITY OF ANY PROJECT,
• ONLY WHETHER AND HOW MUCH, FURTHER PREDEVELOPMENT IS WARRANTED
STAGES OF EVALUATION
• PREFEASIBILITY
• ASSESS PROBABLE RESERVE & APPROACHES TO RECOVERY • IDENTIFY TECHNIQUES & RATES OF EXTRACTION • OUTLINE POSSIBLE FEATURES OF THE FACILITIES • DEVELOP CAPITAL & OPERATING COSTS ESTIMATES • TEST MARKETABILITY OF THE COMMODITY • ASSESS ECONOMIC VIABILITY • DETERMINE WHAT FURTHER EFFORTS ARE REQUIRED TO PROGRESS PREDEVELOPMENT ACTIVITIES PREFEASIBILITY STUDIES SHOULD BE SUFFICIENTLY ACCURATE TO ALLOW A COMPARATIVE ANALYSIS OF ECONOMIC VIABILITY TO BE DEVELOPED FOR
ALTERNATIVE ALTERNA TIVE CAPACITY CAPACITY AND PROJECT CONFIGUR CONFIGURA ATIONS (IE O OPTIONS PTIONS STUDY).
STAGES OF EVALUATION UNDERTAKEN AT TWO LEVELS FEASIBILITY UNDERTAKEN
• FOR INTERNAL FINAL ASSESSMENT PURPOSES OR • FOR OBTAINING EXTERNAL FUNDING (BANKABLE (B ANKABLE FEASIBILITY STUDY). WITH THE OBJECTIVE OF: OF: • ESTABLISHING PROVED & PROBABLE RESERVES WITHIN OVERALL MEASURED INDICATED INDICATE D & INFERRED RESOURCES • PROVING THE TECHNICAL VIABILITY OF THE MINE & EXTRACTION METHODS • DEFINING THE FEATURES & CAPACITY OF THE FACILITIES FACILITIES • ESTIMATING DEVELOPMENT, CAPITAL CAPITAL & OPERATING COSTS OF MINE OVER ECONOMIC LIFE OF RESOURCE • ESTABLISHING THE MARKET FOR THE COMMODITY • COMPLETING ECONOMIC ASSESSMENTS OF THE SELECTED PROJECT CONFIGURATIONS CONFIGURATIONS • ASSESSING THE ECONOMIC SENSITIVITY OF THE PROPOSED DEVELOPMENT TO VARIOUS FACTORS • SETTING A FRAMEWORK FOR THE IMPLEMENTA IMPLEMENTATION TION OF THE CAPITAL INVESTMENT IN
THE DEVELOPMENT. DEVELOPMENT.
BY WHOM? WH OM? • LARGELY DEPENDENT ON SIZE OF COMPANY AND AVAILABLE RESOURCES • SCOPING - BY OWNERS USING INHOUSE RESOURCES & STAFF, ASSISTED BY SPECIALISTS OR CONSULTANTS ASSIGNED SPECIFIC TASKS • PREFEASIBILITY - BE LED BY OWNER’S INHOUSE STAFF WITH AREAS ASSIGNED TO CONSULTANTS • FEASIBILITIES - BE MANAGED BY OWNERS STAFF, ASSISTED BY PROJECT ORIENTATED STAFF, WITH
DEFINED AREAS OR DISCIPLINES TO CONSULTANTS OR CONTRACTORS.
FEASIBILITY STUDY DOES NOT MEAN FEASIBLE • THERE APPEARS TO BE A MISCONCEPTION BY BY SOME IN THE INDUSTRY ABOUT WHAT A FEASIBILITY STUDY IS AND THE STEPS REQUIRED TO GENERATE GENERATE ONE.
• YES, WHEN SOMEONE SAYS SAYS FEASIBILITY WE ALL KNOW WHAT PEOPLE ARE TALKING ABOUT, BUT AS COMP COMPANIES ANIES TRY TO EXPEDITE THE PROCESS OF BRINGING PROJECTS ONLINE THESE STEPS ARE BEING SKIPPED.
• UNFORTUNATELY, SKIPPING THESE STEPS CAN
END UP DELAYING THE PROJECT AND COSTING MORE MONEY
• BASICAL BASICALL LY THE PITF PITFALLS ALLS RESUL RESULTING TING PITFALLS OFMAIN AVOIDING STEPS FROM NOT FOLLOWING THESE STEPS ARE PROJECT DELAYS AND COSTS, INCLUDING LOST OPPORTUNITY COSTS.
• EXPERIENCE HAS SHOWN THAT SKIPPING THE PREFEASIBILITY PREFEASIBILITY STUD STUDY Y DOES NOT SA SAVE VE TIME AND MONEY BECAUSE ISSU ISSUES ES THA THAT T SHOULD HAVE BEEN IDENTIFIED EARLY IN THE PROCESS ARE ARE NOT, CREATING CREATING DELA DELAYS YS WHILE THESE ISSUES ARE ANALYZED AND ADDRESSED, WHICH RESULTS IN INCREASED
COSTS.
• DELAYS ARE TYPICALLY CAUSED BY THE PITFALLS OF AVOIDING STEPS NEED FOR ADDITIONAL EXPLORATION DRILLING FOR EVERYTHING FROM ORE BODY DEFINITION, TO GEOTECHNICAL STUDIES, TO METALLURGICAL SAMPLING
• CONDUCTING A SCOPING OR PREFEASIBILITY QUICKLY IDENTIFIES SUCH PROBLEMS AND FURTHER WORK ON THE PROJECT CAN BE SUSPENDED UNTIL THE ADDITIONAL EXPLORATION DRILLING IS COMPLETED THUS SAVING TIME, EFFORT,
AND EXPENSE
ORE RESERVE ESTIMATION
INTERP INT ERPOL OLA ATING TING A SURFACE SURF ACE FRO FROM M SAMPLED POINT DATA
Interpolating a Surface From Sampled Point Data Assumes a continuous surface that is sampled Interpolation Estimating
the attribute values of locations that are within the range of available data using known data values
Extrapolation Estimating the attribute values of locations outside the range of available data using known
data values
Interpolating a Surface From Sampled Point Data
Interpolation Estimating a point here: here: interpolation Sampl e data
Interpolating a Surface From Sampled Point Data
Extrapolation Sampl e data Estimating a point here: here: extrapolation
Interpolating a Surface From Sampled Point Data Sampling
Strategies for Interpolation
Regular
Random
Interpolating a Surface From Sampled Point Data
Global Interpolation
Uses all known known sample points to estimate a value at an unsampled location Sampl e data
Interpolating a Surface From Sampled Point Data
Local Interpolation Uses a neighborhood a neighborhood o sample points to estimate a value at an unsampled location
Sampl e data Uses a local local neighborhood to neighborhood to estimate value, i.e.
closest n number o points, or within a given search radius
INVERSE DISTANCE WEIGHTED (IDW)
Inverse Distance Weighted Local
method
Exact Can
be linear or non-linear
The weight (infuence) o a sampled data value is is inversely proportional inversely proportional to its
distance rom distance rom the estimated value
Inverse Distance Weighted (Example) z d z ( x, y ) or z ( x, y ) z 1 1 d n
i 1
i
p
i
with
i
i
i
n
i 1
p
i
10 0 4 3 2
16 0
IDW: Closest 3 neighbors, r=2
20 0
KRIGING INTERPOLATION
KRIGING INTERPOLATION
Kriging is named after the South African engineer,, D. G. Krige, who first developed the engineer method.
Kriging uses the semivariogram, in calculating estimates of the surface at the grid nodes.
KRIGING INTERPOLATION
The procedures involved in kriging incorporate measures of error and uncertainty when determining estimations.
In the kriging method, every known data value and every missing data value has an associated variance. If ‘C’ is constant (i.e. known value exactly), its variance is zero.
Based on the semivariogram used, optimal weights are assigned to known values in order to calculate unknown ones. Since the variogram
changes with distance, the weights depend on the known sample distribution.
ORDINARY KRIGING
ORDINARY KRIGING
Ordinary kriging. kriging is the simplest form of
It uses dimensionless points to estimate other dimensionless points, e.g. elevation contour plots.
In Ordinary kriging, the regionalized variable is assumed to be stationary. stationary.
PUNCTUAL (ORDINARY) KRIGING
In our acase Z, at point p, Zeof(p) be calculated using weighted average thetoknown values or control points:
z ( p ) w z ( p ) e
i
i
This will and mostthis likely differ from the actual valueestimated at point value p, Za(p), difference is called the estimation error :
p
e
z ( p ) z a ( p )
PUNCTUAL (ORDINARY) KRIGING
If no drift sum exists exists used in the estimation to and one, the one, thenweights the estimated value is said to be unbiased. The scatter of the estimates about the true value is termed the error or estimation variance, n
σ 2 z
i 1
[ z e ( pi ) z a ( pi )]i2 n
CLASSIC OPEN PIT MINING ISSUES AND CHARACTERISTICS
CLASSIC OPEN PITS CHARACTERIZED BY OVAL SHAPE, BENCHES, SPIRALING ROADS
These pits expand without Moving and generally T Target arget a vein or steeply
Dipping stock on ore
THE SLOPE SLOPE EFFECT What happens i we Change the slope Angle?
What just happened to the overburden volume?
What just happened to our stripping ratio?
Conclusion – Pit Slope Makes a Big Pits
Dierence in Open
IMPLICATIONS FOR SLOPE EFFECT • IN LONG AREA STRIP MINES WHERE THINGS BROKE DOWN TO 2 DIMENSIONS SLOPE DID NOT IMPACT STRIPPING RATIO • HERE IN THIS STATIC 3D PIT GEOMETRY THE IMPACT IS HUGE • OBVIOUSL OBVIOUSLY Y HAVING A STEEPER SLOPE IMPROVES ECONOMICS
LIMITING SLOPES • ONE LIMIT IS GEOLOGIC – HAVING THE PIT SLIDE IN ON YOU IS BAD FOR INVESTMENT (AND POSSIBLY YOUR HEALTH IF YOU ARE AT YOU AT THE BOTTOM)
• ONE EXERCISE COMMONLY TAUGHT IN ROCK MECHANICS COURSES IS PLOTTING FRACTURES FRACTURES ON STEREO NET
• ILLUSTRATES HOW MANY FRACTURES ARE OPENED UP BY BENCHES
Daylighted racture Oers an opportunity To To slide o.
Non-Daylighted racture oers little Risk
PROBABILITY PROBABI LITY OF FAILURE AILURE DAYLIGHTED YLIGHTED FRACTURES WILL SLIP • NOT ALL DA • NOT EVERY NON-DAYLIGHTED FRACTURE WILL HOLD
• MORE MAJOR MAJ OR EXTENSIVE DA DAYLIGHTED YLIGHTED FRACTURES FRACTURES MORE LIKELY A MAJOR FAILURE IS • ONE NEW MEXICO MINE LOST ENTIRE PIT AS SLIDE SLIPPED
IN OVER SEVERAL MONTHS
SIGNIFICANCE SIGNIFICA NCE OF FAIL AILURE URE • SOME SMALL FAILURES WILL T TAKE AKE A FEW HOURS TO CLEAN UP – CAN RISK THESE TO SAVE MONEY • LARGER REGIONAL FAILURES ARE FATAL, PROBABLY CANNOT ENDURE MUCH RISK Can tolerate daylighted
Daylighted ractures on over-all over-all
Pit slope are another matter
Fractures on benches
A LESSON IN OPEN PIT TERMINOLOGY Berm Crest Bench
Toe Toe
Over-all Pit Slope
Note that the toe to Crest slope is much Steeper than the over-all over-all
Localized single bench ailures rom a steep toe to crest slope are much Tolerable T olerable than a an n over-all over-all pit slope ailure ailure over the e entire ntire side o o a pit.
PIT SLOPES • QUARRIES IN STRONG ROCK CAN SUSTAIN ABOUT 80 TO 85 DEGREE DEGREE TOE TO CREST SLOPES SLOPES • GEOLOGY DETERMINES LIMITS BUT ABOUT 58 TO 72 DEGREES IS A COMMON RANGE FOR TOE TO CREST IN OPEN PIT METAL.
• OVER-ALL SLOPES OFTEN MORE CONSERVATIVE • FREQUENTLY LESS THAN 45 DEGREES • CANNANEA MEXICO MEX ICO IS NEARL NEARLY Y 60
THE EQUIPMENT CONSIDERA CONSIDERATIONS • WHY BENCHES? • BENCHES STOP ROLLING ROCKS (A ROCK ROLLING DOWN 600 FT AND HITTING YOU IN THE HEAD WILL SPLIT YOUR SCULL – EVEN IF THERE ARE NO BRAINS) • BENCHES ACT AS ROCK CATCHERS – THEY NEED TO BE WIDE ENOUGH FOR THIS – WITH THE AID OF A BERM (AROUND 10-15 FEET) Woops! DIGGING HEIGHT • BENCHES MATCH EQUIPMENT
Bigger shovels allow bigger bench Height – but require bigger trucks
WHY BENCHES CONTINUED • FLAT AREA ON BENCHES PROVIDES ROOM FOR EQUIPMENT TO MOVE • BIGGER TRUCKS HAVE BIGGER TURNING RADIUS T Truck ruck
Shovel Plan view o bench work area
GRADE GR ADE CONTROL AND LIMITS ON BENCH HEIGHTS USUALLY Y HAVE TO DIG WH WHOLE OLE BENCH TOE TO CREST • USUALL • CANNOT SELECT ORE
• SOME MINING DEPENDS ON SELECTING ONLY BEST ORE FOR PROCESSING • CAN LOOSE SELECTIVITY AS BENCH HEIGHT INCREASES
ECONOMICS AND ADVANTAGES OF BENCH HEIGHT BENCH AREA INVOLVES A COST • MAINTAINING • LESS BENCH AREA = LESS COST • HIGHER BENCHES ARE CHEAPER (USUALLY)
• IN DRILLING FOR BLASTING IT TAKES TIME TO SET UP FOR EVERY HOLE DRILLED • HIGHER BENCHES ALLOW LARGER MORE ACCURATE HOLES • ALLOW GREATER SPACING – USES DRILL TIME MORE
EFFECTIVELY
DETERMINING A BENCH HEIGHT • GRADE CONTROL WISE THE LIMIT IS 40 FEET • ROCK MECHANIC WISE THE LIMIT IS 60 FEET • LOADING MACHINE LIMITATION LIMITATION HEIGHT IS 47 FEET F EET
• THE MOST LIMITING LIMITING F FACTOR ACTOR IS GRA GRADE DE CONTROL
• WE NEED TO KEEP BENCH HEIGHT AT 40 FEET
DETERMINING A BENCH WIDTH • TO STOP ROCKS FROM ROLLING NEED AT LEAST 10 FEET At least 20 t
75 t Turning Radius Shovel
About 40 eet or 37 oot length 5 t wall clearance 5 + 75 t turn radius + 37 eet length + 5 oot rom edge = 122 (say about 125 oot bench width or working.)
THE DEPTH EFFECT • NOTE THAT AS A PIT GOES DEEPER THE STRIPPING RATIO INCREASES UNTIL IT REACHES AN ECONOMIC LIMIT • RULE 1 – AS SLOPE DECREASES S.R. INCREASES • RULE 2 – AS DEPTH INCREASES S.R. INCREASES
PRACTICAL PRA CTICAL STEEPE STEEPENING NING CO CONSIDERA NSIDERATIONS TIONS • THE SLOPE LIMITING F FACTOR ACTOR W WAS AS THE NEED T TO O HA HAVE VE WORKING RO ROOM OM FOR THE EQUIPMENT • BUT DO I NEED TO BE ABLE TO WORK ON EVERY BENCH AT THE SAME TIME? • THERE ARE USUALL USUALLY Y PRACTICAL LIMITS TO THE NUMB NUMBER ER OF LOADERS LOADERS AND TRUCKS YO YOU U CAN RUN WITHOUT GOING NUTS • MOST MINES WILL HAVE ABOUT 2 TO 5 LOADERS. • USUALLY THEY WILL HAVE SOME EXTRA WORK PLACES TO MOVE THE LOADERS TO SO THEY CAN PREPARE AHEAD
• TRICK #2 – DOES THE THE PIT HA HAVE VE TO EXP EXPAND AND IN ALL DIRECTIONS AT THE SAME TIME.
• CAN USE “PUSH BACKS” – HAVE A FULL WORKING SLOPE ONLY IN CERTAIN DIRECTIONS AT ANY ONE TIME.
WORKING PITS USUALLY AT WORKING SLOPE • PITS • OFTEN INITIALGO PITIN IS MINED TOP DOWN TO OPEN THE DEPOSIT • MINE THEN PICKS A DIRECTION AND DISTANCE TO PUSH-BACK • PUSH BACK IS WORKED AT THE WORKING SLOPE • SLOPE IS STEEPENED AS LIMIT OF THE PUSH BACK IS REACHED
• MINE THEN PICKS THE NEXT PUSH-BACK DIRECTION
• THEY HAVE HAVE TO OPEN A NUMBER OF WORKING BENCHES • AS THESE BENCHES ARE OPENED THE SLOPE DECLINES TO THE WORKING SLOPE
• CYCLE REPEATS UNTIL THE FINAL PIT SLOPE IS REACHED.
THE DISTANCE DISTANCE FACTOR FACTOR • AS PITS GO DEEPER THE ROADS TO THE SURFACE GET LONGER
• TRUCKS DRIVE FURTHER FURTHER SO THA THAT T ORE AND WASTE WASTE FROM THE BOTTOM BOTTOM OF THE PIT IS MORE EXPENSIVE TO MOVE THAN THAT AT THE TOP
• SOMETIMES THE IMPACT OF DISTANCE CAN LIMIT THE PIT DEPTH BEFORE THE STRIPPING RATIO RATIO DOES
IMPACT OF DISTANCE • GREATER HAUL COST REDUCES THE EARNINGS ON A TON OF ORE • GREATER HAUL COSTS INCREASE THE COST OF OB REMOVAL • IF HAULAGE IS ABOUT 35% OF DIRECT MINE COST • O.B. REMOVAL REMOVAL NEAR THE BOTTOM WOULD BE ABOUT 135% OF NORMAL (WHEN HAUL COSTS DOUBLED) • 5/1.35 = LIMIT MAY BE ABOUT 3.73: 1 AT THE BOTTOM
INDUSTRY RESPONSES TO THE LIMIT • IN-PIT CRUSHING AND CONVEYING – HAVE THE TRUCKS CARRY THE ORE TO A POINT IN THE PIT A CONSTANT DIST DISTANCE ANCE AW AWA AY – THE THEN N CRUSH AND CONVEY • RESULT RESULT – YOU KEEP THE FLEXIBILITY OF HAUL TRUCKS FOR MINING BUT THE INCREASED HAUL DISTANCES IN MORE MINED OUT UPPER AREAS OF THE PIT ARE HANDLED BY CONVEYORS WHICH HAVE A LOWER UNIT COST FOR MOVING MATERIAL
RADICAL IDEAS • PUTTING INCLINED HOISTS ON THE PIT SURFACE OR JUST IN THE WALL AND HAULING THE ORE STRAIGHT UP THE SIDE WITH A SKIP • WAS DONE AT AT LEAST ONCE IN NEW MEXICO • HAS BEEN THE OBJECT OF MANY STUDIES OVER TIME
CALCULATING STRIPPING RATIOS FOR SIMPLE OPEN PITS
OPEN PIT ON PIPE SHAPED DISSEMINA DISSEMIN ATED DEPOSIT DEPOSIT
Cone 1/3*Base*Height Cylinder
Base * Height You’ve seen these Formulas derived in Your calculus classes
GETTING OUR CONE Our Frustum Cone = The Big Cone we Imagine -
The Little Cone Cone We are missing
GETTING OUR OVERBURDEN
The Frustum Cone we just calculated calculated -
The Part of that Volume that is
PAY DIRT!
CALCULA CALCUL ATING STRIPPI STRIPPING NG RATIO Just One Catch Calculation we just did Was based on Volumes
Stripping Ratio = Overburden / Ore
We assumed no material Was rehandled and all Ore was recovered
Called a Geologic Volumetric Stripping Ratio
THE PROBLEM WITH WITH VOLUMETRIC VOLUMETRIC STRIPPING RATIOS PIT MATERIALS AREBY LIMITED IN THE TRUCKS • MOST • THEOPEN ECONOMICS ARE DRIVEN BYWEIGHT WEIGHTS NOT VOLUMES VOL UMES
• EASY TO FIX • OVERBURDEN TONS =OB VOLUME VOLUME * TONS/UNIT VOL • ORE TONS = ORE VOL VOLUME UME * TONS/UNIT VOL
• MAKE SURE YOU DON’T MESS UP YOUR UNITS • DIVIDE AGAIN TO GET WEIGHT BASED SR
INTERESTING OBSERVATION What happens if we Change the slope Angle?
What just happened to the overburden volume?
What just happened to our stripping ratio?
Conclusion – Pit Slope Makes a Big
Difference in Open Pits
COMPUTER AIDED MINE DESIGN (PART I – ULTIMATE PITS)
COMPUTER AIDED MINE DESIGN • MANY SURFACE MINES (ESPECIALLY METAL/INDUSTRIAL MINERAL) ARE DESIGNED WITH COMPUTER PACKA PACKAGES GES • MINTEC EXAMPLE • PACKAGES ARE COMPREHENSIVE FROM EXPLORATION TO OPERATION
• MANY MORE LIMITED PACKAGES THAT DO PARTS OF DESIGN • AUTOCAD AND SOME OF ADD-ONS
OUR SCOPE • WE ARE NOT N OT GOING TO L LEARN EARN A PACKAGE • (THEY CHANGE ANYWAY AND COMPANIES HAVE SPECIFIC PREFERENCES)
• WE WILL LOOK AT WHAT WHAT THE BASIC STEPS ARE AND AN OVERVIEW OF HOW THEY WORK EXPL AINED AT A CONCEPTUAL UNDERSTANDING LEVEL • WILL BE EXPLAINED • WILL NOT ATTEMPT TO TEACH HOW TO DO OR PROGRAM THE CALCULATIONS
HOW DOES COMPUTER AIDED DESIGN WORK • FIRST - GEOLOGY OF THE MINERALIZATION IS WORKED OUT • EXPLORA EXPLORATION TION DA DAT TA WO WORKING RKING WITH GEOLOGISTS • REALLY SAME STEP AS TRADITIONAL METHODS
• SECOND – THE DAT DATA IS CONVERTED INTO A 3D THE MINERALIZATION • ABLOCK CRUDE MODEL MODEL ISOF 100 X 100 X 100 BLOCKS (IE. 100,000) – DETAILED OVER 1,000,000
• MINERAL CHARACTER AND OTHER PROPERTIES OF EACH BLOCK ARE ASSIGNED TO THE BLOCK (COMPUTERS PROCESS AS ARRAY)
HOW ARE BLOCK MODELS BUILT • SAMPLING PROGRAMS OBTAIN SPECIMENS OF THE MINERALIZATION MINERALIZA TION AND ROCK
• OFTEN DONE WITH CORE DRILLING
• GEOLOGIC AND PRELIMINARY EXPLORATION NORMALLY IDENTIFIES THE STRUCTURE AND BASIC MINERAL ZONES LIKELY PRESENT • COMPUTER PACKAGE PACKAGE IS USED TO HELP DETERMINE WHERE TO SAMPLE TO OBTAIN OBTAIN THE MOST USEFUL INFORMATION WITH THE
LEAST EXPENSE
THE BUILDING OF BLOCK BLOCK MODELS • SAMPLES ARE ANAL ANALYZED YZED FOR THE KEY PARAMETERS THAT WILL DETERMINE THE VALUE VALUE OF THE MINERALIZA MINERALIZATION TION • PUT INTO A SAMPLE DATA BASE
• COMPUTER THEN INTERPOLATES THE SAMPLE DA DAT TA TO A GRID OF BLOCKS USING KRIGING
AT THE END OF THE DAY • YOU HAVE HAVE A SERIES OF BLOCKS • OFTEN SEPARATE ROCK FORMATIONS ARE MADE SEPARATE SETS OF BLOCKS
• THE BLOCKS ARE EACH ASSIGNED GEOLOGIC PARAMETERS PARAMETERS THAT THA T DEFINE THE VALU VALUE E OF THE “ORE” • FOR METAL MINES THIS WILL MOST LIKELY BE ORE GRADE (PERCENTAGE OF THE ROCK THAT IS THE MINERAL OF INTEREST)
THE CUT-OFF CUT-OFF GRADE ISSUE • VALUE OF THE MINERAL MIN ERAL IN THE BLOCK IS DETERMINED BY THE MARKET • COST OF MINING AND PROCESSING A BLOCK IS DETERMINED BY WHAT IS DONE WITH IT • IT WOULD COST MORE TO GRIND A BLOCK TO POWER AND PUT IT THROUGH A FLOTATION MILL THAN TO DUMP IT. • DECIDED ON WHETHER THE EXTRA EXPENSE OF ORE TREATMENT TREA TMENT IS RECOUPED FROM THE MA MATERIAL TERIAL
• NEED TO DETERMINE A “CUT-OFF-GRADE” • ONLY MATERIAL ABOVE A CERTAIN GRADE IS PROCESSED AS ORE
MORE CUT-OFF GRADE ISSUES • MAY BE MORE THAN ONE TYPE OF PROCESSING AND D PUT T THROUGH HROUGH FLOA FLOAT TATION • CU ORE CAN BE GROUND AN • CU ORE CAN BE LEACHED IN VATS OR PILES
• CU ORE CAN BE DUMPED • MAY HAVE MORE THAN ONE CUT-OFF GRADE
• POLYMETALLIC DEPOSITS CONTAIN MORE THAN ONE MINERAL OF INTEREST
• LEAD ZINC AND SILVER OFTEN TOGETHER • CUT-OFF MAY BE BASED ON SALES VALUE OF SEVERAL MINERALS
CUT--OFF GRADES CUT GRADES AND BLOCK MODELS • IN TRANSLATING TRANSLATING GEOLOGIC BLOCK MODEL TO ECONOMIC YOU HAVE HAVE TO DETERMINE COV BEFOR BEFORE E YOU CAN ASSIG ASSIGN N COSTS
• COMMON COV IS THE “BREAK EVEN CUT-OFF GRADE” • T TAKE AKE COST OF PROCESSING ROCK • CALCULATE THE MINIMUM MINERAL CONTENT THAT WILL PAY THE COST • THA THAT T IS YOUR YOUR BREAK-EVEN BREAK-EVEN CUT-OFF CUT-OFF GRADE
HOW DO YOU DO THAT? • SIMPLEST METHOD TO EXPLAIN CALLED “FLOATING CONE MINER” • COMPUTER BEGINS EXAMINING THE TOP BLOCKS ONE AT A TIME • LOOKING FOR A BLOCK WITH A POSITIVE VALUE • IF IT FINDS A POSITIVE BLOCK IT WILL MOVE THE BLOCK TO ITS “MINED” BLOCKS RECORD • REPLACE THE BLOCK WITH AN AIR BLOCK
• IT JUST CYBERMINED A BLOCK OF ORE
FLOA FLO ATING CONES CONTINUE • OFTEN TOP LEVEL OF BLOCKS ARE NOTHING BUT AIR OR OVERBURDEN • USUALLY FINDS NOTHING
• COMPUTER THEN EXAMINES NEXT ROW DOWN • LOOKS FOR A BLOCK WITH POSITIVE VALUE
• IF IT FINDS A BLOCK IT WILL LOOK AT THE BLOCKS ABOVE • BLOCKS ABOVE ARE USUALLY AIR OR OB • (BECAUSE IF IT WERE ORE IT PROBABLY ALREADY GOT CYBERMINED) • BLOCKS ABOVE ARE ADDED WITH THE ORE BLOCK
• IF THE ADDED TOTAL IS POSITIVE THE COMPUTER PUTS ALL THE ORE BLOCKS BLOCKS IN THE ORE MINED COL COLUMN UMN AND ALL THE
OB BLOCKS IN THE OB COLUMN COLUMN AND REPLACED THEM WITH “AIR BLOCKS IN THE BLOCK MODEL • THEY WERE JUST CYBERMINED
WHATS ABOVE ME?
How About This? Can you really Mine straight up And down?
This one – of course
-$5.40
-$5.40
-$5.40
-$5.50
-$5.50
-$5.50
-$5.40
$45
$0
$0
$0
-$5.50
-$5.50
-$5.50
Computer is programmed programm ed with a “Cone Angle” – Tells Tells it how to Look at the blocks above and determine if they need to be mined As you see this cone floating around on the model in search of minable m inable ore begin To understand why it is called a floating cone miner.
ADDING THINGS UP
-$5.40
-$5.40
-$5.40
-$5.50
-$5.50
-$5.50
-$5.40
$45
$0
$0
$0
-$5.50
-$5.50
-$5.50
$45 -$5.40
$34.20 > 0
-$5.40 =$34.20
ACTION
-$5.40
-$5.40
$0
$0
$0
$0
$0
-$5.50
-$5.50
-$5.50
$0
-$5.50
-$5.50
-$5.50
Now we are ready to move on to the next block
CONE ANGLES • ROUTINES DIFFER IN HOW PIT SLOPE ANGLES ARE HANDLED • SOME USE A SINGLE INPUT PUT ANGLE • GO UP WITH A CONE • ANY BLOCK THAT GETS HIT OR NICKED IS INCLUDED IN THE CALCULATION OF BLOCK GROUP V VALUE ALUE
• SOME ROUTINES KEEP A MAXIMUM SLOPE IN EACH BLOCK
• IE THEY DID D ID NOT COMPLE COMPLETEL TELY Y CONVERT THE GEOLOGIC BLOCK MODEL TO AN ECONOMIC BLOCK MODEL ALLOW P PAR ARTIALL TIALLY Y MINING A BLOCK • THEY MAY ALLOW
• THESE CONE ANGLES COME OUT OF YOUR YOUR ROCK MECHANICS WORK ON SLOPE STABILITY
WHAT HAPPENED TO WORKING SLOPE? • YOU MAY MAY REMEMBER THAT NEED A CER CERT TAIN AMOUNT OF BENCH ROOM FOR EQUIPMENT TO WORK
• USUALLY USUALLY MADE SLOPE LESS STEEP THAN A FINAL PIT SLOPE BASED ON GEOLOGY
• WE ARE WORKING ON “ULTIMATE PIT” AFTER EVERY SLOPE AND TON OF ORE THAN CAN BE MINED HAS BEEN MINED
ROUTINE CONTINUES • COMPUTER MOVES DOWN TO THE 3 RD LEVEL LOOKING FOR POSITIVE VALUE BLOCKS • IF IT FINDS ONE IT CONES UP TO THE SURF SURFACE ACE AND ADDS UP THE VALUE • CYBERMINES THE WHOLE THING IF VALUE IS POSITIVE • MOVES ON LOOKING MORE IF THE CONE COMES UP NEGATIVE
• COMPUTER KEEPS DROPPING ONE LEVEL AFTER
ANOTHER TILL IT IS DONE • “ULTIMATE PIT” IS THE SET OF AIR BLOCKS IN THE MODEL
WOOPS FACTORS -
-$15 + $10 =
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
$10
-$5
-$5
-$5
-$5
-$5
-$5
$25
$25
-$5
-$5
-$5
$70
-$5
-$5
-$5
-$5
WORKING ON WOOPS -$40 + $70 =
$30
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
-$5
$10
-$5
-$5
-$5
-$5
-$5
-$5
$25
$25
-$5
-$5
-$5
$70
-$5
-$5
-$5
-$5
CYBERMINING Now the Cone Is Profitable -$5
-$5
-$5
$0
$0
$0
$0
$0
-$5
-$5
-$5
-$5
-$5
$10
$0
$0
-$0
-$5
-$5
-$5
$25
$25
-$5
-$5
-$5
$0
-$5
-$5
-$5
-$5
To catch situations like this, most floating cone Miners will start searching from the top of the Model time they cybermine a cone to look For oreevery on the edge.
HARDER TO FIX This T Pit is Not Profitable
-$5
-$5
-$5
-$5
$0
$0
$0
$0
$0
$0
-$5
-$5
-$5
-$5
-$5
-$5
-$5
$0
$0
$0
$0
-$5
-$5
-$5
-$5
-$5
$25
$25
-$5
-$5
-$5
$0
-$5
-$5
-$5
-$5
WEAKNESSES OF FLOATING CONES This Pit is Profitable -$5
-$5
-$5
-$5
$0
$0
$0
$0
$0
$0
-$5
-$5
-$5
-$5
-$5
-$5
-$5
$0
$0
$0
$0
-$5
-$5
-$5
-$5
-$5
$25
$25
-$5
-$5
-$5
$0
-$5
-$5
-$5
-$5
Unfortunately Floating Cones will never see this Since they look at only one block at a time and Sometimes profitability requires looking at groups
SOLUTIONS • FLOATING CONE MINERS ARE IN A CLASS CALLED HEURISTIC ROUTINES • BASED ON A GUESS A PLUG APPROACH
• IS AN ANALYTICAL SOLUTION CALLED METHOD OF CONVEX-HULLS • DON’T ASK ABOUT THE MATH (YOU DON’T WANT TO KNOW) • WILL CUT THROUGH A BLOCK MODEL AND GET THE LARGEST BLOCK OF GROUND THAT STILL KEEPS
INCREASING PROFIT • ROUTINE IS CALLED “LEARCH GROSSMAN” AIRLY POWERFUL POWERFU L COMPUTER COMPUT ER (WHICH WE EASILY EASILY HAVE • REQUIRES FAIRLY TODAY) TODA Y)
CHOICES CHOICE S AND A ND LIMIT LIMITA ATIONS • LEARCH GROSSMAN INCLUDES SOME FAIRLY RESTRICTIVE ASSUMPTION ABOUT UNIFORM SLOPES • REAL PIT SLOPES THAT ARE STABLE MAY V VARY ARY B BY Y DIREC DIRECTION TION AND ROCK TYPE
• HEURISTIC ROUTINES CAN HANDLE LOT OF FLEXIBILITY, BUT ARE SUBJECT TO ERRORS • WHITTLE PROGRAMMING HAS TRIED TO IMPOSE OF FEW HEURISTIC VARIATIONS ON A TRUE LEARCH GROSSMAN
• BOTTLE-LINE - IN THE END YOU WILL HAVE HAVE AN ULTIMA UL TIMATE TE PI PIT T THAT IS SOME SOMEWHAT WHAT CLOSE TO THE TRUE OPTIMUM
MINE CLOSURE
CLOSURE LEGACY
DRIVERS FOR CHANGE • HEIGHTENED FOCUS ON MINE CLOSURE, THE DEVELOPMENT OF A CONSIDERABLE BODY BODY OF GUI GUIDELINES, DELINES, LEGISLATION AND REGULA REGUL ATION • 70% OF ALL CLOSURES ARE UNPLANNED (LAURENCE UNI NSW). • RAMIFICATIONS OF ALTERNATIVE LEGISLATIVE MECHANISMS WITHIN AUSTRALIA AND OTHER PARTS ARTS OF THE WORLD • INCREASED CLOSURE PLANNING DURING THE OPERATIONAL OPERA TIONAL PHASES OF THE MINING M INING LIFE LI FE CYCLE.
APPROVALS
AND
• MAY TRANSLATE INTO EFFECTIVE MINE CLOSURE IMPLEMENTATION – TIME WILL TELL?
INCREASED CLOSURE PLANNING BY COMPANIES LINKED TO MINE LIFE CYCLE CYCLE
IMPORT IMPOR TANCE O OF F CLOSURE PLANNING PLANNING • AIDS ENVIRONMENTALLY ENVIRONMENTALLY BENE BENEFICIAL FICIAL MINE PL PLANNING ANNING AND D DESIGN ESIGN • PROMOTES PROGRESSIVE REHABILITA REHABILITATION TION • CONST CONSTANTL ANTLY Y WO WORKING RKING TOWARDS CLOSURE OBJECTIVES: PROACTIVE VS REACTIVE
• EVER CHANGING NA N ATURE OF CLOSURE PLANS PL ANS ENSURES OPERATIONS CAN BE • MODIFIED TO REDUCE RISKS TO CLOSURE OBJECTIVES • PLAN IN PLACE IN CASE OF UNEXPECTED CLOSURE • FINANCIAL PROVISIONING AVAILABLE
• STAKEHOLDER STAKEHOLDER INVOLVEMENT INVOLVEMENT IS PROACTIVE NOT REACTIVE IN ESTABLISHMENT EST ABLISHMENT OF CLOSURE CRITERIA, OBJECTIVES AN AND D STANDARDS • REDUCES CLOSURE TIMEFRAMES AND ENVIRONMENTAL PERFORMANCE BONDS
CLOSURE CL OSURE CRITERIA AND OBJECTIVES - AIMS • DEFINE APPROVED POST MINING LAND USE • REDUCE TOTAL AMOUNT OF DISTURBANCE BY ADOPTING BEST PRACTICE PLANNING PRINCIPLES IN MINE DESIGN • AIM TO REFLECT CHARACTERISTICS OF AESTHETICS, ECOSYSTEM FUNCTION, LANDFORM FUNCTION, EROSION LEVELS AND HYDROLOGICAL PATTERNS REPRESENTATIVE OF THE EXISTING ENVIRONMENT IN ALL REHABILITATED
AREAS
• CREATE REALISTIC AND MEASURABLE STANDARDS BY WHICH REHABILITATION SUCCESS CAN BE EVALUATED
STAGES OF MINING – THE BUSINESS IS “MINING” STAGES CLOSURE PLANNING IS INHERENTLY TODAY PART OF THE BUSINESS
Figure 1:
Integrating Stages o Mining and Mine Closure Planning (adopted rom DITR 2006a, ICMM 2006)
BUILDING THE BUSINESS CASE FOR FUTURE
MITIGATION OF RISK
KEY CLOSURE PLANNING PL ANNING CON CONSIDERA SIDERATIONS TIONS
STATED: RECENTLY “BHP BILLITON EMBEDDED CLOSURE PLANNING INTO ITS BUSINESS SYSTEMS BY INTEGRATING CLOSURE ENGINEERING AND PLANNING INTO ITS LIFE OF ASSET PLANNING PROCESS”.
FIVE PRINCIPLE CLOSURE PLANNING DRIVERS:
• CLOSURE PLANNING PLA NNING FUNDAMENTALS. FUNDAMENTALS. • RISK MANAGEMENT. • ENGINEERING, EXECUTION E XECUTION AND PROJECT MANAGEMENT. MANAGEMENT.
• COST ESTIMATION. ESTIMATION. • MANAGEMENT TO MITIGA MITIGATE TE CLOSURE RISK RI SK DURING OPERATIONS. OPERATIONS. • DEVELOPED A CHECK-LIST OF 28 KEY CLOSURE PLANNING CONSIDERATIONS. CONSIDERA TIONS. (BENTEL 2009)
FIGURE 1. CLOSURE PLANNING - KEY STAGES OF CLOSURE PLANNING INTEGRATION INTO BUSINESS PRACTICE
BUSINESS IS ABOUT RISK MANAGEMENT (INTEGRATION (INTEGRA TION AND BUSINESS PRACTICES)
ICCM Drat Figure 1: Key Stages o Closure Planning
INTEGRATIO N INTO BUSINESS PRACTICES
WHERE ARE THE TREES?
WHAT WHA T ABOUT THE SL SLUDGE? UDGE?
EXAMPLE
CASE STUDY REHABILITA REHABILIT ATION OF ENSHAM OPEN-CUT OPEN- CUT COAL MINE SITE
Rehabilitation of the Ensham open-cut coal mine near Emerald in Central Queensland.
Image courtesy of Ensham Resources
Before mining
Image courtesy of Ensham Resources
Aer mining
Image courtesy of Ensham Resources
Aer rehabilitaon The purpose of rehabilitation is to return the site to an agreed land use. This is a legal requirement of the EPA (Environmental Protection Authority).
Image courtesy of Ensham Resources
Open cut coal mining
‘Spoil’ is the overburden removed to reveal the coal seam. Previous spoil is piled behind the pit. In this way, the pit advances, progressively filled with new spoil. Rehabilitation will ultimately occur over the previous spoil behind the mine.
Direction of advance of the pit
Image courtesy of Ensham Resources
The Ensham Mine The pit at the Ensham mine is progressing to the right in the picture. Removal of surface overburden is in progress on the highwall side (right) and is dumped on the spoil pile (left) to fill the pit.
Image courtesy of Ensham Resources
Rehabilitation planning An aerial view of the mine shows the plan for rehabilitation, with the areas to be rehabilitated in green.
Image courtesy of Ensham Resources
An Environmental Impact Study (EIS) is conducted to assess the flora and fauna that exists prior to mining. An Environmental Authority (EA) is then issued with the mining lease to regulate how the mining company is to interact with therequirements environment.are The rehabilitation
different for every mine. The mine proposes a rehabilitation plan and the government then adds its own conditions prior to approval.
Image courtesy of Ensham Resources
This map highlights areas of “Endangered”, “Of concern” and “Not of concern” ecosystems within and surrounding the mine site.
Image courtesy of Ensham Resources
Before mining
Image courtesy of Ensham Resources
Aer mining
Image courtesy of Ensham Resources
Rehabilitaon
Image courtesy of Ensham Resources
Restored land
Image courtesy of Ensham Resources
Stockpiling of topsoil pre-mining
Before mining begins, topsoil is stockpiled on the highwall side. It is kept for a period until the mine has progressed and the slope of the spoil is ready for the topsoil to be replaced. Most mines salvage 200mm of topsoil but at the Ensham mine 300mm is kept.
Image courtesy of Ensham Resources
Dumping of spoil After surface overburden has been removed by trucks, the highwall is detonated to transfer as much burden as possible to the other side of the pit. Draglines pile this overburden into high spoil piles.
Image courtesy of Ensham Resources
Steep slopes are unsuitable for rehabilitaon
The volume of rock swells by 25 percent after it is detonated. Even after the coal seam is removed, the spoil piles created by draglines create hills with steep slopes formed as the spoil is dumped.
In years past, these slopes were rehabilitated. However, the slope was found to be too steep to be stable. This picture shows how unstable such a hill is with regard to erosion and landslides.
Image courtesy of Ensham Resources
Reshaping of the slope
Bulldozers and trucks are used to reshape steep spoil piles
into gradual slopes that are suitable for rehabilitation. Generally, the maximum gradient of slope accepted by the Generally, Environmental Authority is one in ten (ten percent), although sometimes one in fifteen is accepted.
Image courtesy of Ensham Resources
A site levelled prior to rehabilitation, awaiting another truck and shovel dump of spoil.
Image courtesy of Ensham Resources
Image courtesy of Ensham Resources
Once the required gradient is obtained, bulldozers are used to smooth the surface. Working the material in this manner has the added advantage of making it finer on the surface and more conducive to plant growth.
Image courtesy of Ensham Resources
Prior to rehabilitation, the surface resembles a big, flat moonscape. It takes some four or five years from commencement of mining to reach this stage. It’s not possible to rehabilitate right up to the mining point and a further delay results because the ground must be left to settle for twelve months.
1 10
A slope of 1 in 10
Image courtesy of Ensham Resources
Swelling of the rock means that it's not possible to return the land to its original contours. A gently sloping hill with a flat top is constructed behind the mine.
Image courtesy of Ensham Resources
Laying of topsoil
Topsoil stockpiled prior to commencement of mining is trucked to the rehabilitation site.
Image courtesy of Ensham Resources
Image courtesy of Ensham Resources
Image courtesy of Ensham Resources
Image courtesy of Ensham Resources
Topsoil is dumped, ready to be spread by bulldozers or graders.
Image courtesy of Ensham Resources
Image courtesy of Ensham Resources
Spreading of topsoil
Image courtesy of Ensham Resources
Image courtesy of Ensham Resources
Topsoil is generally spread to a depth of 200mm. At the Ensham mine, 300mm.
Image courtesy of Ensham Resources
The importance of topsoil (left) is most apparent adjacent to a site where topsoil is yet to be laid (right).
Image courtesy of Ensham Resources
Laying of manure
Manure is laid over the topsoil to further encourage plant growth.. growth. .
Image courtesy of Ensham Resources
Manure is spread using a belt-driven bin behind a tractor. tr actor. At the Ensham mine, 15 tonnes of manure is spread per hectare.
Image courtesy of Ensham Resources
Pegging the contours
Surveyors and environmental engineers peg lines of equal height to mark the contours on the rehabilitation site.
Image courtesy of Ensham Resources
Deep ripping along the contours
A bulldozer follows the pegs to deep rip along the contours to a depth of
about one metre. This increases infiltration of water and provides a rough surface to reduce runoff and erosion. Once grass has established itself on this surface, the contours will completely eliminate any rainwater runoff.
Image courtesy of Ensham Resources
Image courtesy of Ensham Resources
Image courtesy of Ensham Resources
Controlling drainage
Drainage is further controlled by means of 20-30m wide horizontal benches between every 100m of sloped rehabilitation land. This reduces the likelihood of rainwater running off in torrents.
Small rock walls called ‘rills’ are constructed around the rehabilitation area to stop runoff from the mine washing away the topsoil or killing the grass.
Image courtesy of Ensham Resources
Different grasses and legumes are seeded on rehabilitation sites according to the final land use of the site. At the Ensham mine, grasses that are ideal for cow fodder, f odder, such as Buffel grass and Rhodes grass, are used commonly, in addition to six other species according to the soil type. While some mines use both native and
introduced species, Ensham has found that the introduced species quickly take over, so native species are no longer seeded.
Image courtesy of Ensham Resources
Scattering of seed
Grass is seeded at the rate of 25kg of seed per hectare by a contract farmer. The seed is spread by a fertiliser spreader on the back of a farm tractor. Summer grasses require a certain soil temperature to strike and grow, so in winter, 20kg per hectare of wheat seed is added to the mix. Wheat provides cover in the winter, ready for grasses to come through in summer.
The aim is to get as much ground cover as quickly as possible so as to reduce erosion.
Image courtesy of Ensham Resources
Spreading of ferliser
Fertiliser is spread at the rate of 100kg per hectare.
Image courtesy of Ensham Resources
Wheat stubble (hay) is spread as mulch to give the land stability and water-holding capacity before the grass is established. 20 six-foot round bales of wheat hay are spread per hectare.
Spreading of mulch
Image courtesy of Ensham Resources
Image courtesy of Ensham Resources
Image courtesy of Ensham Resources
Early growth
Image courtesy of Ensham Resources
Grass is seeded within a week of the site having been ripped. Assuming good rainfall there will be cover within a month.
Image courtesy of Ensham Resources
Mature grass, going to seed within six months of planting
Image courtesy of Ensham Resources
Planng of trees The question of whether to plant trees on a rehabilitation site can be complex. Some mines are required to return a certain number of acacia and eucalypt stems per square metre. At Ensham, where the land will ultimately be restored as grazing land, trees are not always desired by farmers.
Trees can only be planted on this site after the grass is established. Otherwise, trees can get out-competed by the grass from the outset or trees can hold up the growth of the grass and result in erosion. The most effective way to stabilise the slopes against erosion is with grasses.
Image courtesy of Ensham Resources
Seeding trees is not as successful as growing trees from established saplings. Irrigation through dripper lines increases the success rate in the hot climate at
the Ensham site, but this is challenging to establish over such vast areas. Trees may become more common on rehabilitation sites if there is value attached to them in a carbon trading scheme in the future.
Image courtesy of Ensham Resources
Benchmark sites Benchmark sites of undisturbed land called "analogue" sites are used as references for rehabilitation sites.
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Image courtesy of Ensham Resources
Restored land Every mine site has different conditions and requirements for rehabilitation. At the end of the life of the Ensham mine, the site will likely be returned to grazing land. Some other mines have a rehabilitation requirement defined as "native self sustaining ecosystem," so any native species able to grow on that site are encouraged.
The government provides a financial incentive to rehabilitate because the bond that mining companies are charged for their use of the land applies only to disturbed land. Every hectare of rehabilitation reduces this bond. At Ensham, between 150 and 200 hectares of land are rehabilitated every year. The company set a Queensland record in 2009 with a total of 280 hectares rehabilitated. Image courtesy of Ensham Resources
Rehabilitaon costs
Rehabilitation is a costly exercise: $12000 /h /ha $8800 /h /ha a $500 $5 00 /h /ha a
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Bulk ea earth thw works to to sp spread th the sp spoil an and es establish th the e sl slope Topso soiil - hauling in a tr tru uck & sp sprreading with a scr cra ape perr or dozer Drai Dr ainag nage e wo work rks s - dr drai ains ns,, bu bund nds, s, ba bank nks, s, di dive verti rting ng ru runo noff ff
$500 $500 $200 $2 00 $600 $6 00 $400 $4 00 $200 $2 000 0
/ha /ha /ha /h a /ha /h a /ha /h a /ha
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Manure Manu re - pu purc rcha hase se,, fr frei eigh ghtt an and d sp spre read ad @ 10 10t/ t/ha ha Ferti Fe rtililise serr - pu purch rchas ase, e, fre freig ight ht an and d sp spre read ad @ 10 100k 0kg/h g/ha a Deep De ep ri ripp ppin ing g - to 1m de depth pth,, on th the e co cont ntou ourr, on 2m ce cent ntre res s Seed Se ed - pu purc rcha hase se,, fr frei eigh ghtt an and d sp spre read ad @ 25 25kg kg/h /ha a Hay Ha y - pu purch rchase ase,, fre freig ight ht an and d spr sprea ead d @ 20 ro roun und d ba bale les/h s/ha a
$25 000/ha
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Total cost
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Image courtesy of Ensham Resources
GOLD REEF CITY EXAMPLE
The End!!!!
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