whittle modules

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Gemcom Software International

Four-X Analyser Modules

The Four-X Analyser product suite consists of the following modules:

FoundationMulti-elementMining WidthMilawa AlgorithmMulti Analysis

Advanced AnalysisStockpile and Cut Off OptimisationBuffer StockpilesBlending

Foundation:Data ImportationThe Four-X Analyser Foundation will accept data in the industry standard Whittle format. Resource model files and Pitdesign/Reserve files can be imported, with or without a Parameters File. Four-X imports and exports data throughspecialized interfaces, most of which are built into generalized mining packages for convenience. Gemcom, Micromine,Medsystem, Surpac and others include such an interface in its block modelling software. On completion of importation, abrief summary is presented to enable reconciliation with the original data.

Model ManipulationThis function analyses an existing Block Model, performs transformations on it, and creates a new (re-blocked) BlockModel. The transformations that can be performed include:

Adding expensive blocks for the purpose of biasing the pit optimisation (Add blocks tab). This can be used forexample, tostop pits encroaching on lease boundaries etc. Adjusting the model framework (Adjust framework tab).This is usually performed to allow pits to expand to areas outside the model framework.

Calculating positional cost adjustment factors for mining and processing costs with user-defined expressions.

Adjusting the shape and size of the blocks (Adjust blocks tab).

Combining mineralised parcels, to improve mining selectivity modelling.

Additional functions are included under the Tools Menu for advanced data manipulation.

Pit Slope Modeling

This is the most comprehensive and flexible slope modelling system available for pit optimisation.

Pit slope definitions can be defined for the whole model in a variety of flexible ways. Up to fifty slope profiles are defined.Each profile consists of up to eight bearing / slope pairs. Profiles can then be assigned to different parts of the block modelin the following ways:

Rectangular slope regions.

Rock-types in the Model file.

Zone Numbers in the Model file.

Profile Numbers in a Profile Number file.

The slope model can also include user-defined additional arcs which are used to define complex relationships betweendifferent parts of the model, and link together blocks, which must be mined together.The slope model is used to control the manner in which pit shells are generated in the pit optimization process.

Gemcom Amrica Latina

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Pit OptimisationPit optimisation is carried out by a Whittle implementation of the well-known Lerchs Grossmann algorithm. It is able torespond to:

Very simple or very complex pit slope modelling, including the application of user-defined additional arcs.

Expensive blocks, defined by the user in the reblocking node. Expensive blocks can be used to represent lease

boundaries or immovable objects such as processing plants, which cannot be under-mined.Price, cost and processing models can be based on very simple inputs or very complex user-defined expressions.

Cost and prices can be expressed simply as dollars per tonne or dollars per gram, or they can be modelled usinguser-defined expressions. User-defined expressions can include a range of variables and functions. For example, it ispossible to build an expression to vary the cost of processing depending on the grade and position in the model fromwhich the ore came.

Recoveries can be represented as a simple percentage, or the expression builder can be used to build a complexvariable recovery function.

The pit optimization is controlled by a range of user-controlled setting, which affects the precise manner in which theoptimization proceeds. Up to 100 optimal pit outlines are produced in a single run of the Pit Shells node.

Economic ScenarioThe economic scenario sets the base case for scheduling and analysis, including costs, prices, throughput limits,recoveries etc. Users can apply the same settings that were used in the pit optimization or they can change them in order

to apply special analysis techniques. The vast majority of the settings in the Economic Scenario can be changed overtime, adding to the sophistication of the model.

Analysis and GraphsThe user can specify the use of three different life-of-mine scheduling techniques, and view graphs of the results, or exportdata for analysis in a spreadsheet. The options include:

Schedule Graph shows tonnes mined and tonnes processed for each period in the mine life.Pit-by-Pit Graph shows tonnage and NPV values for a range of different pits using three different schedulingmethods. It is possible to have as many as 300 life-of-mine schedules represented in a single graph.

Size v. Value Graph A variation on the Pit-by-Pit Graph showing the total mine tonnage and NPVs for threedifferent scheduling methods.

Custom Period Graph A user-defined analysis for a single life-of-mine schedule. The user can choose fromhundreds of variables to display in the graph. All data that is displayed in graphs can be exported for further analysis

in a spreadsheet program. Each analysis generates a comprehensive report, outlining all the assumptions andsettings, and the details of all the life of mine schedules produced.

Data ExportFour-X Analyser Foundation allows a large range of data and reports to be exported or printed. They include:

Audit reports for each model import; pit slope modelling; pit optimization and analysis/life-of-mine scheduling.

Block models.

Schedules.

Pit outlines.

Analysis data.



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Data VisualisationFour-X Analyser Foundation includes an interactive 3D visualiser, which allows pit contours to be viewed instantly. Thisviewer is very fast, so pits can be moved and spun around in real time. Viewing one pit to another is instantaneous. Aswell as the pit contours, data planes show grades, or other model file information. Users have control over how thecontours look and can switch data planes on or off and set up custom grade colour schemes. This same visualiser can beused to:

View model files examine the model in three dimensions. Examine all the variables in the model.

View pit shells examine the pits overlayed on the block model if you wish.

View mining schedule watch the pit grow from period to period.

Multi-elementThe Multi-element module allows up to ten elements to be defined in the model. Individual elements and reportedseparately and the grades and quantities of each element are available for use in user-defined expressions, graphs andreports. Multi-element capabilities are very useful for analysing multi-product mines. The capability can also be used for:

Applying grade-dependent costs, prices and recoveries. It could be that the recovery of one element is dependent onthe grade of another.

Allowing for deleterious elements by applying stochastic liberation estimation to the recovery function.

Mining WidthUsers are able to very rapidly adjust their pushbacks to allow for mining width constraints. The speed and repeatability ofthe process means that users can experiment with different mining widths to see what impact they have. Because theprocess is contained within Four-X Analyser, the results can be quickly analysed and compared to other scenarios.

The mining width module allows users to modify a selection of shells from the pit shells node, allowing for mining widthconstraints. It is achieved in a fraction of the time it would take to adjust the shells manually in a GMP, and unlike manualmethods, it can be strictly controlled and repeated at will. Eleven different settings control the manner in which theadjustments proceed.

Milawa AlgorithmThe Milawa Algorithm adds a new dimension to life-of-mine scheduling. It optimises the schedule, taking into account allyour production and economic constraints, while seeking to maximise the utilization of available mining and processingcapacity.

The Milawa Algorithm is a proprietary algorithm which schedules phases in order to maximise NPV. It responds to allproduction constraints, price and cost models within Four-X Analyser and also provides additional controls over theschedule.

How does it work? The Milawa Algorithm consists of three parts:

The first part takes a set of variables and generates a feasible schedule from them. A full set of the variablesdescribes the life of mine schedule. The number of variables required depends on the number of benches in theultimate pit, pushbacks, and time periods in the life of the mine. The possible values for these variables areconstrained by what is technically feasible in terms of the pit shell precedence rules and any constraints imposed bythe user (mining, processing, selling constraints, maximum and minimum lead, maximum vertical advance per period).

The second part is an evaluation routine, which calculates the NPV for an individual schedule.

The third part searches the domain of feasible schedules for the one, which has the highest NPV. This routine alsohas logic built in to decide when to stop searching.



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Milawa does not generate and evaluate all feasible schedules as the number of feasible schedules can be extremely large.Rather it strategically samples the feasible domain and gradually focuses the search (without necessarily narrowing it) untilit converges on its solution. The number of evaluations required to converge on a solution varies, but 5000 is typical, andthis usually takes less than a minute.

The feasible domain can be viewed as a multi-dimensional volume (one dimension for each variable used to describe thelife of mine schedule), where each point in the volume has a corresponding NPV. The optimum solution is the point whichhas the highest NPV, but it is possible for there to be more than one point with the maximum NPV. It is also possible forthere to be a range of other solutions, which have NPVs, which are very close to the maximum. Milawa cannot guaranteeto find a schedule with the absolute maximum NPV, particularly if the highest happens to occur on a very sharp peak.However, experience has shown that it will find a solution with a very high NPV.

The Milawa Algorithm can also be run in 'balancing mode'. In balancing mode, the Milawa Algorithm substitutes anevaluation routine, which returns higher, values when production facilities are fully used early in the life of the mine. Howgood are the results produced by Milawa? The best way to evaluate the results is to compare them to the best case andworst case schedules, which provide very convenient internal high and low benchmarks for the NPV of the project for theconfiguration and constraints under examination.

Multi AnalysisThis module significantly extends the capabilities of Four-X Analyser by allowing multiple imported models per project, and

branching of the analysis trees thereafter. You can, for example attach several pit slope nodes to an imported model node,each representing a different set of assumptions. Four-X Analyser keeps track of all the data dependencies for you. Youcan build hugely complex analysis models, which can be viewed, accessed and managed simply.

Scenario branching allows you to build up an analysis tree, with all the data dependencies managed by Four-X Analyser,and all the relationships clearly represented on the screen. Features include:

Nodes can have multiple child nodes attached to them. In turn, those child nodes can have their own children, leadingto an expanding tree of analysis.

Nodes and branches can be cut, copied and pasted.

Branches can be collapsed or expanded to hide or reveal the detail.

Advanced AnalysisThis module allows Four-X Analyser to perform very complex analysis. This is extremely useful to designers who are

interested in extensively testing sensitivities, and performing risk analysis. Features include:

Custom Grand Total Graph. The user can define any one of hundreds of variables (such as mining costs,dilutions, recoveries) to vary over a range, and Four-X will produce a life of mine schedule for each case. The usercan display any number of results (e.g. NPV, strip ratio, IRR, ore tonnes) in a graph or export the results to aspreadsheet.

Custom Schedule Graph - The user can display any number of results (e.g. NPV, strip ratio, IRR, ore tonnes) in agraph or export the results to a spreadsheet.

Advanced Grand Total Analysis - The user can define one or more of hundreds of variables (such as miningcosts, dilutions, recoveries) to vary over a range, and Four-X will produce a life of mine schedule for each case. Forexample, varying 3 parameters each over ten steps would lead to the generation of 1000 life of mine schedules. Theuser can write any number of results (e.g. NPV, strip ratio, IRR, ore tonnes) into a table and either view it, or export theresults to a spreadsheet.

Spider Diagram - This is a special type of multivariate sensitivity analysis, which is represented in a spider graph.The user chooses several parameters to vary and a percentage to vary them by. The user also chooses which resultshould be shown in the graph.

Stockpile and Cut-off OptimisationThis module provides comprehensive grade-stockpile and cut off optimisation with the objective of maximizing NPV. Themodel re-schedules the mining sequence, taking in to account all the constraints and setting in Four-X Analyser andoptimising the stockpile utilisation and cut off strategy. It can be used for:

Determine the optimum usages of grade stockpiles in order to maximise NPV.



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