1.6 Production Planning & Scheduling

Production planning sets the intended output and the means of achieving it; production scheduling assigns extraction, development, processing and supporting work to periods in a feasible order. Together they connect the mine design to material deliveries, resource demand and cash flow. Surface and underground schedules differ in their physical dependencies, but both must decide what can be done, when, and with which resources.^[1]

Connecting Planning Horizons

A useful planning hierarchy distinguishes decisions by their consequences and flexibility. A life-of-mine plan establishes the overall development and extraction strategy. Longer-term schedules test how that strategy can be delivered over successive periods. Near-term schedules translate it into work that is sufficiently defined and ready to execute. Smith's strategic planning framework connects business assumptions, exploitation choices and supporting execution plans through repeated review.^[2]

These are connected perspectives, not universally fixed calendar ranges. The appropriate period length depends on the decision, information maturity and operating cycle. A shorter schedule must retain the longer plan's essential commitments, while evidence that those commitments are infeasible must travel back to the planners responsible for revising them.

Establishing a Common Planning Basis

Scheduling starts with a spatial inventory and the designs that make extraction possible. Relevant inputs include material quantities and qualities, mining recovery and dilution assumptions, ground conditions, access geometry, processing response, infrastructure and waste destinations. Table 1 of the Australasian JORC Code, 2012 Edition, identifies these relationships in its reserve-reporting criteria. Its reporting context should remain distinct from the internal scheduling task.^[3]

Record the current condition separately from future assumptions: already mined areas, completed development, work in progress, opening stockpiles and committed maintenance. Otherwise, two schedules can appear to disagree simply because they start from different physical states. A plan version should identify the data cut-off, design revision and operating assumptions used to generate it.

Quantities need consistent bases. Distinguish mined material from plant feed and saleable product; specify whether mass is dry or includes moisture. Mining recovery measures the fraction of specified in-situ material recovered during extraction; metallurgical recovery measures the fraction of a specified feed constituent recovered to a defined product. Economic comparisons also require consistent prices, costs and treatment of infrastructure. The JORC checklist separately addresses moisture, mining factors, metallurgical factors, costs and revenue assumptions.^[3]

The inventory also retains its geological confidence and reporting basis. Under the cited JORC framework, assigning extraction dates does not by itself establish reportable Ore Reserves: a study at least at Pre-Feasibility level must demonstrate technical achievability and economic viability with relevant Modifying Factors considered.^[3]

Linking Readiness, Sequence and Material Destinations

An extraction sequence expresses dependencies. Surface mining may require removal of overlying material and maintenance of workable access. Underground production may depend on development, preparation and the chosen support or backfill sequence. The relevant relationships follow the mining method and layout; a precedence pattern appropriate to one method cannot establish feasibility for every operation.^[1]

Dependencies also involve services and release conditions. Completing an excavation does not by itself demonstrate that the next activity can start. The schedule needs to represent whichever inspections, installations or other readiness conditions the design and operating arrangements require. A production target with no corresponding route to ready workplaces is an unsupported commitment.

Extraction and processing are separate events. Material may move directly to treatment, enter a stockpile for later reclaim, or go to an appropriate waste destination. Each movement consumes resources, and material held at period end becomes part of the next period's starting inventory. A stockpile balance therefore needs identifiable inflows, outflows and remaining contents.

Blending links quality targets to material availability, processing destinations and handling capacity in each scheduling period. An acceptable life-of-mine average cannot establish that suitable feed exists in every period.^[1]

Jupp and colleagues distinguish storage, buffering, blending and grade separation as different stockpile functions in iron ore mining. Their priorities can conflict. The planned purpose and physical stacking and reclaim arrangements must therefore be explicit; stored tonnes alone do not establish the quality of the next delivery.^[4]

Testing Capacity as a Connected System

Capacity is meaningful only with a defined activity, time basis and operating condition. A loading rate, a haulage capability and a plant throughput cannot be compared without accounting for the material stream and the time available. Planned maintenance, shared work areas and competing assignments belong in that assessment. A nominal equipment rating alone does not establish deliverable period output.

For a proposed schedule, ask which constraint prevents additional useful output. It may be access to prepared ore, a transport link, processing time or another shared service. Increasing a capability that is already sufficient may leave the limiting relationship unchanged. The practical test is whether the proposed change improves the required downstream delivery under the same assumptions.

Bloss's published account of bottleneck management identifies support, stabilisation and use of the limiting operation alongside capacity increases. It also identifies variability at that operation as relevant to throughput. These considerations support examining operating conditions before selecting an expansion response.^[5]

Consider an illustrative situation with no project data: development falls behind while plant feed remains the immediate target. Reassigning a crew might help one heading but delay another. Drawing down stockpiles may sustain feed temporarily while reducing future flexibility. The revised plan must check both the immediate delivery and the access and inventory conditions inherited by subsequent periods.

Objectives, Models and Uncertainty

Schedules can be evaluated against discounted cash flow, delivery commitments, quality requirements and resource use. Optimisation searches among decisions permitted by the model; simulation examines how a specified system behaves under the represented operating conditions. Neither method establishes that omitted access, service or operating constraints have been satisfied.^[1]

Separate mandatory feasibility conditions from targets that permit a trade-off. A penalty for missing a preferred feed target expresses a different decision rule from a hard upper bound on an available resource. The distinction must remain visible when comparing alternatives. A result described as optimal is conditional on its objective, constraints, input data and the solution status actually obtained.

Uncertainty changes how alternatives should be compared. Armstrong and colleagues evaluate adaptive open-pit schedules using geological scenarios and explicit extraction and processing capacities. Their study concerns geological uncertainty and does not incorporate financial uncertainty. A scenario study can reveal consequences within the uncertainty represented; it cannot establish that unmodelled risks are covered.^[6]

Sensitivity analysis can isolate the effect of changing one assumption, while coordinated scenarios examine combinations that could occur together. Record whether an alternative merely performs well under the preferred assumptions or remains workable when a critical input deteriorates. A contingency also needs an identifiable decision trigger and a practical response, rather than an unexplained allowance in the schedule.

Execution, Reconciliation and Revision

The Global Mining Guidelines Group's 2019 underground short interval control guideline describes repeated review of operational data to address deviations. Useful feedback combines actual progress, awareness of available resources and understanding of planning priorities; collecting measurements without a decision process does not complete the control loop.^[7]

Compare actual and planned results at compatible locations, periods and material boundaries. A tonnage shortfall, an unexpected grade and a late development milestone need different investigations. Preserve the original comparison baseline when revising the forecast so that an updated target does not erase evidence of the deviation.

Adaptive revision also respects work already done. In Armstrong and colleagues' rolling-horizon formulation, new grade information updates the remaining decisions while previous extraction decisions stay fixed. This illustrates why replanning must start from the achieved mine state rather than regenerate an unconstrained preferred history.^[6]

The resulting schedule should be reviewable as a linked set of decisions: work by location and period, material destinations and inventory movements, resource demand, prerequisite milestones and the assumptions that remain uncertain. Responsibilities for implementing and changing those decisions complete the connection between the planning model and mine operations.