Development and Production Sequencing

Development and production sequencing establishes the order in which access, preparation, extraction and associated work can proceed. The sequence defines relationships between activities and the conditions that release their successors. Scheduling then places those activities in time and assigns resources.^[1] A dated list alone does not explain why one task must precede another or whether several tasks can proceed together.

Here, development means work that enables access to, or preparation of, future production areas. The distinction is functional: an excavation may generate material while also enabling later production. The planning question is what it makes possible, when that capability becomes available, and what completing it commits the mine to do next.

Define Work and Completion Milestones

Use activities with identifiable locations, outputs and completion criteria. An access drive, a service installation and extraction from the area they serve should remain distinguishable when they have different resources or release conditions. Combining them into a single undifferentiated production allowance hides the reason for delay.

Hou and colleagues examine underground access layout together with production scheduling in a hypothetical mine example. Their formulation links development drives and the stopes they serve. It illustrates why an access layout and an extraction order need to be considered together; the example's geometry and modelling assumptions do not establish a preferred layout for other deposits.^[1]

Define intermediate milestones where they matter. “Excavation complete,” “required services available” and “area released for the next activity” answer different questions. Track the actual enabling result rather than assuming that reaching a planned date creates it. Similarly, measured development advance is useful only in context: completing work on one branch does not release production on another branch.

The activity boundary should also make interruptions intelligible. If work can stop and resume, record the remaining work and its state. If stopping changes how it must be restarted, represent that consequence. Otherwise, a planner may move a partially completed activity as freely as an untouched task although the physical situations differ.

Distinguish the Reasons for Dependency

Several different relationships can produce an apparent requirement to do one activity before another. Keeping their reasons separate helps determine which changes need engineering approval and which are resource-allocation choices.

These categories are a way to examine the model; they are not interchangeable scheduling rules. In particular, adding another machine may relieve competition but cannot remove an access dependency. A forecast completion time estimates when a release condition might be met; it does not provide evidence that the condition has been met.

The 2019 Western Australian ground-control guideline explains that sequencing can create unfavourable geometry, produce adverse high or low stress conditions around pillars, abutments and remnants, or increase exposure to ground hazards. It also links scheduling with timely support, backfill and access provision. Such relationships require a geotechnical basis appropriate to the mining method and ground conditions. A resource-efficient order may therefore be unacceptable even when every task has an available crew.^[2]

Apply the Logic to Surface and Underground Work

In an open pit, consider which excavation makes another area accessible and which routes remain usable as mining advances. The sequence must be evaluated against the geometry at each stage, rather than only the eventual pit layout.

Lipovetzky and colleagues model excavator movements in a surface operation where removing material can open alternative paths. Their work shows how accessibility and travel time can depend on the sequence already completed. Its scope is a set of pre-blasted ore blocks, with excavators modelled explicitly; truck scheduling and vertical mining precedence are outside that model. It therefore supports the need to check changing access, rather than providing a complete pit-development sequence.^[3]

Underground, a production area may depend on several branches of enabling work. Completing the access excavation can leave services or preparation unfinished. For compatible cyclic operations, Åstrand and colleagues represent successive activities at a workplace and equipment movement between workplaces. This is useful for distinguishing the local cycle from the sequence of areas across the mine, without imposing one cycle on every method.^[4]

Where the mining method relies on backfill before adjacent extraction, filling is part of the production dependency. Preparation, placement and the condition required for subsequent mining need separate treatment. O'Sullivan and Newman's Lisheen case explicitly links extraction and backfill activities, including a setting period before dependent work. That project's specified delay is a case parameter, not a universal curing duration or proof that elapsed time alone establishes acceptable fill performance.^[5]

A sequence also needs to preserve facilities still required by unfinished work. Before withdrawing access or removing an enabling excavation from service, identify everything still dependent on it. Distinguish a deliberate decision to abandon dependent work from an accidental loss of access hidden inside the schedule.

Coordinate Enabling Work and Production

Evaluate development by its contribution to future readiness as well as by its own output. A useful review asks which production areas each completed task will release, which remaining tasks stand between them and extraction, and which resources are needed to finish those tasks. This makes a disconnected advance target easier to identify.

There is a trade-off between completing enabling work early and committing effort before it is needed. For any proposed buffer of prepared areas, explain the uncertainty it is intended to cover and the consequences of maintaining it. The appropriate allowance depends on the reliability and substitutability of those areas; a universal number of months of developed inventory would obscure those differences.

Services can constrain the combination of activities, not merely their initial start. Ogunmodede and colleagues connect underground production scheduling with ventilation and refrigeration through activity location, equipment use and associated heat loads. Their deterministic model uses steady-state thermal assumptions, including no heat carry-over between periods. The broader planning implication is to test the proposed concurrent workload against the supporting system; the model does not supply a universal thermal criterion or replace a mine-specific ventilation assessment.^[6]

When a production area changes, review the enabling tasks and service demands attached to it. Moving tonnes from one location to another does not automatically transfer installed capacity, access or completed preparation. Conversely, accelerating an enabling task has little scheduling value if another unresolved prerequisite still prevents its successor from starting.

Check the Dependency Model Before Relying on It

Review relationships with the functions responsible for their technical basis. Record whether each link comes from physical geometry, an approved design, service readiness or an operational preference. Check for missing predecessors, inconsistent activity identifiers and circular requirements that leave no possible starting point. A software result can only respect the relationships represented in its inputs.

O'Sullivan and Newman found that some inherited precedence links reflected previous planning choices rather than unavoidable physical relationships. They also identified activities missing necessary links. Their case includes haulage-pillar extraction that can make dependent areas inaccessible. The lesson is to validate both unnecessary restrictions and omitted dependencies: removing an arbitrary preference can create alternatives, while removing a real access condition can produce an unusable plan.^[5]

For a waiting interval, document its starting event, calendar basis and release test. Do not hide work inside a lag when it requires a crew or plant: it needs a resource assignment. Equally, adding productive effort does not necessarily shorten a waiting condition. These distinctions make delays explainable and prevent a nominal duration from becoming an unexamined operating rule.

Update the Sequence from Observed Conditions

Consider a qualitative case in which a planned ventilation connection is delayed after the access drive is complete. Production dependent on that connection remains constrained even if extraction equipment is available. The planner can examine alternative areas whose own access, ground-control and service prerequisites are satisfied, but must also check their shared resources, material destinations and effects on later work. The response could alter enabling-work priorities as well as production timing. It cannot assume that the incomplete connection has become available simply because a revised schedule needs it.

The Western Australian guideline links design implementation with inspection, monitoring and comparison of actual ground behaviour against expectations. Where conditions or performance depart from the design basis, the sequence and its controls need reassessment.^[2]

Update completed work, remaining requirements and release status together. Preserve the reason for each significant sequence change so that later plans do not reinstate a superseded assumption. Verification should demonstrate that the next activity's prerequisites are satisfied and that proceeding leaves the remaining sequence physically and operationally coherent.