Stope Production Scheduling to Mine

Scheduling is an essential component of the stope planning process, as it adds a time dimension to all the functions within the process. Schedules specify the sequence, timing, and allocation of resources to events that extend from daily operations to the life of mine scenarios (Trout, 1997). Scheduling has

time frames that may vary from mine to mine. Mines with a shorter life will have a different scheduling perspective to larger mines. In general, the objective of production scheduling is to provide direction to the mine production personnel ensuring that established metal targets are accomplished.

Planning personnel must have an understanding of the overall production targets and issues required in order to achieve desired outcomes within a business plan. In practice, mine scheduling is usually carried out either at a broad level or, conversely, at a more detailed level. Production schedules are used to establish the long-term strategic issues in conjunction with their economic implications. Activity schedules are used to set out the details of how the production schedules will be achieved (Trout, 1997). While the production schedules deal with a broad picture, the targets set within the activity schedules must be compatible with the long-term scheduling goals.

The details included in a schedule change with the size of the source. Small stopes generally require a schedule with shorter time intervals and more detail (Trout, 1997). Usually, the geological information, and hence the degree of confidence, increases for the activity schedules. The entire mine planning team including geologists, surveyors, mining engineers, and production supervisors must be familiar with the targets set during all levels of production scheduling.

In general, scheduling identifies critical production activities while providing the baseline means for monitoring progress and whether any deviation from the overall objectives is occurring. The schedule must identify key or critical events to guide the mine management decision-making process. The design status of each production source should be identified within a production schedule.

Typical scheduled items include development and production targets, capital and operating expenditures, equipment replacement, maintenance, and diamond drilling. A document is required to document the critical issues and assumptions of a particular production schedule. The stopes scheduled to be extracted may also be represented in plan views and longitudinal sections on which the scheduled targets (development, stope extraction, and filling) are clearly identified.

A number of generic processes are available for undertaking mine scheduling. These include manual techniques using computer spreadsheets, project management (critical path) approaches, and other methods available in computerized mine-planning software in which all the interdependencies and constraints are taken into account (Trout, 1997). The procedures, frequency of preparation, time periods, level of detail, format information, and communication process for mine scheduling may differ between mine sites.

Medium-Term Activity Schedules

The second level of scheduling undertaken in underground mining is called medium-term activity scheduling. This schedule usually consists of a 2-year (or similar length of time) production period. Similarly, to a long-term schedule, production targets, backfill, development, raising, and diamond drilling requirements are considered within this schedule. However, the activities are updated (using a rolling format) and issued every 3 months. Usually, a 1-year budget schedule is developed and adopted within a medium-term activity schedule. This full-year forecast is a critical document that sets the formal budget for the subsequent production year. The forecast is based on preliminary stope designs, in order to ensure that the budget metal, capital, and operating expenditure can be effectively achieved. Depending on the size of the mine and the number of ore sources, mine size and number of sources, the full-year forecast may be reviewed and updated each month. Priorities are then determined to ensure that the budget targets are met.

Short-Term Activity Schedules

Short-term activity scheduling plays a tactical role while providing a detailed schedule over a short time horizon. The activity schedule contains sufficient details to allow underground personnel to plan and perform their work (Trout, 1997). Usually, this schedule considers the production activities within a 3-month period. It is updated and issued each month, primarily to assist production personnel in identifying the short-term activities (day-to-day mine operation) required to fulfill yearly budget targets. The short-term activity schedules are usually presented during a meeting between the planning and production personnel, where stope preparation (stope access development, ground support, services installations, stope drilling) and production issues (blasting, material handling, and filling) are discussed.

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