Article #2: The Value of Target-Based Scheduling
The first post in this series explained the difference between a strategic mine plan and a tactical mine plan: a strategic mine plan is a long-term plan covering the entire life of mine; a tactical mine plan turns the decisions outlined in the strategic plan into a schedule that will govern the mine’s day-to-day operations.
It also discussed some of the challenges involved in developing a successful tactical plan, including determining how to:
- collect, collate, and update all pertinent data, such as topography, pit design, and scheduling parameters
- translate the schedule into a variety of formats (spreadsheets, graphical plots, etc.) and communicate it in the most appropriate format for each audience, and
- define extremely complex material movement systems that exactly replicate their real operations.
This post looks at how to begin tackling those challenges by first understanding the differences between rules and targets and how each needs to be treated.
Rules vs. targets
The vast majority of the inputs to a tactical mine plan are scheduling parameters, which include production rates, mining directions, bench height, haulage specs, stockpile capacities, and so on. For the purposes of creating a tactical mine plan, you should think of these parameters as your mining rules: they must be followed in order for your schedule to match reality in the field.
You should think of other important inputs — including such things as optimal mill feed grade or stripping ratio — as your mining targets: the levels you must achieve through your mining sequence (your plan for which blocks you mine and when) to ensure profitability over life of mine.
Following vs. chasing
To build a successful tactical mine plan, you must follow your rules while you chase your targets, which means tactical mining planning is almost always an iterative process.
There are a variety of tools available today, including Dassault Systèmes’ MineSched, that use heuristic blending algorithms to choose which blocks get mined and when in order to meet your specific material ratio and quality targets. They also allow you to produce virtually unlimited iterations of short- and long-term schedules: you make a change to a rule, analyse the results, and repeat, until you find the schedule that lands you closest to your desired target. You can also turn a change on or off to play “what-if” and compare the results of multiple possible mine sequences.
Comparing the results
The various iterations of the mine schedule will provide a wealth of useful information, including information about material movements — what material went where and when — on a period-by-period basis. From those results, you will then be able to determine haulage calculations, stockpile balances, costs of all kinds, the spatial shape of the excavations, and more.
Once you’ve arrived at, say, two or three schedules that you think both follow your mine rules and meet your mine targets, you can then move on to completing a 4D simulation of each possibility to determine the optimum mine sequence.
Next in this series
The next article explains 4D tactical mine plan simulation. After that, I will discuss how to prepare financial models for the plan you have decided to follow, and how to share that plan with all stakeholders.
Please let me know if there is anything else related to tactical mine planning that you’d like to learn about and I will make sure to cover it in this series.
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