Today’s post comes from Cory Case, one of our Technical Support Consultants.
A common question when setting up more advanced GEOVIA Whittle™ projects is how the client can gain more control or organization over the optimization process. The first place to look would be the Expressions function, denoted with the f(x) symbol, which is available for the majority of fields in the Pit Shell and Operational Scenario node.
With Expressions there can be more control over prices, costs, recoveries, grades, etc. Users are not limited to using static values for these cases. The expressions function contains a section titled User Variables; which by default will list a grade and product for each element and a quantity for each rock type.
This list can be added to open up options and enable some more advanced setup options. Here are the three most commonly used options:
1. Centralizing equations
Oftentimes, the same equation will be used in multiple locations or will need to be edited frequently. It is convenient to have all the expressions in one place to be used all over the project. This can be done by creating an expression on the Expressions Tab of the Pit Shell node, which will be copied to the operational scenario node automatically. Here are expressions for Mining and Processing Cost Adjustment Factor.
These expressions will now show up under the user variables options when the expression builder is entered in the appropriate boxes on the Mining and Processing Tab.
By having all Expressions on one tab, is much more efficient to see them all in one list and they can be changed without having to hunt through the project. When Expressions are applied by period in the Operational Scenario Node, their change year-by-year can quickly be seen, without the hassle of many additional forms.
2. Block based conditional attributes
A lot of the time, some of the variables to be used are not dependent on simple expressions or logical functions but rather physical constraints of the orebody design or other outside forces. An example is recovery being dependent on rock type, zone type and weathering: the recovery may change radically across the project with no discernable pattern. It is very useful to use the User Variables in conjunction with the Multi-Element Node. The recovery is brought in an element where the recovery of a given block is the “grade” of that block.
This can then be used by going to the Processing path and selecting the expression button for the recover. In the image, below, AU.P is the amount of gold and AU.G refers to its grade, while MX.Q is the quantity of MX rock type.
3. Flag fields
Very similar to the above option, an optimization is often completed only on the Measured and Indicated, but not on the Inferred Blocks. The estimation certainty is not directly the rock type, and when there may already be many rock types in the model, it is not a very elegant solution to break up each rock type into three separate types. A much more elegant solution is the concept of using a flag field, which can be done with these steps:
- Code the block as 0, 1, 2 or 3 for not-estimated, measured, indicated and inferred in a float field in the model.
- Import this field as an element so that the flag is the grade of the block.
- Under the User Variables tab, select this grade in an “if” statement or range to filter out inferred in the recoveries.
These are just three possible ways to use these User Elements to gain more control over convoluted and advanced projects. For more an explanation into what is possible or how these can help your specific project, please contact GEOVIA Support.
Looking for more Whittle Tips & Tricks? Read Cory’s post on Understanding the Difference between Mining Width and Net Present Value Practical Pushbacks Modules.
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