Assigning Ore and Waste Mining Costs using Calculate Expression

Micromine Beyond’s Pit Optimiser allows users to define the mining cost of Ore and Waste separately; understanding that dumping locations, mining requirements and haulage distances for each material type can affect the mining cost.

Expressions can be used to define the mining cost of Ore and Waste and can be accessed by clicking on the = symbol as seen in Figure 2 below.

Figure 1. Opening the Expression Editor in the Pit Optimiser Mine Setup

Figure 2 shows the Expression Editor open with several panes listing block model variables, functions and logical operators which can be used to create expressions. An example for using an expression to define a cost is to allocate specific costs for ore sent to different locations.

Figure 2. Expression Editor and an example of an expression

In Figure 2, the expression below is used:

if ([PTYPE]="CIL") then (3)
elseif ([PTYPE]="HL") then (2)
elseif ([PTYPE]="WST") then (0)
endif

This example expression looks at a field called PTYPE (processing type) and assigns a mining cost based on whether the block is Ore that can go to the mill (CIL), Ore that can go to a Heap Leach (HL) or if the block is waste. If an ore block has a PTYPE value of CLP, that block will have a mining most of $3/t. For HL ore blocks, a mining cost of  $2/t will be assigned. Waste blocks will not have any “Ore Mining Cost” as Waste should not be sent to the plant. Ideally, waste blocks will all be flagged and have their mining costs captured in the Waste Mining Cost fields/expressions.

The underlying first principles logic is as follows:

• If an Ore block is to be sent to a mill, material is to be hauled the full distance to a mill / processing plant.
• If an Ore block is to be sent to Heap Leach , the material is to be sent to a heap that is typically closer in destination compared to a mill.
• If an Ore Block is defined as Waste, it has zero Ore Mining Cost as the mining cost will be defined in the Waste Mining Cost section.

Want to learn more?

Click here to login to our Learning Management System

Click here to request access