Pit Optimization: Quick Start An overview of optimization criteria

Pit Optimization: Quick Start

A key decision for pit optimization is the choice of optimization criteria. Pit Optimizer offers two choices:

• Optimization directed at profit and NPV maximization. For this option select Maximize cash flow in the Ultimate Pit dialog and Optimize NPV in the Sequencing dialog. For a greater range of possible ultimate pits run Pit Optimizer with and without Top-Down discounting.

•  Optimization directed at maintaining balance between mineral elements or rock types according to user defined blending criteria. For this option select either Maximize cash flow or Maximize resources in the Ultimate Pit dialog and Optimize blending in the Sequencing dialog. Follow up with one or more blending criteria. A typical blending criterion is to keep an element grade, or a combination of grades like silica modulus, within certain limits that may vary over time.

• To complete your Pit Optimizer settings:

• Set the ore mining rate and discount rate. These parameters affect mine life-time and NPV estimates.

• Set the slope angles by region or for one global region encompassing the entire block model volume (default). To set the slopes by region you must have imported 3D regions with the block model or created them in NPVS. The available region sets are shown in the Slopes dialog as Slope region files; the regions within a file are identified by labels.

To make a slope region file:

1. Digitize 2D outlines in a Plot view, or import outlines from another application (optional).

2. Import Separating surfaces that partition the block model vertically (optional).

3. Select Define Slope Regions on the Task Pane Optimization screen. To make the regions you can use either 2D outlines, or separating surfaces, or both.

4. Select your Pit limits, if required. Pit limits are 2D outlines imported or digitized in the Plot View. The available pit limits files are shown in the Options dialog.

5. Select the Initial topography if other than the default topography is generated from the block model. Any internally generated or imported surface can be used as the initial topography.

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