Prepare Value Block Model

This command creates a block model that represents the economic value of each block. The value block model can be generated from multiple .blk files, a Geologic Model (.pre file), or from an existing .BMV file. The blocks loaded into this command can be modified with user-defined equations to determine the value of each block. The value block model may then be used with the Optimized Pit Design command. 

When the command is started, the following dialog will appear.

This command will recognize and use both BLK and PRE files, as well as existing BMV files. To load in .blk files, there should be no gaps between the elevation limits of these block models. The ordering of these files is not important, as they will be sorted automatically according to the elevation limits of each .blk file.

Available Beds: This column will list all of the strata/beds in the .pre file that are not already defined with a .blk file. Selecting one of these beds allows for defining the subdivisions for that bed. Alternatively, the subdivisions for all beds may be set at once with ALL.

Set Subdivisions for bed by: This option controls how each bed will be vertically subdivided to create a block model. Hit the ENTER button after entering any value, to update the field.

Subdivision Number: This option will subdivide the bed by the number specified. For example, if this value is set to 2, then the resulting block model of the bed will consist of 3 blocks per vertical column. Note that this value must be greater than or equal to 2.

Set By Average Block Thickness: This option will set the number of subdivisions in order to achieve the specified average block thickness. For example, if this value is set to 10, the bed will be subdivided so that the average block thickness of the resulting model will be as close to 10 as possible.

Set By Maximum Block Thickness: This option will set the number of subdivisions in order to achieve the specified maximum block thickness. For example, if this value is set to 10, then the bed will be subdivided so that no blocks in the resulting model have a thickness greater than 10.

Set By Minimum Block Thickness: This option will set the number of subdivisions in order to achieve the specified minimum block thickness. For example, if this value is set to 10, then the bed will be subdivided so that no blocks in the resulting model have a thickness less than 10.

Attributes for Model: This spreadsheet defines new attributes to add to each block in the model, for later use in equations. These attributes can be set to single values, but can be modified when calculating the value of each block later in the command. At least one attribute must be defined for each bed.

After selecting one of these options, the below dialog will appear.

Any attributes from the input files will be listed on the left side of the dialog. These attributes may be used when writing equations to define the value of each block. Note that when these attributes are referenced, it refers to the value of each block individually - these are not average values for the block model as a whole. In addition to the attributes from input, four additional attributes will always be generated: Z_centroid ,Volume, Strata, and Position in Strata.

The Z_centroid attribute is the elevation of each block's centroid. This attribute is useful to calculate the increased mining cost at lower elevations or depths.
The Volume attribute is the volume of each block, as measured in cubic feet or cubic meters.
The Strata attribute is the strata index number. A value of 0 relates to the upper-most strata in the model, a value of 1 relates to the strata below strata 0, etc. If there is just one block model BLK file, then there will be just the one strata index of 0.
The Position in Strata attribute is the block number counted up from the bottom of the model. For example, the lowest block in the bed will be block 1, the next block up will be block 2, etc.

Economic Value Inputs:

        Attribute: Click Valid Attribute will set the currently selected/highligted attribute as the economic value for each block in the value block model. This is an alternative to calculating the block values from a set of equations. Note that this does not modify the input files - you will be prompted to save the updated model as a .BM file after clicking OK.    

        Define Equations: This option brings up the  equation editor (.db3 file). Additional information about this function is provided below.
   

        Cut Model by Topo: Selecting this option will bring up a dialog to select a grid file. There will be an option to remove blocks found above/below this elevation grid.Export Options:

Block Model Summary: These values display basic information about the value block model.

Total Blocks: The total number of blocks in the value block model. Null blocks are not considered in this counter.
Total Volume: The sum of the volume of all blocks in the model.
Total Economic Value: The sum of the economic value of all blocks in the model. This value will not be populated until the equations have been applied to the blocks or until an attribute has been set as the block economic value.

Define Equations Dialog

After clicking the Define Equations button, the following dialog will appear. After filling out the tabs with the desired design parameters, save this table to a .db3 file. Choose Exit to return to the previous dialog to calculate the value block model.

The dialog will first appear with only one Equation and Predefined attributes. All other equations, constants, conditions, etc. must be manually added.

Attribute List

The right side of the dialog lists all attributes. Add or remove attributes with the two +/- icons shown to the left of the list. Attributes may be one of five types, with each type showing with a unique color for visual organization.

1. Predefined attributes are attributes that have been found in the input .blk file(s).
2. Equations are attributes that will be calculated when the value block model is created.
3. Constants are attributes that have a non-changing value.
   
4. Conditions are logical tests that determine which variables to use. For example, a condition may be defined that sets the processing cost for a block based on grade.
   
5. Conditional Variables are used as a result when Conditions are checked. For example, when setting the processing cost of a block based on grade, the processing cost is the Conditional Variable.
   

When adding an attribute, the below dialog will appear. This is to assign the attribute a name and set the attribute type, as well as any other relevant options.

Attributes may be renamed by clicking inside the cell of interest and typing a new name. When the name of an attribute is modified, the change will be reflected in the Equations and Conditions tabs on the left side of the dialog. The condition type may be changed by selecting an option from the drop-down menu in the Type column.

Equations Tab

The Equations tab will display all defined equations in a spreadsheet view.

The Resulting Attribute column lists the attribute being calculated by the Equation column. For example, if the is a Resulting Attribute named "Tons", the result of the equation column will be assigned to this "Tons" attribute.

The Equation column is used to write the equation for the attribute being calculated. For example, to calculate the "Tons" for each block, the equation could simply read "Volume*Density". This can be read as "Tons equals Volume multiplied by Density", where Volume and Density are other defined attributes. Equations will be calculated in from top to bottom by row, and therefore equations may reference the results from previously calculated equations. For example, the equation on the row 2 of the equation spreadsheet may reference the result from row 1, but it cannot reference the result from row 3.

The Output to File column controls if the attribute is output to the resulting .bm file. By default, attributes will not be saved to the .bm file. If the .bm file is to be used with the Optimized Pit Design command, only the economic value of each block should be output to the .bm file.

One equation, "Result", will always be defined and output to the .bm file. This equation should always define the value of each block and should always be output to the .bm file.

The below operations and the corresponding symbol are supported in the equation column:

1. Addition "+"
2. Subtraction "-"
3. Multiplication "*"
4. Division "/"
5. Grouping of terms "(" and ")"

Conditions Tab

The conditions tab will display all conditions in a spreadsheet view as shown below.

Condition Name column lists the conditions in the order they were created. These cells are not editable.

Condition Expression column is the logical test. In the above example, the first logical test checks if the block has an Iron content greater than 20%.

True column lists the actions to take if the logical test is found to be true. At least two actions will be shown, separated by a vertical pipe. The first action tells the program which condition to evaluate next. The second action actually sets values to the Conditional Variables. In the above example, if a block is found to have an Iron content greater than 20%, the program will check Condition #2, but no Conditional Variable values will be assigned based on this test alone. If Condition #2 is found to be true, the program will not check another condition, but will assign the attributes "IsWash" and "IsOre" values of 1. This is similar to a nested "if" statement.

False column lists the action to take if the condition is found to be false. This follows the same format as the True column. In the above example, if a block is found to have an iron content less than or equal to 20%, then no other condition is evaluated and the "IsWash" and "IsOre" conditional variables are assigned a value of 0.

Clicking inside a cell of the True or False columns, or selecting the button next to them will bring up the following dialog.

This dialog sets values for the Conditional Variables based on the logic of the Condition. The two tables list Conditional Variables that will be affected by this Condition (IsWash and IsOre in this case). If the program needs to check another Condition rather than assign values to Conditional Variables as a result of this test, then select the appropriate Condition to check below this Table. Conditional Variables may be added/removed from this list using the appropriate icons between the two tables.

Evaluate Before column lists the equations in which the conditions need to be evaluated before. In the above example, the conditions will be evaluated before the Revenue and Result and Processing Cost equations are calculated.
Here is an example of more advanced conditions separated by "and" & and "or" | in the Condition Expression field: 

Test Tab

The Test tab displays all defined attributes in a simple spreadsheet. The purpose of this tab is to define example values for each attribute, along with an expected result. Enter in example values and the calculated result, to see if the test of the equations calculates the same result. After defining one or more tests and saving the .db3 file, then click the Run Tests button to check the actual RESULT output against the expected, user entered output RESULT. If the Test Result matches the expected result, the cells will be highlighted in green, as shown below. If the values do not match, the cells will be highlighted in red.

                                   

Pull-down Menu Location: Geology Module > Block Model
Prerequisite: Must have an existing BLK file