overburden

The overburden module computes the complete volume required to excavate a plume or ore body given the pit wall slope (measured from vertical) and the excavation digging accuracy (we refer to as buffer size).

overburden receives any 3D field into its input port and outputs the same field with an additional data component. Its function is similar to distance to shape, but instead involves computing a new data component based on the nodal values in the 3D field and two user defined parameter values called Wall Slope and buffer size (addressing excavation accuracy). The data component is subset according to a concentration input (based on the subsetting level you want excavated). For example, once overburden has been run for GOLD at a 45 degree pit wall slope, the user would select 45-deg:overburden_GOLD and subset all data below 1 ppm to render a 45 degree slope pit which would excavate everything higher than 1 ppm concentration. A volumetrics calculation could be made on these criteria which would encompass the excavation and the ore body above 1 ppm.

NOTES:

• It is much safer and more understandable to work at Z Scale = 1. Otherwise, the apparent angle of your pit will be very different than the input angle

  • As the Z Scale increases, the angle of pit sidewalls looks more vertical, since the tangent of the apparent angle is the tangent of the actual angle multiplied times the Z Scale.

• The overburden module must be placed before any scaling modules (such as explode_and_scale) to ensure an accurate slope angle during computations and subsequent visualizations.

• The grid resolution and resulting cell aspect ratios are very important.

  • You cannot see any pit wall slope differences if those differences create a slope which is less than one cell wide from the bottom of the pit to the top.

  • Therefore, very high resolutions in X-Y are needed for large sites with shallow pits. Expect long run times for overburden.

 

Note on angles: Angles are defined from the vertical and are specified in degrees.

• A vertical wall pit is created with an angle of Zero (0.0) degrees
• A 2:1 pitch slope from horizontal would be an angle whose arctangent = 2.0. This is 63.4 degree from horizontal and therefore you would enter 26.6 degrees (from vertical)

Module Input Ports

• Input Field [Field] Accepts a data field.

Module Output Ports

• Output Field [Field] Outputs the enhanced field with overburden data

Create Buffer Around Plume - This toggle determines if the overburden computations are rigorous and determine the buffer on all side of the plume (ore body).  If this is off, the module runs much quicker.

Buffer Size - An accuracy level resulting in the amount of excavation outside the subsetting level of interest. For example, a type-in of 10.0 would result in 10 feet of over-excavation from the subsetting level of interest.

Overburden creates a data component name that includes the wall slope, module name (including #1 or #2 if there are more than one copy in your application), and original data component (analyte) name. (i.e. 30-deg:overburden#1 of Benzene)

The overburden data component may be subset by modules such as plume, isosurface, plume_shell, etc.