Calculate Strip Ratio

On the Stratigraphic tab, in the Seam Block Model group: Click Calculate Strip Ratio to calculate the ratio between the thickness of the coal and that of the overlying rock (overburden) for each column of blocks in a Seam Block Model file.

By calculating the ratio of waste to coal, it is possible, first, to determine whether mining is economic, and if so, which type of mining is appropriate. When more than one seam is involved the term Cumulative Strip Ratio is used.

There are two recognised ways to calculate the strip ratio:

1. Volume Ratio: The volume of waste both above and within coal seams (overburden + interburden) that must be removed to recover the same volume of coal.
2. Tonnage Ratio: The volume of waste both above and within coal seams (overburden + interburden), expressed in cubic metres, that must be removed to recover one metric tonne of coal.

The function writes the Strip Ratios back to the Seam Block Model file. For each column of blocks, the strip ratio (Volume and/or Tonnage) is calculated for every seam and the value is written to the appropriate field (if the fields do not exist, they are created as Float with 2 decimals).

For any seam the (volume) strip ratio is the total waste thickness (overburden plus all interburden) divided by the total coal thickness (the seam in question plus any higher seams). Tonnage ratio works the same way, except that coal thickness is multiplied by density.

Before you run the Stratigraphic | Seam Block Model | Calculate Strip Ratio function, you must use a Define Waste regular expression (see below) to identify Material codes as either waste or seams. The function writes the Strip Ratios back to the Seam Block Model file. It is assumed that the Seam Block Model contains overburden (if not, this can be added using the Generate Waste function).

In the case of errors, blank values are written back to the Seam Block Model file.

Define waste is a simple regular expression match for the Material field. A Regular Expression is a search string that uses special characters to match patterns of text. In this context, it is used to determine which values in the Material field represent waste. The assumption is that any non-matching value is a seam.

Although regular expressions can be both complex and powerful, a couple of simple suggestions should provide an easy way to define waste codes. The first thing to understand is that the Regular Expression must match the complete code, not just a part of it. There are 3 characters and quantifiers that will allow matching of most waste codes. They are:

Character	Description	Pattern	Possible Matches
.	Matches any single character	.B	IB or OB
*	Matches previous element zero or more times	.*IB	AT01_IB or FC22_IB
|	Matches any element separated by pipe (|)	OB|.*IB	OB or AT01_IB or FC22_IB

Some examples:

Waste Codes	Patterns that match
OB, AE_IB, FJ_IB, KL_IB	OB|AE_IB|FJ_IB|KL_IB
	OB|.*_IB
	.*B
OB, PT_AE, PT_FJ, PT_KL	OB|PT.*