Calculating coal waste volume in opencast mines

Due to the limitation of the mining process in opencast mines, thin coal seams that are below the desired level of seam thickness for mining sometimes cannot be mined and the volume of that coal is considered as waste volume.

Using GEOVIA Minex, this waste coal volume can be calculated and an estimation of the waste volume can be performed accurately.

The Process to calculate the waste volume is defined below:

Step 1:

Once pit design and reserve database reparation is complete, report the Coal and waste volume for all the seams irrespective of seam thickness.

The Report will appear like this:

Step 2: 

Now we need to mark the areas in the seam thickness grid, below and above the threshold value of seam thickness for mining, let’s say 0.5m in this case. Sql is the tool to utilize here.

By using Sql, a new grid will be generated with suffix “TL” where there are only two zones, one is below the required seam thickness and one above the required seam thickness for mining.

Step 3:

The newly generated grids with suffix TL are now the inputs for the thickness consideration of the coal seam to calculate total waste volume.

TL need to be added as an additional quality variable in the reserve database where the default coal and waste value should be zero. Following this step, newly generated TL grids need to be updated in the reserve database using the tab “Quality Update”:

Step 4:

Once the quality is updated with the new “TL” grid, the final step is for the seam dilution to be adjusted in-line with this new variable “TL” as top or bottom loss variable. The coal volume of a seam thickness less than 0.5m can then be considered as waste only.

Once this is done, by reporting the reserve again, the report will show as follows:

Now by comparing the output reports generated in step 1 and step 4, the difference of the coal and waste volumes are as shown below:

The Volume reduced from Coal has been added with waste with only 0.003% variation of volume adjustment.