Global Mapper v25.0

Measure Volume Between Surface of Waste Rock Dump and Uneven Topo at Incremental Intervals?

Does anyone know how to calculate the “Measure Volume Between Surfaces” of say a waste rock dump (Pile) sitting on an uneven topography at different incremental intervals? I can “Measure Volume Between Surfaces” for the total/entire waste rock dump, but say I need to know what fill volume is required every 2 m vertically in a 50 m high dump? Also “Pile Volume” doesn’t work as I just interpolates along the boundary/toe line to create an artificial underlying surface that is subtracted from the dump surface.

Global Mapper is great at estimating the volume in a pit at incremental depths using the “Analysis/Measurement – Volume (Measure Cut and Fill)” tool where the user can select the depth range and increment/step size.  GM calculates the cut/fill volumes and areas between an imaginary flat surface (I think of it as a flat water surface) and the walls of the pit and it does an excellent job – very useful!  However, when you turn this problem upside down and the pit becomes a waste rock dump constructed on an uneven topo then the same thinking doesn’t apply…

I have shown a few screen grabs below as an example of what I mean. I tried to attach a small (530 KB) package file of my “dummy workspace” but this forum doesn't permit this. If anyone thinks they how to do this I’d be happy to PM them and send them a package file... 

So, in summary, what I'm trying to do is calculate the fill volume at say 2m vertical increments required to construct this waste rock dump between 1052 mRL lowest elevation and the dump top at 1080 mRL (I know that the total volume required is about 1.536 million m3). I have a crazy workaround that I'm not sure I trust, but happy to discuss with anyone that is interested...

Cheers,

/al




Answers

  • sphillips
    edited January 2021
    I feel your pain! I model Dry Stack Facilities and Tailings Dams and have to perform a stage storage analysis quite often. These days I use mining software but I used to do this in Global Mapper. In a nutshell you have to run the volume analysis twice against a common 'comparison surface'. So in essence you are computing the volume between the terrain and the plane; and then the dump upper surface and the plane. You then subtract one from the other.

    I take no credit for this - please see this site for the general principle: https://ceethreedee.com/?s=stage+storage

    I have attached my notes from back in 2016 for your reference. Please see the Excel spreadsheet I have embedded in the Attachments panel on the left. Right-click on the attachment and hit open or save. If I recall you just paste the values into the green cells and it will do the rest for you.
  • sphillips
    edited January 2021 Answer ✓
    sphillips said:
    I feel your pain! I model Dry Stack Facilities and Tailings Dams and have to perform a stage storage analysis quite often. These days I use mining software but I used to do this in Global Mapper. In a nutshell you have to run the volume analysis twice against a common 'comparison surface'. So in essence you are computing the volume between the terrain and the plane; and then the dump upper surface and the plane. You then subtract one from the other.

    I take no credit for this - please see this site for the general principle: https://ceethreedee.com/?s=stage+storage

    I have attached my notes from back in 2016 for your reference. Please see the Excel spreadsheet I have embedded in the Attachments panel on the left. Right-click on the attachment and hit open or save. If I recall you just paste the values into the green cells and it will do the rest for you.

    I have found an old video I made that accompanies my notes showing how to calculate the stage storage. My apologies for the poor quality video but I had to compress it to within the limits for posts. Might save you reading the notes and I'm sure you will be familiar with all the fundamental steps.

    The Digitizer menu structure has changed somewhat since 2016 but the functions with still be there somewhere.

    Good luck!

  • Hi Steve,

    Awesome! Great minds think alike!

    That is the "crazy workaround" that I referred to in my original message above, but wasn't sure if it was correct or not. I checked the volumes using manual calcs and got apparently correct answers, but you never know with complex shapes... The only difference with what I was doing was that I was creating the "toe line" of the dump and using it as my outer design boundary and then using the measure cut/fill first on the topo and then  with the dump surface in place and subtracting them. Now I've got a lot more confidence in this method!

    Cheers,
    /al
  • sphillips
    Answer ✓
    Hi Steve,

    Awesome! Great minds think alike!

    That is the "crazy workaround" that I referred to in my original message above, but wasn't sure if it was correct or not. I checked the volumes using manual calcs and got apparently correct answers, but you never know with complex shapes... The only difference with what I was doing was that I was creating the "toe line" of the dump and using it as my outer design boundary and then using the measure cut/fill first on the topo and then  with the dump surface in place and subtracting them. Now I've got a lot more confidence in this method!

    Cheers,
    /al

    By the way the volumes are reasonably accurate. I already knew the total volume from Civil3D based on a volume analysis, and I had used the method in the link to perform the stage storage analysis previously. Later on I started to use Deswik CAD to create a mesh-based volume solid and slice it into the desired intervals. All three methods yielded similar results. So as far as I am concerned the Global Mapper method is reasonably accurate considering the original TIN surfaces were converted to raster data, compared to using a workflow that uses only TIN surfaces or Solids.