Q: Thanks Brad. Looks like a good solution for this scenario where the spigots are in a straight line, but how would you go about doing a perimeter discharge (the most common type of TSF). The pathways and guidelines would be crossing over.
A: It’s a good question, I generally wanted to just show the basic concept in the original post. To do a perimeter discharge you just draw pathways coming back the other way and very roughly trim them up.
Here is how I would tackle it using the same method.
I start by making the one spigot discharge into a block. Then use the measure command to space it around the complex at 200m intervals. Align that block to the line and you get something like below.
permiter deposition
I delete a few of the stranger spigots, relocate as necessary then I just keep trimming the lines inside the block until I get to a point where I don’t have too much overlap. Like below. (If I trim in the block, they all change at once. J)
Perimeter Tailings Deposition, trim up block lines before exploding
Trim any major areas of overlap and then check your rough triangles surface, near enough is good enough here, minor overlap will be taken care of by the kriging routine,
Perimeter Tailings Deposition, check result in basic triangulation
This is what we want to achieve (below). A tailing’s deposition that looks realistic, showing flow originating from each point (a spigot) at a specified grade(s) outwards until it is bound by the existing ground or a designed embankment.
But how can we do this quickly without software like Muck 3D and Vulcan?
The method described below in no way replaces these fantastic tools completely, Particularly when creating vast amounts of options/beach slopes etc. But it does produce a realistic result that is very easy to update. Read on to see how I do it. (P.S It’s not the concentric circles technique!)
So here is the general plan before we knew where anything was…
First I determined an approximate spigot spacing with the engineers and then chose a suitable elevation to deposit from. You can work this out with some rough calcs.
(<Change in elevation> * <2d Area>) / 3 – Note: keep adjusting the elevation to gain more/less volume
(20 * 331000)/3 – 2.2Mm³ so if I deposit from about 274 should be approx. right. (it’s easy to adjust later)
Create a base pathway using a 3D poly line (command 3DPOLY)
Engineers have told me they want a 200m spigot spacing, 3 spigots. So offset some 100m guidelines either side of your main deposition path
Draw 3 more path ways on one side of the deposition, a ¾ length a ¼ length and back trail
Now you need to grade all of your lines to your desired tailings beach. Engineers have told me that we can achieve a 0.5% beach slope.
Select start point, type starting elevation, select to the end and type grade on all lines.
Then just mirror them across to other side and delete your guide lines. You should end up with something like below. (copy this off to the side somewhere if you want to change the beach grade later)
Copy the pathways to your spigot locations and rotate as necessary. Then draw some trail lines on the wings. Put all those deposition lines on their own layer and you should end up with something like below.
It’s okay to have a little bit of overlap, but try to avoid it if possible!
Now add these as breaklines to a surface called TS-TAILS_<some description>
Check for any strange anomalies in elevation first. Then you want to run a krig on the surface.
Go to the surface definition and right click on edits -> smooth surface
Change to Kriging and then select parameters as defined in image.
The finished result. Is obviously exactly what you are looking for. Now you just need to create a design embankment to entrap the tailings
If you zoom into the tailings surface where one of the contours meets a break line. You will notice some little spikes. These may be more pronounced on your model.
To fix this issue simply tick off the breaklines from the definition under surface properties.
Once you have designed an embankments to suit your deposition. Just find the intersection between your tailings TS surface and your CP combined natural and embankment
Some Notes
· To vary the deposition height, raise lower the TS surface, or relocate/raise/lower the breaklines.
· If you want to change the grade of the deposition, you will need to regrade all the lines, you don’t have to delete them though. (A good trick is to keep a block that represents one spigot and just regrade that and copy it around.)
· Always keep an unclipped (TS surface) and a clipped (DS surface) so if your design updates it’s easy to recreate a boundary.
· Do all your tailings modelling in a separate dwg file!
· Kriging does not update if you change the breaklines, so try to do all your editing to your pathways pre-kriging then run the krig at the end
This is just a basic example, there are obviously more complex scenarios, like multiple elevation spigot points and bimodal (multiple grade) tailings beaches. But I hope to cover these in a later post.
You may also notice the benefits of kriging for things like groundwater modelling/geological surfaces and air pollution modelling.
Reply to this email if you have any questions, or post on the 3D forum.
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