1. Sequencing Mining Operations with MineSight®
©2007revised 2010 Dr. B. C. Paul
{Note – The Name MineSight® and the Program described are property of Mintec Inc – Tucson, Arizona}

2. Maximizing Returns
NPV is usually increased by bringing more early earnings and delaying expenses
Sequencing pits for high grade ore with lower stripping ratios tends to do this
We Need A Method of Finding the Best Grade Ore to Mine First

3. How to Make That Happen
Method #1 - We try to Fake Out the Learch Grossman Routine
Lerch Grossman will Find the Juiciest set of ore blocks that keeps producing more value
Obviously this must mean that it either finds the maximum metal pit or the most lucrative ore
Because not all ore is equally easy to process it is possible that a set other than maximum metal will be selected
We Need to Get Learch Grossman to Pick the Best of the Best

4. To Do This We Perform What I Call A Price Fake
We tell the computer we have a dismal market and then ask it to find the ultimate pit
Under unfavorable economics only the better grade ore will get included in the “fake ultimate pit”
Learch Grossman however has picked us the set of blocks that yields maximum value per ton which is just what we wanted.

5. We Will Gradually Raise Our Fake Price As We Do Multiple Runs
Each Run will start with the previous pit in place
Each Run will have the real final pit surface as a limiting surface
The result will be a series of nested pits that go from the best ore to ore of progressively lower grade
We have just tricked Learch Grossman into telling us how to optimize our NPV by sequencing our mining

6. The Pit Slope Problem
Our Ultimate Pit Was Calculated at Our Final Pit Slope
Our Stage Pits will have to maintain a working slope
We accomplish this by telling Lerch Grossman to mine at our working slope, but then we tell it that it must never cut blocks beyond our ultimate pit.

7. MSOPIT Search Option #1
Start MSOPIT.

8. We Will Consider Only Screens for MSOPIT unique to our use
My first cut will start with no
Pit but will limit things to
The area of the ultimate pit.
(Note that Pit 1 is the
Ultimate pit generated in
An earlier step).

9. We Manipulate Our Product Price to Try to Guide the Program to Pick smaller pits with the maximum pay metal
I varied copper and
Moly in proportion to
Each other setting copper
At 50 cents in concentrate
Instead of $1.05.
(only the highest grade
Material will be able to
Pay off so it should dig
Up the richest ore first)

10. Processing and Mining Costs are Held Constant well Metal price is artificially deflated
Leach copper was
Set at 60 cents
We should understand
That because our prices
Are fake our block values
Will be wrong. The function
Of this procedure is just
To pick off the richest
pits
This is the Leach Ore Screen

11. I Needn’t worry about Waste Since Recovery is zero.

12. I’m Going to Need a More Limiting Working Slope
Note that while I allow
57 degrees for my
Final slope I am only
Allowing 42 degrees for
Active working areas.

13. Again Select the Base Option

14. Specify the Pit to Store the Output In and Any Limiting Pit Surface
I am going to put my first pit
In Pit 2
I am going to limit the pit
To be within Pit 1 (ie it cannot
Go out of the ultimate pit)

15. Order the Program to Run the Procedure

16. Turning On and Looking We See A Small Initial Pit

17. We Can Also Milk Some Data Out of the Output Report on the Run
It appears to have taken
About 102,000 blocks
102,000*6000*1.308*1.9=
About 1.5 billion tons
It tells us about ore and waste
Blocks but we don’t pay any
Attention to that because the
Price is messed up so the
Processing decisions are
Jibberish.

18. We Now Make A Second Run With a Little Higher Prices (Resulting in a bigger pit)
This time we start our
Run with Pit #2
(our initial pit) already
Present.

19. As You Can See I Moved Up Another Increment In Pit Size
Ok – I did a few things to get this display
I turned off Pit 2, turned on Pit 3 and then
On Pit 3’s cut-offs option I went to properties
And picked blue as a global color
In fact the report indicates we mined an
Additional 1.4 billion tons of material

20. And Then Up Again
The report assures me I have an additional 1.2 billion tons of material

21. And Again Note that Some areas are Now reaching to The final pit slope
The report tells
Me I took another
1.1 billion tons

22. And Again
815 Million
Ton taken
Out in this
phase

23. And Again
An Additional 685 million tons was taken

24. Problems with a Learch Grossman Price Fake
No way to know how big a jump in pit size corresponds to a given price change
Often want nice even guides that correspond to ore for 3 to 5 year increments
Blind guessing of prices can be a long frustrating process
Learch Grossman may inherently not be able to give evenly spaced pits – the Gap
Learch Grossman transforms the problem mathematically and then solves a different problem
The different problem does not have continuous solutions as a function of price – some pit size jumps are mathematically built into the routine.

25. Substitute Floating Cone for Learch Grossman
Floating cone pits can have some rough surfaces. Floating cone projects cone up
from profitable blocks one block at a time. It misses material that could be moved
With the combined worth of several target blocks. – The rough surface is one way
This limitation can be seen. (Learch Grossman produces smoother pits).

26. Problems Remain After the Floating Cone Substitution
Of course with floating cones you are still blinding guessing prices and then
Seeing what happens to the pit.

27. Real Life Pushbacks Pit nesting can’t just control ore tonnage
We have treated working slopes as lower pit slopes around the whole pit.
In fact we may have 3 slopes
A final pit slope that may provide just enough space to catch rock and get a road out (fine for ultimate pit)
An active slope – the benches may not be wide enough to work but we can get equipment in to start to widen them
A working slope that provides space every so many benches for equipment to really work
Our Pushbacks are usually directional and only involve full working slopes in the direction of the expansion
Trying to guess the direction of expansion while guessing prices is so random that the guesses are not practical

28. Solving the Pushback Slope Problem
Accept reality
Your being told where the most profitable ore is at / not being guaranteed you can get to it in that order
Part of the problem of asking for perfect stage pits is that your taking yourself too seriously
MineSight has a Multi-Pit Option
It takes vertical columns of ore blocks and then just picks the upper 90%, 80%, 70%, etc of each column without recalculating prices and values
The approximation misses how prices change the difference between ore and waste – but they are fake prices anyway

29. Lets Try to Rapidly Generate A Series of Nested Pits
In this case I am going to set a working slope less than my ultimate pit slope

30. I Will Use the MultiV Option
The rest of the panels
Are set for ultimate pit.
I click the radio button
For MultiV instead of
Base.
For stage pits I’m also
Considering floating
Cone as good enough
For my approximation.

31. This Requires Me to Fill Out A Special Panel to Control the MultiV
Remember my file 13
Has a number of
Pit surfaces from 0 to
50 available. I have
To say which ones I
Want to fill.

32. I’m Trying for 21 Steps to Go in Pits 10 to 30
The bench and block
Range allows us to limit
How much of the block
Model we run calculations
On. (We’re not going to
Do this. You would do it
If your block model
Covered a large area and
The ore was only in one
Area).
The value factors need some explanation.

33. How MultiV Works
It calculates the value of each block at full metal prices
Then it multiplies the value of each positive block by the minimum factor
It then will run a floating cone to pick the pit it will mine
Next time around it increments the factor one even step up from the minimum value to the maximum
It remultiplies the value of each positive block
It runs a floating cone to pick the next pit surface
And so on
Of course a prices really change which blocks are even positive will change
This is a different way of trying to pick the most valuable ore.

34. I Will Let My Values Go From Almost Nothing to Full Value
Lastly I will order the computer to make sure all my pits are nested
Inside my Lerch Grossman ultimate pit (which I have stored in pit
Surface 2).

35. I’ll Give My Output Orders
Note I am trying to speed
Things up by not storing
Values and destinations
Back into the model.
And I’m naming the run
Appropriately for what I am
Doing.

36. Give the Run Order

37. The Procedure Runs

38. Visual Examinations
I Turn On My Limiting
Ultimate Pit.

39. Nice 3D Views of Expanding Pits But A Little Hard to Get A Read On.

40. Lets Try to Look at Some 2D Cross Sections
Go to the Root Directory in My Data
Manager
Warning – I am about to go
On a detour to show you how
To get a 2D Display
I’ll get back to interpretation
Later!

41. Drop Down The File Menu and Pick Creation of a New Folder
I’m going to create a new
Folder for something
Called a “Gridset” which
I can use to control where
2D cross section views
Are taken.

42. Name My New Folder and Say OK
Alright – maybe I don’t get a prize for
The most creative file-names.

43. Now Click On the Gridsets Folder I Just Made

44. Drop Down the File Menu and Ask The Data Manager to Make Me A Gridset
(Sounds like a logical
Thing to put in a gridset
Folder)

45. Naturally It Wants Me to Name My Gridset
My Gridset will be a series of vertical
Planes in the East West Direction
Which explains the innovative name
I selected.

46. It Then Brings Up the Gridset Panel
I picked a radio button for vertical
East-West Planes
I excepted the default grid
Structure which started the
Grids in the corner of my
Block model
I then specified 10 planes at
250 meter intervals which should
Allow me to take a series of
Cross-sections through the pit
(I knew the coordinates of my
Block model)

47. Now My Pretty New Gridset Shows Up

48. Now I Am Going to “Attach My Gridset to the Viewer”
I will click on the
Funny looking
Green lined block
(Linking a Gridset to
The viewer will allow
The viewer to take
2D cross sectional
Views on the vertical
East-west planes)

49. When I Tell It to Link a Gridset it Goes to a Directory and Asks Me Which One
In my case where I have only one this is
Not rocket science. I highlight my gridset
By clicking on it and then I click OK

50. Now I Go Up to the 2D and 3D Icons and Click on 2D to Put the Viewer in Cross-Section Mode

51. It Shows Me A Cross Section on the 4000 North – East/West Plane
Of course black
Is a crumby
Background color
For this.

52. I’m Going to Change My Background Color
Click on the Viewer
Properties Icon that
Looks like a blue
Topped list.

53. Up Comes the Viewer Properties Box
On the viewer options tab
There is a color pallet for the background
Color. Click on the Color Pallet.

54. Up Comes a Color Tablet Select the color And adjust the darkness Arrow
Then click ok

55. Now I Have My New Background Color

56. I’m Going to Turn On All My Stage Pit Surfaces
I have to do control clicks for each one (because
MineSight won’t let me do a shift and drag
Across).

57. I Right Click and Pick Open on the Pop-Up Menu

58. To Page Through My Cross Sections I Go to My Plane Selection Area and use the arrows to page

59. I Can Start to See My Pits

60. Looking For A Sequence that Is Really Minable

61. Surface Mining Sequence Realities
You'll start with an initial small pit
This pit needs to be large enough for the equipment to work
It will have to be mined top down
Once a pit is open the mine will expand out in pushbacks
Usually push back in only one direction at a time so that only some slopes will have to be shallow
Push back has to be wide enough to allow working room

62. Figuring Out How Wide the Push Back Is
Lets say a working bench has to be 150 feet wide to accommodate working room
Suppose we will have 4 active working benches on a push back
That’s an 600 feet of working space
Suppose a regular bench is 40 feet wide
4 regular benches would be 160 feet
The wider working benches need an extra 440 feet
Thus our minimum push back width is 440 feet
Most large mine pushback are about 150 to 250 meters

63. Pit 10 to 11 Remember our grid work is 250 meters by 250 meters
This pushback has enough
space
This one does not

64. I’m Already Dis-Satisfied
My initial Pit #10 is already pretty large for me to mine top down
I’m going to try to get a smaller initial pit with the price fake method
I’ll need working width benches all the way around to get this pit.
The Multi-V option just reduces the relative profit on a block
Lower prices in a price fake will in fact convert ore to waste
I should be able to force a reasonable size initial pit with with a Price Fake on a Floating Cone

65. Trying for An Initial Mini-Pit
I go to my economic
Panel and set
Very low fake
Prices.

66. Finish Setting My Low Fake Prices

67. Switch to a Base Design Strategy with a Floating Cone

68. Store My Result in Pit 9

69. Run the Routine

70. Well I Wanted Small I’m not sure Digging the pit With Mighty
Tonka Trucks
Was what I had
In mind.
This is just to
Small for me to
Be running the
Same equipment
Around.

71. Try Another Run with Higher Prices
You can see the
Price Fake
Problem – you
Really can’t
Predict in advance
What you will get.
My second try was
Better but I still
Feel it’s a little
Small.

72. Try a 3rd Time This time I’m Satisfied. Now as I do push
Backs the shallow
Slope will only
Be active during
The push back.
I’ll steepen at the
End.
(With the idea that
I will look at push
Backs at the end
Of each phase when
The slope has been
Steepened.
(I’ll now re-run Multi-V with a steeper slope)

73. Restore My Full Predicted Copper and Moly Prices

74. Set for the Steeper Slope

75. Set for Multi-V

76. Over-Write My Old Shallow Pits

77. Run and Check Out My First Push Backs
Looks like I have
Push-backs in two
Directions.
I’m not sure which
Way will go first but
I’ll make a guess.
Push Back 2
Push Back 1

78. Turn On Pit 11 I can see I have A practical Width pushback
To the west,
But not the east
Pushback 3

79. Turn on Pit 12 On the west side I’ll merge pit 11 and 12 into
One pushback of practical width

80. Turning on 13 I can see the 12 to 13 jump has not Given me any
Practical push backs.
I’ll turn on and off pits
And try to see jumps
Large enough to be
Practical pushbacks

81. Looks Like I Have Pushback #4 to the East Now
I’ll push out to the
Ultimate pit on the
East side.

82. I Can See from my Pit 30 Surface that I Probably Need to Lower My Cost Per Bench to Get the Rest
My ultimate pit was
Run with a 5 cent
Per bench penalty
Instead of 12.
I pit crushing and
Conveying will
Probably be what turns
The economics for
The final expansions.

83. Using Plan View Gridsets
Start
Push back 1
Push back 2
Push back 3
Push back 4
Push back 5
Then down to
The bottom.