WhittleMIME 413-513 Workshop 1 2014
WhittleMIME 413-513 Workshop 1 2014
WhittleMIME 413-513 Workshop 1 2014
Fall 2014
OUTLINE
1.
Introduction
2.
Task
3.
Data Files
4.
Instructions
Page 1
Fall 2014
1. Introduction
Part 1 of the project covers the following topics:
1. Definition of the ultimate pit limit.
2. Determining nested pit shells.
3. Designing pushbacks.
4. Effects of extraction sequence of ore/waste blocks on production scheduling and
long term planning.
Concepts behind Whittle Nested Pits
Whittle uses a Model File containing details of the contents of each block, but, for
optimization purposes, we need a single value for each block. This value is the cash flow
(positive or negative) that would result from mining the block. For optimization purposes
it is important to assume that the block has been uncovered. It is unnecessary to allow for
stripping costs, because the optimizer does this implicitly. If we calculate the block
values for a particular model we will get a certain set of block values that, when used in a
pit optimization, will lead to a particular pit outline, the optimal outline.
Example 1
For the purpose of this example, assume the pit outline is outline "A" in the following
diagram.
Within an optimal outline, every block is "worth mining". Each block consists of zero or
more parcels and, possibly, some undefined rock that can be regarded as another parcel.
Page 2
Fall 2014
The resultant cash flow from mining a block consists of the sum of the cash flows
generated be mining the blocks parcels. A parcels cash flow depends on the way we
treat the parcel (i.e. mill, leach, etc.) and the associated prices and costs with the method
of treatment. An increase in all commodity prices while keeping the costs constant may
cause the parcel to be treated differently (e.g. it may now be processed rather than treated
as waste); in this case, the cash flow will always either stay the same or increase.
Increasing the prices will not decrease the cash flow obtained from mining a given parcel.
Thus, if we increase the prices, the value of every block within outline A will increase or
stay the same. No block value will go down. Consequently, every block within outline A
is still worth mining.
Example 2
In addition, if we do another optimization using the new values, the new outline (shown
as outline B below) is certain to include the whole of A. It may also include extra blocks
that were not worth mining before, but which are now worth mining.
Fall 2014
slope requirements, it is simple to determine which sequences are feasible when mining
out a particular pit.
Example 3
In Figure 3, if pit 5 is the ultimate pit, we can clearly mine in the sequence a, b, c, d, e, f,
g, h, etc. If the pits are sufficiently far apart to give working space, another possible
sequence is a, f, b, g, k, c, etc. Regardless, given a set of nested pits, these sequences are
clearly defined and easy for the computer to trace, and thus can be used to show various
mining schedules in order to obtain projected tonnages, grades and cash flows. Although
each set of outlines is only strictly optimal for a particular set of costs, their usefulness
goes far beyond this. Provided that the costs used are of the same order, another
optimization run with different costs will usually produce a set of pits of similar shape,
but are shifted relative to those from the first run. For example, pit number 20 from one
run may be very similar to pit number 25 from the previous run. It is therefore reasonable
to simulate mining with wide ranges of prices and costs using the same set of nested pits.
Once a set of costs has been settled on, a final optimization using those costs and a
repeated simulation can be run as verification.
Page 4
Fall 2014
Slope angle
54
Selling price
19.29 $/unit
Selling cost
N/A
Mining cost
1.8 $/tonne
16.862 $/tonne
8.195 $/tonne
84 %
90 %
Cut-off
0.3 g/tonne
Model Au unit
Grams
Processing capacity
0.2 Mt/y
Extraction capacity
0.5 Mt/y
8%
Page 5
Fall 2014
Page 6
Fall 2014
Fall 2014
Page 8
Fall 2014
3. Data Files
The folder named MIME 413 Project Part 1 contains a single estimated (kriged,
deterministic) orebody model and a parameter file.
A) Model File:
Orebody block model files: These types of files are identified by their extension as
mod. They contain the specification of the block model of the deposit such as block
coordinates, metal grade, ore and waste tonnage etc.
Format: The formats of the parameter and model files are provided in the Whittle
softwares manual and the summarised below.
The first line:
X, Y, Z, Number of Parcels, Positional mining CAF, Processing CAF, tonnage
The second line:
X, Y, Z, Rock Type, Tonnage, Metal Content
If the number of the parcel for a block is zero, the second line doesnt exist for that
block. If the number of the parcels is 1 or more, the second line is written for each of
the parcels for that block.
Page 9
Fall 2014
B) Parameter File
In this workshop, all the necessary parameters for the design and planning of the pit are
provided. For more information, see the Whittle Parameters document included or the
Whittle help manual.
The parameter file: parfile.par
Format: The format of the parameter file is summarised as below.
1
dx
dy
dz
x0 y0
z0
nx
ny
nz
ABI
MCAF
PCAF
PRNT RSTINT
RSTME
[active block indicator, positional mining CAF(1=use CAF, 0=do not use), processing
CAF(1=use CAF, 0=do not use), printing index (1:quantity of unprocessed material
printed, 0:quantity of unprocessed material not printed), restart interval and restart time]
4
nx
ny
nz
30
0.0
(number of slope regions, number of benches to generate structure arcs, default block
tonnage)
6
0.0
54.0
(decimal places to write: block ton, total ton, revenue factor, currency total, currencycharacter)
13
1.000
1.000
1.800
(general block tonnage, dilution factor, [recovery, the selling cost ratio; not used,] air flag
A=consider air blocks in optimization(1) or do not (2), air flag B=air blocks not included
in the result file (1) or air blocks within the ultimate pit are included (2)-Air flag A must
be 1, or all air blocks in the model file are included (3), reference mining cost, ore
selection by cutoff (1) or by cash flow (2))
14
0.1657506
Page 10
18
GOLD
Fall 2014
(element type, position in the file, decimal places for gold in the block: total unit of
element, grades and cut-offs for this element.
20
GOLD
0 19.2900
OXOR
1.000
1.000
MILL OXOR
8.195
GOLD
0.900
0.300
(element type, cutoff controlled (C) or not controlled (N), processing cost/unit, process
recovery fraction, recovery threshold, minimum and maximum grade).
4. Task Instructions
The computer session of this first part focuses on the basics of using the Whittle software.
This is only useful to those who have not used Whittle previously. This section covers
importing data into Whittle, generating pit shells and ultimate pit limits, designing
pushbacks from pit shells and optimization with the Milawa-NPV option. Some of the
traditional sensitivity analysis, such as varying commodity price and processing capacity
are also included in the notes, but is not necessary for this assignment. You are, however,
encouraged to explore these features if desired.
The data set used in this assignment is generated from an estimation method (ordinary
kriging). The estimated orebody model will be used as input and the resulting schedules
and pushbacks obtained in the first part are referred to as the base case during analysis
performed in subsequent assignments.
Page 11
Fall 2014
e. Type project name: Project1, select the project directory by clicking on the
directory icon on the right side - P:\Project1\. Whittle should automatically
create a working directory - P:\Project1\working_Project1. Click on next,
for import type, choose Whittle block model. Browse the folder you created
to find kriging.mod as the model file to import, and parfile.par as the
parameter file to import. Then, click on finish and yes to confirm. If there are
any additional windows that appear asking for parameters, simply keep
selecting Next or Finish until they go away.
Page 12
Fall 2014
f. Check the parameters loaded and run the program by clicking on the third man
icon
g. Under New Block Model, select the Description tab and change the block
models description from New Block Model to Kriged Model.
h. Under the Formats tab, set the Units for Element GOLD to gram. Not
setting the correct units in Whittle can lead to misleading results.
i. Press the Accept button to accept the changes.
j. Now, click on each of the tabs and check what information is provided.
k. When finished, select the Check Data button to ensure that all data has been
correctly entered.
Page 13
Fall 2014
Page 14
Fall 2014
c. Right-click on New Schedule Graph on the left side and choose Cut Branch
from the menu. Repeat for the Pit by Pit Graph node.
d. Click on description tab of the New Operational Scenario node and type
Operational Scenario-1. Click on time cost tab and change the discount
rate. Then, Click on the limits tab on the right side and change the value of
the extraction and processing limits. Additionally, ensure that the units for
Element limits is set to grams. Then, click on accept.
e. Add Pit by Pit Graph: Right click on Operational Scenario-1 and add Pit by
Pit Graph. Click on description tab and type Pit by Pit Graph-1. On
schedule tab, ensure that fixed lead is selected with 0 value. In the
Definition tab, delete all the lines below tonnage of waste rock. Then add a
new value to be displayed by clicking in add select Output on the left and
select Undiscounted revenue and cash flow on the right, and choose Open Pit
Page 15
Fall 2014
Page 16
Fall 2014
f. Generating the pit list: Right click on the Kriging Pit Shells and select OtherExport Pit List. Select the directory you created and change the name to
Page 17
Fall 2014
kriga.pil, click on run. Click on OK for the message. You will need these
pit shells for future assignments.
g. Finding the optimal pit: Click on Pit by Pit Graph-1. Click on output tab
on the right side. It shows the best, specified and worst case scenarios. The
optimum pit can be found from there (checking in the discounted cash flow it
may be seen which pit shell has the highest value and therefore may be chosen
as the ultimate pit).
Page 18
Fall 2014
h. Click on the Graph tab and press zoom button. Click on the preferences. Type
DCF on the Title of Y-Axis. Select only Open Pit Value and unselect the
other options. Click on the 2nd Y-Axis preference tab and unselect Use multiple
Y-Axis because you have chosen only one display (there is no need to display
the 2nd axis). Click on Style preferences and select Open pit value for the
best case. Change the Style to Bar, and Colour to red. Click on Graph tab to
see the modified plot. Repeat these steps to generate your graphs required for
the assignment deliverables. Be sure to comment on your results.
Page 19
Fall 2014
Page 20
Fall 2014
Page 21
Fall 2014
Page 22
Fall 2014
Page 23
Fall 2014
c. Right click on your pushback scenario created in the previous step (Kriging
Mining Width - # Pushbacks), and select Add then New Operational
Scenario. Whittle should add the correct parameters, however if they are
incorrect, be sure to put in the correct parameters (Discount rate and Processing
limit), as per Step 2 (d) . Right click on your new operational select and select
Add then Pit by Pit Graph. Under the Schedule tab, ensure that
Specified Case Pushback Definitions is set to Manual, and you will need to
add your pushbacks. Press the Add button, and then enter your pushbacks in
increasing order (e.g. if you have 4 pushbacks, you would enter 1 2 3 4). Press
OK. Under the Definition tab, ensure that Whittle will generate the correct
graphs that you require. When ready, press the running man button. Under the
Graphs tab, you should now be able to see your graphs for the pushbacks (i.e.
not pit shells, as shown in the previous step). You will need to re-do this
analysis according to the various # of pushback scenarios you have chosen.
Compare what happens in pushback tonnages, ore tonnages, etc. to justify your
decision on number of pushbacks in your design before going on to the next
step.
d. Generating Pit list Krigb.pil: Right click on Kriging Mining Width, toolsexporting pit-list- select the working directory and change the name to krigb.pil,
export it. Here, this pit list contains block coordinates and the number
representing the pushbacks. You will need to do this for which ever design (# of
pushbacks) you deem best. The output file is required for the next part of the
project.
4 Optimization with Milawa Algorithm
a. New Schedule Graph: Create a production schedule by right clicking on the new
operational scenario (whichever was deemed optimal from the previous step),
selecting Add then Schedule Graph. In the Description tab, type Kriging
Schedule Milawa NPV. In the Specified Case Scheduling Algorithm
section of the Schedule tab, select Milawa NPV. Add Manual pushbacks
by clicking add on the right side (Add as many pits as needed e.g. if you have
4 pushbacks, you would enter 1 2 3 4). In the Definition tab, delete all the
lines below Discounted open pit value and click on add. Then, click on
output on the left, and on the right choose element and grade. Choose Qty
of <element> output from <method> (<method><element> /UO*) to have
quantity of gold in the output file. Click on add to selection, choose GOLD,
from MILL for specified case, and OK. Click accept. Feel free to add
whatever graphs necessary to justify your decisions in your reports discussion.
Then, run the program by clicking on 2nd running man. Repeat this step for
Milawa Balanced. Discuss the differences between the output schedules,
which one you think is more effective, etc.
Page 24
Fall 2014
Page 25
Fall 2014
Page 26