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Minemax Tutorial iGantt Optimizer for OP © Minemax 1998 – 2013 of 19

Minemax Tutorial

iGantt

Optimizer

for

Open Pit

Version: 4

Updated: May 2013


COPYRIGHT NOTICE

2013

Copyright in this document is vested in Minemax Pty Ltd.


1. INTRODUCTION

1.1 Purpose

The purpose of this tutorial is to demonstrate the use and the functionality of iGantt

Optimizer for short-term up to long-term detailed scheduling for Open Pit applications.

2.1 Prerequisites

The prerequisite knowledge for this tutorial is an intermediate level of proficiency using

iGantt software to:

Create an iGantt project (attributes, activity types, calendars, report items and

reports)

Load visualization from strings and triangulated surfaces and format the 3D view

Import and map activities

Create precedences for activities

3.1 Scenario

The scenario used for this tutorial is an open pit project for basic load and haul activity

scheduling with locations within multiple pits, pushbacks, and benches down to the flitch

level.

The aim of this project is to generate a long-term schedule with 36 time periods by

maximizing the profit of the project (Net Present Value) while satisfying all mining and

processing capacity constraints.

The total material mined has a fixed truck capacity constraint of 25,000 truck hours per

month. The processing plant has a fixed capacity of 1.5M tonnes per month.

The duration of the time periods varies over time with 1-month increments for the first year,

3-month increments for the following 3 years and yearly increments for the remaining time

periods.

Apart from the standard location and physical attributes such as ore tonnes, waste tonnes

and grades, the revenue, mining and processing costs and truck hours are modelled in this

scenario.


2. TUTORIAL STEPS

1. From your Windows “Start” menu, click “All Programs iGantt Tutorials

Tutorial Files Optimizer OpenPit” to navigate to the tutorial file

“demotutorial_iGantt_Optimizer_OP.igt”. Double-click on the file to load the project into

iGantt displaying activities, 3D visualization and the default report on a single screen.

TIP: If you are a Windows 8 user, right-click the Windows Start screen to view the bottom bar with the “All Apps” icon. Click on the “All Apps” icon and then click

“Tutorial Files Optimizer OpenPit” to navigate to the tutorial file “demotutorial_iGantt_Optimizer_OP.igt.

2. Click the “Project” menu and then select “Project Attributes” to view attributes

previously defined for this project. Click the “OK” button to exit.


3. Click the “Project” menu and then select “Activity Types” to view activity types

previously defined. In this project, we are using one activity type “LH (LoadHaul)”.

TIP: Other activity types such as Drilling or Blasting can be also modelled if

desired.

4. Click the “OK” button to exit.

5. Click the “Project” menu and then select “Edit Project Calendar” to view the current

project calendar. The iGantt Optimizer requires the default calendar “24 hours, 7 days”

with no non-default days.



TIP: If a non-default project calendar is detected by iGantt Optimizer, a warning message will appear with the option to remove all non-default days or times by clicking the “Fix Schedule Automatically” button.

7. Click the “Resources” menu and then “Edit Resources” to view the Resources

window. In this project, no resources are set up as we will create an activity-based

schedule.

8. Click the “Close” button to exit.

9. Click the “Reports” menu and then “Define Reports” to view details about the

“Summary” report by selecting the “Edit Report” button. The “Summary” report includes

summary items for Ore Tonnes, Au Grade, Waste Tonnes, Total Tonnes, Trucks and

Financials per time period.



11. Click the “Optimizer” menu, select “Options” and then click the “Time Periods” sub-

menu to specify the time periods for the optimization.

11.1. To add variable optimization periods, click the “Edit in Advanced Mode” button.

11.2. Change the start time to show “01/07/2013” and then enter the value “36” into the

“Number of Time Periods” field. This will generate 36 time periods.

11.3. Change the “Increment” value to “month” for the first period. Then click the

“Copy Forward” button.

11.4. Scroll down to “Period 13” and change the “Time Amount” value to “3”. Then click

the “Copy Forward” button.


11.5. Scroll down to ”Period 21” and change the “Time Amount” value to “1” and the

“Increment” value to “year”. Then click the “Copy Forward” button.

12. Click the “Constraints” sub-menu to add constraints for our project. In this scenario, we

will constrain the milling process using the “OreTonnes” attribute and the mining process

using the “TruckHours” attribute.

TIP: If cycle times are not available for the truck hours calculation, the total tonnes

can be also used to constrain the mining process.

12.1. Click the “New” button to add a new constraint. This will open up the “Add

Constraint” window displaying the “Details” sub-menu.


12.2. Type the name of the constraint “Milling” in the “Name” field and select the

constrained attribute “OreTonnes” from the drop-down menu.

12.3. Click the “Activity Types” sub-menu to select the activity type that will be

constrained. Click the “LH (LoadHaul)” activity on the left and move it across to

the right area by clicking the “>” button. Then click the “OK” button.


12.4. This will create two entries for minimum and maximum milling constraints per

time period. Enter the maximum value of “1,500,000” tonnes into the monthly

time periods, “4,500,000” tonnes into the quarterly time periods and “18,000,000”

tonnes into the yearly time periods.

TIP: Use the “Copy Row Forward” button to copy the required value to all

subsequent time periods.

12.5. Repeat steps 12.1 to 12.4 to add the “TruckHours” constraint to the grid.

12.6. This will create two entries for minimum and maximum truck hour constraints per

time period. Enter the maximum value of “25,000” hours into the monthly time


periods, “75,000” hours into the quarterly time periods and “300,000” hours into

the yearly time periods.

13. Click the “Options” sub-menu to select the optimization strategy from the three

available options:

Forward scheduling optimizes one period at a time, carrying results from one period

forward to the subsequent period. This option provides a very fast result but doesn’t

guarantee finding the theoretically optimal schedule.


Global scheduling considers all time periods together and can find the true optimal

schedule. If a large number of blocks and time periods are used, global scheduling

can be quite time consuming.

Sliding window scheduling optimizes “x” time periods at once and then moves “y”

time periods forward. The same process repeats in multiple interactions defined by

the “x + y” combination where “x” represents a “sliding window length” value and “y”

represents a “sliding window step” value. This gives a balance of solution time and

solution optimality.

13.1. Tick the “Sliding window scheduling” option. By default, the “2+1” option is

selected. This means that two time periods are optimized at once. After

completing an optimization phase, the result for the first time period is kept and

the window is moved forward by one time period to optimize the next two time

periods. This process repeats until the schedule for the last time period is found.

13.2. Confirm that the “Reset rates to defaults” option is ticked. This option will replace

any manually added activity rates with the default rate which has been set for the

activity type.

13.3. Confirm that the “Adjust rates to fit periods” option is ticked. If your target is not

reached within the time period set while using the default rates, this option will

increase the rate to ensure the target value is reached within the specified time

periods.


13.4. Select the attribute “Profit” from the “Value” drop-down menu. By doing so, iGantt

Optimizer will optimize the schedule by maximizing the profit of the project.

13.5. Click the “OK” button.

13.6. The attribute “Profit” is a calculated attribute that has been previously defined

under “Project Attributes” by selecting the “Project” menu.

TIP: Other attributes can be used as a “Value” parameter as required. For

example, if “Ore Tonnes” are used, iGantt Optimizer will optimize the schedule by

maximizing ore tonnes for the project.


14. Click the “Optimizer” menu and then click “Optimize”. This will open up an Optimize

window showing the first and last periods to optimize. The dates of the first and last time

periods flow through from the “Time Periods” sub-menu set up previously.

TIP: Tick the “Apply” tick-box if you need to change the first or last period to

optimize.

15. Click the “Optimize” button. This will activate the optimization showing a dialog window

with the progress bar. The iGantt Optimizer uses a mixed integer linear programming

(MILP) model to represent the mine and its production constraints using a branch and

bound algorithm.

15.1. In the first step, the dialog window displays the “Initializing…” message while

iGantt Optimizer builds the mathematical model of constraints.

15.2. In the second step, the dialog window displays the “Periods 1-2: Still looking for

result” message. This means that the maximum upper value (bound value) within

the first two time periods is being searched for.


15.3. In the next step, once the bound value is determined, iGantt Optimizer looks for all

possible feasible solutions within the first sliding window and compares them

against the bound value.

15.4. The message “Result found within 14.59%” means that the best feasible solution

so far is at most 14.59% from optimality. The iGantt Optimizer will keep looking for

all other solutions until a solution within 1% is found.

15.5. In the next step, the sliding window will move to the next period and repeat steps

15.2 to 15.3. When the best solution for the last optimization period is found, the

dialog box will disappear.

TIP: It takes approx. 8 seconds to optimize the project using sliding window

scheduling with the “2+1” option. The optimization time will vary based on the

optimization method selected and the number of blocks and constraints in your

project.

16. The “Summary Report” shows total values for each report item per time period. The “Ore

Tonnes” and “Truck Hours” items meet the maximum constraint per time period set in the

“Optimizer” menu.


17. Click the “Visualization” menu and then select “Set Object Colour Scheme”. The

“Colour Scheme Chooser” window will open up and display the default mode of “Colour

By Object Type”.

17.1. Select “Colour By Time Period” from the drop down menu to change the colouring

mode to time periods

17.2. Tick the “Repeat Colours” tick-box to repeat the same colours every eighth time

period

17.3. Tick the “Multi-Time Period Object Colouring” tick-box to splits strings into the

multiple coloured sections

17.4. Tick the “Show in Summary Report” tick-box to show the colouring code in the

“Summary” report

17.5. Click the “OK” button. This will display the colouring mode in the visualization as

well as in the reports.


18. Click the “Visualization” menu and then select “View Schedule” to validate the

schedule using an animation.

18.1. Tick the “Show Remaining” tick-box to step through the remaining reserve.

18.2. Select the viewing date of 01/07/2013 18.3. Select the time interval of 256 ms and then click the “Run” button

19. The animation steps show the progress of load and haul activities by showing the

remaining reserve for the date of 12/12/2016.


20. The animation shows some remaining material that has not been scheduled within the

optimization periods due to economics and precedences included in this scenario.

.

21. Load the iGantt file “demotutorial_iGantt_Optimizer_OP_optimised” to compare your

results.


3. SUMMARY This tutorial has shown you the necessary steps to develop a long-term schedule using iGantt Optimizer. In the first steps, we reviewed project attributes, activity types and reports previously set up in the iGantt project provided. Secondly, we showed you how to set up 36 time periods of variable lengths to be used for setting constraints and optimizing. In the next step, we showed you how to set up a processing constraint using ore tonnes and a mining constraint using truck hours for each time period. In the following step, we discussed optimization options and showed you how to set up the “value” parameter that is used for optimizing. In this scenario, we were maximizing the Net Present Profit value of the entire project. Once the optimization was completed, we also showed you how to set the object colour scheme per time period and analyze results using reports and animations. Congratulations on completing the iGantt Optimizer tutorial for Open Pit applications. Please contact our Minemax experts on [email protected] for additional information about iGantt Optimizer.

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