Block Modelling.pdf

Block Modelling

Block Modelling

Copyright

Block Model Concepts

Creating a Block Model

Constraints

Model Filling

Reporting

Sectioning

Block Maths and Calculated Attributes

Whittle Interface

Column Processing

Advanced Filling

Answers to Questions

Block Modelling with Surpac Vision

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Block Modelling

Contact details

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Table of Contents

Overview

l What You'll Learn l What is a Surpac Block Model? l Block Model Concepts l Open model. l Review l Where To Next

Overview

This section introduces the concepts and terms fundamental to the understanding of the use of the Surpac Block Model.

What You'll Learn

What is a Surpac Block Model?

In the past, resource modelling with Surpac software has relied heavily on traditional polygonal methods of modelling. These methods are simple to use and understand, but are extremely time consuming, particularly if you wish to modify or change parameters used in creating a model.

The Surpac three dimensional Block Model is still very simple to use and understand, but is significantly faster in its creation, and modelling parameters can be added and modified at any time.

The Surpac Block Model is a form of database. This means that its structure not only allows the storage

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and manipulation of data, but also the retrieval of information derived from that data. It differs from a more traditional database, in that data stored are likely to be interpolated values, rather than true measurements. Another major difference is that these values may be spatially referenced as well as being spatially related. A third important difference is that the Block Model is recalled in its entirety into memory which makes dynamic operations such as colouring of attributes possible but imposes significant memory overheads.

For example, consider the Geological database. Records have spatial attributes which relate them to a spatial position. However, the converse does not necessarily hold as spatial positions are not necessarily related to a record in the database.

The Block Model portions space into an exhaustive set of blocks, each being related to a record. The records may be spatially referenced, that is, information may be retrieved for any point in space, not just for points that have been explicitly measured. This spatial referencing allows the addition of a number of operators to the querying capabilities of the database manipulation scheme, namely spatial operators such as INSIDE and ABOVE, which may operate on solids and surfaces. Outside and below may be built using the NOT logical i.e. NOT INSIDE or NOT ABOVE.

The Block Model comprises of a number of components:

l Model Space

The model space is a cuboid volume outside of which nothing exists in terms of the Block Model.

l Attributes

The properties of the model space that are to be modelled are termed attributes. These attributes may be nominal, ordinal, interval or ratio measurements expressed as numeric or character data. Attributes may also be calculated from the values in other attibute fields, for reporting and visualising.

l Constraints

Constraints are the logical combinations of spatial operators and objects that may be used to control the selection of blocks from which information may be retrieved and/or into which interpolations may be made. Constraints may be saved and have file extensions of .CON.

The model itself is a binary image constructed in the model space and defined by the existence or non-existence of blocks. Model files will have file extensions of .MDL

The Block Model may be applied to any situation where properties of a volume of space are to be



modelled in terms of the distribution of values through that space.


The following terms are used in Surpac Vision model definition:

l Origin

The origin of the model is the lower, front, left hand corner (ie. the minimum Y, X and Z coordinates) of the model expressed in Y,X,Z Cartesian coordinates. The origin is the anchoring point from which rotations involving the Bearing, Dip and Plunge are to be performed.

l Extent

The extent of model is the dimensions of the model in the Y, X and Z directions.

For example, if a model was to cover the following area:

3000mN to 3650mN 1500mE to 2100mE 120mEl to 270mEl

The origin will be:

Y=3000 X=1500 Z=120

and the extent of the model will be:

Y=650 X=600 Z=150

l Bearing

The bearing of the model is the horizontal angle in degrees of the direction of the major axis of the model. A bearing of zero indicates a non-rotated model where the major axis of the model is in a north-south orientation.

l Dip

The dip of the model is the vertical angle of the blocks in degrees from the horizontal in a direction perpendicular to the bearing of the model. A negative dip is an angle below the horizontal to the right when looking along the bearing of the model. A dip of zero indicates horizontal blocks normal to the bearing of the model.



l Plunge.

The plunge of the model is the vertical angle of the blocks in degrees from the horizontal along the bearing of the model. This can also be referred to as the tilt of the model. A negative plunge is an angle below the horizontal when looking along the bearing of the model. A plunge of zero indicates horizontal blocks along the bearing of the model.

l User Block Size

The block size in the Y, X and Z directions. The user block size is used as the reporting unit for the Block Model. The user block is also the block size upon which interpolation is performed.

The user block size will depend on the Model purpose (ie. Grade Control, Resource Calculation, Pit Optimization) with reference to the data spacing.

For example, what block size is appropriate for a prospect drilled on a 100m x 100m pattern, which is to have a resource estimate completed? It would not be appropriate to set this model up with a block size of 5x5x5, as the small blocks won't give a ``better'' estimate of the resource, as the original data is widely spaced. Perhaps, 25x25x10 may be more realistic ( ie. one-third to one-quarter of the sample spacing).

l Maximum sub-blocks per side

The maximum number of blocks along each side of the model. This number must always be 2 to the power of an integer. ( eg 2, 4, 8, 16, 32, 64, 128, 256, 512)

This value will need to satisfy a base resolution. For the example used previously: extents Y=650 X=600 Z=150 user block size 25x25x10

The number of blocks along each side will be 26x24x15(extent divided by user block size). This means that the base resolution will be 32 (the number greater than the maximum number of blocks and is 2 to the power of something). If we wish to allow sub-blocking (the sub-dividing of blocks), the resolution will need to be greater than base resolution.

For this example: if maximum sub-blocks per side = 64 smallest sub-block = 12.5x12.5x5 if maximum sub-blocks per side =128 smallest sub-block = 6.25x6.25x2.5

In this way we find it possible to fill a model with interpolated values calculated at a User Block Size, i.e. user block size 25x25x10 and still constrain the data within geological envelopes that are able to be sub-blocked to smaller sizes i.e.6.25x6.25x2.5. This becomes important when considering the size of the model and the number of calculations to be performed to fill the model.



Objective.To ensure you understand the terms used in setting up a Block Model, answer the following questions. (Answers may be found in Appendix 1).

1. What base resolution (maximum sub-blocks per-side) will be needed for a model with extents of Y=1000, X=600, and Z=200, with a user block size of 20x10x5?

2. What resolution (maximum sub-blocks per-side) will be needed for a model which has extents of Y=1500, X=1000, Z=300 and a user block size of 20X20X10, but sub-blocking to 10x10x5 is required?

3. What will be the smallest block size for a model which has, maximum sub-blocks per side=128, extents of Y=500, X=250, Z=100 and a user block size of 10x10x5?

In the following exercise you will view two Block Models, in order that several more Block Model concepts may be demonstrated.

If do not have the training data installed on your computer, run the Surpac2000 setup program on the installation CD and choose to down load the demonstration data.

This is the list of files that are necessary for the completion of this tutorial.

Objective.To become familiar with selecting existing block models.

1. Choose the block modelling menu by right clicking with your mouse at the end of the main menu bar (to the right of Help)

This will bring up the block modelling menu bar.

2. Select Block Model New/Open. Enter the name of the model as shown below. Leave `Load with constraints' field at the default setting of N.



Look at the bottom right corner of the status line - you will see the block model icon and the name of the active model. Only one model may be active at a time -this is referred to as the current model.

This model was created using the following parameters:

Extents Y=160 X=160 Z=16 User Block Size 10 x 10 x 10 Maximum sub blocks per side 16

3. Choose Model Summary from the Block model menu.



This function shows details of the block model, for display purposes only. Clearly displayed are:

l Model originl Model extentl Block sizel Rotation

Also displayed is the Block Resolution, which is the minimum resolution required for this model. The Maximum Resolution, will always be the maximum sub-blocks per side, as defined when the model was set up. In the case of this simple model, the block resolution and the maximum resolution are the same, which indicates that there will be no sub-blocking in this model.



The total number of blocks, is also displayed. Why does this form indicate that this model contains only 1 block? Surely, it would be more reasonable to expect that there would be 16 x 16 x 16 = 4096 blocks? To help conserve memory, the Block Model will minimise the number of blocks required to represent the volume of space. This is known as Block Aggregation. In this case, as each block has no attributes or values assigned, the blocks all have the same value, and so have been combined into one block. The Storage Efficiency indicates how successful this aggregation process has been, where 0% would indicate no aggregation.

The final part of the form shows any attributes that have been defined. Attributes reflect the properties of interest that are modelled. The creation of attributes will be covered later in this manual.

It is possible to display the exterior faces of this model in Graphics.

4. Choose Display Block Model from the Block Modelling menu.5. Apply the following form.

The Block Model will be displayed in plan view. Notice how the model is centred on the screen.

6. To obtain a better view of the model, try the following:

View By Bearing (alias VB) Bearing = 45, Dip = -45 and Zoom Out (alias ZO)

Alternatively try the interactive, on-screen 3D Viewing commands, by simply positioning your mouse in the Graphics viewport, depressing a mouse button (the left button is best to start), and moving the mouse. Turn hidden surface removal on (alias HON).

You will see one large pink block displayed.

7. From the navigator window on the left hand side, find Model2.mdl. Select this, and drag it across into the Graphics window. Apply the following form:



Your model is not being `destroyed', just cleared from memory. There is no need to save it, as we didn't change anything.

Your status line will be updated to reflect the new current model. This model was created using the following parameters:

l Extents Y=100 X=100 Z=100l User Block Size 10 x 10 x 10l Maximum sub blocks per side 16

8. From the Model sub-menu, choose Summary. (Located at the top of the Block Model Graphics menu).



If the model was created with extents of 100 x 100 x 100, why does the model summary indicate the extent to be 160 x 160 x 160? This is because the block resolution specified indicates that the model has sixteen blocks in the Y, X and Z directions. Thus, Surpac increases the extents in these directions to accommodate this. However, this does not mean that there will be blocks located where not required. Notice also that the number of blocks and storage efficiency is different from the first model. To illustrate these principles, we'll look at the model graphically.

9. Apply or cancel the Block Model Summary form.10. From the Display menu, choose Display Block Model.

This model is not centred on the Graphics screen, reflecting the user defined extent (100 x 100 x 100) versus the Surpac extent (160 x 160 x 160) (model space).



11. Draw a 2-Dimensional Grid (20 metre spacing) (alias 2DG).

Notice how blocks have not been created past Y =100 X = 100 (and Z = 100)

12. To obtain a better view of the model, try the following:

View By Bearing (alias VB) Bearing = 45, Dip = -45 Zoom Out (alias ZO)

Alternatively try the interactive, on-screen 3D Viewing commands, by simply positioning your mouse in the Graphics viewport, depressing a mouse button (the left button is best to start), and moving the mouse.

13. From the Display menu, choose View attributes for one block and click on one of the large blocks and then on a smaller block.

You will find you have blocks of dimension 80x80x80 and 20x20x20. Why haven't blocks been aggregated into one large 100 x 100 x 100 block given that all blocks are the same?

This is because when Surpac Vision produces a sub-block, the block size in the Y, X and Z directions is halved, ie. from one 3-dimensional block, eight equal size 3-dimensional blocks are produced. The same principle applies when blocks are aggregated. Thus, from a user block size of 10x10x10, blocks of dimension 20x20x20 can be produced, and then 40x40x40, 80x80x80, 160,160,160 and so on. Following this principle it is not possible to aggregate 10x10x10 blocks into 100x100x100.

Review

You should now be familiar with the concepts and terms used specifically for the Surpac2000 Block Model.

Please review this chapter or consult the Online Reference Manual if you are unclear about the definitions used in this section.

Where To Next

The next section demonstrates the steps involved in creating a Surpac2000 Block Model.




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Table of Contents

Overview

l What You'll Learn l Model Definition l Adding Attributes l Background Value l Saving the Block Model l Review l Where To Next

Overview

In this section you will create a Block Model with the qualities required to satisfy the origins and extents of your data.

What You'll Learn

This section will provide an overview of the functionality of the following:

l Model definitionl Adding attributesl Saving the Block Model

You will be investigating the following scenario:

A gold prospect has been Reverse Circulation and Diamond drilled on a 40 x 40 metre pattern. It remains to estimate the resource based on the drilling.

The geology has been interpreted on section and three distinct geological ore zones have been identified.

1. SAND - mineralisation is associated with a horizontal palaeo-drainage channel, striking 020. The channel has an average thickness of 2.5 metres.

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2. QPY - mineralisation is associated with quartz-pyrite breccia, strike= 035, dip= 40W.

3. BIF - mineralisation is associated with a banded iron formation, strike= 030, dip= 65W.

The base of complete weathering is assumed to be flat lying, and is at 970 m Elevation. The top of fresh rock is assumed to be at 950 m Elevation.

The drill hole data has been stored in a relational database and several files have been created using some of the Data Processing functions available in the Surpac Geological Database. These files are:

Down hole composites

CMPS1.STR - 1 metre down hole composites for SANDCMPQ1.STR - 1 metre down hole composites for QPYCMPB1.STR - 1 metre down hole composites for BIF

Point Data:

SG1.STR - String file containing specific gravity data for waste and the various mineralised zones.

Geological:

SAND1.STR - Geological interpretations (from section) of the SAND zoneQPY7120.STR to QPY7520.STR (every 40m) - Geological interpretations (from section) of the QPY Zone.BIF1.STR, BIF1.DTM - Geological interpretation and wire frame (Surpac Solid Model) of the BIF zone.DHT7120.STR to DHT7520.STR (every 40 metres) - Drill hole sections

Miscellaneous Data:

TOPO1.STR, TOPO1.DTM - String file and Digital Terrain Model of the natural surface.PIT1.STR, PIT1.DTM - String file and Digital Terrain Model of the design open cut pit.

Take time to view some of the string and DTM files in Graphics to familiarise yourself with the data.

Model Definition

Objective.To create a Block Model with the parameters derived from the drilling data and also based on the required reporting requirements.

1. Make sure you have the Block Modelling menu visible. Select Block model New/Open



The SELECT MODEL form will be displayed allowing you to enter a name for your model. The model name may be up to forty characters in length.

2. Enter the model name as shown below and Apply the form.

If the model does not exist the following form will be displayed, confirming that a new model is to be created. .

3. Apply the following form to begin defining the new model.

The Creating New Block Model form allows you to define:

l Description

A description of the model is optional. However, it is useful to record the purpose of the model.

l Origin

Discussed previously

l Extent




l User Block Size


l Rotation


l Maximum sub-blocks per side


4. Enter the parameters as shown below and Apply the form.

The Model Confirmation form will be displayed, allowing you to check the model dimensions, rotation, user block size and minimum sub-block size. If you wish to change any of the model parameters, press the Cancel button. To accept the parameters, press the Apply button.

5. Check your parameters to match those shown below, and apply the form.

The creation of the block model will begin. The model is created rapidly - the icon in the status bar tells you when creation is complete.After the model is created, you cannot alter the extent, rotation, block size, or the maximum blocks per side. You will need to create a new model if you wish to modify the geometry of the model.

Adding Attributes

The next step in the creation of your block model is to add the attributes. Attributes are the properties of the model



space that are to be modelled. These attributes may be nominal, ordinal, interval or ratio measurements expressed as numeric or character data. Attributes may also be calculated from values in other attribute fields.

When creating attributes, you must nominate:

l Attribute Name

Up to 30 characters in length made up of any printable character. Spaces are allowed in the attribute name, but are not recommended - these may complicate the use of the Block Maths function.

l Attribute Type

This may be a character, real, integer, float or calculated. Float saves the data as a single precision number, to 6 decimal places, and requires 4 bytes/block. Real saves the data as a double precision number, to 15 decimal places, and requires 8 bytes/block. Therefore, if it is sufficient to store your data to 6 decimal places, when creating your attributes you should choose an attribute type of float for the most efficient data storage requirements. Integer and character type attributes also use 4 bytes/block to save the data. Calculated attributes are not stored in the model but rather, are calculated ``on demand''. No memory is used in storing calculated attributes

Background Value

All blocks must have some value for each attribute in the model. When you first create an attribute you specify this background value. All blocks retain this value until they are assigned another value, through a block model function. If the background value is left blank and the attribute is numerical, the background value will be 0. Further information on appropriate background values will follow later in the exercise.

Attributes may be added and deleted at any time. You may also use Clear Attribute to reset all or part of the model attribute(s) to their background values. You may change an attributes background value or name using the Edit Attribute function, however you cannot change the attribute type.

Objective.To add attributes to the Block Model.

1. Choose New Attribute the Attributes menu.

The Add Attributes form will be displayed. When nominating the attribute type there are three possible ways to enter the attribute type:

l Type the full word using the keyboard, ie. reall Use the browser icon to choose the required attribute typel Type the first character of the required attribute type and press enter



The last option is very quick and easy and in most cases may be used whenever a browser icon is located next to a field. You need to type in enough characters so that the required field entry is unambiguous. For example, if you created two attributes called silver and sulphur, whenever you are asked to nominate the attribute you wish to work with, typing the characters ``si'' and ``su'' will be enough to nominate either of these attributes.

2. Add the attributes as shown below then Apply the form.

3. Select Model Summary to view the results.



Saving the Block Model

When working on the Block Model, all data from the model is stored in memory, meaning that you are always working on a copy of the model. Any changes you make to the model will not be saved until you choose to exit from Block Modelling, at which time you will be prompted to save the existing model. Thus, it is good practice to save your model at regular intervals, to avoid the grief that ``accidents'' can cause (ie. interruption to the power supply). After a Fill or Columns operation (covered later in the Manual), if any blocks have had their value changed, you will be prompted by a form to overwrite the current model file or to cancel it.

Objective.To save the Block Model.



1. Choose Model Save from the Block Model menu. displayed. Check the message window to ensure that the model training.mdl was saved.

Do not interrupt the loading or saving operations of the Block Model as you will risk the integrity of the model. At all other times you are working on a copy of the original model which is stored on the hard disk but during the saving operation in particular, you might save an incomplete model if the program is aborted during saving.

Review

You should now be familiar with the creation and saving of Surpac Block Models.

Please review this section or consult the Online Reference Manual if you are unclear about the operations covered in this section.

Where To Next

The next section demonstrates the concepts involved in the creation and application of Surpac Block Model Constraints.


Copyright

Copyright (C) 1995 Surpac Software International Pty Ltd. All rights reserved. Printed in Western Australia.

Printing History: November 1995: First Edition.April 1998: Second Edition.November 2000 Third Edition

This software and documentation is proprietary to Surpac Software International Pty Ltd.

Surpac Software International Pty Ltd publishes this documentation for the sole use of Surpac licences. Without written permission you may not sell, reproduce, store in a retrieval system, or transmit any part of the documentation, except for the brief quotations embodied in critical articles and reviews. For such permission, or to obtain extra copies, apply to Surpac Software International Pty Ltd at the address below, or any Surpac office around the world.

Surpac Software International Pty LtdLevel 8, 190 St Georges TerracePerth, Western Australia 6000

Telephone: (08) 9420 1383Facsimile: (08) 9420 1350

International Telephone: +618 9420 1383International Facsimile: +618 9420 1350

While every precaution has been taken in the preparation of this manual, we assume no responsibility for errors or omissions. Neither is any liability assumed for damages resulting from the use of the information contained herein.

UNIX is a registered trademark of AT&T.

Sun, SPARCstation are trademarks of Sun Microsystems Inc.

PostScript is a trademark of Adobe Systems Inc.

Microsoft, Windows and Windows NT are registered trademarks of Microsoft Corporation.

AutoCAD is a registered trademark of Autodesk Inc.

MicroStation is the registered trademark of Bentley Systems Inc.

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Copyright

All other brands and product names are trademarks or registered trademarks of their respective owners.

Last Modified: -8:-2147483648am , January -2147483648, -2147481748

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Constraints

Constraints

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Table of Contents

Overview

l What You'll Learn l Constraints form. l Loading a Constrained Block Model l Review l Where To Next

Overview

One of the very powerful features of Surpac Block Modelling is the ability to apply constraints. Constraints are the logical combinations of spatial operators and objects and may be used to control the selection of blocks from which information may be retrieved and/or into which interpolations may be made.

Constraints can be likened to queries made from relational databases and parallels can be seen with the ``query constraints'' used to select a range of drill holes in the Surpac Geological Database module. The noticeable difference being that the flexibility of the Block Model constraints ``engine'' is much greater.

Constraints may be as simple or as complex as you like, and are most commonly used when:

l Filling the Block Model with valuesl Producing Reportsl Viewing models in Graphics.l Loading a constrained portion of a model

The choice of spatial operators you have are:

l ABOVEl INSIDEl >

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Constraints

l 1.

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Model Filling

This is an example of a Block constraint where you constrain on the value of blocks in the model. This is another powerful method of constraining the model and it is important to understand its application.

3. Use the View tools to interrogate the image.

Ordinary Kriging

Another method of filling a model is using the Ordinary kriging function. This will be discussed in a later section. A necessary pre-requisite is the development of an acceptable variogram. However, the use of the function is similar and as simple as the other methods you have already covered.

The only variation when using this function is that the user may create an attribute to which the kriging variance is stored. This may be used to help classify resource categories for reporting purposes.

Assign Value

ObjectiveTo use Assign Value to fill a new attribute called ``material''.

1. Choose Attributes - New to add a character attribute called material.


Model Filling

2. Choose Assign Value to assign the material values in the following manner:

Answer in Appendix 1. Save the Block model.

When creating character attributes, it is a much better technique to enter a background value of unassigned as opposed to leaving the background value blank. The reason for this is that later on, when reporting on the model by this character attribute, if any blocks have not had this attribute assigned, this will be very evident as ``unassigned'' will show up in the report. If no background value is entered a blank space will show up in the report next to the reported values. This still signifies that these blocks have not had a value assigned, but it is much easier to miss this than if these blocks were clearly tagged unassigned.

It takes no more memory or storage space to have a background value of unassigned as opposed to a blank background value, as the actual text is just stored once in the model file and then referenced.

Anisotropy Ellipsoid Parameters

At this point, we will step back and look at the issues and requirements of the Anisotropy Ellipsoid Parameters.

ObjectiveTo create an anisotropy ellipsoid for visual validation of geostatistical search ellipsoid inputs.

1. Choose Block model -- Estimation -- Ellipsoid visualiser and enter the form as shown.


Model Filling

2. Select the "Save now" button on the form to save a ellipsoid string file at the specified coordinate origin.

The result is a string file representing the orientation and dimensions specified in the form. When exported at a specified coordinate origin it can be recalled into graphics in close proximity to the data and thus be used for visual confirmation.

3. Recall the file ellipsoid_qpy1.str into a graphics layer of the same name and then recall cmpq1.str into a different layer.

Tip: dragging a string file into graphics from the navigator pane automatically places the data into a layer of the same name.

3. Modify the styles of the cmpq1 layer to display the samples as markers instead of lines (alias sss = styles string) .

It should now be possible to determine if the anisotropy ellipsoid is sufficient in range in each of the three dimensions (major, semi-major and minor) to find sufficient samples to inform the block model. It


Model Filling

is also valuable to determine if the ellipsoid is correctly oriented as it is a common mistake to rotate the ellipsoid in the wrong direction.

Note that it is also possible to invoke the ellipsoid visualiser on all of the relevant estimation forms such as inverse distance and ordinary kriging and the rotation parameters specified will populate subsequent forms.

Review

This section has covered some very important concepts relating to populating the Block Model with data. It would be advisable to consult the Online Reference Manual at this stage to ensure that these concepts are clearly understood.

Where To Next

A later section will cover some more advanced filling methods. The next section involves the generation of Block Model Reports.


Reporting

Reporting

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Table of Contents

Overview

l What You'll Learn l Block Model Report l Isosurfaces l Exporting Centroids l Review l Where To Next

Overview

What You'll Learn

This section demonstrates the use of the Block model report function and associated exporting functions:

l Block model reporting l Isosurfaces - 3D contours l Exporting block model centroids

Block Model Report

The Block Model Report function allows you to create a customisable report for printing. You may choose to report average or aggregate values for numeric attributes, as well as ordering the report by attribute. You can create a template for reporting so that subsequent runs of the same report can be

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Reporting

made using different constraints.

This function may be accessed from the main Block modelling menu by selecting Block model - Report. Reports suitable for printing are quick and easy to produce and the next exercise will demonstrate the use of this function.

ObjectiveThe first report you will produce will show the Volume, Tonnage and average gold concentration, every 10 metres in elevation, for several nominated gold concentration ranges.

1. Make sure you have training.mdl loaded up. Either click and drag the model from the navigator to load or chose Block model open. Choose Report from the Block model menu We need to define a format for our report .

You can chose one of a number of different formats for your report to be created in. The choices are:

html - for use with web browsersrtf - format used by many word processing packagespdf - Adobe Acrobat formatps - Postscript files - many printers read this format directlynot - the original Surpac text filecsv - can be imported into spreadsheets and databases easily


Reporting

If you make a format file for your block model report you have a convenient way of obtaining the same format report within various constraints ie you can run this report again for some other part of the ore body without recreating a new format file.

2. Enter the parameters as shown below.

l Report description

Your header may be of any length and will appear on all reports produced with this format

l Attributes to report


Reporting

You may list any number of numeric attributes to be averaged.

l Weight by mass, volume or none

Mass is most common. When using mass a multiplication factor for the volume must be entered eg a specific gravity.

l Report

Average or aggregate (the nominated attribute can be reported as an average, ie. average copper grade or aggregated, i.e. summation of all the stored attribute values).

l Multiplication factor volume

Volume and mass may be reported. If you wish to report for volume mass, then this may be calculated by using a fixed value, or by using a nominated attribute.

l Attributes to group

List here the way in which attributes are to be grouped and the order to appear in the report. In this example, the report will be grouped by elevation (z) from 820 to 1020 every 10 metres, and grouped by gold grade in the nominated cut-off grades. As the z attribute is listed first the report will show each elevation and then the grade ranges for each elevation.

3. Enter the constraint as shown below.


Reporting

The report will be produced. The message window will show the total volume, mass and average gold grade. The full report is contained in the file called training.csv.

The message window should report the grand total volume and tonnes for immediate verification that the report has been completed.

4. The report will appear in the report viewer window.

5. Produce a report grouped by material type and gold grade. You will need to make a new format file. Choose Report from the Block model menu and enter the parameters shown below.


Reporting

You will notice we are producing a report in a different format just so you can see the difference. Each site will have different requirements for reporting.

6. Fill in the block model report form as follows.

7. Enter the character attributes for material as shown below and apply the form..



Reporting

9. The resultant file will appear in the report viewer. The grand total should match the previous report `training.csv'. This is a good check.

10. Try creating a report which reports average gold grade and groups by elevation, material type and gold grade for QPY and BIF.

Isosurfaces

This function generates 3D triangulations of approximations to isosurfaces (that is, surfaces with a constant attribute value) from data stored in the block model.

The 3DMs generated by this function are typically used to enhance the visualisation of data. eg. a 3D contour of the 2 gram cutoff surface for a particular attribute.

As with all functions in Block Modelling, you may apply a simple or complex constraint to the model when generating the isosurface.

Exporting Centroids


Reporting

This function is used to export out a block model for use in another mining software package. There are two different methods - export centroids and export centroids and block faces. These functions produce a string file with the centroid position and selected attributes listed in the descriptive fields. The easiest method to use is found under the Block model menu - Export - Block centroids to string file. The resultant string file is an Ascii file which can be easily read in a text editor.

Review

This section has covered the basics concepts of:

l Block Model Reports l Isosurfaces l Exporting centroids

Further information is available in the Online Reference Manual. Please review and practice these reports to gain a full understanding of them.

Where To Next

The next section deals with the extraction of sections from the Block Model.


Sectioning

Sectioning

[Previous] [Next]

Table of Contents

Overview

l What You'll Learn l Section along Northings. l Plan sections l Review l Where To Next

Overview

Surpac allows you to extract orthogonal, oblique and/or dipping sections through a Block Model. You may extract either block centroids or block outlines. The results are written to a string file, with attributes stored in description fields. The resulting files may be used for further manipulation.Sectioning tools are located on the main block model menu bar.

The following exercises will demonstrate how to extract sections, and some of the potential uses for the resulting files.

What You'll Learn

This section will cover the following concepts:

l Extracting sections normal to the Y axisl Extracting sections normal to the Z axisl Avoiding sections coincident with block faces

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Sectioning

l Plotting sections

Objective.To create northing sections (perpendicular to the Y axis) through our block model

1. Ensure you are connected to the training.mdl. You can check to see if the icon is present on your status bar at the bottom of the screen. Connect by clicking and dragging from the navigator.

2. Choose Sections - Create.

The first step in extracting sections, is to nominate the sectional type required. The choices you have are:

l Normal to the Y, X or Z axis (most commonly used)l Plan or vertical section (need to enter horizontal or vertical constraints for these options)l Axis (using end point), (typically for oblique sections)l Axis (using bearing and dip), typically for inclined oblique sections

The define button is used when extracting plan, vertical, axis (end point) and axis (bearing and dip) sections. It brings up another form which allows you to define your extraction details more specifically.

In this exercise, you will be extracting sections normal to the Y-axis and so will not need to use this button.

3. Enter the parameters shown below, but do not apply the form.


Sectioning

The above example shows a common mistake made when extracting sections.

This model was originally set up with an origin of 7100 North and a block size in the y direction of 10. Therefore extracting a section at 7120 would actually extract values from the blocks extending from 7110 to 7120 and also from the blocks extending from 7120 to 7130. Plotting this section would result in the grades being over plotted as two values would be plotted at every block.

You do not want your section range to correspond with block edges - this results in duplicate strings for each section.

To avoid duplicate segments in the section string file, complete the form as shown below:

It is obviously not desirable to extract sections at 7120.0001 or at 7115.0001 if your drill holes sections are at even multiples of 10. This should be file:///C|/ssi_V4.1-R/share/refman/default/tutorials/blockmodel/sections.htm (3 of 13)02/05/2005 14:57:27

Sectioning

considered when creating the model in the first place. In our example, it would have been better to have the origin or our block model at 7105 or 6995 so that block model sections could be extracted at the same section interval as the drill hole sections and geological interpretations (without producing duplicate segments).

The file created called `defgrp0' is a string file which shows the section boundaries, as a series of strings. It is not very useful for this type of section extraction, but can be very useful when trying more complex extractions, such as Axis (bearing and dip). It allows you to preview where the section will be extracted.

The next step is to nominate an output file location and details of how the section will look.

4. Enter the details shown below and apply the form

.

5. Constrain the extraction to the BIF or QPY blocks as shown


Sectioning

Once processing is complete, your message window will indicate the files created. The section files can now be combined with raw drilling data to help check the validity of the model.

6. By right clicking in the menu area, bring up the geological database menu.


Sectioning

7. From the Display menu, select Section files and enter the following parameters..

8. Now bring in the string file sect7200.str by clicking and dragging from the navigator.

On section you now have the original sample drilling displayed with the model blocks for the 7200 mN section, as shown below. These string files could also be used to produce a plotted map.


Sectioning

Objective.This exercise will demonstrate how to extract sections normal to the Z-axis and produce a simple map which could be used for mine planning purposes.

When the model was set up, the Z origin was at 820 mEl and the Z block dimension was 5 metres. This means that at intervals of 5 metres in elevation (ie. 825, 830, 835, 840...) there will be coincident block faces. If sections are extracted at these elevations there may be two coincident segments for each block outline or centroid. This may then create problems, especially when plotting.

For the purposes of this exercise, assume that mining will be on 5 metre benches and that bench plans are therefore required mid-bench (ie. bench from 970 - 975 has mid-bench of 972.5). The bottom cut-off is 1ppm gold.

1. Choose Sections - Create from the Block model menu and enter the parameters as shown below.

2. Define the section files as shown below.


Sectioning

The name `sect' may be confusing here because, in essence, these are not ``sections'' but plan slices through the model. A better name for this may be `plan' or `bm_plan' but for now we will leave it at `sect', as a pre-defined map for plotting in a subsequent exercise uses this name.

When extracting plan view ``sections'' as above, coordinates can be set to Section View or Real World. See the Online Reference Manual for a detailed explanation on this field and how it affects the function.

3. Enter the Constraints as shown below.


Sectioning

4. Call up the string file `sect9725' by clicking and dragging from the navigator. Bring in the string file lev9725 into the same layer by using Ctrl drag from the navigator.

On screen you should have the ore blocks for the 972.5 mEL and the pit outline. There are blocks outside of the design pit, so before continuing, it would be useful to calculate the volume, mass and average gold content inside the pit limits. This can be achieved using Block model report.

5. Choose Report from the Block model menu and enter the parameters as shown below. We can use the same format file that we created earlier.


Sectioning

6. The only thing we need to change to get our report is the constraint that we use. Enter the constraint shown below. (Note the use of an extended string constraint limiting the report to blocks inside the pit outline).

Your report will come up in the Print Preview window and the results will also be reported to the message windowFinally, we will produce a map to show the results.

7. From the File menu choose Open - Plotting Window.8. Go to Map - Edit and select the map called Ore Blocks. Modify the map as follows:


Sectioning

9. Select Process Map and process the map Ore Blocks.10. Enter the Plot Presentation Parameters as shown below.


Sectioning

11. Once processing is complete, the plot will appear in the plot preview window.

Review

This section has effectively covered the more commonly used vertical section and plan section extractions from the Block Model and also the conventions and pitfalls of sectioning. Information about the other section types:


Sectioning

l Plan or Vertical Sectionl Axis (using End Point) (typically for oblique sections)l Axis (using bearing and dip) ( typically for inclined oblique sections)

can be found in the Online Reference Manual.

Where To Next

The next section introduces the concepts involved in manipulating values stored in the Block Model using general expressions, ie. Block Maths.




[Previous] [Next]

Table of Contents

Overview

l Calculated attributes. l Block maths. l Review l Where To Next

Overview

Block maths functionality allows you to assign values to attributes based on the values of other attributes. With the introduction of calculated attributes, the need to store calculated values is lessened compared with previous versions of Surpac. However a knowledge of the mathematical expressions will allow you to store an attribute or make a dynamically calculated attribute. The advantage of making a calculated attribute is that no memory is taken up to store a value in a block.

In the first exercise we will just do a simple mathematical calculation on our gold value to demonstrate the functionality of calculated attributes. Let us calculate a new attribute to store a gold grade to which an upper cut has been applied (whilst we are not advocating applying top cuts, it is a regularly asked question). Calculated attributes access the same expressions that Block maths accesses. The only decision you need to make is whether or not you store the result or calculate it dynamically.

We will use an IIF statement: iif(gold>10,10,gold). This translates into plain speak as: If the gold grade is greater than 10 make it 10, otherwise leave it as the gold grade.

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Objective: To use calculated attributes and block maths expressions to create a cut gold attribute

1. Make sure you have your training.mdl loaded up - an easy way to check is by looking to see if the icon is displayed in the status area at the bottom of the 3D window

2. Under the Attributes menu select New and fill in the form as follows

3. Apply the form and then save your model (Block Model - Save)

4. Display the model in the graphics window and add a new constraint so that only those blocks with a value for gold of greater than 10g/t are displayed



5. Try selecting one of the blocks to ensure your calculation has worked properly. The function to use is Display - View Attributes for one block. You should see something like the following (although the values will be different)



You can see that a grade greater than 10 has been cut back to 10 in the new calculated cut_gold attribute.

In the following exercise, you will create a character attribute called stockpile. This attribute will be used to determine the destination for ore once it is mined (ie. mill, leach pad, low grade stockpile). The destination of the ore will depend on the material type and the gold grade as follows:

l Mill

any oxide, transitional and fresh ore > 1ppm gold

l Leach

any oxide ore


iif(gold > 1, ``mill'', iif(material = = ``oxide'', ``leach'', ``lowgrade''))

If you were to express this out loud it would read:

IF the grade of gold is greater than 1ppm then send it to the mill stockpile. However, if the gold grade is less than 1ppm and the material type is oxide then send it to the leach stockpile, otherwise send the ore to the lowgrade stockpile. (ie. all fresh transitional ore


Note in the above expression that each iif statement is enclosed in brackets and that character values are in enclosed in double quotes ( `` ``).




You are not prompted to save the model after Block Maths. You may wish to save the model at this time. Without saving, the results of the block maths operation will remain in memory, however if the computer were to lose power, the block maths results would be lost.

4. View the results in Graphics by adding graphical constraints and displaying the attributes for various blocks.

Review

This section should have given you an introduction to the concepts of using Block Maths. Further information can be found in the Online Reference Manual under the sections indexed BM Block Maths and Expressions. (Note that not all general expressions are suitable for Block Maths.)

Where To Next

The following sections mark the beginning of some of the more advanced or specialised topics available



in the Block Model functionality. We will begin with Whittle Model importing and exporting.


Whittle Interface

Whittle Interface

[Previous] [Next]

Table of Contents

Overview

l What You'll Learn l Who uses Whittle? What is Whittle? Why would you use

Whittle? l Who Needs Pit Optimisation? l Exploration Geologists l Project Financiers l Mining Engineers l The Whittle Interface l Review l Where To Next

Overview

A direct interface has been developed within the Surpac block model to Whittle Programming's suite of optimisation products.

What You'll Learn

This section gives a brief overview of the Whittle interface

Who uses Whittle? What is Whittle? Why would you use Whittle?

The abstract below was written by Nick Journet, Principal Mining Engineer of Windrush Mining Technology in Perth, WA. Nick is a specialist in pit optimisation and carries out optimisation studies on

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Whittle Interface

30 different mineral deposits each year. Deposits covered range from gold through base metals to diverse industrial minerals.

Who Needs Pit Optimisation?

These days when we think of pit optimisation software, we think of Whittle. Whittle Programming produce the World-renowned pit optimisation packages called Three-D, Four-D and Four-X. Four-X differs from Four-D in that it can optimise multi-element deposits.

Briefly, if a resource model is optimised for a given set of economic parameters, mining and metallurgical recoveries, and pit wall angles; the result will be a single optimal pit outline. Three-D optimises cash flow which is usually adequate for limited life projects. Four-D and Four-X introduce the fourth dimension, which is time. Both Four-D and Four-X packages will optimise net present value of an open pit for a given set of production and discount rates.

Exploration Geologists

As development capital becomes harder and harder to raise, companies are becoming smarter with the way they spend their exploration budgets. One way that this can be done is to drive an exploration program with pit optimisation.

In attempting to prove up an open pit reserve, it would be pointless to sink holes to extend the known depth of the deposit beyond the economic limit of an open pit. A well organised exploration program could update a simplistic resource model ``on-the-fly'' as new drillhole results become available. Using conceptual economic parameters, the resource model could be regularly re-optimised. There are even techniques to test the blue sky potential of a deposit by artificially extending the depth of mineralised blocks.

Two or more mineralised zones can often co-operate to mine the same portion of waste. Such an excavation can result in a saddle-back. The question is often asked once mining is well underway, ``is the saddle-back barren?'' By employing pit optimisation techniques at an early stage, the explorationist can identify and confirm whether the saddle-back is real or perhaps caused by shortage of data.

Project FinanciersToday pit optimisation is a prerequisite before any new open pit project is given approval and allowed to get off the ground. The Whittle range of optimisation products are recognised as world leaders. In simple terms, bankers and mining executives trust Whittle software can help them meet their objectives which are to:

l maximise return on investment


Whittle Interface

l minimise risk l ensure all corporate objectives are met

Traditionally, Four-D and lately Four-X, have been used to optimise net present value. In today's corporate climate where many mines use sophisticated hedging techniques to forward sell production thereby guaranteeing their revenues, it is often not appropriate to optimise an operation on net present value alone. For instance if a company has locked into a high forward sales price, the average cash operating cost of the optimal net present value pit may indeed be higher than the spot metal price. If this were the case, the company would trade more profitably, and with less risk, if it ceased mining and became a metals trader instead. The trick is to choose a pit outline and mining sequence where the marginal operating cost per unit of metal (say for gold $/oz), is always less than the metal's spot market price. Adopting this approach, the company will maximise benefit from its forward sales policy.

If there are uncertainties in metal price, operating costs and recoveries, it becomes a relatively trivial exercise to run a sensitivity analysis on these parameters. With Four-D and Four-X, it is possible to quantify and develop a risk profile for project within hours. Experience has shown that nine times out of ten, a project is more sensitive to changes in grade than anything else. Therefore, if the resource model is inaccurate, sensitivity to changes in other parameters becomes irrelevant.

Mining Engineers

An optimisation using Four-D and Four-X, generally produces between 40 and 99 nested pit shells. Each shell represents the optimal pit outline for a given metal price or mining cost (all other parameters remaining constant). If the smallest shell is evaluated with a realistic metal price and mining cost, it will provide the fastest return.

Mining engineers can use this to identify the correct position for a ``starter pit''. For larger projects, subsequent pit shells are used to prepare an orderly (and optimal) mine development schedule. The pit's push-back sequence can be guided by nominating specific pit shells. The analysis programs will calculate net present value for:

l the worst case schedule which is flat bench mining to the ultimate pit limit l the best case schedule which is mining incremental shells and is usually not practical, and finally l the specified push back schedule which aims to simulate the actual situation

With the advent of the Whittle Interface to the Block Model, engineers now have a sensational tool to calculate mining and processing costs for individual blocks and rock types using the powerful constraints engine. Traditionally, a project is optimised during the feasibility study stage. Some mines are becoming more sophisticated and optimise each year to define their ore reserve statement. The block model becomes an ideal storage medium for operating cost data as well as grades, rock type and bulk density information. If this data is kept up date, automated re-optimisation can be a macro and a few mouse clicks away. Incredible, imagine being able to use pit optimisation to guide short term as well as


Whittle Interface

long term planning projects.

Used in conjunction with the Surpac block model, the Whittle pit shell outlines, have never been presented better. Using all the sophisticated block model query tools at your disposal, you can calculate isopachs which show the difference between an optimal pit shell and the current topography or another pit design. Results, when visualised with Surpac's rendering and colourisation tools will leave you stunned.

For more advice on pit optimisation and its use with Surpac, contact Nick Journet, the Principal Engineer for Windrush Mining Technology, Perth, WA. Nick can be reached though e-mail at [email protected] or through your local SSI support centre.

The Whittle Interface

The Whittle interface is accessed on the Block modelling menu bar under Block model - Export - To Whittle

The form shown below is the only form to complete (other than the constraints form, if constraints are to


Whittle Interface

be applied to the export).

The cost adjustment factors are stored as attributes in the model. Therefore adding these to your block model is an important part of the pre-processing, and this will generally be performed using the block maths function.

The results from the Export to Whittle 4D are two files, the Whittle model file and the Whittle parameters file.

The form below is completed as would be typical when performing an export from the block model to Whittle 4D. As you can see, the interface itself is very straightforward. The `work' involved is all in ensuring your model is valid.


Whittle Interface

Upon applying this form, the function will start processing. The processing feedback scroll bar will go across once, from 0 to 100%, which gives excellent feedback as to how long the process will take. Also, the function line reads ``Exporting Whittle file filename.mod''.

The result is a valid Whittle model file and parameters file.

After running the Whittle pit optimisation, to bring the results back into Surpac2000, when prompted for a model to load, simply choose the Whittle file. This will either have a .mod, .eco or .res extension.

A specific example is available in the dem\examples\whittle directory of our demonstration data distributed with Surpac.

The data used in this demonstration is the Simba Mining Corporation data also referred to in the Online Reference Manual. It has been converted to be used in conjuction with the Block Model interface.

Review

This section gives a broad overview of the concepts of Whittle model import and export using the Surpac Block Model.

Where To Next

The next section covers some of the column filling functions of the Surpac Block Model with emphasis on their use in economic modelling.


Column Processing

Column Processing

[Previous] [Next]

Table of Contents

Overview

l View data l Classify blocks into Ore and Waste l Reduction Dilution l Recoverable Product l Thicknesses l Review l Where To Next

Overview

This section takes an existing block model and uses Surpac's block model column processing functions to evaluate the economics of the block model.

The supplied data is a block model containing only one attribute, `grade', and a DTM representing surface topography. This section will go through the following processes:

l Classify blocks as ore and waste based on a cutoff grade and minimum mining thickness. l Apply reduction and dilution at ore/waste contacts l Calculate recoverable product l Determine bottom of economic ore l Calculate economic ore volume, grade and total recoverable product.

ObjectiveTo familiarise yourself with the data graphically.

1. Load the block model called blockmodel.mdl into graphics by clicking and dragging from the navigator. Colour on grade (use a grade range of 0;6;8;999) by using Display - Colour model by attribute. View in 3D. Constrain to blocks where grade > 0. You should be able to generate an image on the screen similar to the one shown below.

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Column Processing

The purpose of this section is to teach the block model column functions, not to teach block model fundamentals. If you are unsure of how to generate the image, you should re-do the first half of this manual which contains details on the block modelling basics

This is a perspective view looking at a bearing of 330 degrees and a dip of -10 degrees. The light source is from the south at 0,1,0.5.

The blocks in this model are 35 metres in the x and y dimensions and 3 metres high. Because the vertical extent of this model is limited compared to the horizontal extent, we will vertically exaggerate this model five times using the View Scale function (under View - Data view options - View scale factor).

After exaggerating the model five times, to get our view at a bearing of 330 degrees and a dip of -10 degrees back, we need to set the View by Bearing function to a dip of -2, the dip you want divided by the vertical exaggeration. Orbit Up once (by the default rotation increments of 10 degrees) so you are viewing the model at a bearing of 330 and a dip of -20.

2. Recall the topography DTM, Blocktopo1.dtm into Graphics and view this at the same time as the block model. Note the


Column Processing

separation between the topography and the highest blocks with any grade. This separation is the overburden.

3. Use the on-screen viewing tools to become familiar with the model. Perhaps slice the model to see the internal structure, as shown below.

4. To slice the model, first change your view back to plan view. Zoom All is an easy way to do this. Choose the function Add Slice. With the mouse, click and drag a slice orientation from left to right close to the south end of the model as shown below, just inside the model area.

5. For slices at a 250 metre spacing, as shown above, complete the form as shown in the second form below.


Column Processing

After applying the form above, a 35 metre slice (one block width) will be generated every 250 metres, as shown below. These slices can then be viewed in 3D

Once familiar with the model, we are ready to start the economic modelling process.

ObjectiveTo classify blocks into Ore and Waste based on minimum mining thickness and cutoff grade. The functions used will be BM Column Tops and BM Ore Waste Discrimination.

The first part of this process is to create surfaces which represent the top and bottom occurrence of material above the cutoff grade. The reason for this is that you will never mine a block as ore at the top or bottom of your ore body if its grade is below cutoff grade. Ideally, you will start and stop mining ore at the first and last occurrence of a block above cutoff grade, for a given column.

It must be stressed that the column processing functions are just that, column processing. They process each column independently of all other columns and so do not take into account grades in adjacent columns. This methodology has some applications in determining economic mining depths, as this exercise will show, but it is only one dimensional and should in no way be considered as a substitute for a


Column Processing

three dimensional pit optimiser such as Whittle.

The first step is to run Column Tops to create surfaces which represent the top and bottom occurrence of material above cutoff grade. These surfaces will then act as constraints for the ore/waste discrimination. In this way no sub-grade blocks at the top or bottom of the ore can get grouped in with the ore during the ore/waste discrimination process.

1. Choose Column processing - Column tops and complete the forms as shown below.

This will search down through the block model extracting a point at the top of the first block in each column where the grade is greater than 8. The result will be a string file called `top_cutoff1.str'. The `nominal value above top' (first form) is the default elevation which will be assigned if no blocks in the column satisfy the constraint. As a rule of thumb, when extracting upper surfaces, the nominal z elevation should be set to an elevation below your model and when extracting lower surfaces it should be set to an elevation above your model.

2. Repeat the Column Tops function to create `bot_cutoff1.str'. This time the search is in the Z direction (positive Z is up) and the nominal elevation should be set to 400.


Column Processing

3. Create DTMs from `top_cutoff1.str' and `bot_cutoff1.str', specifying N to use strings as break lines. Use Surfaces - DTM File functions - Create DTM from string file.

4. View DTMs in Graphics to ensure all is OK. Upper DTM shown below. Note how it follows the top of the first block above cutoff grade.

5. Choose Layers Status (alias L) and make all layers not visible so only the block model remains visible on screen. (The block model is on its own layer which does not show up when using layers function).


Column Processing

The next step is to add two attributes to the model which will be filled in the Ore/Waste Discrimination function. These are: composite_grade and ore_waste_flag.

6. Choose Attribute - New and complete form as shown below.

The ore_waste_flag is a flag which will signify an ore block if set to 1 and a waste block if set to 0. The composite_grade attribute will store the grade for a contiguous set of ore and waste blocks in a column.

7. Choose Column processing - Ore/Waste discrimination and complete the form as shown below.


Column Processing

We are specifying minimum mining thicknesses of ore and waste of 6 metres and a cutoff grade of 8.

This function classifies blocks as ORE or WASTE according to a cutoff grade and minimum thickness criteria. The ore/waste classification is stored as an integer value in the ore_waste_flag attribute which facilitates colouring the model on ore/waste. A master attribute is specified (grade) and an attribute to store the composite grade for each resulting ore and waste layer. Further attributes can also be composited if they exist, based on ore/waste classifications on the master attribute.

The mining method to use is also specified in the Digging Zones field (Truck and Shovel, Dragline, or None). This determines whether different ore and waste minimum thicknesses are specified depending on the location of the blocks within the bench. This is because the mining equipment can have different selectivity capabilities depending on where the mining is taking place within the bench. At the top of the bench, the equipment can be more selective than lower in the bench. For the initial economic evaluation, we will choose no digging zones and the ore and waste minimum thicknesses will be consistent throughout the model.

For further detail on the digging zones and the Maximise field, refer to the Online Reference Manual.

8. Fill in the constraints form as follows:


Column Processing

Note: it is very important that this function be applied using the above constraint. This way no outlying sub-grade waste blocks will be included in the top or bottom ore layers. This constraint should be saved for future processing

A summary is shown below.

9. View the results of this function graphically. Colour the model on the ore_waste_flag attribute as shown below. Ensure you are viewing the blocks within your new constraint file - top_bot_cutoff.con.


Column Processing

This should colour the model as shown below.


Column Processing

The yellow blocks are ore and the blue blocks are internal waste. Note that the minimum mining thickness of 6 metres (2 blocks in elevation) has been taken into account.

10. Choose Display - View attributes for one block and select a block. The composite grade will be reported. This is the average grade for all contiguous ore or waste blocks in that column. If you select a block above or below this block in the same layer, it will have the same grade. All ore layers have a composite grade greater than 8 and all waste layers have a composite grade below 8.

11. Show only the internal waste in the model so we can see its distribution in 3D, like the image below.

Choose Display - New graphical constraint and add the constraint = BLOCK ore_waste_flag 0.

These functions can also be used for calculating such things as cumulative grades in a stope in any orientation. The above example is only utilising the Z direction for compositing columns.

Reduction Dilution

Because of the practical realities of mining, it is impossible to mine exactly to an ore/waste contact. There will be some material blending at the contact. Chances are there will be some ore which will be mined with the waste, and some waste which will be mined with the ore.

The Reduction Dilution function in the block model allows you to specify your expected reduction and dilution parameters, and then this function will calculate a diluted grade for each ore and waste layer. This will give the best estimate of the grade of material actually mined.

The first step is to add another attribute to the model.

Objective.To use the Dilution & Reduction function.


Column Processing

1. Choose Attributes - New and add an attribute called diluted_grade, of type float and background value -99.

2. Choose Column processing - Dilution and reduction and complete the form as shown below.

l Digging Zones.

This is a very specific tool designed to modify the amount of dilution and reduction that occurs at different places within a bench. You may have more reduction and dilution near the bottom of the bench than near the top of the bench. For this reason, you can input the type of


Column Processing

mining method and then specify different reduction and dilution factors at different depths. If you are uncertain whether or not you have digging zones we suggest that you leave this as none. In this example we will leave Digging Zones at the default of none, and the dilution and reduction for all internal ore/waste contacts will be the same.

l Volume Factor

It is possible that the reduction and dilution thicknesses are not equal. For example if the ore is extremely high grade, then it may be desirable to ensure that all ore is mined, even though this may result in extra dilution. Because blocks themselves cannot change in size in the block model, a volume factor attribute in the model is used to keep track of the effect on the volume of unequal reduction and dilution at ore/waste contacts. This volume factor is then used in the volume report and all volumes reported for ore and waste to be mined will be correct. For our example, the reduction and dilution factors are equal and therefore there is no need to use the volume factor.

l Thicknesses - Column. Top & Bottom. Reduction & Dilution.

This is the reduction and dilution at the top and bottom of the constraint. In our case the constraint is first occurrence of grade above cutoff. This will be the top of the upper ore bench and the bottom of the lowest bench. It is entered as a vertical thickness of the entire block. Therefore a dilution of 1 on our 35 metre square blocks would equal 1225 cubic metres of waste being mined as ore. Reduction refers to the amount of ore mined as waste.

l Thicknesses - Ore Layer, Top & Bottom, Reduction & Dilution.

This is the reduction and dilution at the top and bottom of each internal ore/waste contact. That is every ore/waste contact within our constraint other than the top and bottom of the constraint. As above, it is entered as a vertical thickness of the entire block.

l Change waste above cutoff to ore? Change ore above cutoff to waste?

The result of the reduction and dilution may be that the grade of a waste layer actually increases to a grade above the cutoff grade, or the grade of an ore layer is diluted to such an extent that the overall grade for that layer falls below cutoff. If these scenarios occur, you have the option of reclassifying those layers as ore or waste based on their new grade.

This reduction and dilution should be performed within the constraint as shown below. This constraint was saved during the ore waste discrimination function

A summary is shown below.


Column Processing

Step 3: Recoverable Product

This function calculates the volume of recoverable product for each ORE block, and stores this as a ratio of volume of recoverable product to total volume in that block. Therefore it can be considered as the volume of recoverable product in one unit of volume, ie. in one cubic metre if working in metric. The value is stored this way because Surpac2000 dynamically sub-blocks and super-blocks. The aggregate


Column Processing

option in the block model reporting function is then used to produce volume reports showing total volumes of product.

For each ore layer, the function also calculates two ratios. It is these ratios which give a measure of whether an ore layer at that depth is economic.

The first ratio is the ratio of the total volume of material in that ore layer and the waste layer immediately above it to the volume of recoverable product in that ore layer. This gives an indication as to whether that ore layer contains sufficient product to ``carry'' the waste layer immediately above it.

The second ratio is the ratio of total volume of material of that ore layer and all ore and waste layers above it (to surface) to the volume of recoverable product in that ore layer and all ore layers above it. This gives an indication as to whether mining to that depth is economic. Because even though that ore layer may carry the waste immediately above it, if, for example, there is a large amount of overburden in that column, mining to that depth may not be economic.

Again remember, these are one dimensional calculations. Grades in blocks in adjacent columns are not taken into consideration. Each column is processed independently of any other columns.

The economic bottom of ore is then determined as the first ore band encountered when searching up through the block model where both the individual and cumulative ratios are lower than a specified ``cutoff'' ratio. This cutoff ratio is determined by the economic mining factors, such as commodity price, cost of mining, cost of processing, etc.

The Recoverable Product function requires that all blocks processed by this function be classified as either ore or waste. Presently we have overburden on our model which is still unclassified. Before running the Recoverable Product we must classify our overburden as waste. We do this using the Assign value fill function.

1. Choose Estimation - Assign value. Complete the forms as shown below.


Column Processing

This will assign those blocks above the top of our ore, and below the topography ie the overburden blocks to waste.

Before we run the Recoverable product function, we should add the attributes which will store the results of this function.

Note: the attributes do not have to be added ahead of time, as in this function, as in the ore/waste and reduction/dilution functions, if the attributes specified to store the results do not exist they will be created. However it is a better technique to add them first for two reasons. The first reason is that if they are added by the function they are created as real attributes and not floats and therefore will require double the storage space. The second being that you have control of the background values when adding them yourself. For data management reasons you will want to standardize your background values. In this exercise we are using -99.

1. Choose Attributes - New. Complete the form as shown below.

Unlike most other attributes, the ratio attributes are given a high background value. A high value of the ratio of volume to product denotes less economic material. We will be searching for the first value below a certain value. If we picked a low background value, when searching for the first block below a certain value using the column tops function, we would always find the top or bottom of the model because this is outside of our constraint and so remains at the background value.


Column Processing

2. Choose Column processing - Recoverable product and complete the forms as shown below.

Try graphically editing some of the blocks and looking at the values for recoverable_product and ratios. Do the ratios make sense? Edit a few blocks until they do, remembering the lower the ratio the better. One would expect an ore layer with only a small amount of overlying waste to have a lower individual ratio than an ore layer with a higher thickness of overlying waste. Also, once would expect the uppermost ore layer to have the same value for the individual and cumulative ratios. If this does not make sense, please re-read the description above on the Recoverable product function.

The Block Edit function should give you results similar to those shown below.


Column Processing

The final steps of the process are to extract and create surfaces representing the top and bottom of economic ore. The bottom of economic ore will be a surface created when searching up through the model, using the Column Tops function, for the first block where both individual and cumulative ratios are below a cutoff ratio. For this exercise we will use a cutoff ratio of 12.

3. Invoke Column processing - Column tops and complete the forms as shown below.

4. Create a DTM of the bottom of the ore. This function is accessed from the Surfaces - DTM File functions menu - Create DTM from string file. .


Column Processing

5. Click and drag the new DTM file from the navigator into graphics. This will go into a new layer. 6. Use the 3D viewing tools to view the block model from below, as shown below.

It is clear to see that the economic bottom of ore matches the lowest occur

Documents

Block Modelling.pdf