Operational Improvement using Geotechnical Block Models

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Operational Improvement using Geotechnical Block
Models

• By Megan Little
• Datamine Forum
• Kievits Kroon
• 15 - 16 March 2007

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Outline

• Introduction to PPRust
• Geotechnical block modelling
• Model applications
• Geotech Modeller product
• Future development

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Outline

• Introduction to PPRust
• Geotechnical block modelling
• Model applications
• Geotech Modeller product
• Future development

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Location and Geology
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Current and future open pits
PPRust North
Zwartfontein South
Sandsloot
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Current open pits
PPRust North depth 30m length 300m width
100m
Zwartfontein South depth 100m length 1400m
width 600m
N
Sandsloot depth 250m length 2km width 600m
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PPRust Mining

• 3 open pits Sandsloot, Zwartfontein South and
  PPRust North started in 1992, 2002 2006
  respectively
• 2006 production 67Mt ex-pit 4.8 Mt of ore to the
  plant
• 2007 production ramps up to 90Mt and new plant
  commissioned
• 2008 production ramps up to 120Mt
• Exploration to the south and west for future open
  pits and underground operations

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Mining Sequence - Sandsloot
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Local geology
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Local geology at Sandsloot
E
W
Platreef
Reef pyroxenite and parapyroxenite
Hangingwall norite
Footwall calc-silicate
Max pit depth260m
Strong brittle rock
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Outline

• Introduction to PPRust
• Geotechnical block modelling
• Model applications
• Geotech Modeller product
• Future development

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Model process
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Geotechnical data collection

• Borehole Logging
• Face Mapping
• Rock testing
• SiroVision digital photogrammetry
• All exploration and in-pit drilling at PPRust is
  logged geotechnically and point load tested.

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Exploration Drilling

• gt 380 km of geotechnical logging
• gt 1100 boreholes logged geotechnically
• 27 orientated boreholes
• gt 15,000 point load tests
• gt 300 UCS tests
• gt 150 met. tests

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Geotechnical logging

• Major Structures
• Joint sets spacing, condition
• Rock Mass Ratings Bartons Q, Bieniawskis RMR
  and Laubschers IRMR (3 international stds for
  different applications)

Zone 1
Zone 2
Zone 3
Zone 4
Zone 5
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SABLE RMR input logs
data per joint set
data per geotechnical unit
All data needed for 3 RMR systems collected at
once plus extra information for detailed analysis.
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Point load testing
a simple field test for rock strength which
gives a point load index which is converted to a
UCS.
? 10 point load tests per rock type per hole ?
Average UCS used in RMR calculations
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Lab rock strength test logs

• Lab tests taken per rock type from boreholes
  when required
• Average UCS in RMR calculations
• Over 25 type of test results stored

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Geotechnical mapping

• Major Structures
• Joint sets spacing, condition
• Rock Mass Ratings Bartons Q, Bieniawskis RMR
  and Laubschers MRMR, Hoeks GSI

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MineMapper bench plans
Data is stored and viewed by bench plan
which can be viewed and edited in 3D space
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MineMapper Geotech data capture
RMR mapping and line survey data stored
Point load and lab tests also collected in tables
Zone 1
Zone 3
Zone 2
Zone 4
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SiroVision digitised structures
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Datamine - data import and viewing
Boreholes, facemaps wireframes
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Geotech zoning
All the geotechnical data is used to define
geotechnical zones for each pit and each
cutback. The block modelling is based on these
zones.
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Geotechnical data

• Borehole logging, face mapping, rock testing and
  SiroVision are used to calculate rock mass
  ratings, define major structures and identify
  geotechnical zones in the pits.
• This, combined with the geological data is used
  to define the geotechnical block models.

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Geotechnical interpolation
Interpolated parameters
Calculated parameters

• UCS
• Fracture Frequency
• RQD
• Density
• Point Load Index
• Bartons Q
• Bieniawskis RMR
• Laubschers IRMR

• MRMR
• Slope angle
• Blastability Index
• Energy Factor
• Drill Blast Cost
• Drop weight index
• Elastic properties

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Geotechnical block model
Each cell has parameters UCS, FF, RQD, Rock
type, IRMR, RMR, Q, PLI, Elastic properties,
Slope angle, Risk, BI, EF, DB cost/m3, DWTi
10m x 10m x 10m cells (for 10m benches)
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Outline

• Introduction to PPRust
• Geotechnical block modelling
• Model applications slope design
• Geotech Modeller product
• Future development

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Haines and Terbrugge slope design chart
Laubschers MRMR ? slope angle _at_ set FOS and
slope ht
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Slope optimisation

• Pit design overlaid on the block model filtered
  on slope angle compares data vs actual.
• Different slope heights must be considered.
• Structural control may be more NB than RMR
  results.

Vertical slice through model
Slope too flat
100m
Pit design
Model filtered on slope angle
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Sandsloot Risk - Reward design chart
WHITTLE 4D OPTIMIZATION
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Slope optimisation

• The geotechnical block model
• Highlights data deficient areas
• Allows for more localised slope design
• Gives an indication of unsafe areas
  over-designed slopes
• Gives an indication of possible economic gains -
  under- designed slopes
• Enables more accurate NPV calculations

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Outline

• Introduction to PPRust
• Geotechnical block modelling
• Model applications blast design
• Geotech Modeller product
• Future development

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Blast design at PPRust
1-2 Mt of rock are blasted each week in 10
blast blocks. Blast patterns are individually
designed for every blast block. The rock is
very hard and high powder factors are used to
achieve fragmentation targets. To reduce damage
to slopes, limit blasting practices are used.
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Blast optimisation
Blastability Index (Lilly 1986) simple rock mass
rating for blasting guys Kuz-Ram equation
(Cunningham 1990) calculate the mean fragment
size of a blast based on the rock mass properties
and the blast design (powder factor, stemming,
subdrill etc) Therefore if you know your BI and
target mean fragment sizes you can calculate the
ideal powder factor and thus better design your
blast pattern burden and spacing and predict
Drill and Blast costs.
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Plant requirements
Ideal fragmentation reduces crushing and milling
costs and improves mill throughput and recoveries.
Fines -150mm
Coarse 150mm
Fragmentation Target P50 150mm
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Loading requirements
Target Instantaneous Loading Rate 3200t/hr for
RH200 face shovels Target mean fragmentation
230mm based on analysis on 238 blasts
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Split fragmentation analysis
Blasted muckpile
Split Digital image
Photo
Split size distribution analysis
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Fragmentation Curves
Calibration of Design vs. Actual Fragmentation
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Block model used for blast optimisation
Geotech. zones parameters ? Blastability Index
(Lilly) BI target fragment sizes ? powder
factor (Cunninghams Kuz-Ram equation) Powder
factor ? blast pattern burden and spacing ?
Drill and Blast cost
AutoCAD menus
waste
ore
blast pattern
Model filtered on EF
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Blast design in AutoCAD
Blasters can now design the patterns based on
rock mass properties and available drill and
blast equipment.
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Model Evaluation, Planning Scheduling

• EVALUATE MINING BLOCKS
• AVERAGE INFORMATION FOR BLOCK
• BI 52
• MRMR 59
• EF ORE 1.26 kg/m3
• EF WASTE 0.96 kg/m3
• COST ORE R 4.30 / m3
• COST WASTE R 2.70 / m3
• SLOPE ANGLE 62 Degrees

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Drill bit selection based on UCS in block model
160 MPa
180 MPa
200 MPa
BLAST PATTERN
250 MPa
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Results Loading and Milling Performance
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Comparison of Crushing and Blasting Costs
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Summary Operational improvement process

• Characterise the Ore Body
• Define Customer requirements milling and
  loading targets
• Develop relationships between rock properties
  and blast results
• Optimise the Blast Performance
• Monitor Plant Performance
• Ensure the Initiative is Sustainable ? Geotech
  Modeller

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Outline

• Introduction to PPRust
• Geotechnical block modelling
• Model applications
• Geotech Modeller product
• Future development

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Outline

• Introduction to PPRust
• Geotechnical block modelling
• Model applications
• Geotech Modeller product
• Future development

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DATAMINE MULTI-PARAMETER MODELLING SOFTWARE
Phase 2
Phase 1a
Phase 1c
Phase 1b
Multi-Parametric Model for Planning and Mine
Optimisation
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Underground Applications - Sunrise Dam Gold Mine
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Underground Mine Design
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Future developments

• Rock testing results used for predicting mill
  throughputs.
• Include hydrological data in the models
• Economic evaluation done with all geology,
  geotech and mining data.
• Integrate SiroVision
• Underground application
• ? a multi-parametric model that integrates all
  information and maximises its usefulness!

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Questions?