the development of a new geometrical blast david la rosa ... · invent introduce the development of...

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introduce

The development of a new geometrical blast fragmentation model and its application to

Grade Engineering®

David La RosaPrincipal Mining EngineerCRC ORE

STEP-CHANGE INNOVATIONS THAT DELIVER WHOLE-OF-MINE VALUE

CRC ORE:A NEW APPROACH

OUR PARTICIPANTS

ResearchersMETSMINING

Taking a New View of Ore Deposit Heterogeneity

Sustaining Whole of System Value and Execution

Selecting Effective Coarse Separation Technologies

Mapping Economic Benefit Over Life of Mine

Grade Engineering®

CRC ORE 4

Novel coarse separation technologiesSeparating mineral from non-valuable rock at the earliest part of the process.

CRC ORE 5

Naturalgrade

deportmentby size

Induced deportment

through differential

blasting

Sensorbased bulk

sorting

Sensorbased stream sorting

Coarsegravity

separation

Five coarse separation levers of Grade Engineering®

NATURAL DEPORTMENT

CRC ORE 6

88% of the metal has deported into 36% of the mass(-19mm fraction)

INDUCING DEPORTMENT

The block below contains;200kt @ 0.68% Cu

Same block now contains;60kt @ 0.28% Cu

140kt @ 0.85% CuCOG = 0.40%

Process 200 kt for 1360 t of copper• Process 140 kt for 1190t of copper• Save costs processing 60 kt sub-economic material and free

up capacity in concentrator

Inducing deportment has the potential to increase head grade , save energy and optimise resource extraction

EXPLOITING INDUCED DEPORTMENT

INDUCED DEPORTMENT - EXAMPLE

April 2011

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INDUCED DEPORTMENT - EXAMPLE

Grade uplift of ~ 100%

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April 2011

MOTIVATION FOR A GE AWARE FRAGMENTATION MODEL

In a perfect world, perfectly bi-modal size distributions (low grade = coarse and high grade = fine) will maximise the potential of induced deportment, alas we don’t live in a perfect world.

Screen Size

EMPIRICAL MODELS AND LIMITATIONS

• Significant operational experience with Crushed Zone Model (better the devil you know!)

• BUT blast-centric (e.g. burden x spacing is consistent)

• For induced deportment evaluations, PSD and grade, on a hole by hole basis is necessary.

• This would allow rockmass characteristics to be considered spatially when modelling the response of the rock mass to blasting.

THE HYPOTHESIS

Can the Crushed Zone fragmentation model be further augmented by applying the radial cracks to the insitu rock mass structure?

BREAKAGE MECHANISMS

Rock mass characterised by:• UCS• T• Block Size (2D)• Fines size distribution• E• ν• P and S wave velocities

Explosives characterised by:• VOD• Blast hole diameter• Charge length

Fines created in the crushed zone

Radial cracks break existing in-situ structure for the coarse portion of the PSD

No allowance for timing

THE BREAKAGE ‘STAR’

Defined by:• n cracks• CZ Diameter• Crack extension• Tip angle (set at 2°)

Creates fines and breaks insitu structure (described by a 2D collection of polygons)

MODELLING FLOW

Create Holes

Load Holes

Create CZ and radial cracks

Overlay in-situ structure

Extend cracks

Break in-situ structure

Add fines and coarse fragments

Fit curves and report

Can be defined by:

• Actual hole location (preferred)• Burden x Spacing x rows x hole

per row

MODELLING FLOW

Create Holes

Load Holes

Create CZ and radial cracks

Overlay in-situ structure

Extend cracks

Break in-situ structure

Add fines and coarse fragments

Fit curves and report

Explosives per hole:

• VOD• Density• Length

• used to proportion breakage to the entire bench

• Calculate volume of fines

MODELLING FLOW

Create Holes

Load Holes

Create CZ and radial cracks

Overlay in-situ structure

Extend cracks

Break in-situ structure

Add fines and coarse fragments

Fit curves and report

Will be able to eventually use Geotechnical block model to adjust rock mass characteristics on a hole by hole basis.

MODELLING FLOW

Create Holes

Load Holes

Create CZ and radial cracks

Overlay in-situ structure

Extend cracks

Break in-situ structure

Add fines and coarse fragments

Fit curves and report

Can be:• Regular sized• Gaussian distribution in x and y

directions (defined by σ and sd)

MODELLING FLOW

Create Holes

Load Holes

Create CZ and radial cracks

Overlay in-situ structure

Extend cracks

Break in-situ structure

Add fines and coarse fragments

Fit curves and report

Extends crack tips to next boundary to preclude odd shaped particles.

MODELLING FLOW

Create Holes

Load Holes

Create CZ and radial cracks

Overlay in-situ structure

Extend cracks

Break in-situ structure

Add fines and coarse fragments

Fit curves and report

Fines

Unbroken block

Broken block

MODELLING FLOW

Create Holes

Load Holes

Create CZ and radial cracks

Overlay in-situ structure

Extend cracks

Break in-situ structure

Add fines and coarse fragments

Fit curves and report

Fines

Post blast blocks

In-situ blocks

MODELLING FLOW

Create Holes

Load Holes

Create CZ and radial cracks

Overlay in-situ structure

Extend cracks

Break in-situ structure

Add fines and coarse fragments

Fit curves and report

RR Fit

Swebrec fit

Raw PSD

CASE STUDIESParameter Case 1 Case 2 Case 3Orebody type Greenstone Gold Iron Oxide Copper Gold Copper PorphyryBench Height (m) 10 15 15Burden and Spacing (m) 3.5 x 4.5 5.7 x 6.5 9.5 x 10.5Sub-drill (m) 1.0 1.5 1.5Hole diameter (mm) 152 311 270Explosive Type Emulsion Emulsion EmulsionExplosive Length (m) 7.5 11.5 9.5Explosive Density (kg/m3) 1200 1250 1000VOD (m/s) 5000 5200 3700

Parameter Case 1 Case 2 Case 3UCS (MPa) 170 240 24T (MPa)* 17 20 2.4E (GPa)* 84 40 31Vp (m/s) 5000* 6731 5000*Rock Density (kg/m3) 2700 3700 2700Poisson's Ratio* 0.25 0.25 0.25Gamma* 3 3 3Pressure decay factor* -1.5 -1.5 -1.5In-situ block size 0.3 +/- 0.3 0.89 +/- 0.25 0.2 +/- 0.2Fines x50 5 5 5Fines n 0.7 0.7 0.7Crushed zone diameter (m) 1 2.2 3.2Number of cracks 7 10 14Crack extension (m) 1.7 3.2 4.4

Blast Design

Rock mass

CASE STUDY RESULTS

Adjusted parameters

In-situ structure - mean was obtained from the top-size of the available image analysis PSD, with adjustment to the SD

Fines Distribution – same for all three cases, P50 ~ 5mm

CASE 3 HISTOGRAM

In-situ blocks

CZ

The main drivers for the final distribution are the fines generated around the blast hole and the breakage of the in-situ rock mass structure.

APPLICATION IN THE GE® CONTEXT

• Limitation of CZM is that it results in a blast wide PSD

• Concept of the Roxel (sure there are other names for it but this is what I use)

• Automates the calculation of the volume of rock around each blast hole.

Finer High Grade Roxel

Coarser Low Grade Roxel

A SIMPLE EXAMPLE

0.09% 0.59%

0.29%Parameter Value

Processing Cost $12.26 $/t

Recovery 87.7%

Sale Price 6000 $/t

$527,401

Parameter Value

Processing Cost $12.26 $/t

GE® Cost $0.30 $/t

Recovery 87.7%

Sale Price 6000 $/t

$588,231 (+11.5%)

-90mm

+90mm(leach or waste)

0.28% CuHELE

Traditional Mining

Exploiting Induced Deportment

@ -31.9% feed tonnes+15.4% feed grade

Profit

FUTURE WORK and CONCLUSIONS

Future Work• More validations• Block model integration to assign hardness

and grade characteristics to each roxels worth of broken rock,

• Deterministic calculation of fines distribution from comminution parameters (Dwi, Axb)

• Incorporate inter-hole timing (?)

Summary• The hypothesis that this model was founded on appears to have some validity based on the

assumptions and data presented in this paper.

invent

introduce

Thank you!