rubio ubc-fundamentals and design

8/21/2019 RUBIO UBC-Fundamentals and Design

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Slide 1

Design and Planning of

Block Caving OperationsEnrique Rubio, PhD

July 2006


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Slide 2

Outline

Introduction

Geotechnical Characterization

Block Cave Fundamentals

Caveability

Fragmentation

Stresses

Flow

Mine Design

Mine Planning


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Slide 3

Workshop Scheme

9:00-10:30 Lectures

10:30-10:45 Coffee Break

10:45-12:15 Lectures

12:15-13:00 Lunch

13:00-14:30 Design Examples

14:30-14:45 Coffee Break

14:45-16:15 Design Examples 16:15-16:30 Closing

16:30-18:00 Personal Readings


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Slide 4

Introduction


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Slide 5

Mining Methods

Open ( usually partially extracted)

Supported

Caving

Surface mining


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Slide 6

Pillar SupportedArtificiallySupported

Caving

Room and PilarSublevel and

Longholestoping

Bench and Fillstoping

Cut and FillStoping

ShrinkageStoping

VCRStoping

LonwallMining

SublevelCaving

BlockCaving

Increases Displacements

Increases stresses on the abutment areas

Underground Mining Methods


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Evolution of daily production rates atselected large underground mines

0

20000

40000

60000

80000

100000

120000

140000

160000

1880 1900 1920 1940 1960 1980 2000 2020 2040YEAR

TONNESPERDAY

Bingham Canyon

Climax

Salvador

Kiruna

Mount Isa

San Manuel

El Teniente

MiamiRidgeway

Emergenceofmodernmining

geomechanics.Foundingof

ISRM

International

CavingStudy

ImperialCollege

underground

excavationsproject

Olympic Dam

Andina

Freeport IOZ/DOZ

Henderson

Malmberget

Palabora

PremierKidd Creek

Brown (2004)


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Evolution of maximum mining depth forselected mines

YEAR

0

500

1000

1500

2000

2500

3000

3500

1880 1900 1920 1940 1960 1980 2000 2020 2040

DEPTH(m)

Mount Isa

AndinaRidgeway

Palabora

Kidd Creek

Bingham Canyon

Freeport (DOZ)Kiruna

Olympic Dam

Emergenceofmodernmining

geomechanics.Foundingof

ISRM In

ternational

CavingStudy

ImperialCollege

underground

excavationsproject

El Teniente

Henderson

Salvador

Brown (2004)


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Caving Mining

Cave mining refers to allmining operations in whichthe ore body cavesnaturally after undercutting

the base. The cavedmaterial is recovered usingdraw points. (Laubscher,1994)


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Caving Mining System

Caving

Undercut Drilling

Undercut Level

Production Level

Haulage Level

Ventilation Level

2ndHaulage

Crusher

Tipping point

Draw Point

Secondary Breakage

Ore Passes

Feeder

GrizzlyConveyor


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Panel Caving, De Wolf 1981


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Free Caving Methods

Block caving mostcommon method

Lowest working cost pertonne

Long ramp-in periods

High up-front capital

Pit or Hybrid gearing

91m lowest block height Cave de-stressing


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Facts About Block Caving

Used by many of the worlds largest undergroundmines

High production: 12,000 to 48,000 tpd

Lowest mining costs per ton of any undergroundmining method

Excellent productivity per person and per unit ofequipment once developed

Suitable for automationLow degree of selectivity

It requires skilled working force


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Characteristics

Production rates 12000 a 48000 tpd

Dilution 20%

Mining Recovery 75% Cost 2.1-5$/t


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Ore Bodies Suitable to Use BlockCaving

Geology: Pipes, Porphyry, massive mineralization

Geometry: ore bodies that could sustain a large openfootprint

Rock Mass: weak enough to initiate caving and strongenough to maintain the production crown pillar stable(4A-2B, Laubscher 1990)

Structural patterns to orient sequence and propagatecaving to surface

Jointing is desired to produce fine fragmentation Low grade variability, to avoid selective draw


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Slide 16

Why is Block Caving relevant?

El Salvador

Andina

El Teniente

Bingham

Canyon

Chuquicamata

Freeport_DOZ

RTZ_Argyle

De Beers-Finsch

RTZ_Northparkes

Philex_Padcal

RTZ_PalaboraDe Beers-

Premier

IVANHOE

New Mines

Mines in operations 2003

Henderson


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Slide 17

Chuquicamata, Chile


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Slide 18

Bingham Canyon, US


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Slide 19

Highland Valley

Copper,Canada


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Slide 20

A Few Examples

Mina Pais Layout Produccin (Mt) Productos

El Teniente Chile LHD/Parrillas 54 Cobre

El Salvador Chile LHD 10 Cobre

Andina Chile LHD/Parrillas 16 Cobre

Henderson USA LHD 5.4 MolibdenoBell Canada LHD 0.9 Asbestos

Premier Sudfrica LHD 3 Diamantes

Shabanie Zimbawe LHD 1.3 Cobre

Philex Filipinas LHD/Parrillas 10 Cobre

Lutopan Filipinas Parrillas 9.4 CobreFreeport Indonesia LHD 18 Cobre/Oro

Northparkes Australia LHD 3.9 Cobre/Oro


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Slide 21

Costing

September 2004 CIM Bulletin S.FUENTES S. and J. CCERES S.


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Slide 22

Production Rates for DifferentMines around the World

-

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1 11 21 31 41 51 61 71 81 91 101 111 121 131

Period

Tons/mont

h

RU Palabora RU DOZ RU Esmeralda RU Padcal RU_ RN RU_ICW RU_IN RU_3pLHD


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Slide 23

Block Cave Operating Costs

1.5

2

2.5

3

3.5

4

0 20 40 60 80 100 120 140

Mining Rate (Ktpd)

OperatingCost($/t)


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Slide 24

Block Cave Operating Costs

Extraction costs Pre undercutting caving 1-1.2 $/t

Advanced undercutting 2-2.4 $/t

Traditional undercutting 1.4-1.9 $/t

Loading and Haulage costs 0.3-1.0 $/t trains and trucks

Hauling

0.5-1 $/t automatic trains


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Slide 25

Component of Operating Costs

Labor 49%

Supplies 23%

Third parties services 26% Others 2%


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Slide 26

Management Costs

Maintenance

Suppliers

Service equipment Services to people

Administration

The overall management cost adds up50% of the operating costs


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Slide 27

Development Costs ($/m2)

Layout Hc CC $/m2

Tte 8 350 1.324324 1251

Pilar 2021 280 0.935897 708

Andesita 300 0.677419 549Dacita 250.00 0.289855 196

Pipa 17x20 200.00 1.904762 1029

Diablo 17x15 300.00 1.354167 1097

Andina_LHD 13x13.5 350.00 0.878613 830

Andina_grizzly 8.5x8.5 280 1.205128 911


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Slide 28

Development Costs Trend

y = 1.2791x - 21.026

R2= 0.8796

0

100

200

300

400

500

600

0 50 100 150 200 250 300 350 400

Reserves (Mt)

CapitalCo

st(M$)


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Slide 29

Rock Mass Characterization

for Block Caving


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Slide 30

Rock Mass Properties Affecting theMine Planning Process

Ore Body

Cavability Fragmentation

Mining Sequence

Gravity Flow Dilution

Stresses

Undercut Design

Draw Control

Draw rate, Uniformity, etc

Layout Design

Draw Height


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Slide 31

Parameters to be Considered

Intact properties

Rock mass

Structures

Hydrogeology

Stresses

Induced stresses by blasting

Topography

Geological models


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Slide 36

Full geotechnical log

RQD

Hardness

Number of joints/ joint spacing

Small/ large scale condition

Joint infilling

Alteration

Data can be turned into ratings


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Slide 37

Rock Mass Classification Use 3 rating systems

MRMR

- Support design

- Draw point spacing

- Cavability

- Glory hole definition

- Rock mass strength estimates (DRMS values)

Bartons Q

- ore pass stability assessment (Stacey 2001)

- check support design, shotcrete thickness

- Decline/ shaft support through soft near surface rocks RMR/GSI

- Modeling input parameters


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Slide 38

MRMR: Modified Rock MassRating (Laubsher, 1977, 1984)

RMR(1976) and includes :

In situ and induced stresses

Blasting effects

Weathering of exposed rock masses

RMR was originally modified to be appliedin caving mining


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Slide 39

IRMR Laubscher Lakubec (2000)


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Slide 40

GSI, Hoek 1995


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Slide 41

RQD

Concern of different measurement methods

3 main methods of RQD measurement

25% RQD error results in a 4 rating point error in RMR

52% RQD error results in an 6 rating point error in the RMR

Changes the caving Hydraulic Radius by 3 to 6m RQD may not be the problem ?


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Slide 42

MRMR SYSTEM Critical points are the adjustments

Adjustments make the rock mass worse or better

Total worse case adjustment to rating is downgrade by 50%

Eg MRMR = 25 for RMR of 50

Therefore when the cave is being developed does weathering.

Stress, blasting and joint orientation have a +/- effect on the rockmass

-An adjustment of 1 or 100 has no effect

-Joint orientation and stress hardest adjustments to apply

-A stress or joint adjustment of 85% means veryeffects

-120% stress adjustment has a confining effect on the rock mass-Major error to use caving adjustments for support design


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Slide 43

BC geotech issues

2 CAVE TYPESHARD CAVES (MRMR >45, 1000m depth K ratio 1-2)

Cave stall

Fragmentation

Rock/strain bursting

SOFT CAVES (MRMR 35


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Slide 44

Fundamentals


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Slide 45

Method Fundamentals

Caveability

Fragmentation

Flow Stresses


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Slide 46

Caveability

Often caveability measures the capacity ofan ore body to be caved

A few important aspects of caveability

Would it cave?

Hydraulic radius to induce caving

Caving rate (m/day)

Cave ratio, cave propagation


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Slide 47

Undercutting aims

AIMSWhat are we trying to do?

Extract a void to allow caving to occur

Initiate caving with minimum stressdamage

Propagate the cave to reduce undercutabutment stresses


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Slide 48

State of Caving

Stress Caving, is thestate at which cavingpropagates towardssurface, shear failure

Subsidence Caving,when caving breaksthrough surface,tension cracks onsurface

Flores, et al 2004


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Slide 49

Idealized Caving Model (after Voegele et al1978)


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Slide 50

Cave PropagationInitial cut defines a beam and thefailure process begins with

tension failure at the back of thecave

Cave back starts to shapeconcave due to shear failure

at the back

The deformation area increases atheight and the seismic activitydecreases

Flores et al(2004b)

C bilit Ch t (L b h 1988 d


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Slide 51

Caveability Chart (Laubscher 1988 andBartlett 1998)


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Slide 52

Caveability Chart Including El TenienteObservations

0 10 20 30 40 50 60 70 800

10

20

30

40

50

60

70

80

90

100

MiningRockMassRating,

MRMR

Hydraulic radius of the undercut area, HR(m)

Caving zone

Stable zone

INCA OESTE SECTOR

NORTHPARKES

Applying Stability Chart to Estimate Caveability


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Slide 53

Applying Stability Chart to Estimate Caveability(Mawdesley et al2001)


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Slide 54

Caveability Using Numerical Models


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Slide 55

Cave Rock Volume for Different states ofthe Hydraulic Radius (ICS, 2000)

Cave rate changes ascaving propagates tosurface


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Slide 56

Measuring Cave Propagation Using TDRsat DOZ (T. Szwedzicki, 2004)

C


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Slide 57

Measuring Cave Propagation Using TDRsat DOZ (T. Szwedzicki, 2004)

Cave rate changes fordifferent rock types for marble 0.25 to

1.10 m per day for magnetite skarn

0.15 to 0.95 m perday for forterite skarn

0.08 to 0.30 m perday.

Also cave rate changesat different depths

Caving propagation factor (CPF)


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Slide 58

Caving propagation factor (CPF)(Flores, 2003)

Stress over strength

(Flores et al2004b)

Estimating Major Stresses using


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Slide 59

HP

HC

hC

B

K

=

=

=

=

=

400 m

500 m

150 m

100 m

1.5

S1

HP

HC

hC

B

K

=

=

=

=

=

400 m

500 m

150 m

100 m

1.5

HP

HC

hC

B

K

=

=

=

=

=

400 m

500 m

150 m

100 m

1.5

S1

Estimating Major Stresses usingNumerical Modeling


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Slide 60

CPF for a given rock mass

CPF f Diff t R k M


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Slide 61

CPF for Different Rock Masses

Back analysis of Inca Oeste Caveability


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Slide 62

Back analysis of Inca Oeste Caveabilityusing CPF (Flores et al2004b)

Block Height and Footprint width for Caving


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Slide 63

FOOTPRINT WIDTH (m)

Flores et al(2004a)

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800

0

50

100

150

200

250

300

350

400

450

500

BLOC

K

HEIG

HT

(m)

H=2B H=B

Difficultconnectio

n tosurface

Connection to

surface

Easyconnectio

n tosurface

Block Height and Footprint width for CavingPropagation (Flores, et al 2004)


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Slide 64

CAVING INITIATION CAVING WITHOUT CONNECTIONCAVING WITHOUT CONNECTION

CONNECTION TO THE PITBOTTOM

TRANSITIONAL CAVING STEADY-STATE CAVING

(Flores & Karzulovic 2003b)

Caving Connecting to an Open Pit

Based on modeling

It shows slidingfailure of the pit

Two cases Palaboraand Northparkes thepit failures have beenrather toppling thansliding


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Slide 65

Summary Caveability

Caveability affects productivity since it definesthe hydraulic radius of a block and the sequenceat which they need to be undercut

Draw rate must be lower than cave rate Caving performance will affect the formation of

stable arcs

Depending on the cave propagation there couldbe point stresses at the edges of the layout


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Slide 66

Fragmentation

The Relevance of Fragmentation in


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Slide 67

The Relevance of Fragmentation inBlock Caving

Equipment selection and Ore HandlingStrategy

Productivity by affecting the oversize and

hang up frequency

Ultimate defines the utilization of the orebody

The Relevance of Fragmentation in


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Slide 68

The Relevance of Fragmentation inBlock Caving

Defines the draw point spacing to achieveinteraction

Mixing and dilution entry

F t ti


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Slide 69

Fragmentation

Primary fragmentation

Secondary

fragmentation/

material flow and

friction

Primary fragmentation

Fragmentation at Premier SouthAfrica


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Slide 70

g(after Butcher 2002a)

Block Volume Estimation to Asses


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Slide 71

Block Volume Estimation to AssesFragmentation (Cai et al2004)

Block Volume


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Slide 72

Fragmentation at Esmeralda , El Teniente


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Slide 73

Fragmentation input data

Primary- Mean dip/ dip direction

- Spacing statistics

- Rock mass strength

- Dip/ direction of the cave face

- General stress regime

Secondary- Aspect ratio

- Rate of draw

- Cushing/ fines

- Cave height and muck pile pressure

Main Components of Rock Mass


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Slide 74

Main Components of Rock MassFragmentation Assesments

Joint setting

Blocks

Fractures within the blocks

Draw rates

Particle size reduction through draw

Height of draw General caving performance


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Slide 75

Fragmentation Determination

Empirical tables (Laubscher 2000)- Primary

- Secondary

- effects

BCF (Esterhuizen 1994)

- Primary secondary- Secondary

- Draw rates and hang-up frequency

CHASM (Butcher 2000)

- Primary fragmentation- Visualization tool

JKFrag ( Harries 2001)

-Primary-Rigorous tool


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Slide 76

Fragmentation (Laubscher, 1994)


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Slide 77

BCF Fragmentation Software


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Slide 78

Fragmentation (BCF)

F t ti f Diff t St I d


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Slide 79

Fragmentation for Different Stress Index(Eadie 2003)

In si tu


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Slide 80

El Teniente method (Blondel et al1995)

Geotechnical characterisation (structural domaindefinition, set definition, orientation and spacingstatistics, rock strengths, rock mass classifications)

Establish stresses in the confinement zone ahead ofcaving

Determine anisotropy indices for the structural domains

Establish the geometry of the natural unit block (on thebasis of three orthogonal discontinuity sets)


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Slide 81

El Teniente method continue..(Blondel et al1995)

Generate a statistical distribution of blockvolumes produced by primary fragmentation(before further fracturing)

Measure fragmentation at draw pointsexcluding fine material and construct particlesize distribution curve

Compare predicted and measured results

Validation of El Teniente method (Blondel et al 1995)


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Slide 82

Validation of El Teniente method (Blondel et al1995)

+

+

+

+

++

+

++

Structural Domain 1

Cumulativ

e%

Volume (m3)

Sets 1-3-4

MeasuredTotal

Sets 2A-3-4

MeasuredPartial

Set 3 and drift mapping

MeasuredMetallica Consulting

+

W ld F i C


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Slide 83

World Fragmentation Curves

Comparison of primary fragmentation from different deposits around the world

0

20

40

60

80

100

0.001 0.01 0.1 1 10 100 1000

Block Volume (m3)

CumulativeVolum

ePercentLessThan

GRSBC

Kucing Liar

DOZ Fos-MagDOZ Diorite

Palabora Less Fractured

Palabora Well Fragmented

Bingham Coarse

Bingham Fine

Argyle

MLZ Overall

Annavarapu S, Un-Published

Evolution of Fragmentation as


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Slide 84

Evolution of Fragmentation asDraw Points Mature at DOZ

Fragmentation within different HOD's

0

20

40

60

80

100

0.001 0.01 0.1 1 10

Volume (m3)

Summary%cum

ulativ

hod 0-50 m_Skarns

hod 50-100 m_Skarns

hod 100-150m_Skarns

hod 150-200 m_Skarns

hod >200 m_Skarns

Annavarapu S, Un-Published

E i l i


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Slide 85

Equipment selection

> 2 or 3m3: >2m3(4.6m3LHD bucket- 1400E)

>3m3(6.4m3LHD bucket-0010)

Primary Frag >2m3

=40% Secondary Frag >2m3=15%

There is a considerable size reduction as material

draws down

F t i P l b S df i


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Slide 86

Fragmentacin, Palabora Sudfrica

F t ti Aff ti P d ti


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Slide 87

Fragmentation Affecting Production

Hang Ups Observations at


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Slide 88

Hang Ups Observations atPalabora

Hang Up Freq at Different dpts Maturity

Hang Up Freq dpt productivity

S d B k


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Slide 89

Secondary Breakage

Bock caves are like red wineolder better

Coarse rock start at cave

A few large rocks manyproblems

Rock removal is an art Hard caves at beginning is

critical

Effects production by 30%planned

25% total project cost blowout

Skill training seen as criticalfrom start


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Slide 90

Movie


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Slide 91

Gravity Flow in Block Caving

G it Fl M d l


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Slide 92

Gravity Flow Models

Just a representation

We use empirical models when there are nofundamental models to explain the un derlying

behaviour Scientific method may help to construct robust

models

Observation

Formulation

Calibration and validation

YENGE 1980


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Slide 93

YENGE 1980

Broken rock flow behaviour can notbe satisfactory explained by theories

developed to describe the flow ofother materials such as grains andsand

I t d ti


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Slide 94

Introduction

Sand boxexperiments Kvapil1961-1982

There is a zone of

movementcharacterized by anellipsoid shape

The geometry of the

ellipsoid of movementis a function of theextraction

Different Theories


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Slide 95

Different Theories

How the broken ground is drawn/ flows Draw point spacings to reduce dilution/

increase recovery

Still not well understood

Physical models/ bunkers- Kvapli & Jenike1960s

Mathematic/ numerical plastic flowPariseau1960s

Full scale marker testsKvapli , Just &Janelid 1960s

Physical models Laubscher, Taylor etc -1970-1980s

Kvapil curves revisited/ Laubscher- Bull &

Page 1998-2000 ICS 2001-present

Physical models

PFC

Ring marker trials

Apparent Density and Draw


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Slide 96

Apparent Density and Draw

Low density areaBehringer R P, Baxter W, 1994. Pattern

Formation and Complexity in Granular Flows

A low density area is formed as a result of drawingdown broken material from a draw point

Geometrical Parameters to


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Slide 97

Describe the Zone of Movement

The ellipsoid of movementdelineates the area that isbroken to the in situ rock

The ellipsoid of extraction isthe one that represents the

extracted ore

The relation between theellipsoid heights is 1:2.5

The relationship between thevolumes is 1:15

Draw cone representation (Kvapil 1980)

Fragmentation and the Geometry


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Slide 98

g yof the Ellipsoids

The eccentricity is afunction of thefragmentation

The coarser thefragmentation thewider the ellipsoid ofmovement

n

nn

a

ba 5.022 )( Draw cone representation (Kvapil 1980)

Example


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Slide 99

Example

Excentricidad 0.98

Hn 200

bn 19.9

bg 48.7 5.0215.1 ng hb

20 m

49 m

5.02 )1(2

n

n

hb

200 m

Isolated Draw Diameter


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Slide 100

Isolated Draw Diameter

The volume of materialmoving is a function ofdraw

Dta: Isolated draw

diameter (Kvapil, 1962) Fragmentation

Fragmentation variance

Friction angle

Others: water, inducedstresses

Low Density

Movement Zone

g

Draw

Dta

Isolated Draw Diameter (Laubscher,


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Slide 101

(1994)

Isolated Draw Diameter from Sand


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Slide 102

Isolated draw

diameter (Dta)

Draw Point Spacing

(Dpe)

Box

Fragmentation and Isolated Draw


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Slide 103

gDiameter

Draw cone width and particle size relationship(Richardson, 1981)

Areas del Elipsoide de Extraccin


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Slide 104

Areas del Elipsoide de Extraccin

Plastic failure zone, largedeformations

Summary


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Slide 105

Summary

2 zones- Ellipsoid of extraction

- Ellipsoid of movement

Moving rock

- continues draw zone- zone of plastic failure due to induced shear stress

Within the ellipsoid

- Material moves faster at the center of the ellipsoid

- Fine material produces thin ellipsoids- Coarse broken rock produces wide ellipsoids

- The ellipsoid geometry depends also on the size of the dischargehole


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Slide 106

Principles of Draw Theory

Gravity Flow More than one Draw


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Slide 107

Point

Apparent densitygradient

Source of energy to

take the system to alower level of disorder

Particles move toreach a balance

within the muck pile

Flores, 2004. Different Stages of Cavepropagation. Massmin 2004

Apparent Density


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Slide 108

Apparent Density

Density adjusted byvoid ratio

As void ratio

increases apparentdensity decreases

POPOV K,2003. J.Serb.Chem.Soc.68(11)903907(2003)

Apparent Density Gradient


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Slide 109

Apparent Density Gradient

A function of Fragmentation and its

variance within the muckpile

Draw point spacing

Draw performance amongneighbored dpts

Finally the shape of themovement will dependstrongly on the material

angle of friction Behringer R P, Baxter W, 1994. PatternFormation and Complexity in Granular Flows

Fragmentation and Flow


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Slide 110


The variance offragmentation along thedraw column reduces thevoid ratio, increasing the

apparent density of themix

Then differentfragmentation curveswould induce differentdensities within the muckpile

Barker G C, 1994. ComputerSimulation of Granular Materials



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Slide 111


Binary mix between twosphere size

X, % of smaller particlesin the mix

Y, sphere packing volumeused by the mix

Then the mix of differentfragmentations would

affect the particlespacking, thus theapparent density Barker G C, 1994. ComputerSimulation of Granular Materials

Primary and Secondary


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Slide 112

Fragmentation BCF

Draw Point Spacing and Flow


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Slide 113

Draw Point Spacing and Flow

The gradient ofapparent densitywithin the muck pileincreases as drawpoint are spacedwider apart

Draw and Flow


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Slide 114

Draw and Flow

Draw performance The uniformity at which

drawing is performed betweena dpt and its neighbors isrelevant to define the zone of

low density The more even draw is

performed the higher would bethe changes to erode thepillars between low density

zones produce by the isolateddraw diameter

Friction Interfaces

Friction Interfaces

Plan view of different Dta of a dpt

and neighbors

Tonnagedrawn

Draw Performance and Flow


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Slide 115

Draw Performance and Flow

PFC2D 2.00

Itasca Consulting Group, Inc. MinneapMinneapolis, Minnesota USA

ob Title: Idealized

Step 28000 18:11:01 Wed Jun 9 2004

View Size:X: -1.749e+002 7.425e+001Y: -6.253e+001 2.132e+002

Ball

Contact

Displacement Maximum = 7.474e+001 Linestyle

Wall

PFC2D 2.00

Itasca Consulting Group, Inc. MinneapMinneapolis, Minnesota USA

ob Title: Idealized

iew Title: consolidation stateStep 28000 23:04:48 Wed Jun 9 2004

View Size: X: -1.803e+002 7.983e+001 Y: -6.253e+001 2.129e+002

Ball

Contact

DisplacementMaximum = 7.242e+001 Linestyle

Wall

Even Draw Isolated Draw

Isolated draw behaviour tends to produce a high density areasurrounding movement zones which induces high hang upsfrequency

Rubio E et al, 2004. Massmin2004


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Slide 116

Interactive Draw Theory for

Block/Panel Caving

Interactive Draw Theory


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Slide 117


If draw point spacing is wider than theisolated draw diameter would it beinteraction between draw points?

Isolated draw

diameter (Dta)

Draw Point Spacing

(Dpe)

?



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Slide 118


It is relevant to understand the concept ofinteraction since it allows to define whether themethod is suitable for hard rock masses

If draw points can be spaced wider there arecost benefits as well as the possibility of usinglarger equipment

Larger equipment improves productivity

Interactive Draw Experiments (HeslopL b h 1982)


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Slide 119

Laubscher, 1982)

Uneven Draw Exper iments

Wide spaced (216mm), Dpe/Dta=2.2 draw points,showing no interaction

Close spaced draw points (108mm), Dpe/Dta=1.1,showing no interaction

Interactive Draw Experiments(H l L b h 1982)


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Slide 120

(Heslop Laubscher, 1982)

Even Draw Exper iments

Wide spaced draw points (158 mm), Dpe/Dta=1.5showing little interaction

Close spaced draw points (108mm), Dpe/Dta=1.1showing full interaction

Draw Point Spacing


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Slide 121

Draw Point Spacing

1,5 times the isolated draw diameter seems tobe the draw point spacing limit to achieveinteraction, this assumes perfect even draw

Isolated draw can jeopardize the mine design byintroducing dilution channeling

If draw is controlled and managed the draw pointspacing can go upto 1.5 accepting a dilution

entry of 60% and overall dilution of about 20%.

Height of Interaction Zone


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Slide 122

Height of Interaction Zone

For a given densitygradient within themuck pile

An energy buffer isneeded to equilibratethe system

Height of interaction

(HIZ)

HIZ

a

(Duplancic & Brady1999)

Height of Interaction Zone (HIZ)


119/254

Slide 123

Height of Interaction Zone (HIZ)

The HIZ is a mainlya function of

Draw point spacing Fragmentation

Variability offragmentation withinthe mining block

Spacing between drawpoints

HIZ

HIZ from ffm model


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Slide 124

HIZ from ffm model

Dilution ffm rating

1230 22

Average = 12

OreDivided into three

ffm rating zones

Rule of thumb

How to get ffm rating from RMRLFfm rating=RMRL*0.4

Laubschers RMR 1989

HIZ Estimation (Courtesy Dennis Laubscher)


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Slide 125

HIZ Estimation (Courtesy Dennis Laubscher)

ff/m

Schematic illustration of granular flow paths for(a) an isolated drawpoint, and (b) several drawpoints worked


122/254

Slide 126

concurrently (Laubscher 2000)

Schematic illustration of the void diffusion mechanismfor (a) an isolated drawpoint, and (b) several drawpoints


123/254

Slide 127

operating concurrently (Laubscher 2000)

Modelo de Laubscher, 1994


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Slide 128

Modelo de Laubscher, 1994

Another version of HIZ chart in which the RMR is the main geotech parameter. It has been foundthat the ff/m rating chart fits better the observations made in Chile

Draw Control Factor (dcf)


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Slide 129

a Co o ac o (dc ) Dcf is a measure of

differential draw between a

drawpoint and its

neighbors

It should be computed in amonthly or weekly bases

Dilution will be postpone

by performing as high DCFdcf

Coeficient of varitation of tonnage

between a draw point and its neighbours

1.0

0.3

1.0 3.0 5.0 7.0 11.09.0

0.75

0.5

Buen control Mal control

Drawpoint

Neighbours

Percentage of Dilution Entry


126/254

Slide 130

g y

PDE is the percentage of orecolumn draw at which dilution

is seen at the dpt.

HIZ is an indicator of the

amount of mixing within the

draw column. Therefore

affects the PDE

PDE is highly influenced bydifferential draw

HIZ

Waste

Hc

Estimation of Percentage ofDil ti E t (PDE)


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Slide 131

Dilution Entry (PDE)

The percentage ofdilution entry iscomputed as follows

Where Hc is the height of the

draw column

HIZ is the height ofinteraction zone

dcf is the draw controlfactor

S is the swell factor

c

c

H

dcfsHIZH

PDE *

Mixing with Volumetric Algorithm, (Heslop andLaubscher 1982)


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Slide 132

Laubscher 1982)

Se define el % deentrada de la dilucin(PDE)

El PDE es el % de

extraccin de columna insitu al cual se observamaterial diluyente

c

c

H

sdcfHIZHPDE

)*(

PDE Diluyente

Mineral

Hc

Hc

Mineral

Diluyente

PDE

cH

HIZ

dcf

s

Porcentaje de entrada de la dilucin

Altura de columna

Altura de interaccin

Factor de control de tiraje

Factor de esponjamiento

Volumetric Algorithm


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Slide 133

g

Depending on COGthe column heightmined could beshorter or larger than

the Hc

The mixing simulatesthe grade of the draw

point affected by thegravity flow process

PDE Diluyente

Mineral

Hc

Examples Volumetric Algorithm


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Slide 134

g

-

0.20

0.40

0.60

0.80

1.00

1.20

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

Altura Columna (m)

%Cu

In Situ

Mezclada

PDE=45%

-

0.20

0.40

0.60

0.80

1.00

1.20

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

Altura Columna (m)

%Cu

In Situ

Mezclada

PDE=80%

Denis Laubscher s Model Using

Multiple Iterations


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Slide 135

Multiple Iterations

1 0

98

7 3 + 2 *# Ite = 5

6 # Ite = 1

5

4 3 2 3 4 5

3

2

1

1

2

3

4

5

6

7

8

9

1 0

1 0

98

7

6

5 3 + 2 *# Ite = 10

4 # Ite = 4

3 3 2 3 4 5 6 7 8 9 1 0

2

1

1

2

3

4

5

6

7

8

9

1 0

10

9

8

7

6

5

4

3

2

1Ba

BiBa+2#Ite=Bi

Traditional Laubscher

Algorithm

PDE PDE

Volumetric Algorithm with MultipleIterations


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Slide 136

Iterations

-

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1.10

010

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

Altura de Columna (m)

%C

u

Laubs 1 Laubs 2 In Situ %Cu Laubs 3

PDE=65%

Issues with the VolumetricAlgorithm


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Slide 137

Algorithm

It does not explicitly integrates the drawcolumn fragmentation and its evolution asdraw point matures

It does not allow to modify HIZ along thedraw column

It works for 1 iteration for multi iterations

results have not been calibrated

PC-BC Mixing Model (Diering, 2000)


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Slide 138

Mixing Horizon

It is based on mixing fractions When a block is depleted

mixing progresses up to theMH

The model repeats the processsimulating the depletion of theentire column

)*( sdcfHIZUCLMH

UCL Undercut level elevation

HIZ

dcf

s

Heoght of interaction

Draw control factor

Swell factor

Hc

MH

0.1

0.2

Mixing in PC-BC (Premix)


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Slide 139

0

0.2

0.4

0.6

0.8

1

1.2

200

180

160

140

120

10080604020


%Cu

InSitu

Mezclada100

50

0.2

0.3

Grade profile changes

considerable betweenthe scenarios withand without mixing

PC-BC Multiple Iterations


136/254

Slide 140

p

0

0.2

0.4

0.6

0.8

1

1.2

2019181716151413121110987654321

Banco

Ley(0.2-0.1)

1ite 2ite 3ite 4ite 5ite InSitu

Hc

MH

#Ite

#Ite

PC-BC Calibration and LaubscherPDE


137/254

Slide 141

PDE

0

0 .2

0 .4

0 .6

0 .8

1

1 .2

1 .4

1 .6

0 5 1 0 1 5 2 0 2 5

# Ite

HIZ/OreColumn-Height

P DE 5% -12 %

P DE 64 % -73 %

P DE 48 % -62 %

P DE 28 % -40 %

P DE 16 % -27 %

P DE 73 % -85%

PC-BC and Fragmentation


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Slide 142

Mixing fractions as afunction of theamount of fines withinthe draw column

Vertical flow is fasterfor fine material thancoarse

Coarse Fines

0.1

0.1 0.2

0

Examples Different Fragmentations


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Slide 143

0.3

0.3

Coarse Fines

0.03

0.07 0.06

0

0.5

0.5

Coarse Fines

0.05

0.05 0.1

0

Coarse contribution 0.07Fines contribution 0.09

30% Fines 50% Fines

Coarse contribution 0.05Fines contribution 0.15

PC-BC Sequential Mixing


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Slide 144

Mixing is performedas material is drawnfrom the dtps

The shared

component of thedraw column movesdown as function ofthe draw performance

Further calibration isneeded

Hc

MH

#Ite

Seqeuntial Mixing for Different MHs


141/254

Slide 145

0

0.2

0.4

0.6

0.8

1

1.2

200

180

160

140

120

10080604020


%Cu

InSitu

Mezclada

0

0.2

0.4

0.6

0.8

1

1.2

200

180

160

140

120

10080604020


%Cu

InSitu

Mezclada

Mixing fractions for coarse and fines 0.3 y 0.2

MH=50 MH=100

Issues with PC-BC


142/254

Slide 146

Fixed mixing fractions HIZ constant along draw column

Mixes the whole column on premix mode

Celular Automaton MixingAlgorithm


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Slide 147

Algorithm

It mixes for a givendepletion treshold dt If dt>

1. The depletion volume isreplaced with theneighbored dpts in the

proportion shown in amixing fraction matrix2. If the neighbors are

depleted dt then themethod is recursive onthis block

It is extremely efficientto simulate differentmatrixes mixing fraction

0.1

0.05 0.15 0.05

0.2 0.3 0.15

Celular Automaton Mixing Models


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Slide 148

Very easy to use They require a PFC model first to compute the

mixing fractions for different geotech domains

Fine diffusion models can be fast simulatedusing the celular models

Volumetric algorithm is the first celularautomaton model

Henderson mine showed an interestingapplication of matrix mixing fractions in 2004

Summary


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Slide 149

Flow

Rock MassGeotech

MineDesign

Drawperformance

Conceptual Model of Flow, CIM, UofChile.

Uniformity Index and Flow (CIM,Susaeta 2004)


146/254

Slide 150

Susaeta 2004)

There is a free flowbehaviour above thedrawpoint and interactiveflow above the major apexpillar

Both zones of movements(isolated zone and interactivezone) are characterized bytheir vertical flow rates vaand vi

Degree of interaction Gi =vi/va degree of interaction

HIZ

Production drift

Va Vi

a

ii

v

vG

Model Components (T A-I) (Susaeta 2004)


147/254

Slide 151

Interactiv

e zone

Isolated Zone

Interaction betweendrawing zones.

Plastic shear failure

Dpe draw pointspacing

Height ofInteraction zone

Isolated

drawdiameter

Isolated drawvelocity

Interactive flowvelocity vi

Flow Model for El Teniente Layout


148/254

Slide 152

(Vta)

(Vti)

Uniformity Index


149/254

Slide 153

An indicator to quantify the uniformity ofdraw for a given draw point and itsneighbors

Definition

Susaeta 2004

Flow Behaviour


150/254

Slide 154

For a degree ofinteraction greater than0 there is interactionabove the major apex

pilar

Flow propertieschanges as draw isperformed


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Slide 155

a) Flujo Interactivo (Vti=Vta) b)Flujo Aislado Interactivo (Vti


152/254

Slide 156

Uniformity Index

What matters is the % of thetime that a draw point hasbeen drawn isolated to affectits degree of interaction

The more time a dpt is drawnisolated the higher thechances to have the draw pointwith no interaction with theneighbors

Model Calibration


153/254

Slide 157

Initial calibration showagreement betweenUniformity Index and %dilution entry at ElSalvador mine

A large applied researchproject is undergoing atthe University of Chile totest the hypothesis withall CodelcoUnderground Mines

We shall have resultsearly 2007

Dilution Model


154/254

Slide 158

% Extraccin (%)

% Dilucin (%)

Lateral

Dilution

Vi=0

Vi>0

Vi=Va

Dilution from theisolated zone (Pedza)

Dilution from the

Interactive Zone

(Pedzi)

Dilucin INC-N0503E (Oficial)

Dilution Observations at El Salvador Mine


155/254

Slide 159

( )

-10

0

10

20

30

40

50

60

70

80

0 20 40 60 80 100 120

% de Extraccin

%D

ilucin

Dilucin INC-N0504E (Oficial)

-10

0

10

20

30

40

50

60

70

80

0 20 40 60 80 100

% de Extraccin

%D

ilucin

The observations fit the model. Thewhole process of computing andcapturing dilution observations isunderway. Lots to refine in themethodology. So far good

Grfico % Extraccin v/s % Riolita(medio) Sector Parrillas Andina


156/254

Slide 160

Presencia de Riolita vs Porcentaje de Extraccin en reas 1 y 2 Parrillas

0.0%

2.0%4.0%6.0%8.0%

10.0%12.0%14.0%16.0%

18.0%20.0%22.0%24.0%26.0%28.0%

25.0% 35.0% 45.0% 55.0% 65.0% 75.0% 85.0% 95.0% 105.0

%

115.0

%

125.0

%

135.0

%

% Extraccin

%R

iolita

PEDZAPEDZI

Under review many data problems

Flow Considerations


157/254

Slide 161

None of the mixing models take intoaccount the cave propagation process

Particles re distribution

Differential of apparent density Draw influences fragmentation and

fragmentation draw

Mine design and flow characteristics arenot independent


158/254

Slide 162

Stresses

Mining Method


159/254

Slide 163

Geotechnical properties of rock mass lead intoanalyzing SLC or BC (manual, mechanized)

Stresses behaviour defines the undercutting

design, > 46Mpa will be pre undercutting caving Undercut design will affect fragmentation and

cavability of rock mass

Mining Method Major Stresses

Panel caving 45 Mpa

Induced Stress by Caving


160/254

Slide 164

The horizontal cut reduces confinement and induces rotation of thestress tensor increasing the shear stress up to 2.5 times the pre miningcondition

Panek, 1981

Plan section through the three dimensional modelused to calculate ground reaction curves (Lorig 2000)


161/254

Slide 165

Production Area

Ground reaction curves calculatedfor drift 2 (Lorig 2000)


162/254

Slide 166

Schematic diagram showing regions of rockbehaviour defined on the basis of the calculated ground

reaction curves (after Lorig 2000)


163/254

Slide 167

( g )

Production Areas

Caving Mining System


164/254

Slide 168

Caving

Undercut Drilling

Undercut Level

Production Level

Haulage Level

Ventilation Level

2ndHaulage

Crusher

Tipping point

Draw Point

Secondary Breakage

Ore Passes

Feeder

Grizzly

Conveyor

Undercutting Design

Aims


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Slide 169

Aims

Undercut Strategies Management

Configuration

Control

Draw

Control

Pre Post Advanced

Extraction method

Fan Flat Inclined Lags/Leads Blast

Draw

Undercut Mining Sequences


166/254

Slide 170

Barraza and Crorkan, 2000

Different Methods toavoid abutment stresszones

Difficult to implement lots of mine

development needs to be done in ashort period of time to avoidcompaction. UCL implemented asproduction level

Undercutting strategies


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Slide 171

Pre undercutting Reduced stresses, production delays, compaction

remnants

Post undercutting

Faster production, stress induced damage

> 60% extraction ratio - severe draw horizon damage,500m operation limit

Advanced undercutting

Limited draw horizon damage

< 60% critical draw horizon extraction limit

U d t St


168/254

Slide 172

Undercut

extent

Stress

condition Remarks25% of HR Low Limited damage

50% of HRBecoming a

concernOnset of critical

damage

75-110% of HR Maximum Severe damage

Super caves (MRMR > 45): Stress level

becomes a concern fo r extract ion > 75% ofHR

Pre Undercuting


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Slide 173

Undercut developed before drawhorizon

Advantage

Reduced stress damage

POST UNDERCUTTING(conventional)


170/254

Slide 174

Draw horizon full developed then undercut Advantage

Block brought into production quicker

Disadvantages Draw horizon stress induced damages, drift

repair, production delays

POST UNDERCUTTING(conventional)


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Slide 175

Draw horizon damage relates to stressmagnitude and draw horizon extraction

Stress magnitude 2-3 times higher than the pre-undercut levels

Severe damage occurs at 60% draw horizonextraction

Collapse occurs at 80% draw horizon extraction

Limiting operational depth 500m

ADVANCE UNDERCUTTING


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Slide 176

Limited amount of development on draw horizonbefore undercutting

Drifts before undercut, crosscuts and drawbellsafter undercut

Keep draw horizon extraction < 60 % (Butcher1999)

ADVANCE UNDERCUTTING


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Slide 177

Advantages draw horizon damage is reduced

the cave is brought into production quickerthan with a pre-undercutting strategy

a separate level is still required forundercutting

this strategy is slower than post undercutting

Disadvantages

Some draw horizon Slower than post undercutting

Angle of Draw


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Slide 178

Undercut Level

Undercut Sequence

Vertical Cross Section

Angle of Draw

HOD Profile

Rubio, 2005

Induced Shear Stress as a functionof the Angle of Draw


175/254

Slide 179

-100 -80 -60 -40 -20 0

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.080

0

700

600

500

400

NormalizedD

eviatoricStress

Distance from the cave front (m)

Angle of Draw

Rubio, et al 2004

Extraction level support and reinforcement by bolts,shotcrete, mesh and straps, Koffiefontein Mine, South

Africa


176/254

Slide 180Flores et al(2004a)

Pillar and drawpoint support,El Teniente 4 South, Chile (Flores 1993)


177/254

Slide 181

Failure of yielding arch support at a drawpoint,El Salvador Mine


178/254

Slide 182 Photo: M. L. Van Sint Jan

Extraction level support and reinforcementdesign cases


179/254

Slide 183

Blocks falling or sliding; unravelling

General plastic yield

Localised brittle slabbing or spalling

Instability controlled by major structures

Dynamic failures induced by rockbursts

Combined modes of failure

Collapse of an extraction level drift at Ten 4 Sur,El Teniente Mine, 1989


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Slide 184

CONCRETEDAMAGE

CONCRETEDAMAGE

1.5 m


181/254

Slide 185

Models of rock mass response at the Brunswick Mine(Diederichs et al2002)


182/254

Slide 186

Isometric view of key block truncated by the undercut,production level, Panel II, Rio Blanco Mine, Chile, 1989


183/254

Slide 187

5

24

3

1

Three dimensional view of keyblock before truncation by the

undercut, production level, panelII

Construction of the SeismicEnvelop


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Slide 188

Monitor the principalstresses located at theseismic events in awindow of 1 month aheadof mining activity

August 04, Jan 05 andMay 05

Looking at rock types,stress tensor and seismic

moment

),( 31

Seismic Envelop

Aug04, Jan05 and May0560.0


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Slide 189

Expected SeismicActivity

1= 1.6 3+ 8

R2

= 0.89

-

10.0

20.0

30.0

40.0

50.0

- 5 10 15 20 25

3 (MPa)

1(MPa)

Induced Seismicity


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Slide 190

As mining propagatesto surface seismicevents are induced asa response of therock mass to highstresses

Seismic events canhelp to indicate wherethe cave back islocated at any giventime

PMC Seismic Database


187/254

Slide 191

Rockbursts


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Slide 192

A rockburstis the uncontrolled disruption of rockassociated with a violent release of energyadditional to that derived from falling rock

fragments (Cook et al1964)

A rockburstis a seismic event which causesviolent and significant damage to tunnels and

other excavations in the mine (Ortlepp 1997)

Seismic events


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Slide 193

Seismic eventsarise from conditions of unstableequilibrium and involve the release of storedstrain energy and the propagation of elastic

waves through the rock mass

Brady & Brown (2004)

Necessary conditions for rockbursting


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Slide 194

The induced stresses must be high enough toinduce slip on a pre-existing discontinuity (e.g. afault) or fracture of the rock

The resulting slip or fracture must bemechanically unstable, releasing energy thatcannot be absorbed in the processes of slip or

fracture themselves

Unstable slip on a fault


191/254

Slide 195


192/254

Slide 196

Mine Design

Block and Panel caving


193/254

Slide 197

Block cavingThe whole footprint is undercut.Usually the ore body footprint is divided intosmall blocks of 80x80 m. It reports high lateraldilution

Panel cavingBlocks are undercut in acontinuous manner forming an angle ofinterface between broken ore and dilution. Thismethod was invented to minimize the amount of

lateral dilution

Block Caving Miami


194/254

Slide 198

Panel Caving


195/254

Slide 199

Henderson, DeWolf 1981

Panel Cave (De Wolf, 1982)


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Slide 200

Draw Point Spacing


197/254

Slide 201

Geotechnical Information

RMR 0-20 20-40 40-60 60-80ff/m 50-7 20-1.5 5-0.4 1.5-0.2

Rock size range (m) 0.01-0.3 0.1-2 0.4-5 1.5-9

Loading width/Isolated draw diameter (m)5m 11.5 13

4m 9 11 12.5

3m 6.5 8.5 10.5 12

2m 6 8 10

Grizzly Method LHD Mechanized Method

Pilar Mayor

Draw layouts 1.5 IF


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Slide 202

Draw Point Spacing Across the MajorApex Pillar for Different Fragmentations


199/254

Slide 203

Mine

Ertsberg

El Teniente

Grace

Henderson

Creighton

ClimaxUrad

Thetford

Mather

San Manuel

Median Fragment Size (m)

0.7

0.7

0.8

0.5

0.5

0.90.6

0.5

0.2

0.4

Draw point spacing (m2)

236

224

165

148

110

10680

58

32

24

Types of block cave


200/254

Slide 204

Grizzly Slusher

LHD/panel

Front cave Inclined draw point

Production Systems


201/254

Slide 205

Grizzly/ manual

LHD

Fine material complete gravity flow modelHighly productive 0.75 t/m2/da, loweroperations cost 2.5 $/t high capital cost1500 $/m2

Coarse rock, equipment can handledifferent volumesProductivity 0.55 t/m2/da, Operation cost3.5 $/t Capital cost 700$/m2

Grizzly (Pillar 1981)


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Slide 206

SLUSHER (HARTLEY 1981)


203/254

Slide 207

SLUSHER (Hartley 1981)


204/254

Slide 208

Block caving -LHD


205/254

Slide 209

Front cave


206/254

Slide 210

Inclined draw point


207/254

Slide 211

Inclined drawpoint


208/254

Slide 212

LHD Flat Undercut System


209/254

Slide 213

Multi Lift Northparkes (BlockCaving)


210/254

Slide 214

Crinkle Cut for Advanceundercuting


211/254

Slide 215

Fan Ring Undercuting at ElTeniente


212/254

Slide 216

LHD Layouts (Diering y Laubscher1992)

Herringbone y offset are


213/254

Slide 217

Herringbone y offset are

suitable for mechanicequipment, electric equipment

Henderson method has beenfound to be the best forelectric equipment

Offset is the best design toachieve interaction across themajor apex pilar

El Teniente method is the bestfrom the stability point of view

Herringbone layout


214/254

Slide 218

Offset herringbone layout


215/254

Slide 219

Henderson layout


216/254

Slide 220

El Teniente Layout (Chacon et al,2004)


217/254

Slide 221

(a) (b)

Isolated Draw Diameter forDifferent Mine layouts


218/254

Slide 222

Interactive Draw (Laubscher


219/254

Slide 223

1994)

Palabora Mine, South Africa (Calder etal2000)


220/254

Slide 224

Lift 2, Northparkes E26 Mine, Australia


221/254

Slide 225

Drawpoint support, Koffiefontein Mine,South Africa


222/254

Slide 226

Drawpoint support, Henderson Mine


223/254

Slide 227

LHD Method at Tte 4 South Ovalleand Chacon


224/254

Slide 228

LHD Layout Tte 4 Sur


225/254

Slide 229

Undercut Fan Drill Pattern


226/254

Slide 230

Drawpoint support, Koffiefontein Mine,South Africa


227/254

Slide 231

Drawpoint support, Henderson Mine


228/254

Slide 232

Esmeralda Teniente


229/254

Slide 233

Padcal, Filipinas


230/254

Slide 234

DOZ, Freeport Indonesia


231/254

Slide 235

IOZ, Freeport Indonesia


232/254

Slide 236

Extraction methods


233/254

Slide 237

Block cave fan undercut without separate level

Extraction methods


234/254

Slide 238

Conceptual Plan of flat undercut showing possible problem areas

Extraction methods


235/254

Slide 239

Inclined undercut potential problem areas

Undercut managementRate of advances


236/254

Slide 241

Advance as rapidly as possible to HRwithout incurring problems

Reduce rate of advance from HR

Cave tons > undercut tons - preventarch induced abutment crushing

Rate of advance 2300m2/month

Experience 5 recent caves


237/254

Slide 244

Drifts 4.2m X 4.2m Drift spacing 28- 34m (30m)

Draw point spacing 14- 18m (16m)

Offset-herringbone- reduced spans

Distance to UC 15m

MASSMIN 2000


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Slide 245

Caving Subsidence

Subsidence process


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Slide 246

1. Propagate the cave to surface

2. Centre subsidence

3. break back

Macro /angle of break/cave definition

Angle of cave is a Function of


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Slide 247

- Rock mass strength

- Muck pile support (H)

- Depth of ore\body

- Major structures

- Rock mass\shear strength

Angle of break= angle of cave +perimeter fracture zone (Tc)

Stage 3 progression


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Slide 248

Subsidence Angle Estimation(Laubscher Approach)

RMR 80

MRMR 72


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Slide 249

Min SpanHeight of cave material 400

Depth 700

Min Span 200

Max span 800

factor Min_span 14

factor Max_span 3.5

Angle Min_span 85

Angle Max_span 80

RMR 50

MRMR 45

Min Span

Height of cave material 400

Depth 700

Min Span 200

Max span 800factor Min_span 14

factor Max_span 3.5

Angle Min_span 75

Angle Max_span 65

Macro Subsidence definition(Karzulovic 1999)


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Slide 250

Important definitions

Alpha = angle of break to surface fracture zone


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Slide 251

Beta = angle of cave to the edge of glory hole

Tc =Fracture zone around the glory hole

Ti =underground fracture zone

H = muck pile height As = final width of glory hole

Subsidence Angle Estimation(Andina Approach)


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Slide 252

Karzulovic -1997


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Slide 253

Types of discontinuous subsidence(Flores & Karzulovic 2004a)

Bl k i P i h i ll H i ll t li


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Slide 254

Block caving Progressive hangingwallcaving Hangingwall toppling

Ore

Caved

ore

Toppl ing

CraterPerimeter

Cavedrock


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Slide 255

Subsidence resultingfrom Grasberg IOZpanel caving operation,Indonesia

Subsidence generated by Salvadors block andpanel caving operations, Chile


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Slide 256

Craterperimeter

Cavedrock

Subsidence generated by El Tenientes block andpanel caving operations, Chile

Quebrada

T i t

N Craterperimeter


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Slide 257

BradenPipe

Teniente

Teniente 4Fortuna

Teniente 4Regimiento

Teniente 5Pilares

Teniente3 Isla

TenienteSub 6

Teniente4 Sur

Caved

rock

Design chart for the angle

f b k b d li it


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Slide 258

of break based on limitequilibrium analyses(HT = 600 -1700 m)

(Flores & Karzulovic 2004a)

Design chart for extent of

f i fl b d


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Slide 259

zone of influence based onnumerical analysis(HT = 600 -1700 m)


Practical example using

d i h t t ti t


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Slide 260

design chart to estimateangle of break(HT = 1200 m)


Practical example using

d i h t t ti t


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design chart to estimateextent of zone of influence

(HT = 1200 m)


rubio ubc-fundamentals and design

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