4a-interaksi Bp Dan Batuan.pdf

4a. Interaksi Bahan Peledak dan Batuan

Proses Peledakan Batuan Rock mass • Strength • Structure

Constraints • Budget • Pit geometry • Equipment • Legislation

Control

Explosive Rock Interaction

Blast Design Explosive type, Blast geometry Delay time & Initiation pattern

Blast results • Safety • Fragmentation • Muckpile profile • Ore loss / dilution • Blast volume • Damage • Vibrations / airblast • Fly rock • Cost

Fasa Detonasi Stemming

Un-detonated explosive

KPa >50ºC

Detonation zone

Explosion state

GPa >2000 - 300ºC

 Tekanan detonasi adalah tekanan dalam CJ Plane dan dapat dihitung sbb. Pd = K  VoD2  Tekanan peledakan/lubang tembak adalah tekanan di belakang CJ plane dan biasanya setengah dari tekanan detonasi

Fasa Gelombang Kejut Open fracture

Compressive wave

Expanded blasthole

 Gas-gas peledakan memperluas lubang tembak sampai kondisi Tensile wave kesetimbangan tegangan  Energi BP berkembang sampai di gambar ini didefiniskan sebagai shock Spalling energy  Energi dalam fasa ini digunakan untuk mengembangkan jaringan fraktur

Radial cracks

Original blasthole Crushed zone

Compressive stress > Dyn Compressive strength –- crushing Tangential stress > Dyn tensile strength –- radial cracking

Fasa Pengembangan Tekanan Gas Fracture extension

p i

p

Hydrostatic zone

i

p i

Free face

Gas-gas peledakan memasuki fraktur dengan kecepatan 0.1- 0.4 sonic velocity

pi

State of stress on an element in hydrostatic zone

i

Fasa Pergerakan Burden Stemming ejection

Crushed zone

Original blasthole

Interaksi BP dan Batuan pe

p

b

Response of the blasthole A wall to explosive loading Equilibrium state Starting of burden movement

B

Pressure peq 1 2 p ( t m in

C

)

Gas escape into the atmosphere

4 3

p ( t ter) P Ve Vb

D

6 Q Veq

5

7

R V( t m in

)

Volume

S V(t ter )

Peledakan Lubang Tembak Tunggal Anzomex Primer  = 1.65 gr/cc; VOD = 7.2 km/d;, PD = 21 GPa Magnum II PD = 8 GPa Power Gel PD = 6 GPa Shock energy + Gas energy = Fragmentation energy Gas energy = Heave energy

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8

Peledakan Batuan Lunak & Keras

 Deformasi plastik, peremukan terjadi sekitar lokasi muatan  Tidak perlu high peak pressure  Fragmentasi bergantung kepada pembukaan rekahan & penetrasi gas  GV akan lebih besar pada hard rocks  Perlu heave energi yg tinggi

   

Perlu pembentukan rekahan baru Perlu tekanan lubang tinggi Resiko bising & fly rock Perlu energi fragmentasi tinggi

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Soft rock

9

Hard rock

Fragmentasi Peledakan  Hancurnya batuan utuh  Pemisahan matriks in-situ

Pengaruh Pengungkungan Perkembangan crack akibat kenetrasi gas Disebabkan oleh shock dan Bidang lemah alami

Gas flow direction

Laju penetrasi gas = 100 – 400 m/s

Videos – showing gas penetration

Gas flow direction

Pemilihan BP untuk memenuhi struktur batuan dan kekuatan Medium VOD High density

Strength

High VOD High density

High VOD Low density

Low VOD Low density

Fractures

Throw requirement

Pemilihan BP untuk memenuhi tujuan peledakan

Low VOD Med-High density

Low VOD Low density

Fines requirement

High VOD High density

High VOD Med density

Explosive Energy Partitioning 100% Available Energy

“Shock” Energy Component

“Heave” Energy Component Increasing Velocity of Detonation

When Gas Heave Generation is Desired Cast Blast for Coal Stripping

Low Pile for Loaders

When Gas Heave is Not Desired Dilution Control

Through Seam Blasting in Coal

When Gas Heave is Not Desired Controlling Backbreak

Along Final Walls

4b. Pengaruh Kondisi Geologi Terhadap Unjuk Kerja Peledakan

Geologic Factors to Consider      

Rock Properties Rock Structure Strata Variations Water Reactive and Hot Ground Coal Seam Characteristics

Model of Failure 

Brittle 

 Stiffness indicates  The mode of failure  Type of fragmentation  Stiffness is represented by the Young’s modulus



  

Fractured

Plastic

 Stiffness can be measured by the stress – strain curve in a stiff testing machine

Dynamic Properties Grady and Kipp, 1987

Intermediate loading rate

Explosive loading rate

Slow loading rate

 Dynamic properties are generally higher than static measurements  Dynamic measurements are expensive to conduct  Static measurements should be used to represent relative strength rather than absolute

Rock Properties cont…  Poisson’s Ratio - relationship between lateral and longitudinal deformation under load (lower values indicate success for presplitting)  Young’s Modulus - aka modulus of elasticity, ability to resist deformation (higher values indicate rock will be harder to break)  P Wave velocity - the speed of sound in the rock, high P Wave velocities generally indicate the need for high VOD explosives

Rock Properties cont… Rock Type

Density Compressive Tensile (g/cc) Strength Strength (MPa) (MPa)

Young's Modulus (GPa)

Poisson's Ratio

P Wave Velocity (m/s)

Basalt

2.9

149

11

62

0.27

5229

Dolomite

2.5

55

3

28

0.32

4024

Gneiss

2.8

224

14

81

0.22

5732

Granite

2.7

186

9

43

0.33

4844

Limestone

2.7

159

5

55

0.25

5000

Marble

3.1

251

15

106

0.28

6705

Sandstone

2.5

134

1

7

-

3933

Sandstone

1.8

11

0

6

0.31

2095

Schist

2.9

166

9

77

0.2

5482

Slate

2.6

85

6

66

0.17

5168

Taconite

2.9

251

17

93

0.25

6140

Rock Structure Structure describes the features which primarily determine the fragmentation performance of the rockmass  Jointing  Bedding  Faulting

Rock Structure

Block size < 0.2m

Friable and Powdery Massive

Block size > 2m

Rock Structure Block size 0.2 - 1m

Blocky

Block size Fractured 0.1 – 0.25m

Rock Structure

Blocky structure Bedding planes dipping into the pit

Rock Structure

Hard and massive Soft and fractured

Multiple Seams

Multiple Rock Types

60

Hard

50

Soft

40 30 20 10

Medium Rider

Soft

Consider bedding when deciding where to open shot

Structure Orientation

Dipping towards the face

Dipping away from the face

Explosive Charge Separation

Column Separation and Cutoffs 300 ms 200 ms 100 ms 200 ms 300 ms

200 ms

100 ms

Weak Bands

Stemming Explosive

Decking

Weak Seam Explosive

Weak Bands

Gas penetration Differential rock movement

VOD Trace Showing Effect of Weak Band Stemming 10’

Top booster (500 ms)

Weak band

Bottom booster (475 ms)

Column Seperation Along Bedding Planes

Column Seperation

Effect of Hard Rock Bands on Cast Shot

Effect of Hard Rock Bands on Cast Shot

Floaters  Requires that drillers record floater locations in holes  Difficult to control blasting in floaters – 3D problem Floaters

Soft Clay

Hard Rock

Reduced Pattern

Deck Loading

Cavities  Poor fragmentation, toe etc  Excessive flyrock and noise  High powder factors

Hard Rock

Blasthole Plug

Impact of Roof Characteristics on Coal Loss Coarse Sandstone

Conglomerate

Hard roof requires more energy for good breakage • Less standoff • High energy explosives • Quick burden response and movement • More prone to coal loss

Hard sandstone Coal Seam

Soft roof requires less energy for good breakage • Higher standoff • Low energy explosives • Longer burden response times, hence more confinement

Soft Siltstone

Coal seam

Rolling Seams and Faults

•

Geological models are based on exploration holes with wide grid spacing, hence they are not accurate

•

In order to get a better accuracy, normally one in every fifth hole is drilled to coal

•

Design and implementation of stand off

Coal Type Description COAL CHARACTERISATION DULL DULL <1% bright

DULL w/MINOR 1-10% bright DULLBANDED 10-40% bright INTERBANDED 40-60% bright

BRIGHT BANDED 60-90% bright BRIGHT >90% bright

BRIGHT

Coal Seam Characteristics Brightness profiles

0

Breakage characteristics

BLASTHOLE STEMMING

100

200

80

Gl4

increasing breakage

300

70

400

mid to high rank, banded coals

PLY 1

NP BB (1.67)

500

60 600

700

NP DB (1.67)

PLY 2

PLY3

800

900 PLY 4

1000

RAMP 27 LD CORE

mass % passing T10 (5mm)

CHARGE

(Esterle 1988)

2D IB (1.1) 50

2D DB (1.1) DU BB (0.88)

40

DU IB (0.88) DU D (0.88)

30

WW B (0.75) WW D (0.75)

20 low rank, dull coals

TK B (0.62) TK BB (0.62)

10 increasing energy

TK DB (0.62)

0 0.000

0.050

0.100

0.150

energy (kWh/t)

0.200

0.250

Partings and Clay Bands

coal edge movement 3 - 4m

Cleats orientation

Measurement While Drilling

(MWD)

Analysis and Presentation Drill Monitor

Correlation Betwee Measure While Drilling Parameters and Point Load Test 60%

Strength (ROP)

50%

Strength (PLT)

40% 30% 20% 10% 0% 30

60

90

120

150

180

210

240

Strength = K1 x Pull down pressure x (RPM / ROP)K2

Drill Penetration at Various Depths

Water  Influences explosive selection  Dewatering may be a cost effective alternative if water is relatively static  Dynamic ground water is difficult to pump and degrades bulk explosive  Pumped explosives  Bottom loading  Slower loading rates  Less sleep times  Multiple priming is recommended

Definitions of Hot and Reactive Ground Reactive Ground: Pyritic material in the rockmass that reacts with ammonium nitrate based explosives, ultimately resulting in the exothermic decomposition of the explosive. AN based explosives which come into contact with pyrites start to fume, generate heat and finally deflagrate or detonate, depending on the circumstances. Hot Ground: A rockmass that is not reactive, but which has a rock temperature in excess of 50oC. Typical hot ground situations result from geothermal heating or heating from burning coal seams Hot ground is sometimes subdivided into:  Warm Ground – rock temp of 50oC to 74.9oC;  Hot Ground – rock temp in excess of 75oC.

Reactive Ground Nitrates in explosives will react with sulphides the rockmass, leading to:  Heat (can exceed 650o C) and toxic gases  Premature detonation of the explosive If reactive ground is present, it is essential to:  Establish a set of procedures which control the blasting in reactive ground  Use inhibited explosives or  Line holes with impermeable sleeve to prevent contact between explosive and sulphides  Charge and fire the holes with minimal delay

Hot Ground The most common examples of hot ground are:  A volcanic rockmass where rockmass temperature is governed by the presence of nearby body of magma (e.g. Lihir Gold Mine)

 A rockmass where the spontaneous combustion of a coal seam has elevated the rockmass temperature (Lidel and Muswellbrook coal mines) All explosives increase in sensitivity with increasing temperature:  TNT melts at 80oC (TNT is a principal ingredient of cast boosters)  NONEL tube melts at 115C  Diazo deflagration point 180C  Lead Azide deflagration point 320 – 360C  HMX/Al (in NONEL tube) deflagration point 287C  PETN deflagration point 202C  TNT deflagration point 300C