D&B Overview_Cikara Bhuana UNSRI

Drill Blast Process

&

Electronic Initiation System

Contents

A

B

C

Drill Blast Process Overview

Geological Effect on Blast Performance

Explosive Introduction

D Explosive Selection

E

F

Blast Design

Blast Design Implementation

CIKARA BHUANA – TEKNIK PERTAMBANGAN UNSRI 2

Why did Drill & Blast … ?

• Limitation of digger ability.

• Drill and Blast is the first step in the breakage or loosening process.

And it impacted to all of the subsequent downstream process.

• Drill and Blast still the most cost effective method to breakage or

loosening the large volume of rock.

Blast Intensity


A. D&B Process Overview

Blast Planning

Drill Pad Preparation & Drilling

Charging, Stemming, Tie-in, Firing

Blast Analysis

Determine proposed

boundaries

Survey area

boundaries

Confirmed blast

schedule

Post blast/observation

report

Data collection

Drill Pad preparation

Priming

Fragmentation /

Productivity analysis

Determine D&B

parameters

Survey set out drill

pattern

Charging of Bulk

Explosive

Final Blast analysis

Drill&Blast design

Drilling

Stemming

Recapitulation of

actual ID & depth

Tie-in

Clearance & Firing


Blasting Process

Rock Mass

• Structure

• Strength

Constraints

• Equipment/Utilities

nearby

• Pit Geometry

• Budget

• Safety (Lightning,

Electrical/Radio, Traffic,

etc..)

Blast Design

• Blast geometry

• Bulk Explosive type

• Initiation pattern (delay time)

Blast Result

• Fragmentation

• Muckpile profile

• Cost

• Ore Lose/Dilution/Loss Coal

• Damage

• Vibration/Airblast

• Fly Rock

• Blast Fumes


B. Geological Effect on Blast Performance

Geological Factors to Consider:

❑ Rock Properties

❑ Rock Structure

❑ Strata Variation

❑ Coal Seam/Ore Deposit Characteristics

❑ Water

❑ Reactive and Hot Ground


❑ Rock Properties

Rock Strength

Model of Failure

Rock properties:

❑ Young’s Modulus: modulus of elasticity,

ability to resist deformation. (Higher value

indicate rock will be harder to break)

❑ P Wave Velocity: the speed of sound in the

rock. (High P Wave Velocity generally

indicate the need for High VOD Explosive)

❑ Poisson’s Ratio: relationship between lateral

and longitudinal deformation under load.

(lower value indicate success for presplitting)


Rock Properties … (what is the rock type at your Site?)

Hardest to Blast

Need Lowest VOD Explosive

Easiest to Presplitt


❑ Rock Structure

Structure describes the features which primarily determine the

fragmentation performance of the rock mass and block size:

o Jointing

o Bedding

o Faulting

o Mean Size

o Distribution

Block size < 0.2m

Friable and powdery

Massive

Massive

Block size >2m

Block size 0,1 – 0,25 m

Fractured

Block size 0,25 - 1 m


Rock Structure…

❖ Massive Structure

Mainly found in Igneous or Metamorphic rocks

o Little or no bedding

o Massive rock types can be anything from extremely hard

and tough (eg basalts or granites) to soft and easily

disrupted (eg limestones)

Massive rock types require the explosive to provide both

the fracturing and the displacement (consider shock as

well as heave performance).

❖ Bedding Structure

Mainly found in Sedimentary Rocks

o Potential for separation along the bedding planes

o Persistence and continuity of planes a key criteria

o Gaps, infill or cementing on planes

o Orientation to face:

• Horizontal

• Inclined - shallow or steeply dipping

• Vertical

• Parallel to the face or angled

Blasting performance is determined by the frequency and

coherence of the bedding planes and the rock strength

across the planes.


Jointing

FreeFace

FreeFace

Large diameter holes in an expanded pattern provides

less energy distribution.

Smaller diameter holes in an reduced pattern provides

more uniform energy distribution.


Bedded Structure

Explosive placement

Deciding where to open the shot


Bedded Structure

3

1

3

2

Gas penetration velocity ~ 300 – 1000 m/s

Damage can occur and unfired holes behind.

Blast Video


Floaters and Cavities

‣ Difficult to deal with, often missed in

drilling and/or drill Log.

‣ Requires reduced patterns and deck

loading to ensure energy distribution

within the hard rock.

Undetected cavities can result in

overloaded holes which leads to:

‣ Premature venting

‣ Flyrock

‣ Excessive explosivesconsumption

‣ Poor fragmentation and hard digging


❑ Water

Water in blastholes is a major influence on the type of explosive used and

costs

o Dewatering all or part of the pit may be a cost effective alternative in mines where the

ground water is relatively static

o Dewatering holes just prior to loading can also be effective if recharge flow rates are low

o Dynamic (relatively fast flowing) ground water is often difficult to

mining cost effectively

o Dynamic water can also degrade/destroy bulk water resistant

physical abrasion

o May need packaged product

o Multiple priming is recommended in wetholes

pump out ahead of

explosive columns by


❑ Reactive and Hot Ground

Reactive Ground

Nitrates in explosives will react with sulphides therock mass, leading to:

• Heat (can exceed 650 ° 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

• Line holes with impermeable sleeve to prevent contact between explosive and sulphides

• Charge and fire the holes with minimal delay

pH of Rock Mass

• Acidity level in the rock mass is most reliable indicator of potential for exothermic reaction

with AN basedexplosives

Moisture Content

• The reactivity increases with increasing moisture initially, however: flooding the material

will quench the reactions

Intimacy of Mixing

• In the bottom of the hole and at the explosives/stemming interface, the degree of mixing is

highest and reactionis most likelyto occur in these areas

Bucket Test Video


Hot Ground

A rock mass that is not reactive, but which has a rock temperature in

excess of 50 o C. Typical hot ground situations result from geothermal

heating or heating from the burning of coalseams.

Hot ground is sometimes subdividedinto:

• Warm Ground – rock temp of 50 o C to 70 o C;

• Hot Ground – rock temp in excess of 75 o C.

The Institute of Manufacturers of Explosives in the USA has made a

recommendation that explosive materials should not be exposed to

temperatures in excess of 66°C.

All explosives increase in sensitivity with increasing temperature:

• TNT melts at 80 o C (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


C. Explosive Introduction

o Products:

• Bulk Explosives

• Packaged Explosives

• Initiation Systems

o Properties:

• Density

• Water Resistance

• Stability

• Weight Strength

• Bulk Strength

• Sensitivity and Propagation

o Explosive Selection:

• Wet or Dry holes

• Hot or Reactive Ground

• Fragmentation requirements

• Rock Properties/Structure

Definitions

Explosion: Chemical reaction of an explosive which involves

the rapid expansion of gasses usually with considerable heat

generated.

Explosive: A chemical substance or mixture which can react

to produce an explosion independently of external

reactants once initiated.

Detonation: Supersonic chemical reaction (Very fast)

Deflagration: Subsonic chemical reaction (Fast)

Combustion: An exothermic reaction producing flame,

sparks or smoke.

Burning: The propagation of combustion by a surface

process.


❖ Explosive

High explosives:

• Detonate faster than speed of sound

• Generated high pressures

• Eg: ANFO, Bulk Emulsion, PETN,NG, TNT

Low explosives:

• Deflagrate or burn slower than speed of sound

• Generate lower pressures

• Eg: Black Powder

Ideal explosives:

• Molecular Explosive

• High VOD, can be calculatedtheoretically

• Very low critical diameter (No diameter Effects)

• High density

Non ideal explosives:

• Composite Explosive

• Variable VOD, impossible to derive simply

• Higher criticaldiameter (diameter affected to

detonation rate)

• Low density

Ideal explosives:

Non ideal explosives:


❑ Bulk Explosive

Commercialbulk explosives are based on AmmoniumNitrate (AN).

Ammonium Nitrate

• Produced by the reaction of ammonia with nitric acid

• Resulting solution evaporated and converted to prill (Drying rate determines quality of prill)

• Coatings applied to prevent caking

o ANFO

Ammonium Nitrate (94%) and Fuel Oil (6%)

o Emulsion

A colloid in which small particles of one liquid are dispersed in another liquid and are stabilized by an

emulsifier hydrophobic. Kind of Emulsifier are: hydrophobic (i.e. water repelling) and hydrophilic (i.e. water attracting).

Typical emulsion explosives are based on:

1. Dispersed phase

An oxidiser prepared as an aqueous solution/melt from nitrate salts (ammonium nitrate).

Alternatives include:

• Calcium Nitrate,Ca(NO 3 ) 2

• Sodium Nitrate, NaNO 3

• Monomethyl Amine Nitrate, CH 3 .NH 2 .HNO 3

2. Continuous phase

A fuel phase which contains oils, fuels and hydrophobic emulsifier.

o Heavy ANFO

Blend of Emulsion and ANFO. Emulsion (10-40%) + ANFO (90-60%)


Bulk Explosive…

• LD AN about 15% Porosity

• HD AN ≤ 2% Porosity


❑ Packaged Explosive

• Wax added to increase stiffness

• Sensitive to detonator #8

• Excellent water resistant


❑ Initiation System

Types of Initiation system:

• Safety fuse and cap

• Electric Detonators

• Detonating Cord (VOD greater than 7000m/s)

• Non-Electric Detonators (Shock tube VOD approximately 2000m/s)

• Electronic Detonators. see separate presentation

PETN mass as Dets Base Charge:

#6 ~ 240 mg

#8 ~ 475 mg

#12 ~ 790 mg


❖ Explosive Properties

Physical Properties:

• Density

• Viscosity

• Chemical Stability

• Water Resistance

• Fume Characteristic

• Sleep time

Detonation Properties:

• Velocity of Detonation (VOD)

• Detonation Pressure

• Energy/Strength

• Critical Diameter

Safety Properties:

Describe the handling requirement of Explosive.

❑ Physical Properties:

o

Density

• Indicate amount of explosive loaded in a unit

length of bore hole ( Loading density in kg/m ).

• Increasing density leads to increasing VOD up

towards critical density.

• Higher density for non-ideal explosives risks

dead pressing.

o

Water Resistance

• Ability of explosive to exposure to water

without losing sensitivity or efficiency.

• Depend on water conditions:

✓ Static or dynamic water.

✓ pH will affect to sleep time.

• Post blast NOx fumes could be indication of

water damage to explosive.


Dead pressing

Loading Density


❑ Physical Properties: …

o

o

Chemical Stability

Ability to unchanged (chemically) when stored

correctly. Key parameter to determine shelf life.

Factors affecting shelf lifeinclude:

• Formulation/Raw material quality

• Temperature and humidity of storage

• Contamination

• Packaging

Signs of deterioration include:

• Crystallization

• Color/Stiffness/Viscosity change

• Poor field performance

Sleep Time

Ability to sitting in the ground without changing

the quality.

Factors affecting sleep time:

• Wet or Dry ground

• Hot or Reactive ground

• Acidity of ground

o

o

Fume Characteristic

Oxygen balanced explosives yield non toxic gases

(CO 2 , N 2 and H 2 O).

When explosive formulation not reach the

Oxygen balance:

• Oxides of nitrogen (NO x ) resultfrom an

excess of oxygen in the formulation

(positive oxygen balance/under fuelled)

• Carbon monoxide (CO) results from a

deficiency of oxygen in the explosive

(negative oxygen balance/over fuelled)

Viscosity

Determine of flow characteristic and affect to

pumping rate.

Factors influence to selection of explosive

viscosity:

• Fractured ground

• Pump ability


❑ Detonation Properties

o

Velocity of Detonation

Speed of the detonation wave travels through

the explosive. VOD will influence the partition of

energy into shock and heave.

VOD will influence by:

• Explosive Density

• Hole Diameter

• Rock Type

• Degree of Confinement

• Explosive Formulation

• Primer Size & Type

o

Detonation Pressure

Pressure in the detonation reaction zone

(expressed in MPa). This generate Shock in the

ground/rock.

Estimation of Pd in commercial explosive:

P d = 0.25 x VoD 2 x

Example:

• ANFO = 0.85g/cc VOD = 3600m/s

P d = 0.25 x 3600 2 x0.85 = 2.75GPa

• Emulsion Blend = 1.15g/cc VOD = 5000m/s

P d = 0.25 x 5000 2 x 1.15 = 7.19GPa


mm

Detonation Properties …

o

Energy / Strength

Energy released by an Explosive calculated using

Thermodynamic code. Based on the ingredients

of Explosive.

❖ Absolute Weight Strength(AWS)

• Calculated by Thermodynamic code, base

on ingredients

• Refer to Explosive Technical Data Sheet

• AWS of ANFO = 3.73 MJ/kg

❖ Absolute Bulk Strength(ABS)

Energy per unit volume.

• ABS Explosive = AWS Explosive x ρ Explosive

o

Critical Diameter

Defined as the minimum diameter at which a

stable detonation. It important for determining

hole size/explosive typecompatibility.

100

75

50

25

0

❖ Relative Weight Strength (RWS)

AWS Explosive compared to ANFO

PETN TNT Dynamite ANFO Cartridge Bulk

Emulsion

❖ Relative Bulk Strength (RBS)

Energy of Bulk Explosive compared to ANFO


❑ Safety Properties

Related to Sensitivity. Which defined as ease of initiation (minimum energy required to

detonation). Sensitivity from: Impact, Initiation, Heat, Friction, Reactive ground.

initiate


D. Explosive Selection


E. Blast Design


VoD (m/s)

❑ Hole Diameter

o

o

o

Influences energy distribution

Small diameters: 65 – 165 mm

• High unit costs: drilling, accessories

• Good energy distribution - low gradient

• Lower VOD

Large diameters: 170 – 450 mm

• Lower unit costs, less time

• Poor energy distribution - steep gradient

• higher VOD

5000

4000

3000

2000

1000

0

0 50 100 150 200 250 300 350

Charge Diameter (mm)


❑ Burden

o

Burden: distance explosive charge to the nearest free face.

Real life - face

Fly rock

Over size

Ideal - face

Burden Stiffness = Bench height ÷ Burden Burden Stiffness < 2 : Difficult to break


❑ Detonation Phase & Shockwave

X Y

This condition of stability condition for stability exists at hypothetical X, which

is commonly referred to the Chapman-Joquet(C-J) plane. Between the two

planes X and Y there is conservation of mass, momentum and energy.


Shockwave propagation

Gas Pressure Expansion

• VOD of explosive is function of Heat reaction

of an explosive, density and confinement.

• The detonation pressure that exists at the C-J

plane is function of VOD of explosives. The

detonation in cylindrical columns and in

unconfined conditions leads to lateral

expansion between the shock and C-J planes

resulting a loss of energy. Thus, it is common

to encounter a much lower VOD in

unconfined than in confined ones.

• Rapid the detonation process (quicker the

energy release from explosives mass), in the

form of a shockwave followed by gas

pressure, is applied to the borehole wall.

• When the shock wave reaches the borehole

wall the fragmentation process begins (the

zone immediately crushed).

• if the compressive shockwave pulse radiating

outward from the hole encounters a fracture

plane, discontinuity or a free face, it is

reflected and becomes a tension wave with

approximately the same energy as the

compressive wave.

• This tension wave can possibly “spall” off a

slab of rock.


Inclined Hole

Advantages

o increased angle of projection

o less ground vibration

o less damage at toe (top of coal)

Disadvantages

o harder to charge

o difficult to position drill

o increased deviation at toe and collar

o increased drilling length

o harder to flush cuttings


Deviations may occur frequently?

Excessed Burden Stiffness Ratio

Poor confinement, excessive energy

Uneven Shape

Preconditioned material-failed survey


❑ Delay Timing

Why not Instantaneously?

o Vibration

o Movement

o Damage

Why Delay Blast?

o Control the energy released

• Create free faces to promote tensile failure

• Maintain intensity of ground vibration

o Control Confinement of Energy

• Provides space for the blasted rock to swell

• Directional control of movement

• Provides relief to reduce blast damage

o Achieve the desired blast results

• Create adequate breakage/fragmentation for downstream processing

• Sufficient movement of broken rock for load and haul


Delay Timing…

Timing Design Guideline

Source: John Floyd 1998

• Delay time Inter-holes in a row should be between 1 to 5 millisecond per m of burden.

• Delay time Inter-rows should be from 2-3 times longer than delay time of inter-holes.


Delay Timing…

Soft

o Soft rocks move late and slowly compared to hardrocks.

o Critical burdens for hard rocksare smaller compared to soft rocks.

o Fragmentation: Fire close to each other so that the shock waves can

interact and increase fracturing. (for hard rock)

o Looseness and Damage: Increase the timing so that the later holes

will have sufficient space to move and accommodate the swell.

o Ground Vibrations and air blast: Avoid the reinforcement of vibrations

from different holes and unwanted frequencies (low frequencies).

o In highly fracturedrocks: long delays may create cut offs.


Delay Timing…

Burning Front, Scatter (pyrotechnic delay)


Blast Design Approach

1. Collect data

❑ Rock properties & Structure

❑ Desired blast result

❑ Cost & Constraints

2. Analyse data

❑ Define Rock Properties &

Structure

❑ Define desired blast result,

Constraints, and Cost

• Fragmentation (top size, mid

size and fines)

• Throw and looseness

• Hazard & Damage (vibration,

Air blast, Fly rock, Fumes)

• Drill Machine selection

❑ Explosive Selection

3. Develop design

❑ Use models, thumb rules and

experience

❑ Develop a design to achieve the desired

results in the given conditions

4. Trial and monitor the outcomes

❑ Trial the designs (Start with a design that

provides the best outcome prediction)

❑ Monitor the result

5. Implementation

❑ Compare with desired results

❑ If satisfied develop SOP to implement

designs

❑ If not satisfied, modify designs and go

through step 3 and 4


F. Blast Design Implementation

❑ Pattern Layout

• Pattern accuracy is essential for the blast outcomes and subsequences pattern layout.

• Any error at this stage has potential problem later.

• Post drilling survey control is important to known the deviations and plotting subsequence

pattern.

❑ Drilling

• Collar accuracy is critical for energy distribution in the rock mass (accuracy burden, spacing).

• Depth accuracy is critical for diggable at the floor level.

• When drilling completed, cannot change the parameters (collar location, burden, spacing, hole

depth, hole diameter). Extra cost & process to change.

❑ Charging the Blasthole

• Measurement the hole depth (actual), to prevent over/under charge and over/under the plan

depth.

• Water present in the blast hole.

• Ensure the primer sitting into the bulk explosive (not sludge at the bottom and floating at the

top).

• Measurement of bulk explosive column rise (if using bulk emulsion), and to ensure the level of

column charge not drop down due to fracture/cracking of the rock.

• Avoid contaminating bulk explosive with water or drill cutting from the collar.

• QC of the bulk explosive: mixing consistency (AN:FO), density (gassing), uniformity product

loaded.

• Report any abnormalities of explosive (physical characteristic, packaging, and performance).


❑ QC for Bulk Explosive

In-Hole VOD Measurement

• VOD provide the first filed check on explosive detonation performance.

• VOD is subject to or influenced by:

✓ Rock Type

✓ Charge Diameter

✓ Explosive Density

✓ Explosive Formulation/ingredients

✓ Degree of Confinement

✓ Primer (size & type)

❖ Primer Location & Wet Hole Loading

In most practices the priming will be located at the

bottom of the hole. If the priming was located at the

top of the bulk explosive column, the energy would

break through the surface earlier in the explosion

process, gasses would vent sooner and much of their

contribution to the fragmentation process would be

lost.

Video:

Right Retract

Wrong Retract

MMU Charging


G. Blast Result

❑ Fragmentation

❑ Muckpile Movement

❑ Dilution

❑ Damage

❑ Ground Vibration / Airblast

❑ Fly rock

❑ Fumes

❑ Safety


❑ Fragmentation

‣ Excavator

‣ Crusher

‣ Mill

‣ Recovery

‣ Secondary blasting

Optimum Fragmentation?

• Less oversize/boulder

• Efficient digging and loading

(1/3 bucket size)

• Not produce excess fines

Depend on …

✓ Excavator size & type

✓ Material type (Ore / Waste)


❑ Muckpile movement

‣ Depend on digger type.

❑ Dilution

‣ Less accurate of Ore

movement, lead to increased

dilution or loss.


Blast Movement Monitoring


❑ Damage

‣ Safety

‣ Difficult drilling or

loading for the

subsequent blast

❑ Vibration/Airblast

‣ Complaint from general public

‣ Effected to slope stability

‣ Restrict blast size and efficiencies


❑ Fly Rock

‣ Impacted to Safety, Equipment movement, Production loss/Dilution.

❑ Fumes

‣ Impacted to Health, Environment/Public relation, Productivity.



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