Suez Cement Title 1 Place, date

Advanced Blasting Course

Suez Cement Title 2

Drilling

Suez Cement

Drilling Types

Rotary Type by using:

- Tricone bit (water & oil).

- Drag bit (core drilling).

Rotary & Percussion Type by using:

- Top Hammer (drifter.) < 20m.

- Down The Hole (DTH) > 15m.

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Top

Hammer

(drifter.)

Digital

Alignment

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Down The Hole

(DTH)

DTH

Hammer

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Advantages of Drifter & DTH

Down The Hole (DTH) Top Hammer (drifter.)

Short holes: constant. Short holes: very fast.

Long holes: very fast. Long holes: very slow.

Straight drilling in Long holes Highly deviated in Long holes

Soft – medium hard rocks. Hard rocks.

More complicated. Very simple to use.

Cost effective in long holes. Cost effective in short holes.

Hole diameters (4.0 -12.0 in) Hole diameters (1.5 – 4.5 in).

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Down The Hole (DTH) Top Hammer (drifter.)

1 - 2 Tube: 2.5 min. 1 - 2 Tube: 0.5 min.

3 - 4 Tube: 2.5 min. 3 - 4 Tube: 1.5 min.

5 - 6 Tube: 2.5 min. 5 - 6 Tube: 5.0 min.

7 - 8 Tube: 2.5min. 7 - 8 Tube: 15 min.

9 -10 Tube: 2.5 min. 9 -10 Tube: 35 min.

Drilling time (30m) = 25 min. Drilling time (30m) = 1:54 h.

Av. Drilling time = 50 sec/m. Av. Drilling rate = 3.8 min/m.

Drilling Rate

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Drilling Machine Components

Drilling Rig: (source of mechanical energy).

Drilling Steel: (transmitting the energy).

Drilling Hammer & Bit:

Flushing Air: (drilling cuttings).

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Rock Properties Affecting Drilling

Hardness:

Compressive Strength:

Elasticity:

Abrasiveness:

Texture & Structures:

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Size of Drilling Machines

Geometrical design of quarry faces:

Quarry production:

Crusher and quarry equipment capacity:

Rock properties:

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Surface Applications

Bench drilling:

- Quarries.

- Constructions.

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Bench Drilling

Free face parallel to blast holes

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• Rock properties.

• Bench height.

• Hole diameter.

• Demands on fragmentation.

• Environmental restrictions

Factors Affecting Bench Drilling

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K

Bench Height

Hole diameter: (Smaller holes lower bench).

Drilling Equipment: (Drifter lower bench).

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Hole Diameter

Factors affecting

Hole – diameter:

• Fragmentation.

• Ground vibrations.

• Need for selective rock excavation.

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Fragmentation

Factors affecting

Fragmentation:

• Downstream operation.

• Loading equipment.

• Larger holes give coarser fragmentation.

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Environmental Restrictions

• Ground vibrations.

• Fly rock.

• Air blast.

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Terminology in Bench Drilling

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Practical rule of burden: V = d

Burden (V ) in meters.

Hole diameter (d) in inch.

Burden

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Burden: is the closes distance to the free face when the blast hole

detonates. It has to match (1) Blastability of the rock. (2) Energy of

the explosive. (3) Delay between the rows or vice versa.

In case the burden is too big: The energy and burden velocity will be to small. This will not create

enough space in front of the next row, for it to swell. These will

causing vibration, fly rock and air blast. The muck pile will have a

high profile and compact, it will be well fragmented, but with boulders.

In case the burden is too small: If the burden is to small the energy will be to big with a high

probability for face bursting and fly rock. Burden velocity may be to

high. The front row may move to far and not shield from fly rock from

the next row resulting in fly rock and air blast. The muck pile profile

will be very low, covering a big area and poorly fragmented.

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Maximum Burden

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Spacing

E

E = (1.25 – 1.6) x V

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Spacing (Span): is a function of burden and the break out angel

of the holes.

In case the spacing is too large: If the spacing is to large the rock between the holes is poorly

fragmented, and often creates Delta shape. This problem will

increase the burden of the next row, with a probability for air blast,

fly rock and back break.

In case the spacing is too small: The energy overlap between holes will be to large with a probability

of face bursting, fly rock and air blast. Some times the hole

damages the adjacent holes during its initiation.

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The break out angel is typically 90º to 160º and will

increase by decreasing burden.

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E V

Burden/Spacing Ratio

Rule of thumb 1

Vmax in meters = hole diameter in inches.

Then reduce Vmax for inaccurate

drilling and rock proporties.

Rule of thumb 2

The spacing should be

approxemetly (from 25% to

60%) larger than the

burden.

E = (1.25 - 1.6) x V

V/E ratio: 0.6 – 0.8

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Sub drilling: U = 0.3 x V

Sub-drilling

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Sub drilling = 30% of Burden (U = 0,3xVmax)

Hole Depth

V

U

K

Hole depth= (K+U) / cos α

α

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• Less benches to construct and maintain

• Less sub drilling

• Less boulders

Bench Height

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• Better hole accuracy

• Higher penetration rate over

the hole depth

• Maximised burden/spacing

Less benches to

construct and maintain

Less sub drilling

Less boulders

Bench Height

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+ Reduced drilling and explosive costs due to increased burden

+ More stable bench edge

+ Less risk for back break

– Increased risk of hole deviation

Inclination of Drilling Holes

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Calculation of Drilling Angle

V

K

α

L

Drilling Angle = (α)

(L / K) = tan (α)

(α) = tan-1 (L / K)

Ideal blasting angle: 45o

Ideal drilling angle: Vertical.

Ideal drilling & blasting angle: 18o

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Inaccurate Drilling

Theoretical

Laying out

Collaring

Alignment

Feed

Rock properties

Equipment

Practical

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Hole Deviation

Would you blast in a drill pattern looking like this?

Example of measured drill pattern at 30 m depth.

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Accurate Drilling

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The burden in the front of the holes does deviate from

the planned:

Burden of Front Row

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Incident / Consequence:

1) Face burst.

2) Fly rock.

3) Air blast.

4) Vibrations.

Caused by:

1) Back break from the previous blast.

2) Bad blast direction.

3) Jointing and faulting.

How to Detect:

1) Face burden scanning using laser profiler.

2) Drill hole deviation equipment.

3) Manuel inspection of the face.

Burden of Front Row

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Action:

1) Reduce back break by a improving the blasting

direction.

2) Optimise energy and timing.

3) Optimise bench shape and reduce bench stiffness.

4) Reduce edge effects.

5) Reduce fly rock potential by matching the energy to

the actual burden in front of the hole using air deck,

stemming deck.

6) Drilling of extra holes.

7) Backfill of sand.

8) Blasting mats.

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Burden of Front Row

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Burden of Front Row

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Drill-Hole Deviation

Azimuth of blast hole: direction of blast hole in each level.

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Drill-Hole Deviation

Incident / Consequence:

1) Risk of face burst.

2) Fly rock and air blast.

3) Vibrations.

4) Risk of flashover initiation between shot holes and toe

problems.

Caused by:

1) Jointing and faulting.

2) Inclination and directional errors.

3) Bit skidding during collaring, deflection and bending, to

high feed force and low drill steel stiffness.

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How to Detect:

Face burden scanning compatible with drill hole deviation

equipment.

Action:

1) Knowledge of jointing and faulting to compensate for

deviation.

2) Better procedures for marking and collaring reducing

inclination and directional errors.

3) Reduce drill deflection, bending and reducing feed

force.

4) Reducing the hole length.

5) Select bits match rock type.

Drill-Hole Deviation

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Drill-Hole Deviation

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Blast-Hole Recorder

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Blast-Hole Record

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Square Pattern

V

E

Square pattern: 1

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Staggered Pattern

E

V

Staggered pattern: 1.1

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V

H K

B

Specific Drilling

Specific Drilling (q):

Drill meters per cubic meter

of broken rock.

Drill meters = H x number of holes/row

Volume = K x B x V

H x No of holes /row

K x B x V q =

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Drilling Calculation

Descriptions Symbol Example

• Max. annual limestone production t 2,500,000 ton

• Limestone density d 2.0 ton/m3

• Max annual limestone production m 1,250,000m3

• Burden × span V * E 4.0 × 5.5m

• Sub drill U 1.25m

• Bench height (Av) K 30.0m

• Hole depth (K+U) / cos α 31.75m

• Volume of rock / hole V * E * K 698.5m3

• Specific Drilling (Hole density) q 0.045Dm/m3

• Required drilling meter per year 56,250m

• Required drilled meter per day 187.5m

• Required number of holes per day 6 holes

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Shaft Tube Drilling

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Shaft Tube Drilling

Suez Cement Title 52

Blasting

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Explosives History

Safety fuse is invented by William Bickford, the founder

of Ensign-Bickford Company, to replace black powder-

filled cord (mining safety increases dramatically.)

1831

1865 Alfred Nobel, the founder of the oldest explosives

company, and he invents the first blasting cap.

1867 Alfred Nobel invents dynamite, another major step in

explosives safety and efficiency

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The Start of Dynamite

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Characteristics of Explosives

Velocity (VOD):

- High explosive velocity (5000-7000m/sec): hard rock.

- Low explosive velocity (3500-4500m/sec): soft rock.

Strength:

- Relating to the strength of stander gelatin.

Sensitiveness: (propagation ability).

Cap Sensitivity:

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Density: (Kg/L).

Oxygen Balance:

Water Resistance:

Resistance to freezing:

Safety on Handling:

Environmental Properties:

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Governing Rules

Explosives right quality.

Cost.

Environment. control of fly rock.

control of air blast.

control of vibrations.

control of wall damage.

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Classification

High Explosives: - Gelatin Dynamite.

Blasting Agent: - ANFO.

- Emulsion.

Initiation System: - Electrical detonators.

- Non-electrical detonators.

- Electronic detonators.

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Explosives Technology

NH 3

CH 26

Oil

AN

HNO3

Glycol

ANFO

Blasting agent

Manufacturing Cartridge

products

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Explosive Must Contain

SN CN

Wood

powder

Diesel-

fuel

Ammonium-

nitrate

Sodium-

nitrate Calcium-

nitrate

AN

Oxidizing agent

Reduction agent (fuel)

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- Gelatin dynamite is invented by Alfred Nobel, in 1867.

- Velocity: 4500 – 5500 m/sec.

- Density: 1.2 Kg/L.

Gelatin Dynamite

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ANFO

Dry blasting agent.

Velocity: 3500 – 4000m/sec.

Density: 0.8 Kg/L.

Pre-mixes ANFO: (Small & Big bags).

Site-mixed ANFO: (Mixing truck).

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AN

Fuel

Water EMULSION HOT SPOTS

Emulsion

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1. Ammonium nitrate solution

2. Ammonium nitrate prills

3. Sodium nitrate

4. Calsium nitrate

5. Oil

6. Emulsifier

7. Aluminium (used optionally in some producers)

8. Water

Components of Emulsion

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Bulk Emulsion Systems

• Straight Emulsions.

• Blendx:

(Emulsion + ANFO).

• Heavy ANFO:

(ANFO + AL2O3).

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Emulsion Plant

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Gassing agents

Aluminum AN - Prills

Oxidizer Solution Fuel and

Emulsifier

Emulsion mixer Dosage pumps

Emulsion Truck

Control -

panel

Blender

Pump

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Bulk Operation

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Variations of densities

1,26

1,24

1,22

1,19

1,16

1,10

1,15

1,05

1,00 0 1

2 3

6 7

5 4

11 12

10

8 9

13 14 15 16

mete

r

• Critical density of a given explosive is

defined as the density where explosives no

longer can detonate.

• Critical density occurs as a result of:

Dynamic pressure developed by previous

detonations in adjacent boreholes.

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Energy vs. Density

60,0

70,0

80,0

90,0

100,0

110,0

1 1,05 1,1 1,15 1,2 1,25 1,3 1,35 1,4 1,45 1,5

Density g/cc

Energ

y m

easure

d (

%)

Energy measured in 70 mm steal tubes

Energy & Density Relationship

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Bore hole diameter:

Quarries: 2” - 6”

Max pump heigth: 40 m

Max hole length: 40 m

Bulk Operation

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Differential Loading System

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Emulsion composition

Parameters Affecting Emulsion

Charge length

Dry or wet bore holes

Bore hole diameter

Gassing methods

Blast design

Delay system

Geology

Water

Dynamic pressure

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Energy - Measured 5.0

4.0

3.0

2.0

1.0

Loss

AN

FO

Loss

Dyn

am

it

Loss

Em

uls

ion

Weight

Steel tube

Piston

Explosives

MJ/Kg

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Blast fumes - Measured

Visibility (%/kg)

Emulsion

Em

uls

ion

Em

uls

ion

Em

uls

ion

AN

FO

AN

FO

AN

FO

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Emulsion Benefits

Optimum safety

No transportation of explosives

No explosives storage

No explosives before loaded in boreholes

Excellent water resistance

Environmentally frendly - optimum explosives fumes

Maximum flexibility regarding adjustment of energy and density on

site

High loading capasity, 100 - 300 kg/min

High accessability, hole length up to 40 m, up to 40 m difference

in level

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Historically, explosives have been classified as

primary and secondary, high and low, ideal and non-

ideal.

It is stored chemical energy and converted into a

mechanical work by the formed gases (reaction

products).

The term energetic material is perhaps better than

explosive, because it explains what it is all about.

The difference between a Detonation and a

Deflagration is “only” the energy release rate.

Explosives (Energetic materials)

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1 12 14 16

2723 35 39 40

atomsmoleculesmole /10023.61 23

14

SymbolAtomic number

NameAtomic weight [g/mole]

Explosive Energy

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Nitro - Glycerine Energy

H

ONO2

C

H2

ONO2

C

ONO2

C

H2

241

223

225

29353 3 ONOHCOONHC

A complete ideal reaction of one mole Nitro-glycerine:

The temperature of reaction products is 2600 ºC and

the pressure is 4.8 GPa with a total energy of 6.4

MJ/Kg.

1 mole of the molecule

Nitro-glycerine contains 3

mole Carbon, 5 mole

Hydrogen, 3 mole

Nitrogen and 9 mole

Oxygen atoms.

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Diesel contains 10 times more energy than

Dynamite (45 MJ/Kg).

If 1 Kg of diesel is used in a car in 10 minutes

the total effect is 125 KW.

A typical effect of a Jet-engine is 8000 KW.

A Dynamite 25 x 380 mm cartridge has a weight

of 250 g and an energy of 1.1 MJ.

Then this cartridge detonates with a velocity of

4500 m/s its energy is released in 0.1ms. This is an

effect of 11 000 MW.

OHCOnOHC 2222612 1312

Energy and Effect

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The energy level must be sufficient to overcome the

structural strength of the rock and permit displacement.

Energy must be

confined long

enough after

detonation to

establish fractures

and enlarge existing

cracks and displace

material. Optimum

explosive

performance

Energy

confinement

Explosive energy level

Energy

distribution

Energy must be

evenly distributed.

Optimum Explosive Performance

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Explosive energy level and distribution

The energy

level must be

sufficient to

overcome

structural

strength of

the rock and

permit

displacement.

Energy must

be evenly

distributed.

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Energy must be confined long enough after detonation to

establish fractures and enlarge existing cracks and

displace material.

Incident / Consequence:

Explosive gases of high temperature and pressure find the easiest

path to free face. As the rock-mass expands the pressure and

temperature drops. If the gasses went to early they cause air blast

and fly rock.

Caused by:

Burden variations, face cavities.

Drill deviation and positioning error.

Non homogeneous rock mass.

Bad timing.

Energy confinement & timing

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Explosive energy level and distribution

Incident / Consequence:

Excess or shortage of explosive energy will cause air blast, fly

rock, back break and vibrations.

Caused by:

Unfavourable shape of the bench.

Bench to stiff.

Unfavourable bench height, drill diameter, burden and spacing.

Bad selection of explosive,initiations system, drill bits and steel.

Drill deviation.

Cavities or weakness zones.

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Air-Bags:

It makes a part of the hole confined with

air. The stemming is kept in place by the

swelling action of the plastic air-bag,

after the chemical reaction of air-bag

gases .

The length of the air-deck is dependent

on the geological conditions, and the

presence of ground water in the blast

hole. It is often found with trial and error.

Reduction of the energy level in the blast

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Deck Charging:

The explosive divided by decks of

sand / gravel. Each deck is initiated by

a detonator & booster.

The energy of the explosive in each

deck may vary.

The delay time often increase from the

bottom of the hole to the top.

This method is often used to reduce

cost, vibrations and fragmentation.

Reduction of the energy level in the blast

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Core – Air Deck

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Explosive2 diameter, d [mm]

Explosive1 diameter, D, [mm]

Energy difference of a 32 mm Dynamite vs. 104 mm Dynamite in hole 104 mm,

which =(100%).

Decupling of explosive in the hole:

%5.91001005.4*2.1*104*104

5.4*2.1*32*32

2*2*

1*1*2

2

energydensityD

energydensitydEdiff

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Packing Degree

= 100%

= 84%

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VOD

VOD Recorder:

Measures the Velocity Of

Detonation which is only

the reliable instrument to

test the quantity and

performance of explosive

charges inside the blast-

hole, in term of explosive

velocity, as well as

determines delay time of

detonators, in order to

optimize blasting cost

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VOD Data

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VOD Recorder

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Initiation Systems

• Detonating Cord (DC).

• Electric Detonators.

• Shock Tube Systems (Nonel).

• Electronic Detonators.

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Detonatin Cord

PLASTIC

YARN

PETN

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Detonatin Cord

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DC = Top Initiation

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Electric Detonators

Types:

- Ms- serial No 1-20

• 25 ms between

each number.

- Hs- serial No 1-12

• 500 ms between

each number.

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NPED-Technology

Conventional NPED

Leg wires

Fuse head

Seal plug

Base charge

Payro-technical Delay element

Primary expl.

DDT-element

Non

Primer

Explosives

Detonators

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Delay Between Rows

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Firing Pattern

1 2 2 1 1 1 1 1

2 3 3 2 2 2 2 2

3 4 4 3 3 3 3 3

4 5 5 4 4 4 4 4

Straight firing plan

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1 1

2 2

3 3

4 4

2

3

4

5

2

3

4

5

3

4

5

6

4

5

6

7

5

6

7

8

6

7

8

9

7

8

9

10

8

9

10

11

9

10

11

12

Directed firing plan

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1 4 4 3 3 2 2 1

2 5 5 4 4 3 3 2

3 6 6 5 5 4 4 3

4 7 7 6 6 5 5 4

V-Shap firing plan

Firing Pattern

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Comparison firing plans

1

2

1 1 1 1 1

2 2 2 2

2

3

2 2 2

2

3 3 3 3 3 3

3

3 3

3

3

4

4

4

4

4 4

4 4 4

4

4

4

4 4 5 5 5 5

5

5

6

5

5

6

6

6 7 7

Fragmentation

Back break

Throw

Longer

More

Cours

er

Fin

er

Less

Short

er

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Shock Tube Systems

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500 ms 525 550 575

0 ms 25 50 75

Nonel = Bottom Initiation

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The proper delay between rows depends on:

42 ms 67 ms

Previous blast mucked out

No of rows Equipment

Delay Between Rows

Charge concentration

Rock proporties

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Dynoline

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Nonel Tube

Det. Cord

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Dynostart

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NONEL

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= SL 25 (25 ms)

= SL 0 (0 ms)

NONEL Firing Pattern

Straight firing plan

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= SL 25 (25 ms)

= SL 0 (0 ms) Directed firing plan

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= SL 0 (0 ms)

= SL 67 (67 ms)

Normal firing plan

NONEL Firing Pattern

= SL 25 (25 ms)

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= SL 25 (25 ms)

V-Shaped firing plan

NONEL Firing Pattern

= SL 0 (0 ms)

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= SL 0 (0 ms)

= SL 17 (17 ms)

= SL 25 (25 ms)

= SL 42 (42 ms)

V-Shaped firing plan

NONEL Firing Pattern

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Electronic Detonators

The electronic initiation system designed to optimize

your blasting results.

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The electronic system is an important advance in

technology, enabling users to achieve the precision and

flexible timing benefits, with the easy connections of current

non-electric shock tube systems.

Electronic Detonators

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Electronic Detonators

Electronic detonators is an Auto-programmable system

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i-Kon (Orica)

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Delay between the rows

is too long.

Timing

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Incident / Consequence:

Front row moves to far, resulting in fly rock and air blast.

The muck pile profile is flat.

The fragmentation is coarse.

Timing is related to explosives energy and blastability.

Action: 1) Reduce the energy.

2) Reduce delay between the rows

3) Improve the blastability by changing the blast direction.

Timing

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Delay between the rows is too short.

Timing

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Incident / Consequence:

Front row does not create enough space for the next row to expand

causing stemming injection, air blast and back break.

The muck pile profile is high, and compacted.

The fragmentation is fine.

This problem increase by an increasing number of rows.

Action:

1) Increase the energy.

2) Increase the delay between the rows.

3) Reduce the number of rows.

4) Improve the blastability by changing the blast direction.

Timing

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Dynamic burden movement and relief:

Optimal energy and timing of a blast is achieved if the front row moves

1/3 of the burden before the next row begins to move. This creates a

volume of 33% in front of the row for expansion.

The energy level must be sufficient to overcome the structural strength

of the rock and permit displacement.

This method takes the blastability of the rock into consideration

Burden movement can be studied in a video of the blast. High Speed

Digital Video Camera has 250-1000 frames/s (4-1ms between

frames). Objects of known sizes may be put on the blast for dimension

calibration. The video is captured to a computer with Motion Analysis

Software (MAS) that can advance or print frame by frame.

Timing Optimisation

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Timing Optimisation

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High Speed Video Digital Camera

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L.S. Quarry

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Timing Contour

Timing between:

- hols 17ms.

- rows 42ms.

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Timing Contour

Timing between:

- hols 17ms.

- rows 67ms.

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Blasting Theory

Radial Fraction (Compressive stress wave).

Reflection Breakage (Tensile stress wave) 3.0ms.

Gas Extension Pressure (Rock movement).

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Blasting Mechanism

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Charging

Bottom charge Qb

Column charge Qp

Stemming h0

•Bottom Charge:

• Column Charge:

• Stemming:

• Specific Charge:

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Bottom Charge

Bottom

charge

Qb

Bottom charge diameter

=

Hole diameter - appr 10 mm

Length of bottom

charge

=

V x 1,3 (m)

Cartridged Products

High explosive energy.

Cap sensitive.

Easy to charge into the hole.

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Column Charge

Column

Charge

Qp

Column charge concentration = Kg/m.

Should be 40 - 100% of

the bottom charge

concentration

Bulk Products

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Normaly U = V

Increased stemming

gives less fly rock but an

increased number of

boulders and vice versa.

Stemming

Stemming U

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Incident / Consequence: Air blast, Fly rock and loss of energy.

Action:

1) Increase the length of the deck.

2) Select correct size and quality of the material.

- Avoid fines and drill cuttings in the material.

0.7:Burdenlength Stemming

[mm]diameter hole 0.05Size[mm]

The stemming of the hole does not prevent the blasting

gasses from ejecting trough the stemming.

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Muck pile shape.

Vibration.

Fragmentation.

Available equipment

ensuring efficient digging

and hauling.

Optimal Blasting

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Fragmentation best suited

for the down stream process,

and quality of the final product.

Blasting is the cheapest

method to crush rock.

Often a focus on reduction of

fines and oversize material.

Fragmentation

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Fragmentation digital measurement

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Fragmentation digital measurement

Suez Cement

Transforming intellectual property into cost / productivity

improvements by conducting and implementing structured projects that deliver ongoing, measurable savings.

First step is to baseline the current processes.

Second step is to validate and agree on potential benefits of identified drill and blast projects that directly effect downstream processes.

Third step is to implement systems to lock in benefits for the long term.

Fourth step is to regularly audit the process to ensure the benefit accrues.

Optimal blasting a group approach

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IMPROVE process

Blast design

Product

selection

Drilling

Loading

Blasting

Hauling

Processing

Mine

Planning

Identify

Measure

Prioritise

Respond

Operate

Validate

Execute

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Improve quality control of loading practices

Select explosive and initiation system to do the job

Select shape and layout of blast to optimum explosive performance

Optimise blast size, boundaries and pit slope stability. Mine Planning

Blast design

Product selection

Drilling

Loading

Blasting

Hauling

Processing

Drill holes at correct location and angel to the correct depth, min. deviation.

Optimise explosive performance, creating a fragmentation and muck pile

best suited for the down stream process and quality of the final product.

Max. Value

Maximize blasting value

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Mine planning

Optimise blast size, boundaries and pit slope stability.

Map geological properties and detect optimal blasting

direction.

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NE and SW blasting direction in this quarry did cause

adverse back break, poor fragmentation , air blast and fly

rock.

Mine planning

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Blasting directions of an isotropic rock with shallow dipping

joints & faults.

Blasting

direction

Example Fragmen

tation

Back-break

and Toe

Floor

A Poor Problems Problems

B Good Some

problems

Average

C Good Minor Average

D Good Minor Average -

Poor

Mine planning

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Blasting Direction

Blasting in direction (A) did cause damage to the

wall, massive boulders, poor floor and big

problems for the next blast.

The next blast was also shot in the same

direction, but to avoid similar result the 25 holes

by 16 rows blast was shot with a ~ 2 ms/m

burden delay between holes and a ~ 9 ms/m

spacing delay between rows.

A

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Blasting Direction

Helwan Limestone Quarry:

The cut of quarry face did not

respect the alignment of blast-

holes, sliding behind for more

than 18m, following the existing

fault plane.

The next blast was also shot in

the same direction, but to avoid

similar result the 7 holes by 3

rows blast was shot. The result

was excellent.

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Blasting results are often influenced more by geology

than explosive properties.

Geology Effects

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Bedding, jointing and faulting:

Influences fragmentation and boulder count, back break and wall stability.

Compressive strength:

Strength of rock under compression influences the production of fines close to

the hole.

Tensile strength:

Strength of rock under tension. Crack formation and fragmentation.

Poissons ratio:

The relationship of lateral deformation to longitudinal deformation, influences

wall control and back break.

Youngs modulus

The ability to withstand or resist deformation. Influences blastability.

Rock Impedance

The velocity that rock will transmit compression waves multiplied by the

density of the rock. Influences blastability.

Geology Effects

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Select shape and layout of blast

to avoid adverse edge effects, fly

rock and air blast enabling efficient

blasting and optimum explosive

performance.

Blast design

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A B

C D

E

A: Not bad. Some damage to

corners.

B: Very good shape utilizing to

free faces.

C: Damage to corners.

stemming ejection and air

blast.

D: Damage to corners. High

probability for stemming

ejection and air blast.

E: Box-cut = damage, air blast

and fly rock.

Bench design

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Hole angel.

Number of free faces.

Sub-drill.

Diameter of the hole.

Stiffness of the bench

Effects of Explosive Energy

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Bench design

• The broken rock needs 30 - 40

% extra volume for swell.

• Avoid 90° corners.

• Utilize free faces.

Select a shape, length to depth ratio to minimize back

break, stemming ejection and air blast.

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Bench Stiffness

The stiffness of the bench is the bench height divided by

the burden.

VKS

Stiffnessratio 1 2 3 4

Fragmentation Bad Medium Good Excellent

Air-blast Bad Medium Good Excellent

Fly-rock Bad Medium Good Excellent

Vibrations Bad Medium Good Excellent

Comments BAD DESIGN New

design if

possible

Increasing the

stiffness-ratio

above 4 does

not always give

a positive effect

K : Bench height [m]

V: Burden [m]

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Edge effects and burden movement

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JK Sim-Blast Software

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JK SimBlast Software

Suez Cement

JK SimBlast Software

Suez Cement Title 162

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