WHAT IS AN EXPLOSIVES?
a. Chemical compounds or mixtures that are initiated by HEAT, SHOCK or a combination of both.
b. Decomposes or explodes very rapidly and Violently
c. Produces a rapid release of HEAT and large quantities of High Pressure Gas
Detonation Process
CLASSIFICATION OF EXPLOSIVES
TYPES OF EXPLOSIVES
Comparative Build Up
Definitions That Apply To Explosive Manufacturing
a. PRECURSORS - Non-explosive raw materials used in the preparation of a BLASTING AGENT (Ammonium Nitrate, Fuel Oil, Emulsion Matrix)
b. BLASTING AGENTS - Term used to describe Non-Ideal Explosive mixtures
1. Prepared from Precursors
2. Not Cap sensitive
3. Manufactured on Site
Blasting Agent Precursors
1. Ammonium Nitrate (AN)
a. Principle component (oxidiser )
b. Properties: Low Moisture, Free Flowing, Oil Absorbency, Low Density, Good Friability, Non-Caking
c. Cycles above and below 35 - 37o C
d. Decompose around 250o C release O2
e. Can detonate under extreme conditions
2. Fuel Oil (FO)
a. Fuel component (Distillate)
b. Flashpoint greater than 61o C
c. Fuels such as petrol or kerosene must never be used (flashpoints below 61oC) making them too volatile
3. Emulsion (Matrix)
a. Viscous liquid mixture of oxidiser/water solution suspended in fuel
b. Stabilised with emulsifiers
c. Dangerous Good until density is reduced by adding sufficient ANFO or by Gas or solid sensitisation
Physical Properties of Explosives
1. Density
a. How close or small the particles are the higher the density and greater the weight
b. Measured as grams per cubic centimetre (g/cc)
c. Weight compared to water (1.00g/cc) float or sink
d. Higher density explosives is normally suited to HARD massive rock and low density explosives more suitable to SOFT jointed rock
e. Determines the weight of explosive per blasthole
2. Critical Density
“Critical Density is when the product is so dense that there is not sufficient gas voids for the creation of hot spots to allow detonation”
a. Explosives density and sensitivity are related
b. Deadpressing occurs when gas voids are destroyed (by abuse, shock waves) reducing sensitivity
3. SENSITIVITY
Explosives require the creation of hot spots to maintain the reaction
Types of Test
a. Gap sensitivity
b. Drop Test
c. Minimum Primer
4. BLASTHOLE LOADING DENSITIES
5. WATER RESISTANCE
“Explosives penetrated by water have their efficiency impaired”
Water resistance depends on:
a. Explosives ability to withstand water
b. Packaging of product
c. Type of water
d. Static (low pressure)
e. Dynamic (high pressure)
6. Critical Diameter
“Critical diameter is the minimum diameter that a detonation will occur or continue”
Caused/Determined
By loss of energy from the edge effects of the detonation process
a. Ideal Explosives small critical diameter
b. Non-ideal Explosives much larger
7. Chemical Stability
“An explosives ability to remain chemically unchanged under specified storage conditions (shelf life)”
a. Ideal Explosives Excellent (molecular bonding)
b. Non-Ideal Explosives Less stable (Bonding reliant on chemical additive)
Factors Affecting Chemical Stability
a. Temperature extremes
b. Poor quality raw material
c. Contamination
d. Poor storage facilities
e. Combination of the above may accelerate deterioration
Fume Characteristics
“Gases resulting from detonation”
1. Principal Gases
Non-Toxic Toxic
a. Carbon Dioxide Carbon Monoxide
b. Nitrogen Nitrogen Oxides
c. Water (steam)
2. Causes
a. Water Penetration Lack of Confinement
b. Poor Mixing Not Oxygen Balanced
Velocity of Detonation
“The speed at which a detonation occurs”
Factors that influence VoD
a. Product type Particle size (molecular, liquid, solid)
b. Explosive Diameter Slows closer to critical diameter
c. Degree of confinement Varies in the blasthole and patterns
d. Degree of Priming Steady state VoD or overdrive is achieved faster with with high energy primers
e. Temperature Higher product temperature the faster the reaction
Due to the above variables VoD is not always a good indicator as to product performance
Detonation Pressure
“The application of detonation pressure to the blasthole wall as the reaction zone travels along the charge column that is responsible for the primary shock wave”
Blasthole Pressure
“Pressure applied by the expanding gases to the walls of the blasthole and jointing”
Explosive Energy/Strength
“Field performance has shown that fragmentation and rock displacement are not exclusively reflected in the numerical values of explosives energy/strength”
Detonating Cords
a. Contains a Core of PETN
b. Sizes Vary but generally 3.6g, 5g or10g per metre
c. VoD 6400 m/s
d. Initiated by: No 8 caps
Detonating Cord
(10g should not be initiated with cords less than 5g)
e. Purpose: Used as surface and down-hole initiating lines
Emulsion Cartridges
a. Contains SENSITISED emulsion in wrapped cartridges
b. Sizes Vary from 25mm to 80mm diameters
c. VoD dependant on product type and diameter
d. Initiated by: No 8 caps
Detonating Cord (10g)
Density 1.6 g/cc
e. Purpose: Used for wet and small hole diameter blasting, On occasions may be used as a booster or primer
Bulk Emulsion Blends
a. Emulsion and ANFO blends are water resistance gassed bulk emulsions designed to be pumped from a bulk delivery truck through a delivery hose to the bottom of the blasthole
b. Minimum Hole diameter depends on the product and blend (75 - 98mm)
c. VoD dependant on product type, density, blend, diameter, confinement, primer type…
e. Initiated by:Boosters
f. Density can be 1.00 g/cc to 1.25 g/cc
g. Purpose: An effective Blasting Agent for wet holes that allows complete coupling in the blasthole, allows for variable density across the shot and added ANFO can modify explosive performance if required
Emulsions
Essentially a liquid oxidiser phase Suspended in a Continuous fuel phase with an emulsifier added to the fuel phase to prevent separation.
Heavy ANFO
a. ANFO mixed with emulsion matrix in blends where the majority of the mixture is ANFO. Heavy ANFO are ANFO based explosives with higher detonation properties and better water resistance, they are augred from a bulk delivery truck from the top of the blasthole
b. Minimum Hole diameter depends on the product and blend (89mm - 127mm)
c. VoD dependant on product type, density, blend, diameter, confinement, primer type
d. Initiated by:Boosters
e. Density can be 0.85 g/cc to 1.30 g/cc
f. Purpose: Emulsion provides a water resistant coating to the ANFO, this increases the bulk density, hence higher energy