2. OBJECTIVE
• ROCK IS BLASTED EITHER TO BREAK IN TO SMALLER PIECES SUCH AS IN MOST
MINING AND QUARRYING OPERATIONS OR LARGE BLOCKS FOR DIMENSIONAL
STONE MINING AND SOME CIVIL ENGINEERING APPLICATION, OR TO CREATE
SPACE.
• IN MINING AND QUARRYING OPERATION, THE MAIN OBJECTIVE IS TO EXTRACT THE
LARGEST POSSIBLE QUANTITY AT MINIMUM COST. THE MATERIAL MAY INCLUDE
ORE, COAL, AGGREGATE FOR CONSTRUCTION AND ALSO THE WASTE ROCK
REQUIRED TO REMOVE THE ABOVE USEFUL MATERIAL.
• THE BLASTING OPERATION MUST BE CARRIED OUT TO PROVIDE QUALITY AND
QUANTITY REQUIREMENTS OF PRODUCTION IN SUCH A WAY THAT OVERALL PROFIT
OF MINING ARE MAXIMIZED.
3. TYPE OF EXPLOSION
• THE EXPLOSION IS, ACCORDING TO BERTHELOT, 'THE SUDDEN EXPANSION OF
GASES IN A VOLUME MUCH LARGER THAN THE INITIAL, ACCOMPANIED BY
NOISE AND VIOLENT MECHANICAL EFFECTS'.
• THE TYPES OF EXPLOSION ARE THE FOLLOWING:
MECHANICAL
ELECTRIC
NUCLEAR
CHEMICAL, FROM THE MINING POINT OF VIEW, ONLY THE LAST ARE OF
INTEREST
4. EXPLOSIVE
“EXPLOSIVE IS A SOLID OR LIQUID SUBSTANCE OR A MIXTURE OF SUBSTANCES
WHICH ON APPLICATION OF A SUITABLE STIMULUS IS CONVERTED IN A VERY
SHORT TIME INTERVAL INTO OTHER MORE STABLE SUBSTANCES, LARGELY OR
ENTIRELY GASEOUS, WITH THE DEVELOPMENT OF HEAT AND HIGH PRESSURE”.
OR
“COMMERCIAL EXPLOSIVES ARE THOSE THAT ARE A MIXTURE OF COMPOUNDS,
SOME COMBUSTIBLE AND SOME OXIDIZING WHICH, WHEN PROPERLY INITIATED,
HAVE AN ALMOST INSTANTANEOUS EXOTHERMIC REACTION THAT GENERATES A
SERIES OF HIGH TEMPERATURE GASEOUS PRODUCTS THAT ARE CHEMICALLY
MORE STABLE AND TAKE UP A LARGER VOLUME”
5. DETONATION AND DEFLAGRATION
• CHEMICAL EXPLOSIVES, DEPENDING UPON THE CONDITIONS TO WHICH THEY ARE
EXPOSED, CAN OFFER DIFFERENT BEHAVIOR THAN WOULD BE EXPECTED FROM
THEIR EXPLOSIVE NATURE. THE DECOMPOSITION PROCESSES OF AN EXPLOSIVE
COMPOUND ARE:
COMBUSTION: THIS CAN BE DEFINED AS ANY CHEMICAL REACTION CAPABLE OF
GIVING OFF HEAT, WHETHER IT IS ACTUALLY FELT BY OUR SENSES OR NOT.
THE DEFLAGRATION: THIS IS AN EXOTHERMIC PROCESS IN WHICH THE
TRANSMISSION OF THE DECOMPOSITION REACTION IS MAINLY BASED UPON
THERMAL CONDUCTIVITY. IT IS A SUPERFICIAL PHENOMENON IN WHICH THE
DEFLAGRATION FRONT ADVANCES THROUGH THE EXPLOSIVE IN PARALLEL LAYERS
AT A LOW SPEED WHICH, USUALLY, IS NOT OVER 1.000 M/S.
THE DETONATION: IN THE DETONATING EXPLOSIVES, THE SPEED OF THE FIRST
GASIFIED MOLECULES IS SO GREAT THAT THEY DO NOT LOSE THEIR HEAT
THROUGH CONDUCTIVITY TO THE UNREACTED ZONE OF THE CHARGE BUT
TRANSMIT IT BY SHOCK, DEFORMING IT AND PROVOKING ITS HEATING AND
ADIABATIC EXPLOSION, GENERATING NEW GASES
6. PROPERTIES OF EXPLOSIVE
• THE PROPERTIES OF EACH GROUP OF EXPLOSIVES GIVE PREDICTION OF THE
PROBABLE RESULTS OF FRAGMENTATION, DIS-PLACEMENT AND VIBRATIONS. THE
MOST IMPORTANT CHARACTERISTICS ARE:
• STRENGTH AND ENERGY DEVELOPED
• DETONATION VELOCITY
• DENSITY
• DETONATION PRESSURE
• WATER RESISTANCE
• SENSITIVITY
• OTHER PROPERTIES WHICH AFFECT THEIR USE AND MUST BE TAKEN INTO
ACCOUNT ARE: FUMES, RESISTANCE TO HIGH AND LOW TEMPERATURES, DESENSITIZATION BY EXTERNAL CAUSES, ETC.
7. EXPLOSIVE TYPE
LOW EXPLOSIVE
HIGH EXPLOSIVE
• Slow and deflagrating explosive
(under 2000 m/s)
• Includes Gunpowder, propulsive
compounds for fireworks.
• Practically no application in mining
and civil engg.
• With exception of ornamental rocks.
• Rapid and Detonating explosive ( between 2000-7000
m/s)
Primary explosive
• Sensitive to Stimuli like weak
mechanical shock, spark or flame.
• Mercury fulminate, Lead Azide, Lead
Styphnate
• Generally used in Detonators
Secondary explosive
• Capable of detonation only
under the influence of shock
wave generated by PE.
8. INDUSTRIAL
EXPLOSIVE
BLASTING AGENT
• Mixtures, with few
exceptions, do not
contain ingredients
classified as explosive.
• Explosive needing
another high explosive
• ANFO
• ALANFO
• Slurries and Water gels
• Emulsions
• Heavy ANFO
CONVENTIONAL
EXPLOSIVE
• Essentially made up of explosive
substances.
• Best known that act as a sensitizers
of the mixtures.
• Gelatin dynamite
• Granular dynamite
PERMISSIBLE EXPLOSIVE
• Designed for use in U/G coal mines.
where the presence of explosive
gases and dust is dangerous for
normal blasting.
• Low explosion temperature.
• Medium or low strength
• Detonation velocity between 20004500 m/s.
• Density between 1.0-1.5 g/cc
• Generally poor water resistance
9. PRIMERS AND BOOSTERS
• A PRIMER CHARGE IS AN EXPLOSIVE IGNITED BY AN INITIATOR, WHICH, IN TURN,
INITIATES A NON CAP-SENSITIVE EXPLOSIVE OR BLASTING AGENT.
• A PRIMER CONTAINS CAP-SENSITIVE HIGH EXPLOSIVE INGREDIENTS. OFTEN HIGHLY
SENSITIZED SLURRIES, OR EMULSIONS ARE USED WITH BLASTING CAPS OR
DETONATING CORD.
• BOOSTERS ARE HIGHLY SENSITIZED EXPLOSIVES OR BLASTING AGENTS, USED EITHER
IN BULK FORM OR IN PACKAGES OF WEIGHTS GREATER THAN THOSE USED FOR
PRIMERS.
• BOOSTERS ARE PLACED WITHIN THE EXPLOSIVE COLUMN WHERE ADDITIONAL
BREAKING ENERGY IS REQUIRED.
• OFTEN-TIMES, CARTRIDGE OR PLASTIC-BAGGED DYNAMITES OR SENSITIZED WET
BLASTING AGENTS ARE USED AS PRIMERS AS WELL AS BOOSTERS.
• BOOSTERS ARE OFTEN USED NEAR THE BOTTOM OF THE BLASTHOLE AT THE TOE
LEVEL AS AN ADDITIONAL CHARGE FOR EXCESSIVE TOE BURDEN DISTANCES. THEY
ARE ALSO PLACED WITHIN THE EXPLOSIVE COLUMN ADJACENT TO GEOLOGICAL
10. INITIATING SYSTEM
• ELECTRICAL SYSTEM- TILL DETONATOR OF PRIMING, ONLY ELECTRICAL WIRES
ARE ATTACHED.
• NON-ELECTRIC SYSTEM- THERE IS NO ELECTRIC WIRE IS REQUIRED IN THE
HOLE.
• D-CORD OR DETONATING FUSE
11. ELECTRICAL SYSTEM
• THERE ARE MAINLY THREE TYPES OF ELECTRICAL INITIATION SYSTEM WHICH
ARE WIDELY USED IN MINES.
• INSTANTANEOUS ELECTRIC DETONATORS
• LONG/SHORT ELECTRIC DELAY DETONATOR
• ELECTRONIC DETONATOR
12. ELECTRIC DETONATORS
• IN ELECTRIC DETONATORS ELECTRIC ENERGY/CURRENT (AC/DC) IS SENT
THROUGH COPPER LEG WIRE TO HEAT AN INTERNAL CONNECTING BRIDGE WIRE.
• THE HEAT INITIATES THE HIGH PRIMARY EXPLOSIVE PRESENT IN THE DETONATOR
WHICH, IN TURN, DETONATES THE SECONDARY EXPLOSIVE PRESENT IN THE
DETONATOR.
• ELECTRIC DETONATORS ARE USED TO INITIATE OTHER EXPLOSIVE, DETONATING
CORD AND SHOCK TUBE.
• FOR DELAY PURPOSE PYROTECHNICAL DELAY CHARGE IS USED.
• THREE TYPES OF ELECTRIC DETONATORS
INSTANTANEOUS ELECTRIC DETONATORS
SHORT DELAY DETONATORS (MILLISECOND DELAY)
LONG DELAY DETONATORS (HALF SECOND DELAY)
• TIME DELAYS WITH INTERVALS OF 25, 50, 100, 500, AND 1000 MS ARE AVAILABLE FOR
SHORT- (MS) OR LONG-PERIOD (LP) DELAYS
13. ELECTRIC DETONATORS
• SAFE BLASTING PRACTICES DICTATE THAT PRECAUTIONS ARE USED TO AVOID
BLASTING IN THE VICINITY OF EXTRANEOUS ELECTRICITY SUCH AS STRAY
CURRENT, STATIC ELECTRICITY, ELECTRICAL STORMS, AND RADIO FREQUENCY
ENERGY WHEN USING ELECTRIC CAPS.
15. ELECTRONIC DETONATORS
• ELECTRONIC DETONATOR HAVE AN ELECTRONIC COUNTER ON A MICROCHIP IN
PLACE OF PYROTECHNIC DELAY CHARGE.
• ADVANTAGES:
HIGHER TIMING PRECISION (10 MICROSECOND THAN 1-10 MS SCATTER)
INCREASE CONTROL TIME DELAY
GREATER SAFETY AGAINST ACCIDENTAL IGNITION (CODED FIRING SIGNALS)
• DISADVANTAGES
HIGHER PRICE BECAUSE OF CHIP AND CAPACITOR
BACK TO ELECTRIC WIRING-RISK OF GROUND FAULTS OR POOR CONTACTS
17. NON ELECTRIC SYSTEM
• NON-ELECTRIC INITIATION SYSTEMS INCLUDE A CAP SIMILAR TO THAT OF AN ELECTRIC
CAP, BUT THEY ARE CONNECTED TO PLASTIC TUBING OR A TRANSMISSION LINE THAT
CARRIES AN INITIATION (SHOCK AND HEAT) TO INITIATE THE CAP.
• THE ENERGY SOURCE IN THE TUBING IS EITHER A GAS MIXTURE OR AN INTERNAL
COATING OF SPECIAL EXPLOSIVE.
• NOT USED IN UNDERGROUND COAL OR GASSY MINES
• PROVIDE NEARLY INFINITE NUMBERS OF DELAYS IN BLASTING PATTERNS.
• DELAYS ARE AVAILABLE IN SHORT AND LONG PERIODS AS WELL AS IN-HOLE AND
SURFACE DELAYS.
• ADVANTAGE
ABILITY TO DESIGN BLASTS WITH A GREATER NUMBER OF HOLES THAN TRADITIONAL
ELECTRIC BLASTING.
DANGER OF STRAY CURRENTS ARE ELIMINATED WITH THE USE OF NON-ELECTRIC
19. DETONATING CORD
• DETONATING CORD CONSISTS OF A CORE OF PETN ENCLOSED IN A TAPE WRAPPING
THAT IS FURTHER BOUND BY COUNTER-LACED TEXTILE YARNS. THE CORD IS EITHER
REINFORCED OR COMPLETELY ENCLOSED BY STRONG WATERPROOF PLASTIC.
• THEIR ENERGY RELEASE DEPENDS ON THE AMOUNT OF PETN IN THE CORE, WHICH
GENERALLY VARIES FROM 1.5 G/M TO 70 G/M.
• 10 G/M IS THE PETN WEIGHT OF STANDARD DETONATING CORD WHOSE VOD IS ABOUT
7000 M/S.
• A DETONATOR IS REQUIRED TO INITIATE A LENGTH OF DETONATING CORD WHICH
CANNOT BE NORMALLY INITIATED BY FIRE.
20. DETONATING CORD
• DETONATING CORD HAS TWO FUNCTIONS:
• TO PROVIDE SIMULTANEOUS DETONATION OF SEVERAL INTERCONNECTED
BLASTHOLE CHARGES, THUS AVOIDING THE NEED FOR MULTIPLE ELECTRIC OR PLAIN
DETONATORS
• TO PROVIDE CONTINUOUS INITIATION OF THE FULL LENGTH OF AN EXPLOSIVE
COLUMN IN A BLASTHOLE, AS DISTINCT FROM POINT INITIATION WITH INDIVIDUAL
DETONATORS.
23. • DRILLED BURDEN (B) - IS DEFINED AS THE DISTANCE BETWEEN THE INDIVIDUAL ROWS
OF HOLES. IT IS ALSO USED TO DESCRIBE THE DISTANCE FROM THE FRONT ROW OF
HOLES TO THE FREE FACE. WHEN THE BENCH FACE IS NOT VERTICAL THE BURDEN ON
THIS FRONT ROW OF HOLES VARIES FROM CREST TO TOE.
• SPACING (S) - IS THE DISTANCE BETWEEN HOLES IN ANY GIVEN ROW.
• SUBGRADE (J) - GENERALLY THE HOLES ARE DRILLED BELOW THE DESIRED FINAL
GRADE. THIS DISTANCE IS REFERRED TO AS THE SUBGRADE DRILLING OR SIMPLY THE
SUB-DRILL
• STEMMING (T) - A CERTAIN LENGTH OF HOLE NEAR THE COLLAR IS LEFT UNCHARGED.
THIS WILL BE REFERRED TO AS THE STEMMING LENGTH (T) WHETHER OR NOT IT IS
LEFT UNFILLED OR FILLED WITH DRILL CUTTINGS/CRUSHED ROCK.
• BENCH HEIGHT (H) – IS THE VERTICAL HEIGHT FROM THE TOE TO THE CREST.
• DRILLED LENGTH (L) - IS EQUAL TO THE BENCH HEIGHT PLUS THE SUB-DRILL.
• LENGTH OF THE EXPLOSIVE COLUMN (LE) - IS EQUAL TO THE HOLE LENGTH MINUS THE
STEMMING. THIS COLUMN MAY BE DIVIDED INTO SECTIONS (DECKS) CONTAINING
24. BENCH HEIGHT
BENCH HEIGHT IS DECIDED BY
• PRODUCTION REQUIRED
• TYPE OF DEPOSITE
THICKNESS
GEOLOGY
QUALITY
• EQUIPMENT
26. BURDEN
SOME IMPORTANT EMPIRICAL FORMULAS FOR BURDEN
• B = 24*D+0.85 (VUTUKURI)
• B = (25-30)*D (HAGAN)
• B = K*D*(P*T)^0.5 (PEARSE), WHERE K = CONSTANT (0.7-1), MORE FOR WEAK ROCK
P = PEAK EXPLOSIVE PRESSURE, KG/CM^2
T = TENSILE STRENGTH OF ROCK, KG/CM^2
• BURDEN IS GENERALLY 25-40% OF BENCH HEIGHT DEPENDING UPON ROCK
PROPERTIES, FRAGMENTATION, AND EXPLOSIVE USED.
27. SPACING
• GENERALLY WE TAKE SPACING AS 1.1-1.5 TIMES OF BURDEN.
SUBGRADE DRILLING
• HOLES ARE DRILLED LONGER THAN BENCH HEIGHT TO AVOID TOE PROBLEMS.
THIS EXTRA DRILLING IS CALLED AS SUBGRADE DRILL.
• Sd = 0.1*H
• Sd = 0.3*B
