16613018 Blasting Operations

8/8/2019 16613018 Blasting Operations

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Blasting OperationsBlasting Operations

Prepared byPrepared by

Dr. Ayman ElDr. Ayman El--MidanyMidany

44thth year Miningyear Mining


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WEEK ONEWEEK ONE


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IntroductionIntroduction

GeneralGeneral typestypes ofof ExplosivesExplosives

CommercialCommercial explosivesexplosives

MilitaryMilitary explosivesexplosives


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Ingredient Chemical formula Function

Ethylene glycol dinitrate

Nitrocellulose (guncotton)

Nitroglycerin

NitrostarchTrinitrotoluene (TNT)

Metallic powder

Black powder

Pentaerythritol tetranitrate

(PETN)

Lead azide

Mercury fulminateAmmonium nitrate

Liquid oxygen

Sodium nitrate

Potassium nitrate

Ground coal - Charcoal

Paraffin

SulfurFuel oil

Wood pulp

Lampblack

Kieselguhr

Chalk -Calcium carbonate

Zinc oxide

Sodium chloride

C2H4(NO3)2C6H7(NO3)2O2C3H5(NO3)3

C7H5N3O6Al

NaNO3 + C+ S

C3H8N4O12

Pb(N3)2

Hg(ONC)2NH4NO3O2NaNO3KNO3C

CnH2n+2

S(CH3)2(CH2)

(C6H16O3)nC

SiO2CaCO3ZnO

NaCI

Explosive base lowers freezing point

Explosive base gelatinizing agent

Explosive base

Explosive baseExplosive base

Fuel sensitizer : used in high density slurries

Explosive base

Explosive base

Explosive used in blasting caps

Explosive used in blasting capsExplosive base : oxygen carrier

Oxygen carrier

Oxygen carrier lowers freezing point

Oxygen carrier

Combustible, or fuel

Combustible, or fuel

Combustible, or fuelCombustible, or fuel

Combustible, absorbent

Combustible

Absorbent prevents caking

Antacid

Antacid

Flame depressant (permissible explosives)


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Chemical explosivesChemical explosives

isis aa compoundcompound oror mixturemixture whichwhich isis capablecapable ofofundergoingundergoing extremelyextremely rapidrapid decompositiondecomposition..

AnAn explosionexplosion cancan bebe brokenbroken downdown intointo fourfourphasesphases

ReleaseRelease ofof gasgas

IntenseIntense heatheatExtremeExtreme pressure,pressure, andand

TheThe explosionexplosion


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Chemical explosivesChemical explosives

WhenWhen thethe explosiveexplosive isis detonated,detonated,

gasgas isis released,released, temperaturetemperature ofof thethe gasgas increases,increases,

pressurepressure alsoalso increasesincreases (Charles(Charles law)law)..

movemove andand breakbreak thethe rockrock..


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How to compare explosivesHow to compare explosives

StrengthStrength

DetonatingDetonating velocityvelocity

FumeFume classclass WaterWater resistanceresistance

DensityDensity

PhysicalPhysical characteristicscharacteristics

StorageStorage

FreezingFreezing

DetonationDetonation pressurepressure

EnergyEnergy

SensitivitySensitivity SensitivenessSensitiveness

FlammabilityFlammability


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StrengthStrength :: %% ofof activeactive materialmaterial

VelocityVelocity of of DetonatingDetonating (VOD)(VOD):: isis thethe

velocityvelocity atat whichwhich thethe detonationdetonation wavewave movesmoves

throughthrough thethe explosiveexplosive (ft/s(ft/s oror m/s)m/s)

FumeFume classclass :: thethe amountamount ofof toxictoxic fumesfumeswhichwhich determinedetermine itsits safetysafety toto bebe usedused inin

particular particular situationsituation suchsuch asas undergroundunderground

operationsoperations..


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DetonationDetonation pressurepressure :: isis thethe pressure pressure behindbehind

thethe detonationdetonation frontfront..

EnergyEnergy

SensitivitySensitivity :: thethe minimumminimum energy/pressureenergy/pressure

neededneeded forfor detonationdetonation..

SensitivenessSensitiveness:: measuremeasure ofof explosionexplosion wavewave

spreadingspreading fromfrom oneone stickstick toto anotheranother..

FlammabilityFlammability :: easinesseasiness toto igniteignite byby flameflame oror

heatheat


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WaterWater resistanceresistance :: isis thethe abilityability toto resistresistcontaminationcontamination oror aa reductionreduction inin strengthstrength whenwhenexposedexposed toto waterwater.. SometimesSometimes determineddetermined byby thethe

lengthlength ofof timetime itit cancan bebe submergedsubmerged inin waterwater andandstillstill performperform asas designeddesigned..

DensityDensity :: isis thethe explosiveexplosive wtwt perper givengiven volumevolume..

AA cartridgecartridge ofof 9090 stickssticks perper 5050--lblb casecase isis denserdenserthanthan aa cartridgecartridge ofof 110110 stickssticks perper 5050--lblb casecase.. AidAidinin blastblast designdesign..


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PhysicalPhysical characteristicscharacteristics:: commercialcommercial explosivesexplosives

cancan taketake threethree basicbasic formsforms:: granular,granular, gelatin,gelatin, andand

slurryslurry.. TheThe formform dependsdepends onon thethe formula,formula, andand thethe

choicechoice ofof formform dependsdepends onon thethe usageusage requiredrequired..

TheThe packagepackage forfor thethe samesame explosiveexplosive productproduct maymay

alsoalso varyvary accordingaccording toto usageusage.. ForFor example,example, aa

slurryslurry cancan bebe pumpedpumped intointo aa boreholeborehole withwith nonocontainer,container, oror itit cancan bebe packagedpackaged inin polyethylenepolyethylene

bagsbags toto permitpermit handlinghandling inin smallersmaller amountsamounts..


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StorageStorage:: howhow explosiveexplosive cancan bebe storedstored withoutwithout

affectingaffecting itsits safety,safety, reliability,reliability, andand performanceperformance..

EarlyEarly nitroglycerinnitroglycerin (NG)(NG) dynamitesdynamites werewere

extremelyextremely poorpoor forfor storingstoring duedue toto separationseparation ofof

NGNG fromfrom thethe otherother componentscomponents andand createscreates anan

extremelyextremely hazardoushazardous conditioncondition..

FreezingFreezing :: importantimportant forfor safetysafety andand performanceperformance

especiallyespecially inin coldcold climateclimate.. AnitfreezingAnitfreezing additivesadditives

maymay bebe usedused..


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Drills and drillingDrills and drilling

TheThe drillingdrilling systemsystem consistsconsists ofof thethe drilldrill:: thethe drilldrill

steel,steel, oror rodrod;; andand thethe bitbit.. TheThe bitbit penetratespenetrates thethe

rockrock byby thethe forceforce itit imposesimposes onon thethe rockrock.. BitsBits areare

designeddesigned forfor percussion,percussion, rotaryrotary drilling,drilling, oror bothboth..

HandHand heldheld drillsdrills

ExternalExternal percussionpercussion drillsdrills

DownDown--thethe--holehole drillsdrills

RotaryRotary drillsdrills


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Rock Shear strengthRock Shear strength

RockRock ConditionCondition

ShearShear

strength,strength,

lb/inlb/in22

SandstoneSandstone SoftSoft

MediumMedium

Hard grayHard gray

FineFine--grained browngrained brown

MediumMedium--grained friable graygrained friable gray

15001500

30503050

47204720

36003600

28402840


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Rock Shear strengthRock Shear strength

RockRock ConditionCondition

ShearShear

strength,strength,

lb/in2lb/in2

LimestoneLimestone Hard flossiliferrousHard flossiliferrousHard grayHard gray

Medium crystallineMedium crystalline

4160416065206520

76007600

SiltstoneSiltstoneDolomiteDolomite

quartzitequartzite

300030001270012700

1060010600


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Drill SelectionDrill Selection

SizeSize ofof projectproject :: drilldrill typetype andand sizesize

HoleHole diameterdiameter :: drilldrill typetype andand bitbit sizesize

DepthDepth ofof cutcut :: longlong oror shortshort RockRock hardnesshardness:: percussionpercussion ((44--66..55)) oror rotaryrotary ((22--

33..55)) onon MohsMohs scalescale

CapitalCapital :: machinemachine priceprice CostCost :: costcost per per footfoot ofof borehole borehole needneed

specializedspecialized operatoroperator


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WEEK TWOWEEK TWO


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Firing systemsFiring systems

BlastingBlasting CapCap

DetonatingDetonating systemssystems


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Blasting CapsBlasting Caps

BlastingBlasting CapCap :: areare smallsmall cylindricalcylindrical tubestubes thatthat

detonatedetonate capcap--sensitivesensitive explosivesexplosives.. TheyThey areare

usuallyusually mademade ofof coppercopper oror aluminumaluminum andand

containscontains anan explosiveexplosive..

ThereThere areare threethree typestypes ofof blastingblasting capscaps::

CommonCommon capscaps MillisecondMillisecond delaysdelays (MS(MS delays)delays)

StandardStandard delaysdelays


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Common Blasting CapsCommon Blasting Caps DetonatedDetonated byby aa fusefuse

NowNow theythey areare thethe leastleast commoncommon

CopperCopper oror aluminumaluminum CylinderCylinder

3838 mmmm longlong XX 66 mmmm dia,dia, closedclosed atat oneone endend..

ContainsContains twotwo typestypes ofof chargescharges :: ignitingigniting chargecharge andand

thethe basebase chargecharge..

AA safetysafety fusefuse isis insertedinserted intointo thethe openopen endend ofof thethe capcaptoto ensureensure thatthat thethe flameflame reachesreaches thethe ignitingigniting chargecharge

completelycompletely.. ToTo preventprevent waterwater andand contaminantscontaminants fromfrom

enteringentering thethe capcap andand inhibitinginhibiting detonationdetonation..


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Common Blasting CapsCommon Blasting Caps

WhenWhen thethe fusefuse isis ignited,ignited, thethe powderpowder corecore burns,burns,

actingacting asas aa vehiclevehicle throughthrough whichwhich thethe firefire isis

transmittedtransmitted toto thethe ignitingigniting chargecharge endend ofof thethe capcap..

TheThe burning burning fusefuse spitsspits aa flameflame resemblingresembling aa jetjet

flameflame calledcalled asas ignitionignition spitspit..

WhenWhen thethe flameflame travelstravels toto thethe cap,cap, itit ignitesignites thetheignitionignition charge,charge, whichwhich detonatesdetonates thethe basebase charge,charge,

whichwhich inin turnturn detonatesdetonates thethe explosiveexplosive chargecharge thatthat isis

beingbeing primedprimed withwith thethe capcap..


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Common Blasting CapsCommon Blasting Caps

Base charge

Ignition

charge

Fuse


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Electric Blasting CapsElectric Blasting Caps

MoreMore controllablecontrollable methodmethod

ContainsContains chargescharges likelike thethe commoncommon cap,cap, butbut

insteadinstead ofof safetysafety fusefuse thethe capcap containscontains twotwo wireswiresthatthat meetmeet atat aa bridgebridge wirewire..

whenwhen electricelectric currentcurrent isis applied,applied, thethe bridgebridge wirewire

burns,burns, ignitingigniting thethe chargecharge inin thethe capcap..

EnablesEnables thethe blasterblaster

toto choosechoose thethe suitablesuitable timetime ofof detonationdetonation

toto shootshoot moremore holesholes thanthan thethe safetysafety fusefuse methodmethod


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Delay Blasting CapsDelay Blasting Caps

AreAre capscaps thatthat areare detonateddetonated by by electricityelectricity inin

variousvarious timetime--delaydelay intervalsintervals..

TwoTwo typestypes :: standardstandard andand millisecondmillisecond (MS)(MS).. AdvantagesAdvantages ofof (MS)(MS) areare::

ReduceReduce groundground vibrationvibration

ImproveImprove fragmentationfragmentation

ProduceProduce lessless flyrockflyrock

ReduceReduce costscosts

ReduceReduce overbreakoverbreak


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Delay BlastingDelay Blasting

Flyrock, excessive movement of blasted rock in the

air, caused by not using delay blasting. Second row

cannot move toward face and therefore must

either fly or remain in place.

Free face1st rowFlyrock


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Delay blasting can help reduce flyrock by

permitting the rock to move in the direction

desired rather than moving haphazardly

through the air.

Blasting without delays requires more drilling

and explosive to break the rock because the rock

tends to resist breakage and lack of a sufficientnumber of free faces.

Delay blasting reduces overbreak.


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Free face


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Other Blasting CapsOther Blasting Caps

Vented caps : with vents to delay blasting

to reduce the combustion rate in the

blasting cap.

Composition Electric caps : contains amixture of chemical compounds.


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Detonating SystemsDetonating Systems

The main components of an electric detonating system

Blasting cap

Blasting wire Power source or blasting machine

Detonating cord

Transmit detonations from blasting cap to explosives Less sensitive than blasting caps

Is a high explosive and burns at speed > 4miles/second


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Blasting CircuitsBlasting Circuits

Three types of circuits

Single-series

Straight parallel

Parallel-series


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Blasting CircuitsBlasting Circuits

Problems


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Theory of BreakageTheory of Breakage

Purpose of blasting

One solid piecep smaller pieces (fragmentation)

pto be moved or excavated (movement).

Underground blasting, for example, requires

greater fragmentation than surface blasting

because of the size of the equipment that can be

used and the difficulty of access.

Get the desired results with a minimum cost


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Involves two basic processes:

Radial cracking

Flexural rupture

Rock is stronger in compression than in tension.

Therefore, the easiest way to break rock is to

subject it to a tensile stress greater than itsultimate strength in tension.

Rocks are heterogeneous (contain different types

of rocks). They differ in their density.


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Borehole

Free face

Compressionwaves

Radial cracking


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The distance from the borehole to the free

face is the burden.

The denser the rock the faster the waves

Proper fragmentation when enough to

travel to the face and back overcoming the

tensile strength of the rock.

Along the face the outermost edge is

stretched in tension which causes cracks.


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Flexural RuptureFlexural Rupture

The second process in breaking rock by

bending the rock to the point where the

outside edge, the side in tension, breaks. Caused by the rapid expansion of gases in

borehole.

Analogous to the bending and breaking of abeam.

Movement or displacement are required in

addition to cracking.


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Flexural RuptureFlexural Rupture

After detonation the redial cracks expands

and the gas starts to the movement by

putting a CS

against the borehole wallcausing its bending.

The deeper the hole, the greater the burden

and borehole spacing. M = wl2/8 where w is the load (burden), l is

the borehole length.


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StemmingStemming

Is non-explosive material that is placed in the borehole

between the top of the explosive column and the collar of

the hole.

Sand, drill fines, or gravel

Confine and delay the escape of expansive gases and

increases the explosives efficiency (reduces the explosive

used).

Reduce the flyrocks, increase ground vibration, and air

blast

Rifling : in case of impropoer stemming, blowing of the

stemming material.


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Angle of BreakageAngle of Breakage

Is the measured angle at which a homogeneous material

can be expected to break from the explosive charge to the

free face.

135r

90r

Free face


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WEEK THREEWEEK THREE


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Blast DesignBlast Design

Is the safe and economic way to do blasting

Factors affecting blasting designFactors affecting blasting design

Geological factors (out of blasters control)

Controllable factors

Borehole dia.

BurdenSpacing

Stemming

Design of the delay firing system.


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Hole DiameterHole DiameterDepends on

The availability of the equipment

The depth of the cut

The distance of the nearest structure.

Max dia. Depends on the hole depth L (ft) = 2D (in)

There are four methods to decrease the explosives amount:

Use delay firing

Shorten the depth of the cut

Decrease the hole dia

Use decking technique


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Burden & spacing determinationBurden & spacing determination

Burden is the distance from the blast hole to the nearest

perpendicular free face.

Free face

Spacing

Burden


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Burden & spacing determinationBurden & spacing determination

Andersen Formula B= (dL)0.5

B : burden, ft d : borehole dia, in

L : borehole Length, ft

Langefors Formula V= (db/33) [Ps/cf(E/V)]0.5

V : burden, m db : dia of drill bit, mm

P : degree of packing = 1-1.6 kg/dm3

s : wt strength of explosives (1.3 for gelatin)

c : rock constant, generally 0.45

f : 1 degree of fraction, for straight hole = 1

E/V = ratio of spacing to burden


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Spacing determinationSpacing determination

Spacing is the distance between blast holes fired in the same

row

It is necessary to complete burden calculations before

determining the spacing.

S= (BL)0.5

B : burden, ftL : borehole Length, ft


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Controlled BlastingControlled Blasting

To control overbreak and to aid the stability of the

remaining rock formation.

There are 4 methods

Line drilling (unloaded), Fig.8-2 Cushion blasting

Smooth-wall blasting

Presplitting


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Controlled BlastingControlled Blasting Line drillingLine drilling

Provides a plane of weakness to which the rock can break.

Helps to reflect shock waves,

Reduces the shattering effect of the rock outside the

perimeter. Do not exceed 3 in in dia and are spaced one to four

diameters apart (due to cost).

Are not loaded

Requires more drilling more than the other controlled

blasting methods.

Is not very effective in non-homogeneous formations


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Controlled BlastingControlled Blasting Line drillingLine drilling

Unloadedline drill

holes

Freeface


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Cushion BlastingCushion Blasting Requires a single row of holes ( 2 to 3.5 in) in dia.

Permits a reduction in the No. of holes required by line-drilling

Unlike line-drilling holes, the cushion holes are loaded with light

charges.

Holes are fully stemmed between charges, allowing no air gap, and

are fired after the production shot has been excavated.

The stemming acts as a cushion to protect the finished wall from the

shock waves. The larger the borehole, the greater the cushion.

Not suitable for underground - tough stemming requirements.

Drawbacks: (1) requires removal of excavated material before firing

(costly due to production delay no excavation for entire area at

once). (2) Sometimes the production shot can break back to the

cushion holes, creating redrilling problems and causing loading

changes.


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SmoothSmooth--wall Blastingwall Blasting Similar to cushion blasting


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PrePre--splittingsplitting

Creates a plane of shear in solid rows along the desiredexcavation before the production blast.

All holes are loaded like cushion blasting

Reduces overbreak

Reduces the vibration

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