..

,.., ".'.) Bia.st Design CalvinJ.Konya,Ph.D . PrecisionBlasting Services Montville,Ohio Intercontinental Development,Montville,Ohio44064 ' \::..>.... :;... 1995 by Intercontinental Development Corporation Montville,Ohio44064,U.S.A. Allrightsreserved.Nopart of thisbook may be reproduced,inany formor by any means, without permissionin writingfrom the publisher. Printedinthe United Statesof America 10987654321 ISBN0-9649560-0-4 I 0 ~ .'1 i - I I "" I4 ~!... ~(.1 I """' k I ..., CONTENTS Preface .................................................................................. vii 1Explosives Engineering...................................................... 1 Introduction .................................................................. 1 Sources of Explosive's Energy ......................... 2 Shock Energy .................................................. 4 Gas Energy ...................................................... 5 Chemical Explosives ....................................... 6 Identification of Problem Mixtures......................... 11 2Mechanics of Rock Breakage ........................................... 13 Shock Energy inRock Breakage ................................ 13 Confined Charges inBoreholes .................................. 14 Bench Stiffness .......................................................... 16 Breakage Process ...................................................... 18 3Explosive Products ........................................................... 19 Environmental Characteristics of Explosives .............. 19 Sensitiveness ................................................ 19 Water Resistance .......................................... 20 Fumes ........................................................... 22 Flammability .................................................. 23 Temperature Resistance ................................ 24 The Cycling of Ammonium Nitrate ........... 24 Cold Resistance ...................................... 25 Performance Characteristics of Explosives ................ 27 Sensitivity ...................................................... 27 Velocity .......................................................... 28 Detonation Pressure ...................................... 29 Density .......................................................... 30 Strength ......................................................... 31 Cohesiveness ................................................ 32 Commercial Explosives .............................................. 32 Dynamite ....................................................... 33 Granular Dynamite ........................................ 34 Straight Dynamite .................................... 34 High Density Extra Dynamite ................... 35 Low Density Extra Dynamite .................... 35 Gelatin Dynamite ........................................... 35 Straight Gelatin Dynamite ........................ 35 Ammonia Gelatin Dynamite ..................... 36 Semigelatin Dynamite ............................. 36 Slurry Explosives ........................................... 36 Cart ridgedSlurries ................................... 38 Bulk Slurries ............................................ 38 Dry Blasting Agents .................................................... 39 CartridgedBlasting Agents ............................ 40 Bulk ANFO .................................................... 41 Water Resistance of Ammonium Nitrate ........ 41 Energy Output of ANFO ................................. 42 Properties of BlastingPrills ............................ 43 Heavy ANFO ................................................. 45 Two Component Explosives ....................................... 46 4INITIATORS &BLASTHOLE DELAY DEVICES ................ 47 Introduction ................................................................ 47 Electric BlastingCaps ................................................ 47 Instantaneous EB Caps .................................. 49 LongPeriodDelay Electric Caps .................... 49 Millisecond Delay Electric BlastingCaps ........ 49 Electronic Delay BlastingCaps ................................... 49 Magnadet ................................................................... 50 Magnadet Electric Detonator &Magna Primer WorkingPrinciple .................................... 50 Initiation Source ............................................. 50 Detonator Description .................................... 50 Magnadet Sliding Primers .............................. 51 Safety Features Claimed ............................... 53 Operational Advantages Claimed .................. 53 Sequential BlastingMachine ...................................... 53 Non-Electric Initiation Systems ................................... 54 Detaline Initiation System .............................. 55 Detaline Cord ................................................. 55 II ,. ~ ~ ... ,. . ~ .\.; ...__ Detaline MS Surface Delays .......................... 55 Detaline MS In-Hole Delays ........................... 56 Detonating Cord &Compatible Delay Systems ........... 56 DelayedPrimers ......................................................... 57 Shock Tube Initiation Systems ................................... 58 LP Series Shock Tube Initiators ..................... 58 S.L. Series Primadets .................................... 58 L.L.H.D.Series Shock Tube Initiators ............ 59 Shock Tube Trunkline Delays ........................ 59 EZ Det (Ensign Bickford) ............................... 60 5PRIMER AND BOOSTER SELECTION.............................. 61 Primer Types .............................................................. 61 Determination of Numbers Needed ................ 63 SelectionCriteria for Primer. .......................... 63 Primer Selection Guidelines ........................... 65 Booster ...................................................................... 65 Effects of DetonatingCord onEnergyRelease ........... 66 6BLAST DESIGN ................................................................. 68 Burden...................................................................... 68 Adjustments for Rock & Explosive Type ........ 70 Corrections for Numbers of Rows .................. 72 Geologic Correction Factors .......................... 73 StemmingDistance .................................................... 75 Subdrilling .................................................................. 77 Selectionof Blasthole Size ......................................... 80 Blasting Considerations ................................. 80 Initiation TimingandCap Scatter ................... 82 TimingEffects onFragmentation ............................... 84 Hole-To-Hole Delays ...................................... 85 Row-To-Row Delays ...................................... 85 Borehole Timing Effects ............................................. 87 Fragmentation Size ....................................... 87 Piling or CastingMaterial... ............................ 87 Air Blast andFlyrock ...................................... 87 Maximum Vibration ........................................ 88 Firing Time Overlap ....................................... 88 Ill Effects of Time andDistance ......................... 90 Cap Scatter ................................................... 92 Overbreak, Backbreak andEndbreak ............ 94 7PA ITERN DESIGN .................................................. 95 Principle of ProductionBlasting Patterns .................... 95 Instantaneous Initiation Low Benches ............ 97 Instantaneous Initiation High Benches ........... 98 DelayedInitiation Low Benches ..................... 98 Delayed Initiation HighBenches .................... 99 Maximum Fragmentation ......................................... 100 Rock Fragmentation ................................................. 102 Fragmentation ............................................. 102 Kuznetsov Equation ..................................... 103 Size Distribution ........................................... 104 Field Results ................................................ 105 Limitations of the Kuz-RamModel ...............106 Effects of BlastingParameters on"n"....107 The Effects of Stronger Explosives ........107 Fragmentation Effects onWall Control ........107 Rip-Rap Production .................................................. 126 Rock PilingConsiderations ....................................... 127 SinkingCuts ............................................................. 129 Hillside or Sliver Cuts ............................................... 132 Utility TrenchDesign ................................................133 Secondary Blasting.................................................. 135 Mud Capping(Boulder Busting) ...................135 Blockhoting(Boulder Busting) ...................... 135 Air Cushion Blasting ....................................136 8OVERBREAK CONTROL ...........................................137 ControlledBlasting ................................................... 135 Principles of Operation ................................ 138 Effects of Local Geologic Conditions ...........144 Presplitting ................................................... 145 Trim (Cushion)Blasting ............................... 147 Trim Blasting With Detonation Cord ............. 149 Line Drilling ................................................. 149 IV 0 e ~~ .. ~ ,9 l; -Assessment of Results ................................. 150 Causes of Overbreak ............................. 152 Backbreak ............................................. 153 Endbreak ............................................... 155 Flyrock Control ...................................... 155 9UNDERGROUND BLAST DESIGN .................................. 157 Introduction .............................................................. 157 Shafts ...................................................................... 157 Ring Drilled Vertical Hole Design ................. 158 Burden Determination ............................ 159 Number of Rings ................................... 159 Burden Actual. .......................................159 Spacing of Holes inRing(Estimate) ......160 Number of Holes/Ring ........................... 160 Spacing Actual /Ring .............................160 Depthof Advance .................................. 160 Subdrill .................................................. 161 Stemming .............................................. 161 Look Out ............................................... 161 Timing ................................................... 161 Tunneling ................................................................. 163 Bum or ParallelHole Cuts ........................... 165 Design of Cut Holes ............................... 167 Calculations of Bum Cut Dimensions ...........167 Empty Hole(s)(DH) ...............................167 Calculation of 81for Square1 ...............169 Simplified Bum Cut Calculations ...........170 Depth of Blast Hole (H) .......................... 170 Depth of Advance(L)(Expected) ...........171 StopingHoles ........................................ 171 Lifter Holes ............................................ 171 Contour Holes,(Rib &Back Holes) ........172 Blasthole Timing .................................... 172 Initiator .................................................. 172 V-Cut ........................................................... 174 V-Cut Design ............................................... 176 Determination of Burden ........................ 176 SpacingBetween Holes (Vertically) .......177 V-Angle ........... , ..................................... 177 v Depth of Cut or Advance (L) .................. 177 Stemming Distance ............................... 178 Lifter and Stoping Holes ........................ 178 Contour (Rib & Back)Holes ................... 178 Look Out ............................................... 178 Blasthole Loading .................................. 178 Timing Sequence .................................. 178 FanCuts ...................................................... 180 HeadingandBench Methods .......................181 10VIBRATION AND SEISMIC WAVES .............................. 183 Seismic Waves ........................................................ 183 Wave Parameters ........................................ 183 VibrationParameters ................................... 184 Understanding VibrationInstrumentation ..................185 Seismic Sensor ............................................ 185 Seismograph Systems ................................. 186 VibrationRecords andInterpretation ........................188 Seismograph Record Content.. .................... 188 FieldProcedures and Operational Guides ....190 Practical Interpretations ............................... 191 Factors Affecting Vibration ....................................... 192 PrincipalFactors .......................................... 192 Charge - Distance Relationship ....................192 EstimatingParticle Velocity ......................... 194 Vibration Control... ....................................... 194 Delay Blasting ....................................... 195 Propagation Velocity vs.Particle Velocity ..................................... 196 Scaled Distance .................................... 197 Adjusted Scaled Distance ...................... 200 Particle Velocity - Scaled Distance Graph ............ 200 Ground Calibration ................................ 201 Factors Effecting Vibration .................... 202 VI : : .; 9: ! ~) i ~i .i , ., ' ~ , 1-~ !' ,. ) " .. I : ) ~ ;.i.. 1 . ,. I ' .. ~.41111i\ ~11BLAST VIBRATION STANDARDS ....................... 204 Standards Development ........................................... 204 Recent Damage Criteria .............................. 206 Alternative Blasting Criteria ......................... 207 The Office of Surface Mining Regulations ....209 Characteristic Vibration Frequencies ............ 212 Spectral Analysis ......................................... 213 Response Spectra ....................................... 214 Long Term VibrationandFatigue ................. 214 Walter's Test ......................................... 215 CERL Tests ........................................... 215 Koerner Tests ........................................ 216 VibrationEffects .......................................... 216 Directional Vibrational Effects ................ 216 Non-Damage Effects ............................. 217 Causes for Cracks Other Than Blasting .................................... 218 Sensitivity to Vibration .............................................. 219 Effects of BlastingonWater Wells &Aquifers .......... 221 Aquifers ....................................................... 221 VibrationEffects .......................................... 221 Open Cut ..................................................... 222 12AIR BLAST MONITORING AND CONTROL. ................. 223 Air Blast ................................................................... 223 Overpressure andDecibels ...................................... 223 Glass Breakage ........................................................ 224 Scaled Distance for Air Blast.. .................................. 225 Regions of PotentialDamage for Air Blast.. .............. 226 Near Field .................................................... 226 Far Field andAir Blast Focusing .................. 226 Atmospheric Inversion ................................. 227 WindEffect.. ................................................ 228 Procedures to Avoid Air Blast Focusing ....... 230 VII I - "i - ... ~ ,. l. a 1' .. . ~Preface Thepurposeof thisbookis tofamiliarizeminingandcivil engineers,contractors,andblasters with the basic fundamentals of blastdesign.Blastinghasadvancedfromanarttoascience, whereby,manyoftheblastingvariablescanbecalculatedusing simple design formulas. Thistextisnotmeanttobeahandbookorencyclopedia onblasting,rather it is meant toshow a methodof designwhichis rationalandfollowsscientificprinciples.Thestep-by-stepdesign methodsdescribedinthisbookwillcarrythereaderfrombasic knowledgeonexplosivesthroughconsiderationsforproperblast design.Thebookconcentratesonthefundamentalsofblast designrather thandetails whichcanbelearnedfromother texts or fromfieldexperience.Littletimeisspentdiscussingbasic tie-ins of initiationsystemsandinformationof thistypesinceitisreadily availableinother sources.Thisbook willservethebeginnerand theprofessionalalikesinceitsortsthoughthevastamountof informationavailableandputsforthalogicaldesignprocedure. Thebookbacksupthedesignwithsomeofthebasicprinciples andtheoriesnecessary tohaveanunderstandingwhythings work as they do. Theblastingindustryisrapidlychangingwithnew theories,productandtechniques.Itisthegoaloftheauthorto providethereader withabetter understandingof technologyasit is today.It alsopoint out methodof overcomingcommonblasting problems . Thetechniques,formulas,andopinionsexpressedinthis book arebasedontheexperienceof theauthor.Theyshouldaid thereaderinassessingblastdesignstodeterminewhetherthey arereasonableandwhethertheyshouldworkunderaverage blastingconditions . VIII - I I, .fj .. - "" .. Onearearelatedtoblastingwhichremainsanartisthe properassessmentof thegeologicconditionsathand.Improper assessmentmayproductpoorresultsintheblast.Complex geology andother factorsmayrequirechangesinthedesignfrom thoseshowninthebook,however,themethodspresentedwould bethefirststeptocalculateblastdesigndimensionswhichthen mayhave tobemodifiedtoaccommodateunusuallocalgeologic conditions . Calvin J.Kanya IX . , - I I .1 l ~ ' - ,.. ,. ~ ~ 1. EXPLOSIVES ENGINEERING 1.1INTRODUCTION Most rawmaterials,fromwhichourmodernsocietyisbuilt,are producedbytheuseofexplosivesinminesthroughouttheworld.The constructionofhighways,canalsandbuildingsareaidedbytheuseof explosives.Theplentifulfood,whichisavailableinthiscountry,would notexistwithoutexplosivestoproducethefertilizersandthemetallic ores,whichultimately become tractors andother equipment Theuseofexplosivesinminingandconstructionapplications datesback to1627.From1627through1865,theexplosiveusedwas blackpowder.Blackpowderwasadifferenttypeofexplosivethanthe explosivesusedtoday.In1865,Nobelinventednitroglycerindynamitein Sweden.Heinventedgelatindynamitesin1866.Thesenewproducts weremoreenergeticthanblackpowderandperformeddifferentlysince confinement of the explosive wasnot necessary toproducegoodresults, aswasthecasewithblackpowder.From1867 throughthemid-1950's, dynamite was the workhorse of the explosive industry . Inthemid-1950's,anewproductappearedwhichwascalled ANFO,ammoniumnitrateandfueloil.Thisexplosivewasmore economicaltousethandynamite.Duringthedecadesof the1970'sand the1980's,ANFOhasbecometheworkhorseoftheindustryand approximately80%ofallexplosivesusedintheUnitedStateswas ammonium nitrate andfueloil. Othernewexplosiveproductsappearedonthesceneinthe 1960'sand1970's.Explosives,whichwerecalledslurriesor watergels, havereplaceddynamiteinmanyapplications.Inthelate1970's,a modificationof thewatergelscalledemulsionsappearedonthescene . Theemulsionsweresimple tomanufactureandcouldbeusedinsimilar applicationsasdynamitesandwatergels.Commerciulexplosivesfall intothreemajorgenericcategories,dynamites,blastingagentsand slurries (commonly called water gels or emulsions) . Blastingproblemsgenerallyresultfrompoorblastdesign,poor executionindrillingandloadingtheproposeddesignandbecausethe rock mass was improperly evaluated. Blast designparameters suchasburden,stemming,subdrilling, spacingandinitiationtimingmustbecarefullydeterminedinorderto haveablastfunctionefficiently,safelyandwithinreasonablevibration and air blast levels. Controlledblastingalonghighwaysmustbedonetoreduce maintenance costsandproduce stablesafecontours.Those responsible for theexecutionandevaluationof controlledblastingmustbeawareof theproceduresusedtoproduce acceptableresultsandmustunderstand how geologic factorscanchange the appearance of the finalcontour. Rockstrengthschangeoverbothsmallandlargescale. Geologicstructuressuchasjoints,beddingplanes,faultsandmud seamscauseproblems.These variationsinstructurerequiretheblaster tochangehispatternsandmethodstoobtainreasonableresults. Therefore,onemustassume,fromsurfaceindicators,whattherock mass willbeatdepth.Thedrillingof blastholesprovidesinformationas towhat typeof structureintersects thoseholes.Toenable theblaster to makeenlightenedjudgments,whenadjustinghisblastingpatternto compensateforrockstructure,hemusthaveathoroughunderstanding ofexactlyhowtheexplosivefunctionsduringblasting.Withoutthat understanding,blastingis just arandom trial-and-error process. Thisbookwasdesignedtoprovideasystematicapproachto blastdesign.Theinformationispresentedinapracticalmanner.The bookprovidesthereaderwithinformationtopromoteanunderstanding of thephenomenonandtheanticipatedresults.Theformulaspresented areempiricalandshouldprovidereasonablevaluesforgeneraljob conditions.However,unusualgeologicconditionscanrequire adjustments to calculatedvalues. 1.1.1SOURCES OF EXPLOSIVE'S ENERGY Twobasicformsofenergyarereleasedwhenhighexplosives react.Thefirst typeof energywillbecalledshockenergy.Thesecond typewillbecalledgasenergy.Althoughbothtypesofenergyare releasedduringthedetonationprocess,theblaster canselectexplosives withdifferentproportionsofshockorgasenergytosuitaparticular application.Ifexplosivesareusedinanunconfinedmanner,suchas mud capping boulders (commonly calledplaster shooting)or for shearing structuralmembersindemolition,theselectionofanexplosivewitha highshockenergywouldbeadvantageous.Ontheotherhand,if explosivesarebeingusedinboreholesandareconfinedwithstemming materials,anexplosive withahighgasenergy output wouldbebeneficial. 2 .; ~.t ~. ~.L ~ .fl .fl ~n s etr a eu tI/I fc .b To help formamentalpicture of the differencebetweenthe two typesofenergy,comparethedifferenceinreactionofalowandhigh explosives.Lowexplosivesarethosewhichdeflagrateorburnvery rapidly.Theseexplosivesmayhavereactionvelocitiesof 600to1500 meter per second andproduce no shock energy.They produce work only fromgas expansion.Avery typicalexample of alow explosive wouldbe blackpowder.Highexplosivesdetonateandproducenotonlygas pressure,butalsoanotherenergyorpressurewhichiscalledshock pressure.Figure1.1showsadiagramofareactingcartridgeoflow explosive.If the reactionisstopped when the cartridgehasbeenpartially consumedandthepressureprofileisexamined,onecanseeasteady riseinpressureatthereactionuntilthemaximumpressureisreached. Lowexplosivesonlyproducegaspressureduringthecombustion process.Ahighexplosivedetonatesandexhibitsatotallydifferent pressureprofile (Figure 1.1 ). p r e s u r . Reactionfront] fly Cartridgeof Lowexplosive Gasenergy p r e s s u r . Cortrldgeof Highexploslve Figure 1-1Pressure Profiles for Low and High Explosives Duringa detonation inhighexplosives,the shock pressure at the reactionfronttravelsthroughtheexplosivebeforethegasenergyis released.Thisshock energy,normally isof higher pressure thanthegas pressure.Aftertheshockenergypasses,gasenergyisreleased.The gasenergyindetonatingexplosivesismuchgreater thanthegas energy releasedinlow explosives.Inahighexplosive,there are twodistinct and separatepressures.Theshockpressureisatransientpressurethat travels at the explosives rate of detonation.Thispressureisestimated to account for only10% to15% of the totalavailableusefulwork energyin theexplosion.Thegaspressureaccountsfor85%to90%of theuseful work energyandfollowsthereafter.However,the gasenergy producesa forcethatisconstantlymaintaineduntiltheconfiningvessel,the borehole,ruptures. 3 1.1.2SHOCK ENERGY Inhighexplosives,ashockpressurespikeat thereactionfront travelsthroughtheexplosivebeforethegasenergyisreleased.There are,therefore,twodistinctseparatepressuresresultingfromahigh explosiveandonlyonefromalowexplosive.Theshockpressureisa transientpressure that travelsattheexplosivesrateof detonation.The gaspressure follows thereafter. Theshockenergyiscommonlybelievedtoresultfromthe detonationpressureoftheexplosion.Thedetonationpressureisa functionof theexplosivedensitytimestheexplosiondetonationvelocity squaredandisa formof kineticenergy.Determinationof thedetonation pressureisverycomplex.Thereareanumberofdifferentcomputer codeswrittentoapproximate thispressure.Unfortunately,thecomputer codescomeupwithwidelyvaryinganswers.Untilrecently,nomethod existedtomeasure thedetonationpressure.Now thatmethodsexist to produceaccuratemeasurements,onewouldhopethatthecomputer codes wouldbecorrected.Until that time occurs,one coulduse oneof a number of approximations to achieve anumber that may approximate the detonationpressure.Asanexample,one coulduse: where: p d Ve 4.5x 10-6 Ve2d P=------1+0.8 d Detonationpressure Density of the explosive Detonationvelocity ( 1. 1) (Kbar) (g/cm3) (m/s) Thedetonationpressureorshockenergycanbeconsidered similar tokineticenergyandismaximuminthedirectionof travel,which wouldmeanthatthedetonationpressurewouldbemaximuminthe explosivecartridgeattheendoppositethatwhereinitiationoccurred.It isgenerallybelievedthatthedetonationpressureonthesidesofthe cartridgeare virtually zero,since thedetonationwavedoesnot extendto theedgesof thecartridge.Togetmaximumdetonationpressureeffects fromanexplosive,itisnecessary toplace the explosiveson the material tobe brokenandinitiateit fromtheendopposite thatincontact withthe material.Layingthecartridgeoveronitssideandfiringinamanner wheredetonationisparalleltothesurfaceof thematerialtobebroken reducestheeffectsof thedetonationpressure.Instead,thematerialis subjectedtothepressurecausedbytheradialexpansionof thegases afterthedetonationwavehaspassed.Detonationpressurecanbe effectivelyusedinblastingwhenshootingwithexternalchargesor 4 ' .( charges which are not inboreholes.Thisapplicationcanbe seeninmud cappingorplastershootingof bouldersorintheplacementof external charges onstructuralmembers during demolition (Figure 1.2). Boulder GOOD Figure 1-2Mud Cap Blasting Tomaximize the use of detonationpressureone wouldwant the maximumcontactareabetweentheexplosiveandthestructure.The explosiveshouldbeinitiatedontheendoppositethatincontact withthe structure.Anexplosiveshouldbeselectedwhichhasahighdetonation velocityandahighdensity.Acombinationofhighdensityandhigh detonation velocity resultsina highdetonationpressure. 1.1.3GASENERGY Thegasenergyreleasedduringthedetonationprocesscauses themajorityofrockbreakageinrockblastingwithchargesconfinedin boreholes.Thegaspressure,oftencalledexplosionpressure,isthe pressurethatisexertedontheboreholewallsbytheexpandinggases afterthechemicalreactionhasbeencompleted.Explosionpressure resultsfromtheamountof gasesliberatedperunitweightofexplosive andtheamountofheatliberatedduringthereaction.Thehigherthe temperatureproduced,thehigher thegaspressure.If moregasvolume isliberatedat the same temperature,the pressure willalsoincrease.For aquickapproximation,itisoftenassumedthatexplosionpressureis approximately one-half of the detonationpressure (Figure 1.3). Itshouldbepointedoutthatthisisonlyanapproximationand conditionscanexist where theexplosionpressure exceeds thedetonation pressure.ThisexplainsthesuccessofANFOwhichyieldsarelatively lowdetonationpressure,butrelativelyhighexplosionpressure. Explosionpressuresarecalculatedfromcomputercodesormeasured usingunderwatertests.Explosionpressurescanalsobemeasured directlyinboreholes,however,fewof theexplosivemanufacturersuse the new technique inratingtheirexplosives.Areview of some very basic explosiveschemistryhelpsone tounderstandhow powderedmetalsand other substances effect explosionpressures. 5 Detonation Velocity m/s DetonationExplosion 7500 PressurePressure Kbar 6000300150 200 100 150 Density 4500 10050 g I en'! 50 20 ~ j40 30 3000 20 0.8 15 0.6 105 6 1500 Figure 1-3Nomograph of Detonation &Explosion Pressure 1.1.4CHEMICAL EXPLOSIVES Chemicalexplosivesarematerialswhichundergorapid chemicalreactionstoreleasegaseousproductsandenergy.These gasesunderhighpressureexertforcesagainstboreholewallswhich causesrock to fracture. Theelements,whichcompriseexplosives,aregenerally consideredeitherfuelelementsoroxidizerelements(Table1. 1 ). Explosivesuseoxygenastheoxidizerelement.Nitrogenisalsoa commonelementinexplosivesandisineither aliquidor solidstate,but onceitreactsit formsgaseousnitrogen.Explosivessometimescontain ingredientsotherthanfuelsandoxidizers.Powderedmetalssuchas powderedaluminumareusedinexplosives.Thereasonfortheuseof thepowder metalsis that,uponreaction,powderedmetalsgiveoff heat. Theheatincreasesthe temperatureof thegases,whichresultfromthe other ingredients,causinga higher explosionpressure. Explosivesmaycontainotherelementsandingredientswhich reallyaddnothingto theexplosivesenergy.Theseotheringredientsare putintoexplosivestodecreasesensitivityorincreasesurfacearea. Certainingredientssuchaschalkorzincoxideserveasanantacidto increasethestoragelifeof theexplosive.Commontablesaltactually makesanexplosivelessefficientbecauseitfunctionsasaflame depressantandcoolsthereaction.Ontheotherhand,theadditionof 6 I .i : 4'-:t .; ,- c tablesaltallowstheexplosivetobeusedinexplosivemethane atmospheres because the coolerflame andshorter flame durationmakes itlesslikelythatagasexplosionwouldoccur.Thisisthereasonthat permissible explosivesareusedincoalminesor intunnelingoperations insedimentary rock where methane is encountered. Table 1-1Explosive Ingredients INGREDIENTCHEMICAL FORMULAFUNCTION NitroglycerinC::1Hc;OQN::1 Explosive Base NitrocelluloseCRH7011N::1 ExplosiveBase Trinitrotoluene (TNT)C7Hc;ORN::1 ExplosiveBase AmmoniumNitrate H40::1N? Oxygen Carrier Sodium NitrateNaN0::1Oxygen Carrier Fuel OilCH? Fuel Wood PulpCRHrnOc;Fuel CarboncFuel Powdered AluminumAlSensitizer-Fuel ChalkCaC0::1Antacid Zinc OxideZnOAntacid Sodium ChlorideNaClFlameDepressant Thebasic elementsoringredients whichdirectly produce work in blastingarethoseelementswhichformgaseswhentheyreact,suchas carbon,hydrogen,oxygen,andnitrogen. Whencarbonreactswithoxygen,itcaneitherformcarbon monoxideor carbondioxide.Inorder toextract themaximumheatfrom thereaction,wewantallelementstobecompletelyoxidizedorinother words for carbondioxide toformrather thancarbonmonoxide.Table1.2 showsthedifferenceinheatreleasedwhenonecarbonatomforms carbonmonoxide versusthecasewhereonecarbonatomformscarbon dioxide.Ino r e ~ toreleasethemaximumenergyfromtheexplosive reaction,the elements shouldreact andform the followingproducts: 1.Carbonreacts toformcarbondioxide.(Figure1.4) 2.Hydrogen reacts to form water.(Figure 1.5) 3.Liquidorsolidnitrogenreactstoformgaseousnitrogen. (Figure 1.6) 7 Table 1-2Heats Of Formation For Selected Chemical Compounds COMPOUND Corundum Fuel Oil Nitromethane Nitroglycerin PETN TNT Carbonmonoxide Carbondioxide Water Ammoniumnitrate Aluminum Carbon Nitrogen Nitrogen oxide Nitrogen dioxide FORMULA

CH? C!iHR01?N4 co co? H?O

Al c N NO NO? INGREDIENTS CARBONOIOXIOE co, PRODUCT MOL On or Qr WEIGHT(Kcal/Mole) 102.0-399.1 14.0- 7.0 61.0- 21.3 227.1- 82.7 316.1-123.0 227.1- 13.0 28.0- 26.4 44.0- 94.1 18.0- 57.8 80.1- 87.3 27.00.0 12.00.0 14.00.0 30.0+21.6 46.0+8.1 Figure 1-4Carbon-Oxygen Ideal Reaction 8 I ! e: ! ' -.; el .I

., 2 fl' e: t . . 4r. ' 4t 1 11 - r INGREDIENTS WATER H10 PRODUCT Figure 1-5 Hydrogen-Oxygen Ideal Reaction INGREDIENTS NITROGENGAS Ni PROOUCT Figure 1-6Nitrogen-Nitrogen Ideal Reaction Ifonlytheidealreactionsoccurfromthecarbon,hydrogen, oxygen,andnitrogen,thereisnooxygenleftoveroranyadditional oxygenneeded.Theexplosiveisoxygenbalancedandproducesthe maximum amount of energy . If two ingredients are mixed together,suchasammoniumnitrate andfueloil,andanexcessamount of fueloilisputinto themixture,the explosivereactionissaidtobeoxygennegative.Thismeansthatthere isnotenoughoxygentofullycombine withthecarbonandhydrogento formthedesiredendproducts.Instead,whatoccursisthatfreecarbon (soot) andcarbonmonoxide willbeliberated (Figure1. 7) . 9 INGREDIENlS CA.'mONMONOXIO co PROOUCT INGREDIENlS CARBON c PRODUCT Figure 1-7Non-Ideal Carbon-Oxygen Reaction If toolittlefuelisaddedtoamixtureof ammoniumnitrateand fueloil,thenthemixturehasexcessoxygenwhichcannotreactwith carbonorhydrogen.Thisiscalledanoxygenpositivereaction.What occursis that thenitrogen whichisnormally aninert gas willbechanged fromnitrogengastoanoxideofnitrogen(Figure1.8).Ifoxidesof nitrogenareformed,theywillformrustcoloredfumesandreducethe energy of the reaction. INGREDIENTS NllROGENOXIDE NO PRODUCT INGREDIENTS PROOUCT Figure 1-8Non-Ideal Nitrogen-Oxygen Reaction Theenergyisreducedbecauseotheridealgasesliberateheat whentheyform,nitrogenoxidesabsorbheatinorderforthemtoform. ThiscanbeseeninTable1.2.Waterandcarbondioxidehavea 10 ~h,. e. ov. e, .. ltJ I 0 negativesignwhichmeanstheygiveoffheatwhentheyform.The nitrogenoxidesnear thebottomof Table1.2haveaplussignmeaning that they take inheat when they form. Thenetresultisthatthereactionwilloccuratalower temperature.The gaspressureisloweredif thereactiontemperatureis lowered.Figure1.9showsthereactionproductswhichformifthe reactionis oxygenpositive. OXYGENBA!ANCEQ PRODUCTGASES ~CARBONDIOXIDE (COLORLESS) WATERVAPOR (LIGHTGREY) NllROGENGAS (COLORLESS) LIGHTGREYFUMES ELEMEll.1l2 CARBON H'lllROGEN OXYGEN NllROGEN I I - - - - - - - ~OXYGENNEGATIVE PRODUCTGASES l CARBON (BLACKSOLID) CARBONMONOXIDE (COLORLESS) WATERVAPOR (LIGHTGREY) N!lROGENGAS (COLORLESS) I RESULTANTCOLOR DARKGREYFUMES -'NOIOR CARBONONBOREHOLEWALL OXYGENPOSITIVE PRODUCTGASES J CARBONDIOXIDE (COLORLESS) WATERVAPOR (LIGHTGREY) NllROGENOXIDES (RUST-YELLOWGAS) RUST OR YEU.OWFUMES Figure 1-9Identification of Problem Mixtures 1.2IDENTIFICATION OF PROBLEM MIXTURES (co2) (fl:iO) (NO) (NOz) Therearevisualsignsofproperandimproperenergyrelease. Gascolorsareindicatorsofreactionefficiencyandassociatedenergy release.Whenlightgraycoloredsteamispresent,oxygenbalanceis nearidealandmaximumenergyisreleased.Whengasesareeither yelloworrustcolored,theyindicateaninefficientreactionthatmaybe duetoanoxygenpositivemixture.Oxygennegativemixturesproduce dark gray gases andcanleave carbon onborehole walls (Figure 1.9). Inordertodemonstratetheimportanceofoxygenbalanceto energyrelease,onecanexploretheexampleof ammoniumnitrateand fueloilwhichis a very commonexplosive.If either toolittle or toomuch fueloilis added to ammonium nitrate,non-ideal chemicalreactionsoccur which cause an energy loss . 11 Figure1.10showsenergylossversusthepercentof fueloilin themixture.It canbeseenthat the idealamount of fueloilisnear 6%. Wheninsufficientoilisaddedandtoomuchoxygenremainsinthe mixture,oxidesof nitrogenareproducedandlargeenergylossesoccur. At1%fueloil the energy lossisapproximately42%.If toomuchfuelis added,the energy losses are not assevere as inthe case where toolittle fuelisadded.Whenfueloilisgreater than6%,freecarbonandcarbon monoxide willform. Thesevisualsignscangivetheoperatoranindicationasto whether or not the explosivesare functioningproperly. so:ii: E -40ll: N E R G JOll: y L 020% s s 10ll: Carbon CarbonMonoic1de 02ll:4ll:6ll:ex10ll: OilCONTENT Figure 1-10 Energy Loss in ANFO 12 . ' .; .l ( .I : .I .( : .l .( .t .! .1 I I .: ... ! i - ~r ~1: . ns ift:e lO perpendicular to the length of the column.This wouldbesimilar tobeam loadingconditions.Whenonediscussesbeamloading,thestiffness ratioissignificant.The stiffnessratiorelatesthe thicknessof thebeam to itslength.The effect of thestiffnesscanbeexplainedby using,asan example,afull-lengthpencil.Itisquiteeasy tobreakapencilwiththe force exerted withone's fingers.However,if the same force is exerted on a5cmlongpencil,itbecomesmoredifficulttobreak.Thepencil's diameter hasnotchanged,theonly thingthathaschangedisitslength. A similar stiffnessphenomenonalso occurs inblasting.The burdenrock ismore difficult tobreak by flexuralfailure whenbenchheightsapproach the burdendimensioninlength.When benchheightsaremany times the burdeninlength, the burdenrock is more easily broken . Figure 2-5Axisymmetric Bending Diagram / Figure 2-6Cantilever Bending Diagram Two general modes of flexural failure of the burdenexist.Inone case,the burdenbends outwardor bulges in the center more quickly than it does onthe top or bottom.In the second case,the top or the bottomof theburdenmovesatahigherratethanthecenter.Whentheburden 17 rockbulgesatitscenter,tensilestressesresultatthefaceand compressionresultsnearthecharge.Underthistypeofbending condition,therock willbreak fromthe faceback towardthehole (Figure 2.5).This mode of failure generally leads to desirable breakage. In the second case,the rock is cantileveredoutward (Figure 2.6) andthefaceisputintocompressionandtheboreholewallsarein tension. This secondcase isundesirable.Thismechanismoccurs when cracksbetweenblastholeslinkbeforetheburdenisbrokenandis normallycausedbyinsufficientblastholespacings.Whenthecracks betweenholesreachthesurface,gasescanbeprematurelyvented beforetheyhaveaccomplishedallpotentialwork.Airblastandflyrock canresult along withpotentialbottomproblems. Thebendingmechanismorflexuralfailureiscontrolledby selectingtheproperblastholespacingandinitiationtimeofadjacent holes.Whenblasthole timingresultsinchargesbeingdelayedfromone another along arow of holes,the spacingmust beless thanthat required if alltheholesinarowwerefiredsimultaneously.Theselectionof the properspacingisfurthercomplicatedbythestiffnessratio.Asbench heightsarereducedcomparedtotheburden,onemustalsoreducethe spacing between holes to overcome the problems of stiffness. 2.4BREAKAGE PROCESS Therockbreakageprocessoccursinfourdistinctivesteps.As theexplosivesdetonates,astresswavemovesthroughtherock uniformlyinalldirectionsaroundthecharge.Radialcracksthen propagatepredominantlytowardthefreeface.Aftertheradialcracking processisfinished,highpressuregasespenetrateintothecracks approximatelytwo-thirdsofthedistancefromtheholetotheface throughouttheradialcracksystem.Onlyafterthegashastimeto penetrateinto thecracksystemarethestressesonthe faceof sufficient magnitude,to cause the face to move outward.Before the facebegins to move andbendoutward,fractures are created in the thirddimension asa result of the flexuralfailure or bending. 18 - 3. EXPLOSIVE PRODUCTS 3.1ENVIRONMENTAL CHARACTERISTICSOF EXPLOSIVES The selectionof the typeof explosive tobeusedforaparticular taskisbasedontwoprimarycriteria.Theexplosivemustbeableto functionsafelyandreliablyundertheenvironmentalconditionsofthe proposeduse,andtheexplosivemustbethemosteconomicaltouseto producethedesiredendresult.Beforeanyblasterselectsanexplosive tobeusedforaparticulartask,hemustdeterminewhichexplosives wouldbestsuittheparticularenvironmentandtheperformance characteristicswhichwillsuittheconditionsofthejob.Five characteristicsareconsideredintheselectionofexplosiveswhich concernenvironmentalfactors,sensitiveness,waterresistance,fumes, flammability andtemperature resistance. 3.1.1SENSITIVENESS Sensitivenessisthecharacteristicof anexplosive whichdefines its ability to propagate through the entire lengthof the columncharge and controls the minimum diameter for practicaluse. Sensitiveness ismeasured bydetermining the explosive'scritical diameter.The termcriticaldiameter iscommonly usedintheindustry to definetheminimumdiameterinwhichaparticularexplosivecompound willdetonatereliably.Allexplosivecompoundshaveacriticaldiameter. For someexplosivecompounds,thecriticaldiametermaybeaslittleas amillimeter.Ontheotherhand,anothercompoundmayhaveacritical diameter of 100 millimeters.The diameter of theproposedborehole ona particular job willdetermine themaximumdiameter of explosivecolumn. Thisexplosivediameter mustbegreater thanthecriticaldiameter of the explosive tobeusedinthat borehole.Therefore,bypre-selectingcertain borehole sizes,one may eliminate certain explosive productsfromuse on that particular job (Table 3.1 ). 19 Sensitivenessisalsoameasureoftheexplosive'sabilityto propagatefromcartridge-to-cartridge,assumingthediameterisabove critical.Itcanbeexpressedasthemaximumseparationdistance(in centimeters) between aprimed donor cartridge andanunprimedreceptor cartridge,where detonation transfer will occur. Table 3-1Sensitiveness (Critical Diameter) TYPECRITICAL DIAMETER SO mm Granular Dvnamitex GelatinDvnamitex Cartridaed Slurrvxxx Bulk Slurrvxx Air Emplaced x Poured ANFOx PackaQedANFOxx HeawANFOx 3.1.2WATER RESISTANCE Waterresistanceistheabilityofanexplosivetowithstand exposuretowater withoutit sufferingdetrimentaleffectsinperformance_ Explosiveproductshavetwotypesofwaterresistance,internaland external.Internalwaterresistanceisdefinedaswaterresistance providedbytheexplosivecompositionitself_Asanexample,some emulsionsandwatergelscanbepumpeddirectlyintoboreholesfilled withwater.Theseexplosivesdisplacethewaterupward,butarenot penetratedbythe water andshow no detrimentaleffectsif firedwithina reasonableperiodof time.Externalwaterresistanceisprovidednotby theexplosivematerialsitself,butbythepackagingorcartridginginto whichthematerialisplaced_Asanexample,ANFOhasnointernal waterresistanceyet,if itisplacedinasleeveorinacartridgewithina borehole,it canbekept dry andwillperformsatisfactorily_Thesleeveor cartridgeprovidestheexternalwaterresistanceforthisparticular product Theeffectwhichwaterhasonexplosivesisthatitcandissolve orleachsomeof theingredients,orcoolthereactiontosuchadegree thattheidealproductsofdetonationwillnotformeventhoughthe 20 .! : ' ' ,( ~ ~ :. , ~ I~p: .t, ~