Chapter 6Presplit and SmoothBlastingMainContent6.4PracticesofPresplittingand6.1PresplittingBlastingSmoothBlasting（Omitted)6.2SmoothBlasting6.5Introductionof NewDirectionFractureBlasting Technology63Application ConditionofPresplittingand SmoothBlasting （(Omitted)2016/11/9第六章预裂爆破与光面爆破
2016/11/9 第六章 预裂爆破与光面爆破 2 Main Content Chapter 6 Presplit and Smooth Blasting 6.1 Presplitting Blasting 6.2 Smooth Blasting 6.3 Application Condition of Presplitting and Smooth Blasting（Omitted） 6.4 Practices of Presplitting and Smooth Blasting （ Omitted ） 6.5 Introduction of New Direction Fracture Blasting Technology ：
6.1PresplittingBlastingThereare two same important questions faced by the blasting andexcavation in limited area:@Usingthe mosteffective methodsto fragment well the rockand throwing it if necessary in fixed area to reach the certainengineeringpurposes;②Reducing thedamages to surrounding rock and mostly keeptheirstrength and stability,meanwhile,screeningoffthesurroundingstosomeextentfrom groundvibrationin mainround.VIDIOPresplitting blastingThepresplitting blasting is drilling denseholes along the contour lineand thecracks atthe final contour are created by blasting priorto the drillingofthe rest oftheholes for the blasting pattern,using decouple chargeor lowpower explosive,which screens off damages from themainround tosurroundings,32016/11/9第六章预裂爆破与光面爆破
2016/11/9 第六章 预裂爆破与光面爆破 3 6.1 Presplitting Blasting Presplittin g blasting The presplitting blasting is drilling dense holes along the contour line, and the cracks at the final contour are created by blasting prior to the drilling of the rest of the holes for the blasting pattern, using decouple charge or low power explosive, which screens off damages from the main round to surroundings. There are two same important questions faced by the blasting and excavation in limited area： ① Using the most effective methods to fragment well the rock and throwing it if necessary in fixed area to reach the certain engineering purposes; ②Reducing the damages to surrounding rock and mostly keep their strength and stability, meanwhile, screening off the surroundings to some extent from ground vibration in main round
Mechanical Condition of CreatingPresplitCrack①Theradial pressure of explosiontoholewall lowerthan the dynamiclimitedcompressionstrength,whichnotcrushingtheholewallThe accompanying tangential tensile stress lowerthan the dynamic limitedtensile strength,whichnot createrandomcrackatholewall:O,<ODtThe resultant tensile stress on line of holes centers higherthan the dynamiclimitedtensilestrength,then creatingthe cracks:ORt >Dt2016/11/9第六章预裂爆破与光面爆破
2016/11/9 第六章 预裂爆破与光面爆破 4 Mechanical Condition of Creating Presplit Crack p D p t D t ① The radial pressure of explosion to holewall lower than the dynamic limited compression strength, which not crushing the holewall： ② The accompanying tangential tensile stress lower than the dynamic limited tensile strength, which not create random crack at holewall： ③ The resultant tensile stress on line of holes centers higher than the dynamic limited tensile strength, then creating the cracks： Rt D t
Mechanism of Creating PresplitCracksA1)DecoupledchargeB2) Stress reinforcement on line of holes centers3)GuideholeforeachotherFiring the presplitholes simultaneously2016/11/9第六章预裂爆破与光面爆破
2016/11/9 第六章 预裂爆破与光面爆破 5 Mechanism of Creating Presplit Cracks A B 2） Stress reinforcement on line of holes centers C D 1）Decoupled charge 3） Guide hole for each other 4） Firing the presplit holes simultaneously
Calculation of Charge AmountThree methods:theoretical arithmetic,empirical formula andempiricalvalueEmpirical formulaTunnelingblasting:1.5~4;ProposeddecoupledDeep holeblasting in open blasting orlargecoefficient2~4。cavern :Tunneling blastingq' = 0.034[0压 J0.6 .[a]0.6Calculation ofcharge amountLeep hole blasting—q' = 0.042[0 μ J0-5 .[a]0.6where,qis linedensity,kg/m;O压 is limited compressionstrength，MPa;aisspacing,m62016/11/9第六章预裂爆破与光面爆破
2016/11/9 第六章 预裂爆破与光面爆破 6 Calculation of Charge Amount Three methods：theoretical arithmetic, empirical formula and empirical value Empirical formula Tunneling blasting： 1.5~4； Deep hole blasting in open blasting or large cavern ： 2~4。 Proposed decoupled coefficient 0.6 0.6 q a 0.034[ ] [ ] 压 0.5 0.6 q a 0.042[ ] [ ] 压 Tunneling blasting Deep hole blasting Calculation of charge amount where，q is line density，kg/m； 压 is limited compression strength ，MPa； a is spacing，m