Excavation Chapter 2

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Author:
athoms
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102526
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Excavation Chapter 2
Updated:
2011-09-18 17:09:39
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exc chp2 test1
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Explosive Selection
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  1. Selection Criteria for Industrial Explosive Products (3)
    • -Safe under environment to be used
    • -Produce satisfactory results for intended purpose
    • -Economic and logistic factors (availability,reliability,
    • technical support)
  2. Environmental properties of explosives (6)
    • Sensitivity
    • Fume characteristics
    • Temperature resistance
    • Handling characteristics
    • Water resistance
    • Sleeping characteristics
  3. Performance properties of explosives (5)
    • Density
    • Strength
    • Velocity of detonation
    • Detonation pressure
    • Borehole pressure
  4. Sensitivity: ( 3+3)
    • Hazard sensitivity:
    • -Storage
    • -Formulation
    • -Transportation

    • Performance sensitivity:
    • -Initiation sensitivity:
    • sensitivity to No. 8 cap classify as explosive
    • not sensitive to No. 8 cap classify as blasting agent, (if not cap sensitive, booster sensitive, requires primer and have to know minimum primer size)
    • -Propagation sensitivity or sensitiveness ability to propagate detonation once it has been initiated
    • Critical diameter: min diameter for a stable reaction to propagate reaction
    • -Gap sensitivity: ability to propagate across gap
    • Sympathetic detonation: detonation by impulse from another detonation
  5. Sensitivity Depends On: (6)
    • Composition
    • Particle size
    • Density
    • Charge diameter
    • Confinement
    • Presence of water
  6. Sensitivity/Water Resistance/Fume Quality: Granular Dynamite (4)
    • Hazard Sensitivity: Moderate to High
    • Performance sensitivity: excellent
    • Water Resistance: Poor to good
    • Fume Quality: Poor To Good
  7. Sensitivity/Water Resistance/Fume Quality: Gelatin Dynamite (4)
    • Hazard Sensitivity: moderate
    • Performance Sensitivity: excellent
    • Water Resistance: Good to Excellent
    • Fume Quality: Fair to very good
  8. Sensitivity/Water Resistance/Fume Quality: Cartriged Water Gel (4)
    • Hazard Sensitivity: Low
    • Performance Sensitivity: Good to very good
    • Water Resistance: Very Good
    • Fume Quality: Good to Very Good
  9. Sensitivity/Water Resistance/Fume Quality: Bulked Water Gel (4)
    • Hazard Sensitvity: Low
    • Performance Sensitivity: Good to Very Good
    • Water Resistance: Very Good
    • Fume Quality: Fair to Very Good
  10. Sensitivity/Water Resistance/Fume Quality: Air-Emplaced ANFO (4)
    • Hazard Sensitvity: Low
    • Performance Sensitivity: Poor to good
    • Water Resistance: Poor
    • Fume Quality: Good
  11. Sensitivity/Water Resistance/Fume Quality: Poured ANFO (4)
    • Hazard Sensitvity: Low
    • Performance Sensitivity: Poor to Good
    • Water Resistance: Poor
    • Fume Quality: Good
  12. Sensitivity/Water Resistance/Fume Quality: Packaged ANFO (4)
    • Hazard Sensitvity: Low
    • Performance Sensitivity: Good to Very Good
    • Water Resistance: Very Good.
    • Fume Quality: Good to Very Good
  13. Water Resistance:
    Ability to detonate under wet condition

    Internal --> ingredients

    External --> packaging
  14. Water Resistance Can Be Described By (7)
    the # of Hours an Explosive Can Be Exposed to Water Without Loosing Sensitivity and Efficiency

    • Class: Hours
    • Class 1: Indefinite
    • Class 2: 32-71
    • Class 3: 16-31
    • Class 4: 8-15
    • Class 5: 4-7
    • Class 6: 1-3
    • Class 7: < 1
  15. Sleep Time
    Refers to explosive ability to remain loaded in bore holes before being detonated without loosing sensitivity or effectiveness.
  16. Sleep Time is Affected By: (4)
    • Explosive chemical components interaction
    • Component precipitation or separation
    • Component leaching by ground water
    • Chemical reaction with host rock
  17. Fume Class: (3+4)
    Measure of the Amount Of Toxic Gases Produced:

    • Non-Toxic:
    • H2O
    • CO2
    • N

    • Toxic:
    • CO
    • Nitrogen Oxides
    • NO
    • NO2
  18. Causes of Toxic Fumes (3)
    • Inherent to formulation
    • Incomplete chemical reaction
    • Non oxygen-balanced
  19. Field Conditions that can Lead to Toxic Fumes Generation (7)
    • Insufficient charge diameter
    • Inadequate priming
    • Water deterioration
    • Excessive sleep time
    • Loss of confinement
    • Reaction with surrounding material
    • Plastic borehole liners
  20. Institute of Maker of Explosives (IME) Fume Class Designation (3)
    Fume Class: ft3 of toxic gases/200g of explosive material

    • Class 1: <0.16
    • Class 2: 0.16-0.33
    • Class 3: 0.33-0.67
  21. Temperature Resistance (3)
    • Performance deteriorate in very hot or very cold
    • environments

    • Temp > 90 F decomposition may occur (Some pyritic ores can generate excessive heat due to
    • oxidation, mines in areas of geothermal anomaly)

    Slurry explosives at low temperatures may loose sensitivity
  22. Handling Characteristics (1+1+1+3)
    • Ability to cope with the rugged mining environment
    • Shelf life
    • Transportation
    • Delivery of explosives into borehole
    • -bagged
    • -pumped
    • -augered
  23. Performance Properties (5)
    • Density
    • Strength
    • Velocity of detonation
    • Detonation pressure
    • Borehole pressure
  24. Density: (3+1)
    • Given in term:
    • -specific gravity (g/cc)
    • -cartridge count (# of 1¼ x 8 in 50 lb. case)
    • -loading density (lb. explosive/ft borehole)

    Relates the mass of an explosive to the volume it occupies in a blast hole
  25. Effect of Changing Densities (3)
    • Energy
    • Sensitivity
    • Detonation velocity
  26. Virginia Tech Mining and Minerals Engineering
    Blasting energy directly related to its ___
    For a given volume, higher density explosives
    provide ____ energy than lower density
    explosives.
    • Mass
    • More
  27. Examples Of Varying Explosive Density:
  28. For bulk explosives (that can be compressed) sensitivity _____ and
    velocity of detonation _____ as the density _____.
    • Decreases
    • Increases
    • Increases
  29. Upper limit of density is reached when the explosive is ______ or _______ and lost its sensitivity to the
    point where it can not be _______.
    • Dead Packed
    • Dead Pressed
    • Initiated
  30. Typical Densities:
    • Explosive: Density Range (g/cc)
    • ANFO (loose poured): 0.75-0.85
    • ANFO (pneumatically loaded): 0.8-1.10
    • Low Density ANFOs: 0.20-0.75
    • Emulsions: 1.1-1.30
    • Emulsion Blends: 1.00-1.35
    • Water Gels and Slurries: 1.00-1.30
  31. Strength
    Relative measure of energy released by an explosive:

    • Weight strength or grade strength
    • Volume strength or bulk strength or cartridge strength
  32. Weight Strength
    Energy released by an explosive compared with the energy provided by an equivalent weight of ANFO

    • WeightStrength=
    • (AvailableEnergyofExplosive/AvailableEnergyofANFO)
    • x
    • 100

    Useful when comparing the potential performance of explosives on the basis of the energy factor
  33. Available Energy (4 explosive/density(g/cc)/available energy(MJ/kg))
    • Explosive: Density: Available Energy
    • ANFO: 0.80: 3.78
    • Heavy ANFO: 1.20: 3.46
    • Emulsion: 1.25: 3.12
    • Diluted ANFO: 0.46: 3.50
  34. Volume Strength
    Defined as the energy of the explosive compared with an equivalent volume of ANFO

    Volume Strength = (Weight Strength * Density)/Density Of ANFO

    Useful for comparing the potential performance of an explosive on the basis of equivalent blast hole volume or unit length of a charge of the same diameter
  35. Swedish Weight Strength Relationship
    Sdy= (5/6) (Q/Qo)+(1/6)(V/Vo)

    • Sdy = weight strength relative to dynamite
    • Qo = heat of explosion of 1 kg dynamite
    • Vo=gas volume of 1kg dynamite
    • Qo= 5.0 MJ
    • Vo = 0.85 m3
  36. Swedish Weight Strength Relative to ANFO
    Sanfo= (Sdyexplosive/SdyANFO)

    SdyANFO = 0.84
  37. Explosive Detonation
  38. Velocity of Detonation (VOD) (1+4+2)
    VOD of an explosive is the rate at which the detonation front travels through the explosive charge.

    • Speed of the detonation shock wave
    • Speed of the chemical reaction
    • 5000-6000 ft/sec for slow
    • up to 25,000 ft/sec for high

    • Supersonic --> detonation
    • Subsonic --> deflagration
  39. The VOD controls the rate of release of ____ energy and influences the partitioning of that energy into ____ and _____.

    High VOD: Greater ____ and ____ pressure; _____ effect

    Low VOD: greater _____ pressure
    ______ effect
    • explosion
    • shock and heave

    • shock wave and detonation
    • shattering

    • borehole
    • heaving
  40. Field Conditions that Affect VOD (6)
    • Charge diameter
    • Density
    • Grain size
    • Confinement
    • Coupling ratio
    • Primer size and strength
  41. Detonation Pressure

    Pressure generated by the _____. It is a measure of the ability to ____ the ___.

    Primarily a function of the __ and ____
    • reaction shock wave
    • shatter the rock
    • VOD and density
  42. Approximation of the Detonation Pressure
    P = (4.18 *10-7) (rho(VOD)2)/(1+0.80rho)

    • P=detonation pressure in kilobar
    • VOD=velocity of detonation (ft/sec)
    • rho=density (g/cc)
  43. Borehole Pressure:

    Pressure exerted by ____ ___of ____ _____. Considered to play a major role in breaking most rocks, particularly ___ ____and generating ____ and ____ __ __ ______.
    • expending gases of detonation reaction
    • softer rocks
    • heave and displacement of the muckpile
  44. Borehole Pressure Depends On (4+formula)
    • Volume Of Gas
    • Heat Of Reaction
    • Confinement
    • VOD
    • NP(VOD) = pressure of fully loaded borehole
    • (root(C) (de/dh)) = Coupling Ratio

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