Excavation Chapter 1

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Author:
athoms
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102482
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Excavation Chapter 1
Updated:
2011-09-18 14:26:15
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exc chp1 test1
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Excavation Chapter 1
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  1. Goals in Blasting (2)
    • Make Large Rocks Small
    • Move Rocks Away
  2. Black Powder Era (3)
    • 12th Century
    • 1300 in Fire Arms
    • 1627 use in mines
  3. Dynamite Era (4)
    • 1846 Nitroglycerin
    • 1866 Dynamite
    • 1875 Blasting Gelatin
    • 1950's Ammonia dynamite
  4. Modern Explosive Products (4)
    • 1916 AN plant in Gibbstown, NJ exploded
    • 1955 bagged ANFO
    • 1957 Water gels
    • 1968 Emulsions
  5. Blasting Techniques Depend (7)
    • Production Requirements
    • Size and amount of broken rocks
    • Shape of final cut, desired rock displacement
    • Production, excavation or controlled
    • Type of rock
    • geological structures
    • cost
  6. Blasting Fragmentation (2)
    Stress waves (detonation pressure) - Shock Energy, shattering effect

    Gas pressure (borehole pressure) - Gas energy, heaving effect
  7. Fragmentation Energy Consumed (7)
    • Elastic Deformation
    • Plastic Deformation
    • Deformation Along Boundaries
    • Creation of new surfaces
    • Elastic wave energy dispersion
    • Gas venting
    • Heat and Noise
  8. Rock Fragments in Muckpile (3)
    • Formed by new fractures created by explosive energy
    • Existing rock blocks liberated from the rock mass
    • Formed by the extension of existing fractures
  9. Nature of Rock (5)
    • Composite Material
    • Not homogenous
    • Not isotropic
    • Not continuous
    • Behavior controlled by discontinuities
  10. Discontinuities in Rock Mass (2)
    Macro - bedding planes, joints, contacts, faults

    Micro - Foliation/Schistosity, Fissures/cracks
  11. Rock Failure (2)
    Brittle Failure - Small deformations before failure, energy is consumed in the formation of new surfaces

    In general, explosives with high detonation velocities and pressure are more effective with brittle rocks (shattering effect)

    Ductile failure - Large deformations before failure, energy is consumed in rock deformation rather than in the formation of new surfaces

    Explosives with high borehole pressures are more effective with ductile rocks (heaving efffect)
  12. Explosive Products (10)
    • Dynamite
    • Slurries/Water Gels
    • Emulsions
    • Black Powder
    • Blasting Agents/ANFO
    • ANFO-Emulsion Blends
    • Initiation Explosives
    • Detonators/Blasting Caps
    • Safety Fuses
    • Detonating Cords
  13. DOT Classification (3)
    - regulates shipping of hazardous/explosive material

    Class A - an explosive that possesses detonating or otherwise maximum hazard; such as, but not limited to, dynamite, nitroglycerin, lead azide, black powder, blasting caps and detonating primers

    Class B- an explosive that possesses flammable hazard; such as, but not limited to, propellant explosives, photographic flash powders, and some special fire works.

    • Class C- an explosive that contains ClassA or ClassB
    • explosives, or both as components but in restricted quantities. For example, blasting caps or electric caps in lots of less than 1,000.
  14. BATF Classification:
    • BATF, which enforces explosives control and security
    • regulations, classifies explosive materials into two
    • categories for storage purposes. These are:

    • High Explosive
    • -any product used in blasting which is sensitive to a No. 8 test blasting cap (detonator containing 0.40 to 0.45 g of PETN) and reacts at a speed faster than that of sound in the explosive powder.

    • Low Explosive
    • -any product used in blasting in which the speed of reaction is slower than the speed of sound, such as black powder.
  15. There are two types of explosive materials used as the main product for blasting purposes,
    • Explosive
    • -any chemical compound or mixture, the primary or common purpose of which is to function by explosion, or that reacts at high velocity with substantial release of gas and heat.

    • Blasting Agent
    • -an explosive that meets prescribed criteria for insensitivity to initiation. For storage, any material or mixture consisting of a fuel and oxidizer, intended for blasting, not otherwise defined as an explosive, provided that the finished product, as mixed and packaged for use or shipment, cannot be detonated by means of a No. 8 test blasting cap when unconfined (BATF). For transportation, a material designed for blasting which has been tested in accordance with CFR49, Section 173.14a, and found to be so insensitive that there is very little probability of accidental initiation to explosion or transition from
    • deflagration to detonation (DOT).
  16. MSHA defines a permissible explosive as
    an explosive which is an especially formulated mixture, that is safe to be used in a flammable atmosphere (gassy and dusty) in underground mines; they may be NG-based but today are principally AN.

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