Hydraulic Impact Hammer (hoe ram)

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Hydraulic Impact Hammer (hoe ram)

• How do you determine feasibility and performance
  in rock?

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How do impact hammers work?

• Let us take a look..

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Hydraulic Impact Hammer Operation
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A Little Tutorial

• To make some important distinctions
• How impact hammers break rock
• What rock properties affect performance

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Principles of Impact Hammers

• Impact hammers work on two principles in breaking
  rock, namely
• Primary breakage and
• Secondary breakage

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What is primary breakage?

• Primary breakage is when the impact hammer breaks
  an intact material, such as
• A slab of concrete (with limited thickness) or
• An intact rock mass (devoid of discontinuities)

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Primary Breakage
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What is secondary breakage?

• Secondary breakage is when the impact hammer
  reduces the size of existing blocks of
• concrete or
• rock
• into smaller pieces, such as joint blocks of rock
  as illustrated in the next slide.

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Secondary Breakage In Jointed Blocky Rock
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Secondary Breakage of Rock Blocks
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Rock Properties Control!

• What rock properties control the breakage of rock
  by impact hammer?
• Primary breakage depends on the rock intact
  properties
• Secondary breakage depends on the rock mass
  properties

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Rock Properties

• What are rock
• Intact and
• Mass
• properties?

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Engineering Properties of Rock Rock Intact Mass
Properties
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Rock Intact Properties

• Rock intact properties are determined by testing
  of intact samples in terms of
• Unconfined compressive strength
• Tensile strength
• Total Hardness
• Sonic Velocity
• Etc

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Rock Mass Properties

• Rock discontinuities and their properties
• Spacing
• Nature
• Orientation
• Seismic velocity (similar to use in Caterpillar
  Ripping Chart)
• RQD (Rock Quality Designation)

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Using RQD (relative to depth)Minimum, Average,
and Maximum b
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Using RQD(top of rock to 15 ft)

• Impact Hammer Excavation
• Greens - efficient
• Grays - difficult/slow
• Reds - tedious

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Using RQD (bottom of excavation)

• Impact Hammer Excavation
• Greens - efficient
• Grays - difficult/slow
• Reds - tedious

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Using Fracture SpacingAverage and Maximum
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Using Seismic Velocity

• Would provide the best indication of rock mass
  amenability to excavation by impact hammer
• Needs to be developed further
• If you seek more specific answers, contact us .