Transcript Hydraulic Impact Hammer

Hydraulic Impact
Hammer (hoe ram)
How do you determine
feasibility and performance
in rock?
How do impact hammers work?

Let us take a look……………..
Hydraulic Impact Hammer Operation
A Little Tutorial

To make some important distinctions
 How
impact hammers break rock
 What
rock properties affect performance
Principles of Impact Hammers

Impact hammers work on two principles in
breaking rock, namely
 Primary
breakage and
 Secondary
breakage
What is primary breakage?

Primary breakage is when the impact hammer
breaks an intact material, such as:
 A slab
 An
of concrete (with limited thickness) or
intact rock mass (devoid of discontinuities)
Primary Breakage
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.
Secondary Breakage
In Jointed Blocky Rock
Secondary Breakage of Rock Blocks
Rock Properties Control!
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What rock properties control the breakage
of rock by impact hammer?
 Primary
breakage depends on the rock intact
properties
 Secondary
properties
breakage depends on the rock mass
Rock Properties
What are rock …
 Intact
and
 Mass
properties?
Engineering Properties of Rock
Rock Intact & Mass Properties
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
Rock Mass Properties

Rock discontinuities and their properties:
 Spacing
 Nature
 Orientation
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Seismic velocity (similar to use in Caterpillar Ripping Chart)
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RQD (Rock Quality Designation)
Using RQD (relative to depth)
Minimum, Average, and Maximum b
196400
196200
Using RQD
(top of rock to 15 ft)
196000
195800
195600
195400
195200
Impact Hammer Excavation
 Greens
- efficient
195000
 Grays
- difficult/slow
194800
 Reds
- tedious
194600
979600
979800
980000
980200
980400
980600
980800
196400
196300
196200
Using RQD
196100
196000
(bottom of excavation) 195900
195800
195700
195600
195500
195400
195300
Impact Hammer Excavation195200
195100
 Greens
- efficient
195000
 Grays
- difficult/slow 194900
 Reds
- tedious
194800
194700
194600
979600
979800
980000
980200
980400
980600
980800
Using Fracture Spacing
Average and Maximum
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 …….
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