1. Hydraulic Impact Hammer (hoe ram)
How do you determine feasibility and performance in rock?

2. How do impact hammers work?
Let us take a look……………..

3. Hydraulic Impact Hammer Operation

4. A Little Tutorial To make some important distinctions
How impact hammers break rock
What rock properties affect performance

5. Principles of Impact Hammers
Impact hammers work on two principles in breaking rock, namely
Primary breakage and
Secondary breakage

6. 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)

7. Primary Breakage

8. 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.

9. Secondary Breakage In Jointed Blocky Rock

10. Secondary Breakage of Rock Blocks

11. 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

12. Rock Properties
What are rock …
Intact and
Mass
properties?

13. Engineering Properties of Rock Rock Intact & Mass Properties

14. 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

15. Rock Mass Properties Rock discontinuities and their properties:
Spacing
Nature
Orientation
Seismic velocity (similar to use in Caterpillar Ripping Chart)
RQD (Rock Quality Designation)

16. Using RQD (relative to depth) Minimum, Average, and Maximum b

17. Using RQD (top of rock to 15 ft)
Impact Hammer Excavation
Greens - efficient
Grays - difficult/slow
Reds - tedious

18. Using RQD (bottom of excavation)
Impact Hammer Excavation
Greens - efficient
Grays - difficult/slow
Reds - tedious

19. Using Fracture Spacing Average and Maximum

20. 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 …….