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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
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Hydraulic Impact Hammer (hoe ram) How do you determine feasibility and performance in rock?
How do impact hammers work? • Let us take a look……………..
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 of concrete (with limited thickness) or • An intact rock mass (devoid of discontinuities)
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.
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
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 • Seismic velocity (similar to use in Caterpillar Ripping Chart) • RQD (Rock Quality Designation)
Using RQD (relative to depth)Minimum, Average, and Maximum b
Using RQD(top of rock to 15 ft) Impact Hammer Excavation • Greens - efficient • Grays - difficult/slow • Reds - tedious
Using RQD (bottom of excavation) Impact Hammer Excavation • Greens - efficient • Grays - difficult/slow • Reds - tedious
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 …….