Presentation on theme: "Hydraulic Impact Hammer (hoe ram) How do you determine feasibility and performance in rock?"— Presentation transcript:
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 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.
Secondary Breakage In Jointed Blocky Rock
Secondary Breakage of Rock Blocks
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 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 …….