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145_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011

145_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011 -...

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DF26 o the pile also attenuates (reduces) the force wave as it travels due to internal friction losses o diesel hammers: high impact velocity (long stroke), light ram and short impact duration o air/steam hammers: low impact velocity (short stroke), heavy ram and long impact duration force or velocity In pile air/steam ......... ......... ------- time o to minimize damage to the hammer the ram force is cushioned at the striking surface o to minimize damage to the pile the ram force is cushioned at pile head (except steel piles) o energy losses are greater at impedance changes (e.g. hammer to helmet, helmet to pile, pile section changes, pile stiffness changes, etc.) o the energy transferred to the pile controls the penetration per blow ("set") o therefore the blow count (=1/set) is a function of: pile material hammer type
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Unformatted text preview: pile area rated hammer energy pile length impact velocity pile weight duration of impact pile stiffness type, stiffness, and thickness of cushions pile uniformity soil resistance and location along pile (notice how much of the above has to do with soil-scary yes?) o typical energy transferred to the pile: (courtesy of the Deep Foundations Institute) FHWA Hemmer Performenee SJ\Idy (Rausch. at 81'1 188&) Energy Tnn"er Ratio Hemmer Type Pile Type Mean Std. Dev. Reng. Single Acting Air/Steam Steel 49" 10% 29-71% Concrete or nmber 46" 16% 26-96% Double Acting Air/Steam Steel 33" 9" 24-&1" Concrete or nmber 27% 8% 16-44% Open End Diesel Steel 34% 10" 16-69% Concrete or nmber 26% 6" 13-43% Closed End Diesel Steel 36" 7" 23-48" Concrete or Tim~er 26" 6" 18-33%...
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