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construction ? on pile drivers
A construction crew next door has been driving 60 ft reinforced cement piles into the ground for about two weeks. They drive them about 6 feet down and pull the driver up and out. Why do they drive them below ground? How do they attach to them?
thanks
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steve old rocket inguneer |
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02-09-2012, 07:25 AM
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they will dig out the pile hole and pour in concrete footers around the top of the piles
if done correctly the rebar in the top of the pile will be tied to extra rebar in the poured footer |
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02-09-2012, 07:41 AM
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thanks. How do they access the rebar in the top of the pile when they have been beating on it?
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steve old rocket inguneer |
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02-09-2012, 07:49 AM
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typically they dont drive them below grade.
if this is a Caltrans job, the piles are constructed so that the top several feet (8?) the crew will chip the concrete down to expose the rebar, and then bend or splice the structure directly to it. diesel hammer? but i have never used those types of piles..they are square right? my experience they expose the rebar, and use plywood pads as spacers for the hammer.
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poof! gone Last edited by vash; 02-09-2012 at 07:54 AM.. |
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02-09-2012, 07:52 AM
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they piles have no exposed rebar..like this?
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poof! gone |
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02-09-2012, 07:56 AM
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I once lived on a lake where the entire row of houses had been built on back fill. The owner four houses down was pile driving his new foundation. On the second floor, I thought it was an earthquake and the house shook like jello.
I'd think driving them in instead of digging/pouring helps to compact the ground, or perhaps it is done until a minimum resistance is found. |
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02-09-2012, 08:04 AM
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02-09-2012, 08:06 AM
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The piles are about 14 inch square, 54 feet in length, with no rebar exposed. It is for a parking structure or a new building.
I do see what look like plywood spacers about a foot thick laying on the ground, but not used in the pile driving so far. My building is two hundred yards away and I am on second floor and the pile driving is felt at my desk. I can see the water in my glass vibrating and I can feel it.
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steve old rocket inguneer Last edited by stevepaa; 02-09-2012 at 10:11 AM.. |
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02-09-2012, 08:34 AM
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dont stand down wind.
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02-09-2012, 09:18 AM
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Unless an underground spring pops up after ten years because it was diverted a mile up-hill. |
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02-09-2012, 10:18 AM
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They're called pile caps, not footers. The use of a pile foundation system precludes the use of footings (commonly known as "spread footings" which transfer loads to the underlying soil directly).
They can be friction bearing or end bearing. Totally depends on loads and soil characteristics which foundation system is most appropriate. The connection detail between the pile/cap and the structure above depends on gravity + lateral load characteristics, this is what will determine the rebar configuration, spacing, sizing and layout. There is no "one-size-fits-all" foundation system. There's not even a "one-size-fits-all" configuration for a given foundation system type. It's all very situational dependent.
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02-09-2012, 10:24 AM
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02-09-2012, 10:57 AM
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Quote:
The plywood spacers are actually what we call 'pile cushions.' They are in fact used during the driving to help cushion the tops of the concrete piles during driving. Without 'em the tops of the piles would spall and break. Sometimes they are used to protect the rebar sticking out of the tops of the piles... holes are drilled in the plywood stacks to match the rebar pattern (dowels). Fun fact - they often catch fire from the all the heat generated during the driving of the piles - sortof spontaneous combustion, they literally just out of nowhere burst into flames. As far as why they are diving below grade first - I can't say for sure without looking at the plans, but likely for access. The pile rig and loaders need to access and to excavate the pile caps/grade beams and whatnot would limit thier ability to get around the site, therefore they drive them below grade, then after the pile driving operations, excavate the foundation.
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02-14-2012, 07:41 AM
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