Timber piles embedded in concrete
Timber piles embedded in concrete
(OP)
I have a dock project that requires the use of 12" timber (greenheart) piles with relatively high (7 ton) uplift capacity. The subsurface conditions consist mainly of a thin layer of sand (5 feet or so) underlain by weak fragmented limestone. In order to attain the required uplift capacity we are considering preaugering a socket in the limestone, filling it with grout and subsequently inserting the pile (preforming the timber piles). Does anybody know how to estimate the slip resistance between the timber pile and the concrete socket.





RE: Timber piles embedded in concrete
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RE: Timber piles embedded in concrete
Could there be a problem with skin friction if the diameter at the bottom is larger than the diameter at the top? I envision there being a "void" or at least disturbed soil adjacent to the pile because a larger diameter was driven.
I suppose if it is granular soil, the soil would soon enclose around the pile, but it seems like the confining pressures would be less.
RE: Timber piles embedded in concrete
One temporary application is to employ this "trick" when timber piles are used as spuds in deep water to hold a barge in place. In the right soils, sufficient skin friction develops quickly enough (in a few minutes) to keep buoyancy forces from making the pile "pop" out of the ground.
www.SlideRuleEra.net
RE: Timber piles embedded in concrete
You could drill a hole through the timber pile and place a rebar in it and cast it into the grout at the toe. Now your timber pile uplift force will also be resisted by the shearing of the timber and rebar. I have used these type of detail in pole frame buildings. I do not have the drawing in front of me, but the hole should be at least 4 inches from base of timber pile, and the use of a 25M should be sufficent. Check to see if a 3 ft grout plug would be fine, as now you have additional resistence from the grout plug via friction, which is more than the timber pile / grout resistence.
Regards,
RE: Timber piles embedded in concrete
RE: Timber piles embedded in concrete
RE: Timber piles embedded in concrete
Could you attach a rebar cage to the tip of the piles to provide resistance with the grout/concrete? These could be submerged below the top of the grout/concrete so that they don't show. They could be epoxy-coated if corrosion is a concern. Sorry, marine environments are pretty much outside my current experience.
Hope this helps.
Jeff
Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com
RE: Timber piles embedded in concrete
RE: Timber piles embedded in concrete
Good advice. I gave you a star. For some reason, I don't immediately consider battered piles, except for lateral loading. I need to work on that mental block of mine.
RE: Timber piles embedded in concrete
RE: Timber piles embedded in concrete
I would like to clarify one thing that doesnt look right the way I wrote it. When I say transfer from one side to the other, I mean the vertical load is transferred to the 'top' half circumference face of the pile pushing on the rock. The failure mechanism would include more of the shear strength of the rock and less of the bond of pile to rock.