Driven Piles in Intermediate Sand Layer
Driven Piles in Intermediate Sand Layer
(OP)
The site I am working on has layered strata with stiff to very stiff clay in the upper say 35 ft followed by medium dense to dense sand between 35 ft to 45 ft followed by very stiff clay to a depth of 65 ft followed by medium to dense sand to 100 ft. The client wants to utilize driven square concrete pile and tip the pile at 40 ft depth below grade in to the intermediate sand layer and utilize capacity in skin friction as well as end bearing.
My question is what should be the minimum thickness of sand layer below the pile tip to count on the end bearing capacity in sand?
My question is what should be the minimum thickness of sand layer below the pile tip to count on the end bearing capacity in sand?





RE: Driven Piles in Intermediate Sand Layer
RE: Driven Piles in Intermediate Sand Layer
Added: Stressing has to accommodate the reflected tensile wave to keep the pile from cracking across the section and 'dusting'.
Dik
RE: Driven Piles in Intermediate Sand Layer
IMHO, it does not take much. The way I read your description the pile would be embedded 5' into the sand with another 5' below the pile tip. That should be more than enough for reasonable loads. The big challenge may be obtaining 5' of embeddment in the sand. The pile may not even have much, if any point loading. A clay layer (upper 35') will often be deceptively easy to drive thorough but will establish significant skin friction a day or so after driving is terminated. Friction from the 5' embeddment in sand will contribute to reduce point loading, too.
If the clay layer will provide any needed lateral support, I would terminate driving shortly after reasonable confirmation that the pile has reached the sand. Otherwise, the Contractor may have to switch to a more powerful hammer for the 5' embeddment in sand.
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RE: Driven Piles in Intermediate Sand Layer
RE: Driven Piles in Intermediate Sand Layer
RE: Driven Piles in Intermediate Sand Layer
RE: Driven Piles in Intermediate Sand Layer
Dik
RE: Driven Piles in Intermediate Sand Layer
What I'd like to know is why do you need piles?? What kind of structure?? If you have 35 ft of stiff to very stiff clay which implies overconsolidated soil . . . It would be interesting to know why you can't use spread foundations.
RE: Driven Piles in Intermediate Sand Layer
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