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Piled Raft

Piled Raft

(OP)
Hello

Please excuse my ignorance on the subject.

This is the first time I am designing piled rafts. I have a few questions for which I would appreciate some direction/references.

1.How to determine the thickness of piled raft?A expert give me this formula to determine thickness,But I cant realize this formula.
"10 (700*4.448)^0.5 in mm

2.Say a column load is 700 kips,pile can carry 300 kips,how to transfer safely rest 400 kips load by raft?I know there are some calculation,please anyone share with me.

Thank you

RIFAT

RE: Piled Raft

This is not a simple design effort. You need mentoring.
To get a head start, read all of the previous posts on eng-tips on this subject.
Also get publications by Poulos (AU) for a start.
I would suggest a non-linear soil-structure model (like Plaxis or FLAC).
Do not try to size your mat based on a single formula.

RE: Piled Raft

I am not an expert on this to say the least, but it would be a lot of iteration between settlement of the slab and the stiffness of raft slab for load transfer. The formula that you were given may just be a simple formula to start with and move on to modeling and collaboration with the structural engineers for load transfer.

RE: Piled Raft

Read up on a number of papers by Harry Poulos - you should learn quite a bit from them . . . but, too, you need to speak with others who have experience and judgment in the area of piled raft foundations.

RE: Piled Raft

Think of the raft slab as a suspended slab and the piles as columns (or springs, for that matter).
If you have a column load higher than what a pile can take you shouldn't put it directly over a pile, rather, put 3 piles around the point load in a triangular pattern so that they share the load.

The others here are on the right track, you'll need to properly model all this stuff.

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