Piled Raft 2

[dr. rifat]

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

 

[ATSE]

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.

 

[JohnnnyBoy]

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.

 

[BigH]

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.

 

[atrizzy]

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.