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# B/L Ratio for Raft Model in Plaxis 2D

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## B/L Ratio for Raft Model in Plaxis 2D

(OP)
Hello,

For a rectengular raft, what is the design methodology for Plaxis 2D?

For example, I have seen some approaches that calculates the SQRT(BxL) as the breadth of the raft.

For example, for a foundation of 10x40, raft, what do you do to model it in Plaxis 2D? I accept Schmertmann is correct since it takes in to account B/L ratio. Did you see any paper about this issue?

### RE: B/L Ratio for Raft Model in Plaxis 2D

What are you hoping the Plaxis 2D results will give you?
It is a plane strain analysis, so if your interest is settlement, the "10" dimension will be the one you are looking at on the screen, with the "40" out of the pad.
If you are interested in correcting (reducing) the settlement for 3D effects using the 2D program, you can approximate that with simple hand calcs. For typical mat dimensions, you will get scaling factors in the 0.6 to 0.8 range.
A paper reference (master's thesis) is: FEM MODELLING OF PILED RAFT FOUNDATIONS IN TWO AND THREE DIMENSIONS by Ryltenuis, which uses Plaxis models.

### RE: B/L Ratio for Raft Model in Plaxis 2D

(OP)
ATSE,

Yes, I was looking for a scaling factor. For example squareroot(beta*B*L) where beta is the scaling factor in order to get same results with 2d and 3d analysis.

You are saying that I should take the 10 which is smaller dimension, but you do not justify your answer. Isn't choosing smaller dimension is under-estimate?

I have checked that thesis a few months ago, it was useful for piled rafts, I don't remember that it has anything about rafts, but I will check it again. Thank you.

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