Subgrade modulus of the soil in Plaxis 2D

Dear Nitha,

Currently, this is not possible, however, I will add your request to be considered as a feature for the future versions of PLAXIS.

Can't we do like that, apply prescibed displacement 25mm and obtain maximum pressure (sigma yy) and using sigma yy / allowable displacement (25mm) as the subgrade modulus ?

Hi Mohamad, 

Can you please some screenshots showing how did you model and which points you have used to draw the stress displacement curve? 

Thanks. 

hHere are some screenshots. In phase 1 I performed an excavation of 30 cm (that's the embedment of a raft) and in phase 2 the prescribed displacement line was activated (0.025 m).

I have drawn the footings as a plate in plaxis and take the node in plate (center and edge) and stress point in the soil close to the plate (center and edge respectively). 

Please note that allowable bearing capacity (bearing capacity which respect for the deflection you defined) is decreased with the increase of the footing width. 

And this bearing capacity is responsible for the continuous footing as in Plaxis 2D length will go into the xy plane indefinitely. So if you want to get the bearing capacity of the square footing (or rectangle) model as axisymmetric because the allowable bearing capacity of the square footing is greater than the continuous one as pressure bulb width is lesser in square. 

Thanks. 

Well noted. Thanks a lot!

I have two more inquiries if you may: 

1- If I do model the foundation as axisymmetric, won't the round shape that the software understands have an impact on the calculation?

2- What's your opinion on calculating BC by doing a cross-section right under the line displacement (foundation in our case) and using the cross-section stresses obtained?

Again thank you.

01. If you use axisymmetric model the footing will model as circle obviously, but the stress bulb of square and circular are almost similar but when see the strip it will show huge deviation which inturns provide low bearing capacity. 

02. That also correct I think. You got BC from the center of the footing, so it shows as almost linear. Curve shows linaer at the center and curve for edge . 

Thanks. 

01. If you use axisymmetric model the footing will model as circle obviously, but the stress bulb of square and circular are almost similar but when see the strip it will show huge deviation which inturns provide low bearing capacity. 

02. That also correct I think. You got BC from the center of the footing, so it shows as almost linear. Curve shows linaer at the center and curve for edge . 

Thanks.