Interface_Material Mode and Virtual Thickness

Dear Nitha,

The custom option is for you to be able to directly control the stiffness and strength of the interface behaviour. You can therefore select a dedicated material to better control the interface behaviour. This gives you the option to avoid using the Rinter property which affects both stiffness and strength (as explained in the Reference manual).

Regarding the virtual thickness, this purely affects the numerical part of the analysis. As explained, the virtual thickness does not exist in reality but is the way to handle the presence of the interface in a finite element method world. 
The difference in results can be explained as mentioned in the Reference manual as a consequence of using a larger elastic zone to be considered, which should not be the case.

I would recommend though to try it in a simpler example and not involving water, diaphragm wall and change in soil loading to see in a simpler way how it behaves.

If you have further questions about it please submit a service request. Then, one of our support engineers can help you in detail:
https://apps.bentley.com/srmanager/ProductSupport

Dear Mr. 

@Stefanos Papavasileiou

if we provide the interface elements, we can obtain the interface stresses and we can take that that amount of stresses is transferred to the structures from the soil? and why elastic deformation is ignored as mentioned in the following paragraph?

further i have some questions

01. Virtual thickness of interface=> as mentioned in the reference manual , the deformation depends on the virtual thickness, but based on the equation virtual thickness only affects when we use standard option, if kn/ks is used no effect on it, am i correct? 

Update: I did a simple analysis using cantilever sheetpile with 1.5m depth excavation and results shows if kn/ks method used there is no effect by virtual thickness factor as shown below.

So here i put another question, how do we validate the provided virtual thickness factor is correct or not for a analysis? and how to find the virtual thickness?

02. What is the reason using vi=0.45? any specific reasons or rules and Gi = (R^2)Gsoil <= how it's came?

03. when we reduce the soil structure friction angle we used (2/3)xphi then taking tan function but here it is mentioned as Rinter x tan (phi), why not  tan( Rinter x tan(phi))?

04. The stresses (particularly on the shear stress)  in the soil and the on interfaces varies. My question is, this variation is occurred due to the change of stress angle due to the interface or any other reasons?

Thanks.

Thanks Dennis,

Virtual and actual thickness! Plaxis is a treasure trove of small intricate details. I'm impressed by how much thoroughness the Plaxis team has put into the implementation of the interface. This is why I like this program.

Martin

Thanks Mr. Martin

Hi Mr dennis. Is it possible to model an cased (steel case) pile in Plaxis 3D?? If the answer is positive, how can I do this???

My objective is to model and compare two cased piles with the same diameter varying the steel case thickness.

Dear António,

Yes, that is possible. Just use a cylinder and create a plate on the outer surface of the cylinder. Through the plate properties one can set the thickness of the steel case.

By the way, since this question is not related to the original question, it's better (and common practice) to start a new forum question for it.

With kind regards,

Dennis Waterman

Thank you Dennis. I already started a new forum question.

Thank you Dennis. I already started a new forum question.