To my understanding an interface is added to simulate the interaction between the soil and structure. I am trying to figure out the difference between creating a positive or negative interface. what does the positive and negative part signifies?
Mr. Sriram,
Your question is very interesting..thanks for this type of question useful to all..Positive and negative interface concept is used mainly in case of a retaining wall supported excavation or closed excavation in tunneling under water flow conditions. So, when an interface is set to inactive for flow, it will act as if it is not there, and water can flow across this inactive interface without any resistance. Instead of setting a specific material data set to the "inside" interface, we can now set the inside "Active in flow" state to inactive (positive interface), while we keep the "outside" interface "Active in flow" (negative interface). In an excavation, outside interface mean on the retaining wall after installation, there are two faces one that is inside where excavation taken place (i.e. the wall and soil is in deactivate mode) and other one outside the excavation (i.e. the wall and soil interface - soil is in active). Outside interface (in this case use Negative interface) set to active in flow, and inside interface (in this case Positive interface) set to inactive.
Similarly for a semi-permeable tunnel lining: the correct interface permeability should be given to the interface on the outside of the tunnel lining, whereas the interface at the inside (which will be excavated) should be modelled as fully permeable. Both approaches (positive and negative interface) can also be applied to tunneling related problem. ok all the best pa..
Karthigeyan . S Thank you for providing the clarification sir. It has helped me lot in assigning the interfaces sir. Thanks a lot sir.
It is interesting question. l think that positive or negative interfaces depends on position of structure and soil. Some time, we need to activate negative or positive. There is another case in which we need to activate both negative and positive interfaces such as helix plates in screw piles.
The positive and negative sign of interface is just used to enable the recognizing interfaces at either side of a surfaceline, but it does not affect its behavior.
The sign of an interface (positive or negative) is only used to distinguish interfaces at either side of a surfaceline and does not have any influence on the behaviour. You can also refer to the "Interfaces" section of the reference manual in Plaxis.
Its there to help recognize the two sides of the structure without any influence on the results. You can find its detailed explanation in the Plaxis reference manual.
The sign of an interface is only used to enable distinguishing interfaces at
either side of a , but it does not affect its behaviour.
Prerna Singh Ashish Juneja I think it influeneces the results. I was modelling a plate structure and the values of induced Bending moment were different with and without the interface elements.
Nishkarsha Koirala Yes, it does influence the behavior of the structure. based on the above discussion, the difference between a positive and negative interface refers to the spatial position of the added interface (i.e. either to the left or right-hand side of the element on which the interface is added.)
Nishkarsha Koirala of course interface elements influence the results. Please read the question again, wherein the difference between negative and positive interface is asked.
Please try using different interface values to obtain where your test fits in best.
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