Hello Zac, in a groundwater flow analysis, interface elements can be used to block the flow perpendicular to the interface, for example to simulate an impermeable screen. In fact, when interfaces are used in combination with plates, the interface is used to block the flow since plate elements are fully permeable (plaxis reference manual).

I hope it helps.

Jose.

many thanks Jose

You can use interface Element even if you did not add a plate element.