How to get Rinter value

RE: How to get Rinter value

Dennis Waterman — Wed, 27 Sep 2023 11:06:35 GMT

How the Rinter value works can be found in the PLAXIS manuals, both the Reference Manual and the Material models manual. So I would suggest you look it up there. If you have partial interaction you would have to know something about for instance the reduced friction angle between the different materials to calculate that back to an Rinter value. There are some guidelines in literature, but values are mostly determined by local building codes.
In general, if you have full bonding you could decide to not use an interface at all.

With kind regards,

Dennis Waterman

RE: How to get Rinter value

Safeena Nazeer — Wed, 27 Sep 2023 09:21:40 GMT

As I have understood if there is full bonding condition between the two materials then R inter can be taken as 1 and if there is no bonding then 0.01. Is it how it is taking it? What about a partial interaction how this value will help in deciding the same?

RE: How to get Rinter value

Safeena Nazeer — Wed, 27 Sep 2023 09:19:32 GMT

So how can we define interaction between the two soil layers by this R inter value? Is there any significant parameter in plaxis 2D dedicated for such kind of simulation?

RE: How to get Rinter value

Dennis Waterman — Wed, 27 Sep 2023 06:38:16 GMT

Rinter specifies the strength reduction between both sides of the interface. Whether one side is a structure or both sides are soil or rock doesn't matter. That in practice interfaces are mostly used between structures and soil is true, but that is because we're mostly interested in that interaction and less in the interaction between soil layers not because interfaces cannot handle soil-soil interaction.

With kind regards,

Dennis Waterman

RE: How to get Rinter value

Safeena Nazeer — Wed, 27 Sep 2023 05:43:59 GMT

but what about the interface between the soil layers?. This R inter generally specifies that interaction between the soil and the structure.

RE: How to get Rinter value

Dennis Waterman — Mon, 20 Sep 2021 08:08:26 GMT

Dear Yohei,

There are for instance guidelines for the friction angle of interaction as function of the internal friction angle and the type of structure (concrete, steel SPW, etc) for non-cohesive soils. Several (inter)national building codes prescribe using those guidelines. If one knows the friction angle of the soil and, according to the guideline, the friction angle of interaction, the value of Rinter can be derived at least for non-cohesive soils.

With kind regards,

Dennis Waterman

RE: How to get Rinter value

Stefanos Papavasileiou — Mon, 20 Sep 2021 08:03:46 GMT

Dear Yohel,

Indeed, this value can vary from sand to sand and from clay to clay.

In general, the value of Rinter should never be a critical parameter in your model as it is a very arbitrary factor. That means that if by changing the value from 0.8 to 0.7, you get to see a very different picture it means that using the Rinter is not the right way to simulate the interface between your soil and structure.

Instead, you can use a Custom material that can be assigned to the interface (default is From adjacent soil), which can be a dedicated material with the sole purpose of modelling the behaviour of the interface. Then, you are allowed to directly determine the stiffness and strength of the interface.

As usual in modelling a sensitivity analysis may be necessary to determine which value best fits the expected behaviour.

RE: How to get Rinter value

Berk Demir — Mon, 20 Sep 2021 07:43:14 GMT

Direct shear between soil and (let's say) rock surface and compare with the direct shear with soil. But it is very rare to perform these analyses.

One study is given below. Mostly Plaxis recommendations are updated in projects and academical studies.

communities.bentley.com/.../Potyondy-_2D00_-Skin-Friction-Between-Various-Soils-and-Construction-Materials.pdf