Referring to the question and answer about Rinter (https://communities.bentley.com/products/geotech-analysis/f/plaxis-soilvision-forum/212033/rinter-value)
We typically do not recommend parameter values as this should be based on data collected from your investigation, laboratory data, engineering experience and judgment.
What kind of investigation or laboratory tests are most commonly carried out to obtain Rinter values?
On a very (very) rough estimation, considering interaction with sand and concrete values of Rinter between 0.8-1.0 can be used, and with clay with concrete values between 0.7-1.0. However, it is very difficult to say exactly what value would best fit your analysis.
Are there any literatures or publications that help us to roughly determine Rinter values?
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.
PDF
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.
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
but what about the interface between the soil layers?. This R inter generally specifies that interaction between the soil and the structure.
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,