I have a dynamic/seismic FLAC model with liquefied material at the free boundary. I have used free boundary and this is large lateral deformation at the free boundary (liquefied here), what is the cause and how I can prevent this?
Using liquefied material at the zones near the free field boundary is not recommended. The free field boundary performs a small-strain calculation even though the main grid is executing in large strain mode. In order to reduce the mismatch between large-strain and small-strain calculations, two or three columns of zones near the lateral boundaries are usually assigned with high strength properties to minimize the large deformation, check the earthdam example here: Earth Dam | US Minneapolis - Itasca Consulting Group, Inc.
Thanks. This is what I did for other projects. However, I didn’t do for this one where we got large deformation. Just to confirm this is the case I can use high strength materials.