For such comparison, you may have a look at :Thesis Comparison of PLAXIS 2D and PLAXIS 3D as Different Tools for...

See also https://www.researchgate.net/post/Is_PLAXIS_the_most_reliable_Software_for_simulating_Finite_Element_Modeling_in_Geotechnical_Engineering

Dear Anandha

A retaining wall is a structure that holds back soil or rock from a building, structure or area. The term retaining wall has a general meaning. It may be a bridge reinforced concrete wall, multi-tiered retaining wall or steel sheet pile in earth excavation section with or without lateral support. The height, thickness, foundation, loading or straightness of the retaining wall may vary along its length.

If the retaining wall length was more than 50 m, the wall behavior may be considered as plain strain model conditions, so that using 2D FEM numerical analysis tool (as infinite long plane strain problem) is enough and the results in 3D FEM models were approximately the same as 2D. If the retaining wall length was less than 50 m, the bending moments and lateral displacements of the wall could be clearly differed. This is because of the effects of the retaining wall ends or corners effects in 3D analysis. I think that it is preferable to use 3D FEM model analysis when the retaining wall length is less than 50 m long. Sometimes, using 2D FEM models is conservative or an under estimation of reality. Also earth pressures on the retaining wall in 2D conditions are much larger than those in 3D conditions while surface settlements at the back-fill just behind the wall is smaller. Although, using 3D finite element analysis needs large amounts of computer resources, both memory and time.

For my opinion, in all cases, the end regions should be analyzed using 3D FEM.

Best wishes.

Thanks a lot... Prof.Mohannad H. Al-Sherrawi for your valuable answer

Some of them: corner effects, corner struts (if any), adjacent loading in different locations, irregular shape (layout) of the walls, etc. All possible in Plaxis3D