Plaxis large stiffness difference between layers

[afrochaltey]

Sometimes there is a large stiffness difference between two layers in Plaxis model. In some of the cases, the calculation phase elongates abnormally and sometimes results in failure. What would you suggest in such cases, to obtain a reasonable solution.

 

[killswitchengage]

whats the soil layers made of ? describe them

 

[afrochaltey]

Let's say one layer is stiff Clay with E=30,000kN/m2, modeled in MC.
Below or above it, there is either concrete that is modeled as a LE soil, or rock modeled with HS that has E=30,000,000kN/m2.
Whenever there is such a case, the analysis time increases greatly and for most of the time there is problem with load distribution resulting in local failure zones at the boundaries.

 

[SixDegrees]

Afro,

You could try inserting an interface between the material which have large contrasts in stiffness. This will allow some relative displacement between the materials and confine the local shear failure to the interface rather than distributing it through the elements.

Martin