Varying Stress and Constant Displacement Boundary Condition in Mandel Problem
 

Hello!

I am solving Mandel Problem of Poroelasticity. It is a 2D problem of soil consolidation. I have attached the figure and boundary conditions. I am not able to understand how to apply the force boundary condition at the top.

At a fixed time t, the stress is varying at the top and the total traction is known and displacement at the top is constant but its magnitude is not known. How to apply such a boundary condition.

Kindly help. It is required for my master's thesis.

Thank You,

Rishav