How to introduce fractures in already meshed domain

Hello! :) I have a question:

1) Is there a way to introduce fractures/joints in an already meshed FEFLOW model? (.fem file). If so, how would the procedure be?

My project is fully unstructured tetra elements so I don't know how to do it. I tried to set fractures before meshing (supermesh elements) but I failed, the geometry couldn't be meshed.

The geometrical model is particularly difficult since I have a tunnel inside the hydro-geological region and the fractures go through the tunnel as well, which has deactivated elements. Is there a  way to handle this situation?

Thanks in advance, kind regards.