I have a problem of embankment constructed on clay layer over sandy soil. The clay layer of a depth 11m and cu=60kPa, sand soil of a depth 39m and angle of internal friction 35.
I carried out tunnel of 6m in diameter in clay layer at different depth 5,8,10m.
In all cases when carried out only tunnel the settlement value is upward.
I used hardening soil model for clay and sand. I used program PLAXIS 3d in analysis.