Tunnel and track bed concrete behaviour

[Ashoknanyang]

Dear All,
I am checking the trackbed concrete behavious on the circular tunnel when the tunnel subjected to bending.
Track bed not monolithically connected to tunnel,Hence when the tunnel deflect there will be gap between this two elements.See attachment for clearer understanding.
I am not sure which link to use , whether GAP or T/C friction isolator?

Please help me on this.


Thank you,
Regards,
Asva