After 40 years working in the underground environment. I've not once had to model a tunnel, nor to the best of my knowledge , have any of my consulting engineers done so. That should tell you something. Perhaps you need to focus on the likely geotechnical parameters . Is this in hard rock or incompetant soils??? Kinda makes a major difference snd if you haven't yet identified these paramewter, you need to go back to basics. Tunnel size ??? RQD??? In situ sresses?? Geological discontinuities??