With a Plaxis 3D analysis of a simple tunnel in granular material, I've activated the tunnel structure before deactivating the soil volume within the tunnel in the next stage.
Will this predict the ground settlement and predicted volume loss? Or will this need to be modelled additionally based on a surface contraction?
Also will this give the surface settlement due to the deflection of the tunnel lining (i.e based on tunnel material stiffness) only? Or is the effect of the installation/excavation within the tunnel also considered for the downward settlement/surface volume loss?
Dear James,
You firstly mention that you have only activated the structural elements without deactivating the soil. That means that you would not really see any change in deformation, but only due to the unit weight introducing an out-of-balance in the analysis: https://communities.bentley.com/products/geotech-analysis/w/plaxis-soilvision-wiki/45962/reduction-of-stiffness-does-not-lead-to-a-change-in-displacements
I am not sure how you expect activating a structure to consider volume loss. Indeed, that would require using a surface contraction or simply by allowing the tunnel to converge (stiff rock, hopefully without failing).
In principle, with PLAXIS 3D, you can simulate the exact steps you would have in reality, e.g. check the tutorial of our TBM: communities.bentley.com/.../plaxis-3d-tutorial-06-phased-excavation-of-a-shield-tunnel