Soil-structure interaction of preliminary deformable lining for conventional tunnel in squeezing conditions using HiDSte elements

The construction of deep tunnels is continuously increasing due to both economic and environmental reasons. High cover and poor geotechnical ground make the construction of tunnels difficult (squeezing conditions). Due to the high loads transmitted by the ground, the preliminary lining can be rarely designed following the so-called resistance method. The state of art suggests to approach the design of these lining by allowing the development of the convergences necessary to adequately reduce the rock load (yielding method). In this paper, a new metallic element (HiDSte), not yet employed in real tunnel works, is described. The behaviour of the lining made of steel ribs and the HiDSte is illustrated through 2D numerical analyses. The numerical results allowed the evaluation of the peculiar manner in which soil and lining interact and, more in general, the ability of yielding lining to reduce the in-situ stress level underwent by the lining.