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 principle. The state of the art suggests approaching the lining design by allowing the development of the necessary convergences to adequately reduce the rock load (yielding principle). In this paper, a new steel element (HiDSte), yet to be employed in real tunnel works, is described. The behaviour of the lining made of steel ribs along the HiDSte is illustrated through 2D numerical analyses. The numerical results allowed the evaluation of the peculiar way soil and lining interact and, more in general, the ability of the yielding lining to reduce the in-situ stress level undergone by the lining.