Effect of soil heterogeneity on seismic tunnel lining forces

The crucial role that underground structures play today in transportation and utility networks makes their seismic vulnerability a fundamental topic. The present paper deals with the role of soil heterogeneity in tunnel seismic behaviour. Starting from a real case history regarding a cross-section of the Catania (Italy) underground network, a finite element parametric study was carried out, focusing the attention on the soil discontinuity in terms of the impedance p center dot VS of each layer crossed by the tunnel, being p and VS the soil layer density and shear wave velocity, respectively. Different tunnel depths and seismic inputs were assumed. The numerical dynamic lining internal forces were compared with the analytical solutions proposed by Wang (1993) and Penzien (2000) for homogeneous soil deposits; two new approaches were proposed to use them for heterogeneous soils, highlighting the limitations of the original solutions and the range of applicability of the proposed approaches.