The effect of tunnel lining modelling approaches on the seismic response of sprayed concrete tunnels in coarse-grained soils

Major seismic events have shown that tunnels in cohesionless soils may suffer extensive seismic damage. Proper modelling can be of great importance for predicting and assessing their seismic performance. This paper investigates the effect of lining structural modelling on the seismic behaviour of horseshoe-shaped tunnels in sand, inspired from an actual Metro tunnel in Santiago, Chile. Three different approaches are comparatively assessed: elastic models consider sections that account for: (a) linear elastic lining assuming the geometric stiffness; (b) linear elastic lining matching the uncracked stiffness of reinforced concrete (RC); and (c) nonlinear RC section, accounting for stiffness degradation and ultimate capacity, based on moment-curvature relations. It is shown that lining structural modelling can have major implications on the predicted tunnel response, ranging from different values and distributions of the lining sectional forces, to differences in the predicted post-earthquake settlements, which can have implications on the seismic resilience of aboveground structures.