Numerical Investigation of Seismic Isolation Layer Performance for Tunnel Lining in Shanghai Soft Ground

An isolation layer around the cross-section of a tunnel lining would be the simplest and most effective shock absorption measure which can reduce the intensity of seismic action and minimise the deformation transferred from surrounding soil to the tunnel lining. This study explored the effectiveness of foamed concrete and silicone rubber as potential seismic isolation layers in clay soft soil. A 2D finite element model was proposed to accurately predict the seismic response of the tunnel. Experimental data collected from Shanghai metropolitan tunnel were used to validate the developed model. Different tunnel lining and seismic isolation characteristics, as well as tunnel buried depths, were considered for each seismic isolation layer. It was revealed that the silicone rubber considerably reduced the deformation of the tunnel lining under a seismic load and can therefore be used in a seismic design of a tunnel in soft clay soil.