Numerical and statistical investigation of the performance of closed-cell aluminium foam as a seismic isolation layer for tunnel linings

Traffic congestion and environmental factors in urban areas have increased the use of underground structures such as tunnels. The protection of these tunnels is therefore crucial and requires anti-seismic measures, especially in areas of earthquake prone areas. Typical seismic isolation materials are often used as shock absorbing layers. This study aims to explore the effectiveness of closed-cell aluminium foam (CCAF) as seismic isolation layer on the one hand. On the other hand, to evaluate the effect of the main factors influencing CCAF's performance, and assess the level of impact of each factor. Hence, a 2D nonlinear FE model was established to accurately predict the seismic response of the tunnel. Experimental data collected from dynamics centrifuge tests were used to successfully validate the developed model. Thereafter, a comparative analysis between the seismic response of a tunnel with CCAF as an isolation layer and the widely used foamed concrete was performed. Different characteristics of soil and tunnel lining and tunnel buried depth were considered for each seismic isolation layers. Then, the effectiveness of CCAF as a seismic isolation layer was investigated. Moreover, statistical analysis of the seismic design of the tunnel with the CCAF seismic isolation layer was presented, analysed and discussed. The results revealed that CCAF considerably reduced the deformation of the tunnel lining under a seismic load and can therefore be used in a seismic design of a tunnel.