EASEC-15 October 11-13, 2017, Xi’an, China 1 MODELLING THE RESPONSE OF A TUNNEL LINING IN LIQUEFIABLE SAND Giuseppe Colamarino 1 , Gianluca Fasano 1 , Anna Chiaradonna 1 , Emilio Bilotta 1 & Alessandro Flora 1 1 Department of Civil Architectural and Environmental Engineering, University of Napoli ‘Federico II’, Italy ABSTRACT Soil liquefaction may induce buoyancy of underground structures such as tanks, tunnels and pipelines. Several cases of uplift of underground tanks and pipelines have been observed in the past. Although such an evidence has not been registered yet for tunnels, centrifuge testing has shown that the high mobility of liquefied soil near surface would encourage floatation of very shallow or immersed tunnels. Starting from the back-analysis of the results of a published centrifuge test on a model tunnel in a dry layer of Leighton Buzzard sand that undergoes ground shaking, this work explores numerically the behaviour of the same tunnel after that the sand has been saturated. An effective stress constitutive model, available in a finite element code, was calibrated on the results of laboratory tests on the sand used in centrifuge along monotonic and cyclic stress paths. The ability of the model to predict the dynamic response of the sand layer both in dry and saturated conditions and a reasonable pore pressure build-up in undrained conditions is showed and discussed in the paper. Later, the behaviour of the model tunnel is deeply analysed in terms of displacements and internal forces arising in the tunnel lining during the seismic event. Keywords: tunnel, liquefaction, uplift, buoyancy, centrifuge 1. INTRODUCTION Severe damage affected some tunnels during recent earthquakes that can be associated with the onset of loading conditions incompatible with lining resistance (O’Rourke et al. 2001; Wang et al. 2001). One of the main reasons for the damage of soil structures due to earthquake is liquefaction of saturated soil deposits. Although such an evidence has not been registered yet for tunnels, centrifuge testing has shown that the high mobility of liquefied soil near surface would encourage floatation of very shallow or immersed tunnels (Yang et al. 2004; Chian and Madabushi 2011). Even though many numerical tools have been developed in the last three decades to assess soil liquefaction, prediction of liquefaction is still a challenging task. To this purpose, physical modeling was useful to collect important information and quantitative data on the phenomenon.