Experimental study on the seismic behavior of tunnels with distinct surface roughness in liquefiable soils

Earthquake-induced liquefaction poses grave safety risks to the underground structures. In this study, 1-g shaking table tests were conducted to investigate the uplift behaviors and soil-structure interaction (SSI) of a two-part tunnel located in liquefiable soils, with special attention paid to the influence of structural surface roughness. Two parallel tests, including a free-field test and a soil-tunnel test, were carried out to investigate the field responses and the effect of SSI during liquefaction induced by various input motions. The test results indicate that the ground partially liquefied during the first shaking event, and then experienced full liquefaction in the subsequent events with higher loading amplitude and longer loading duration. The excess pore pressure and horizontal acceleration responses around the tunnel were significantly altered due to the presence of the tunnel, which also led to different patterns of acceleration amplification and strain development in its vicinity. While structural surface roughness influenced the aforementioned responses to some extent, it played a more dominant role in the uplift behavior of the tunnel. The segment with lower surface roughness experienced significantly greater uplift compared to the rougher counterpart. Furthermore, it was found that the structural uplift behavior can be divided into distinct stages that feature different patterns of pore pressure development, and such behavior was notably different under varied loading conditions. The findings in this research emphasize the importance of incorporating the considerations of surface roughness in future numerical or experimental studies so that the structural uplift can be better captured.