Abstract: Study is made on the judgment of the stratum liquefaction grade and the calculation methods for the seismic effect on tunnels, with LuntouShengwudao immersed tunnel as an example. Conclusions drawn are as follows: for tunnels with deep overburden, finite element method can be adopted to determine the stratum liquefaction grade; liquefaction conditions have great influence on the seismic effect calculation results, especially on the internal force of the joints; full consideration should be paid to the seismic influence on the water stop ties at the joints.

Key words: liquefaction, immersed tunnel, seismic effect