Shaking table tests on the seismic responses of underground structures in coral sand

•Seismic response of the underground structures in coral sand was investigated.•Liquefaction degree of the coral sand increased with the groundwater level.•Acceleration amplification factor decreased with the groundwater level.•Settlement of the ground surface increased with the groundwater level. To reveal the seismic response of underground structures in coral sand, a series of shaking table model tests on underground structures at four different groundwater levels were carried out. The seismic responses of the coral sand and the underground structure were obtained and analyzed. The results showed that the excess pore pressure ratio and the liquefaction degree of coral sand increased with increasing groundwater level, resulting in a more significant separation between the sidewall and the surrounding soil. However, the acceleration amplification factor of the coral sand site, the dynamic strain and bending moment of the underground structure could be reduced. Moreover, the increase in the groundwater level contributed to the settlement of the ground surface. However, due to the presence of an uplift force caused by the liquefaction of the coral sand, the settlement of the underground structure decreased as the groundwater level increased. Furthermore, the distribution of the dynamic soil pressure under the groundwater level was found to be quite different from that under dry soil condition.