Research on Seismic Response of Integrated Subway Stations Built in Liquefied Soil Formations

The integrated subway station structure means that there are no construction joints between the station and the accessory structure, and the station structure and the ancillary structure are considered as a whole. This paper focuses on the seismic response of integrated subway stations in liquefied sites. In this paper, the numerical simulation method is used to establish a calculation model under the two working conditions of considering liquefaction and not considering liquefaction. The results are as follows. (1) The liquefaction area is mainly distributed on both sides of the accessory structure, at the junction of the base plate of the accessory structure and the side wall of the station and at the base plate of the station structure, and the liquefaction area at the junction of the base plate of the accessory structure and the side wall of the station gradually disappears with increased in seismic intensity. (2) The amount of uplift of the structure under liquefaction conditions is proportional to the seismic intensity, and at the same time the asymmetry of the seismic wave causes the structure to rotate during the uplift. (3) The inter-story displacement difference, inter-story displacement angle, and swing amplitude of the structure under the liquefaction condition are smaller than those under the non-liquefaction condition. (4) The axial pressure ratio of the station hall level and equipment level under the liquefied condition is smaller than that under the non-liquefied condition, but for the platform level, regardless of the seismic intensity, the axial pressure ratio of its columns under the liquefied condition is larger than that under the non-liquefied condition. It can be seen that soil liquefaction causes uplift of the structure, while the asymmetry of seismic waves causes the structure to rotate. Liquefaction of the soil weakens the strength of the seismic waves and thus reduces the deformation of the structure. The pore pressure caused by soil liquefaction acts directly on the station base plate, causing an increase in the column axial pressure ratio at the platform level, while the station hall level and equipment level, which are farther away from the base plate, are not affected by their column axial pressure ratios.