In order to study the surface settlement characteristics of an overlying soft soil layer in a subway tunnel under seismic loading, the ABAQUS finite-element analysis software was utilized. Taking the construction of Dalian Metro Line 5, which is located in seismic intensity zone Ⅶ and has an overlying soft soil layer, as the engineering background, El-Centro and Kobe waves representing class Ⅱ site seismic waves, as well as an artificial seismic wave with an exceedance probability of 10%, were inputted into the analysis. The settlement characteristics of the ground surface at the construction site of the subway tunnel under the three different seismic waves were investigated, and their behaviors were theoretically analyzed. Then, the surface settlement law with respect to the tunnel roof was studied based on El-Centro wave and soft soil parameters, and a sensitivity analysis of soft soil parameters of surface settlement of the tunnel roof was carried out by the orthogonal test method. The results show that under earthquake action, the settlement of the strata within a certain range of the tunnel roof was significantly greater than that of the surrounding strata, forming a settlement trough with a width of about 8 to 20 m. The width of the settlement trough under the El-Centro wave was the largest, about 19.6 m, surpassing that of the artificially synthesized seismic waves with a probability of 10%, which was about 15.6 m, while the width of the settlement trough under the Kobe wave was the smallest, about 8.5 m. The ground surface within a range of about 20 m above the tunnel roof was most strongly affected by the seismic waves and the special lithology of the overlying soft soil layer, and the settlement was the largest. The settlement law of the settlement trough in the overlying strata of the tunnel conformed to the Peck formula. Increasing the elastic modulus of the silty soil can reduce the settlement of the ground surface above the tunnel roof; increasing the Poisson’s ratio of the silty soil will increase the settlement of the ground surface above the tunnel roof; increasing the cohesive force of the silty soil to 20 kPa will basically stabilize the settlement of the ground surface above the tunnel roof; and increasing the internal friction angle of the silty soil will basically not change the settlement of the ground surface above the tunnel roof. The sensitivities of the soft soil parameters to the settlement of the ground surface above the tunnel roof were in the order of the Poisson’s ratio, the elastic modulus, the cohesive force, and the internal friction angle. Therefore, the research findings of this paper provide scientific support for the problem of surface settlement of the overlying soft soil layer in subway tunnel engineering sites under earthquake action. In addition, these research findings have important theoretical value and engineering application significance, especially in the field of sustainability.

In order to study the surface settlement law of subway tunnel engineering site overlying soft soil layer under the action of earthquake, ABAQUS finite element analysis software was used to study the surface settlement law of subway tunnel construction site overlying soft soil layer under the action of three different seismic waves, including El-Centro wave, Kobe wave, and artificial seismic wave with exceedance probability of 10%, based on the Dalian Metro Line 5 with overlying soft soil layer as the engineering background, and the law was analyzed theoretically. Then, the surface settlement law of tunnel top was studied based on El-Centro wave and soft soil parameters, and the sensitivity analysis of soft soil parameters on surface settlement of tunnel top was carried out by orthogonal test method. The results show that under earthquake action, the settlement of the strata within a certain range of the tunnel roof is significantly greater than that of the surrounding strata, forming a settlement trough with a width of about 8 to 20 meters. The width of the settlement trough under the El-Centro wave is the largest, about 19.6 meters, surpassing the artificially synthesized seismic waves with a probability of 10%, which is about 15.6 meters, while the width of the settlement trough under the Kobe wave is the smallest, about 8.5 meters. The ground surface within a range of about 20 meters above the tunnel roof is most strongly affected by the seismic waves and the special lithology of the overlying soft soil layer, and the settlement is the largest. The settlement law of the settlement trough in the overlying strata of the tunnel conforms to the Peck formula. Increasing the elastic modulus of the silty soil can reduce the settlement of the ground surface above the tunnel roof, increasing the Poisson's ratio of the silty soil will increase the settlement of the ground surface above the tunnel roof, increasing the cohesive force of the silty soil to 20 kPa will basically stabilize the settlement of the ground surface above the tunnel roof, and increasing the internal friction angle of the silty soil will basically not change the settlement of the ground surface above the tunnel roof. The sensitivity of the soft soil parameters to the settlement of the ground surface above the tunnel roof is in the order of Poisson's ratio, elastic modulus, cohesive force, and internal friction angle.