# Study on the Influence of Deep Soil Liquefaction on the Seismic Response of Subway Stations
## 5 Discussion  
The primary objective of this study is to assess how the liquefaction behavior of a deep liquefiable soil layer, situated 20 m beneath the surface under the base slab of a subway station, influences the dynamic response of the station during seismic events. Detailed numerical simulations revealed significant liquefaction occurrences within this deep soil layer. These findings are in agreement with those reported by [PERSON] et al. [27], who also noted similar phenomena in their research on the impact of liquefiable soil layer positioning on the seismic responses of underground structures. The construction of subway stations has been shown to reduce the vertical effective stress on the soil layers below, thereby increasing the likelihood of soil liquefaction. This article posits that the impact of the liquefaction depth should be taken into account in the design of subway stations, aligning with the recommendations made by [PERSON] et al. [21]. The liquefaction behavior of soil layers can lead to an increase in the pore water pressure and a reduction in effective stress within the soil, thus subsequently decreasing the bearing capacity of the soil beneath the station. These findings are in agreement with the research carried out by [PERSON] [23] and [PERSON] [25]. Under the conditions of deep soil layer liquefaction, the horizontal effective stress in the soil adjacent to subway stations increases by 20% to 50%, whereas the horizontal effective stress beneath the stations decreases by 2% to 15%. This phenomenon may be attributable to the reduction in soil effective stress caused by liquefaction, while the presence of structures tends to increase the effective stress within the soil. These results are consistent with the phenomena observed in the vibration table experiments concerning the impact of liquefied soil layer distribution on the seismic responses of underground structures conducted by [PERSON] et al. [28]. It should be noted, however, that the distribution of soil layers was simplified in this study. In actual engineering practice, the characteristics of soil layer distribution can be determined based on geological exploration results. Hence, the applicability of the conclusions should be viewed only from a qualitative perspective. Additionally, although frictional contact issues between soil layers and structures have been contemplated in this study, the characterization of normal and tangential frictional properties has been simplified. Future research could be enhanced by employing more advanced modeling techniques, such as the finite element method combined with multiscale \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Points**} & \multicolumn{2}{c}{**Design Earthquake/kPa**} & \multicolumn{2}{c}{**High-Level Earthquake/kPa**} \\  & **Case 1** & **Case 2** & **Case 3** & **Case 4** \\ \hline S1 & 582 & 2831 & 2231 & 4196 \\ S2 & 3291 & 4164 & 5479 & 4547 \\ S3 & 1816 & 2339 & 3182 & 2597 \\ S4 & 81 & 1460 & 1116 & 2346 \\ S5 & 783 & 2476 & 1964 & 3267 \\ S6 & 1554 & 2272 & 3154 & 2520 \\ S7 & 1485 & 2184 & 3094 & 2597 \\ S8 & 581 & 2195 & 1758 & 3202 \\ S9 & 474 & 2272 & 1954 & 2329 \\ S10 & 2538 & 3275 & 3367 & 4651 \\ S11 & 4238 & 5396 & 5537 & 7467 \\ S12 & 1389 & 4129 & 3633 & 4241 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Peak tensile stress in center column (kPa). analysis. This would assist in a more precise assessment of the impact of liquefied soil on the dynamic response of subway station structures, providing more detailed references for seismic designs. Overall, despite this study's revelation regarding the impact that the liquefaction behavior of deep soil layers has on the seismic response of subway stations, further experimental research is required for the validation and refining of the predictive capabilities of numerical models.