This study aims to identify optimal intensity measures (IMs) for use in probabilistic seismic demand models (PSDMs) for circular tunnels in soft soil deposits. To this end, we performed an extended numerical parametric study involving two-dimensional time history analyses of selected soil-tunnel configurations to evaluate the response of the selected tunnels under transverse seismic shaking. A series of 18 IMs were selected and tested, corresponding to free field conditions. The selected IMs were tested on several metrics, such as correlation, efficiency, practicality, and proficiency, based on an extended number of regression analyses between the IMs and the damage measure (DM), for the studied tunnels. DM is defined as the ratio of the actual bending moment (M) to the capacitive bending moment (M_Rd) of the tunnel lining. The results indicate that the peak ground acceleration (PGA) at the ground surface can be considered as the optimal IM for the shallow tunnels, whereas the peak ground velocity (PGV) can be considered as the optimal IM for both the moderately deep and deep tunnels. Finally, various fragility curves were constructed for the studied circular tunnels under the context of PSDMs. The findings of this study can serve as a reference for the seismic fragility analysis of circular tunnels in soft soil deposits, toward more reliable quantitative risk analysis (QRA), improved resilience, and adaptability of transportation networks.

本研究旨在确定用于软土沉积中圆形隧道的概率地震需求模型（PSDM）中使用的最佳强度测度（IMs）。为此，我们进行了扩展的数值参数研究，其中包括对所选土洞构型的二维时程分析，以评估所选隧道在横向地震振动下的响应。对应于自由场条件，选择并测试了一系列18 IM。基于IMs和损伤度量（DM）之间扩展的回归分析，针对选定的隧道，在相关性，效率，实用性和熟练度等多个指标上对选定的IM进行了测试。DM定义为隧道衬砌的实际弯矩（M）与电容弯矩（M _Rd）之比。结果表明，地面的峰值地面加速度（PGA）可以被认为是浅埋隧道的最佳IM，而峰值地面速度（PGV）可以被认为是最佳的IM。适用于中等深度和较深的隧道。最后，在PSDMs的背景下，为所研究的圆形隧道构造了各种脆性曲线。这项研究的结果可为软土沉积中圆形隧道的地震脆性分析，更可靠的定量风险分析（QRA），提高的回弹力和运输网络的适应性提供参考。