The active layer in permafrost region is inevitably subjected to seasonal freezing-thawing actions. The soil freezing and thawing can change boundary conditions of the bridge pile foundation in permafrost region, which will influence the seismic responses of the bridge. In this study, to investigate the influence of seasonal freezing-thawing soils on seismic performance of high-rise cap pile foundation in permafrost region, quasi-static tests were carried out on two 1/8 scaled models. The hysteretic behaviors and damage characteristics of the pier-pile-soil system in permafrost region with thawed and frozen active layer were analyzed. It is found that the freezing-thawing status of the active layer can relocate the vulnerable position of the pile foundation in permafrost region. Furthermore, the frozen active layer limited the deformation capacity of the pier-pile-soil system, then resulted in the redistribution of the pile stress. Although the frozen active layer in winter season enhanced the bearing capacity of the pier-pile-soil system, it weakened the ductility of the pier-pile-soil system. Additionally, the frozen soil temperature and the shear strength of the active layers will affect the adhesive force of the permafrost layer. These results can provide a scientific basis for the seismic design of bridges with pile foundation in permafrost regions.

多年冻土区活动层不可避免地受到季节性冻融作用。冻土冻融会改变多年冻土区桥梁桩基的边界条件，进而影响桥梁的地震响应。本研究为研究季节性冻融土对多年冻土区高层承台桩基础抗震性能的影响，在两个1/8比例模型上进行了准静态试验。分析了多年冻土区具有解冻和冻结活动层的桩-桩-土系统的滞回行为和破坏特征。研究发现，活动层的冻融状态可以重新定位多年冻土区桩基的脆弱位置。此外，冻结的活动层限制了桩-桩-土系统的变形能力，导致桩应力重新分布。冬季冻结活动层虽然增强了墩-桩-土体系的承载力，但削弱了墩-桩-土体系的延性。此外，冻土温度和活性层的剪切强度会影响多年冻土层的附着力。研究结果可为多年冻土区桩基桥梁的抗震设计提供科学依据。冻土温度和活动层的抗剪强度会影响多年冻土层的附着力。研究结果可为多年冻土区桩基桥梁的抗震设计提供科学依据。冻土温度和活动层的抗剪强度会影响多年冻土层的附着力。研究结果可为多年冻土区桩基桥梁的抗震设计提供科学依据。