Permafrost Degradation Effect on Seismic Response of Bridge Pile Foundation along Qinghai-Tibet Railway

With climate warming, widespread permafrost degradation is found worldwide in recent years. For permafrost regions located in earthquake belts, i.e. the Qinghai-Tibet Plateau permafrost region in China, permafrost degradation effect on seismic performance of the bridge pile foundation is worthy of research. In this study, a pile-soil interaction model considering thermal-mechanical effect is presented and applied to a case study of the bridge pile foundation along Qinghai-Tibet Railway. Seismic responses of the bridge pile foundation are analyzed with consideration of the thawed permafrost. Numerical results show that thawed permafrost can influence the lateral displacement, shear force, and bending moment of the bridge pile foundation under seismic actions. The freeze-thaw state of the active layer should be considered when analyzing the permafrost degradation effect on seismic responses of bridge piles. The seismic safety of the existing bridge pile foundations along Qinghai-Tibet Railway is evaluated. It is recommended that seismic design of bridge with pile foundation in permafrost region should consider the thermal-mechanical effect of pile-soil system and the permafrost degradation effect.