Research On The Influence Of Permafrost Site Conditions On The Seismic Response Of Bridge Pile Foundations

There is a vast area of permafrost in the western region of China,which is also a frequent seismic zone in China.Therefore,the seismic safety of engineering structures in permafrost regions is a major test for the construction,operation,and maintenance of infrastructure in the region.In this paper,the dynamic characteristics of frozen soil,the seismic response of permafrost sites,and the seismic response of bridge pile foundation permafrost site system have been systematically studied,in order to provide a reference for the seismic design of linear traffic engineering in permafrost regions in western China.The main work carried out in this paper is as follows:Firstly,taking typical silty clay in the western region as the research object,the paper describes the morphological characteristics of frozen silty clay using the unclosed degree,width,area,and backbone curves of the frozen soil hysteretic curve,and explores the effects of soil temperature,water content,confining pressure,and loading frequency on the morphological characteristics of frozen silty clay hysteretic curve,maximum dynamic modulus of elasticity,reference dynamic strain amplitude,and equivalent hysteresis damping ratio.The comprehensive influence formulas of soil temperature,water content,confining pressure,and loading frequency on the maximum dynamic elastic modulus,reference dynamic strain amplitude,and minimum equivalent hysteresis damping ratio are obtained through multiple regression,providing data support for seismic response analysis of frozen soil sites.Secondly,on the basis of clarifying the dynamic characteristics of permafrost,a twodimensional model of a permafrost site was established using Abaqus finite element method.0.3g,0.45 g,0.6g El-centro waves and 0.3g Kobe waves were input to explore the impact of the permafrost layer temperature and thickness,the seasonal active layer temperature and thickness on the seismic response of the site,of the permafrost site,it mainly includes the impact on the site surface acceleration response spectrum,surface PGA amplification coefficient,and site horizontal stress.It is found that the seismic response of permafrost site decreases with the decrease of permafrost temperature and thickness and the decrease of seasonal active layer temperature and thickness.The amplification coefficient of surface PGA increases with the decrease of permafrost temperature and thickness,and the increase of seasonal active layer temperature and thickness.Finally,using the same soil layer conditions and loading conditions as those of the permafrost site model,a three-dimensional finite element model of the permafrost site pile cap system was established using Abaqus to explore the impact of permafrost site conditions on the seismic response of bridge pile foundations,mainly including the acceleration response spectrum of the pile cap,as well as the bending moment,shear force,equivalent plastic stress,equivalent plastic strain,tensile damage Compression damage.I It is found that increasing temperature and decreasing thickness of seasonal active layer will increase seismic response of bridge pile foundation on the whole.Under earthquake,the influence of permafrost temperature and thickness on bridge pile foundation is uncertain,which is affected by input wave pattern and seismic wave peak.