多年冻土区铁路桥梁高承台桩基础地震破坏机理及易损性研究  

Seismic failure mechanism and fragility of pile foundation with elevated cap of railway bridge in permafrost region

作　　者：张熙胤[1] 于生生 王万平 张益舶 徐振江 黄安琪 孙斌洁 Zhang Xiyin;Yu Shengsheng;Wang Wanping;Zhang Yibo;Xu Zhenjiang;Huang Anqi;Sun Binjie(Lanzhou Jiaotong University,Lanzhou 730070,China)

机构地区：[1]兰州交通大学,甘肃兰州730070

出　　处：《土木工程学报》2022年第7期77-89,共13页China Civil Engineering Journal

基　　金：国家自然科学基金(51808273,52068045);甘肃省科技计划项目-杰出青年基金(20JR5RA430);中国博士后科学基金面上项目(2018M643767);第五届中国科协青年人才托举工程项目(YESS20200278);兰州交通大学天佑青年人才托举工程项目(张熙胤)。

摘　　要：多年冻土区铁路桥梁工程中广泛采用高承台桩基础形式,多年冻土层的存在会对铁路桥梁高承台桩基础抗震性能产生显著影响。为系统研究多年冻土区铁路桥梁高承台桩基础地震破坏机理及抗震性能,确保其合理的抗震设计,首先开展冻土-桩基础相互作用拟静力室内模型试验,并建立多年冻土区铁路桥梁桩基础有限元模型,分析多年冻土层对高承台桩基础地震破坏机理及抗震性能的影响规律;其次在验证有限元建模方法正确性的基础上,对拟静力试验中的原型桥梁桩基础进行IDA时程分析,并对96条地震波作用下桩基础地震反应的平均值进行线性回归分析,进而得到不同条件下桥梁高承台桩基础在不同破坏状态所对应的地震易损性曲线。结果表明,多年冻土层的存在能有效提高桩-土体系的水平承载力及变形能力,增强其整体刚度和耗能能力,同时也会改变桩基础的地震破坏模式,使桩基础的塑性区域扩大,破坏程度显著增加;随着地面峰值加速度PGA的增加,不同损伤状态下桥梁桩基础的破坏概率逐渐增加;随着多年冻土的退化,桩身最大曲率明显减小,高承台桩基础的破坏概率大幅度下降,而墩顶最大位移明显增大,降低了桩基础的地震稳定性;随着桩身自由段长度的增加,桩身最大曲率和墩顶最大位移均呈增大趋势,桥梁高承台桩基础的地震易损性逐渐增大。因此,对多年冻土区铁路桥梁高承台桩基础进行抗震设计时,应充分考虑多年冻土层和桩身自由段长度对其抗震性能产生的不利影响。The pile foundation with elevated cap has been widely used for railway bridges in permafrost region,and permafrost can significantly affect seismic performance of the railway bridge pile foundation with elevated cap.In order to study the seismic failure mechanism and performance of railway bridge pile foundation with elevated cap in permafrost region and ensure the reasonable seismic design,the quasi-static test on the pile foundation-frozen soil interaction was firstly carried out,and the finite element model of railway bridge pile foundation in permafrost region was established,so that the influence rule of permafrost on the failure mechanism and performance of railway bridge pile foundation was analyzed.Secondly,based on the verified finite element model,the IDA time-history analysis of the prototype pile foundation of railway bridge was carried out.The average of the seismic response of the railway bridge pile foundation under the action of 96 earthquake records was analyzed by linear regression method,then the seismic fragility curves of the railway bridge pile foundation with elevated cap under different failure states were determined.The results show thatthe permafrost can effectively improve the lateral bearing and deformation capacity of the pile-soil system,and thus the stiffness and energy dissipation capacity of the pile-soil system were also enhanced.Besides,the permafrost may change seismic failure mode of the railway bridge pile foundation,leading to an amplification of the plastic zone range and aggravation of the failure of the pile foundation.It is also found that the fragility of the railway bridge pile foundation increases with the increase of peak ground acceleration(PGA).With the decrease of permafrost table,the maximum curvature of pile shaft decreases obviously,and the fragility of the pile foundation decreases.But the maximum displacement of the pier top tends to increase when the permafrost table decreases,which shall be unfavorable to the seismic stability.It is further observed that th

关 键 词：多年冻土区 高承台桩基础 桩-土相互作用 拟静力试验 IDA时程分析 地震易损性 

分 类 号：U442.55􀆰[建筑科学—桥梁与隧道工程]