预应力锚索抗滑桩减震外锚结构振动台模型试验研究  

Shaking table test on pre-stressed anchor cable anti-slide pile with an external anchor structure and a buffer spring

作　　者：杨芸 蒋良潍[1,2] 罗强[1,2] 张桐 张瀚文[1,2] 葛学军 YANG Yun;JIANG Liangwei;LUO Qiang;ZHANG Tong;ZHANG Hanwen;GE Xuejun(School of Civil Engineering,Southwest Jiaotong University,Chengdu 610031,China;MOE Key Laboratory of High-Speed Railway,Southwest Jiaotong University,Chengdu 610031,China;China Railway Eryuan Engineering Group Co.,Ltd.,Chengdu 610031,China)

机构地区：[1]西南交通大学土木工程学院,成都610031 [2]西南交通大学高速铁路线路工程教育部重点实验室,成都610031 [3]中铁二院工程集团有限责任公司,成都610031

出　　处：《振动与冲击》2023年第18期295-303,共9页Journal of Vibration and Shock

基　　金：国家自然科学基金(51878560)。

摘　　要：锚索失效会导致锚索桩受力模式突变而造成结构整体倾覆,如何避免地震作用下的锚索动力超载是锚拉型支挡工程抗震亟待解决的问题。基于柔性减震原理在锚索与桩体间的外锚结构处串联缓冲弹簧,按几何比尺1∶15设计并开展桩底铰支的路堑边坡锚索桩振动台模型试验,测试了地震动峰值为0.2 g,0.4g,0.6g条件下锚索轴力、桩后土体加速度和桩身外倾角的时程特性及弹簧缓冲锚头对结构各响应的影响效应,结合锚索拉力频响特征从能量角度探究了弹簧引起轴力减载的作用机制。试验表明:设置弹簧后桩身中部加速度放大系数稍有下降,桩身外倾角普遍超过普通锚索桩,其增幅随峰值地面加速度(peak ground acceleration,PGA)加大而趋缓;弹簧锚头桩锚索轴力和应力幅均大幅减小,时程峰值和波动幅值的减载程度一致且与PGA近似呈线性负相关,3种地震量级下减载比分别达65%,57%,46%,以线性累积损伤理论计算得出的锚索疲劳总损伤值下降约2~3个数量级;设置缓冲弹簧能显著削减锚索拉力响应能量,Fourier幅谱呈现带宽收窄、低频集中的频响特征,降低了地震过程中多次加卸载产生的中高频疲劳损伤风险,有效改善锚索受力。Failure of anchor cable will lead to a sudden change of the stress mode of anchor cable piles and result in the whole structure overturning.It is an urgent problem how to avoid dynamic overload on anchor cables under earthquake.Based on the flexible buffer principle,an anchor cable pile of cutting slope was designed by connecting in series a buffer spring with the external anchor structure between the anchor cable and pile body.The time-history characteristics of the axial force of anchor cable,the acceleration of soil behind pile and the inclined angle of pile under earthquakes of 0.2 g,0.4g and 0.6 g dynamic peak were investigated,and the effect of the buffer spring anchor head on structural responses were tested.Combinedly considering the frequency response characteristics of the anchor cable tension,the spring weakening mechanism was explored.The results show that the acceleration amplification factor at the middle part of the pile body decreases slightly when the spring was installed,the inclined angle generally exceeds that of the ordinary pile,and the growth degree decreases with the increase of peak ground acceleration(PGA).The axial force and stress amplitude of the anchor cable of the spring anchor head pile are greatly reduced,and the load reduction degrees of the time-history peak value and the fluctuation amplitude are consistent and in approximately linearly negative correlation with PGA.The load reduction ratios under the three earthquake magnitudes are 65%,57%and 46%respectively,and the total fatigue damage value of the anchor cable calculated according to the linear cumulative damage theory decreases by about 2-3 orders.Setting the buffer spring can significantly reduce the tension response energy of anchor cable,and the Fourier amplitude spectrums show that the frequency response characteristics have the property of narrow bandwidth and low-frequency concentration,which reduces the risk of medium and high frequency fatigue damage caused by repeated loading and unloading during earthquake and eff

关 键 词：预应力锚索桩 弹簧缓冲锚头 振动台模型试验 锚索轴力减载 时频特性分析 

分 类 号：TU43[建筑科学—岩土工程]