隧道交叉穿越边坡的动力响应振动台试验研究

Shaking table test study on dynamic response of tunnel crossing through slope

为研究隧道交叉穿越边坡时的地震动力响应特性,设计并开展振动台试验。基于试验结果,重点分析交叉隧道结构及边坡的加速度及动应变响应,并引入希尔伯特黄变换对边坡的频谱特性进行定量分析。研究得到以下结论:(1)交叉隧道结构的加速度响应表现出明显的区域性差异,在上跨隧道的拱顶及仰拱、下穿隧道的交叉段及洞口段等部位的加速度响应均较为强烈。(2)地震作用下隧道衬砌承受拉-压循环荷载作用,上跨隧道拱顶及仰拱受到的压力较大,地震附加弯矩主要集中在左侧拱腰和仰拱,这些部位应为主要的抗震设防区域。(3)隧道交叉穿越边坡时,隧道结构与边坡发生协同变形作用;上跨隧道的存在会加快或恶化边坡中上部的震害损伤,而在边坡变形失稳过程中,地震惯性力和滑坡推力又反作用于隧道结构,从而导致衬砌损伤甚至破坏失效。(4)沿高程增大坡体各测点的边际谱幅值随之增大,且基岩、软弱夹层、坡体及衬砌结构等岩层分界面对地震波的滤波效应不同,地震波的频谱组成成分发生改变,从而导致边际谱幅值的突变。(5)随输入地震波幅值的增大各测点的地震能量响应向相对低频迁移;靠近上跨隧道拱顶及坡顶测点的边际谱幅值出现多个峰值且突变最为明显,表明边坡上部尤其是上跨隧道拱顶及坡顶是地震作用下的敏感区域。

To study the seismic dynamic response characteristics of the tunnel crossing slope,a shaking table test was designed and carried out.The acceleration and dynamic strain responses of the cross tunnel and the slope are analyzed based on the test results.The spectral characteristics of the slope are analyzed quantitatively by introducing the Hilbert-Huang transform.The conclusions are as follows:(1)The acceleration responses of cross tunnel structure exhibit significant regional differences.Furthermore,the acceleration response is particularly intense at the crown and invert of the upper-span tunnel,the intersection,and the portal section of the under-crossing tunnel.(2)The tunnel lining is subjected to tensile-compression cyclic loading under earthquake.Additionally,the crown and invert of the upper-span tunnel bear relatively large pressure.The seismic additional moment is mainly concentrated in the left arch waist and invert,which should be the main seismic fortification area.(3)There is a synergistic deformation effect between the tunnel structure and the slope when the tunnel crosses the slope.The presence of the upper-span tunnel will accelerate or worsen the seismic damage in the middle and upper parts of the slope.Simultaneously,the seismic inertia force and landslide thrust are counteracted on the tunnel structure in the process of slope deformation and instability,resulting in lining damage or even failure.(4)The marginal spectral amplitude of each measurement point increases with the increase of elevation.The filtering effect of seismic waves is different for rock stratum interface such as bedrock,weak interlayer,slope,and lining structure.Furthermore,the spectral composition of seismic wave has transformed,resulting in a sharp change of marginal spectral amplitude.(5)The seismic energy response of each measuring point migrates to a relatively low frequency with the increase of the input seismic amplitude.The marginal spectral amplitudes of the crown of the upper-span tunnel and top of the slope show multiple peaks whose abrupt changes are the most pronounced.It shows that the upper part of the slope,especially the crown of the upper-span tunnel and top of the slope,is a sensitive area under seismic loading.