浅埋偏压条件下特大断面隧道地震动态响应的试验研究

Seismic responses of large section tunnelwith shallow cover and unsymmetrical loading

以福州市二环路金鸡山隧道为工程原型,设计制作了浅埋偏压条件下特大断面隧道的1/30缩尺模型,完成了20种工况下的模拟地震动试验,重点关注隧道模型加速度、衬砌接触压力、衬砌表面应力的地震动态响应。隧道中轴面各测点PHA放大系数随高程呈近似对数型增大,改变了原场地高程效应的表现形式;隧道模型的第一卓越频率与EL波的卓越频率较为接近,其共振效应使得EL波激励引起的高程效应明显大于其他地震波。靠山侧衬砌结构所承担的地震动附加压力显著大于临空侧,且在大振幅激励下,其拱腰所承担的地震动附加压力反而大于拱脚。隧道衬砌结构的扁平率和几何曲率,对其动应力峰值的分布均有显著影响,尤其是在大振幅激励下,靠山侧拱脚处的动应力峰值显著大于其他部位。衬砌结构的裂缝发展形态特征,与接触压力峰值及动应力峰值沿衬砌环向分布的规律是相一致的。上述成果为浅埋偏压条件下特大断面隧道抗震设防提供了参考。

Taking the Jinjishan Tunnel in Fuzhou 2 nd ring road as prototype,the 1/30 downscale model for the large section tunnel with shallow cover and unsymmetrical loading is fabricated. Then the shaking table tests with16 loading cases are carried out,and the seismic responses of model acceleration,lining contact pressure and lining stress are focused. The PHA amplification coefficient along the tunnel axial plane increase logarithmically,which implies that the existing of large section tunnel changes the elevation effect of original ground significantly. The first dominant frequency of tunnel model approximates to the dominant frequency of EL wave,so that the elevation effect caused by EL wave is greater than other three waves obviously. The earthquake-induced contact force upon the lining backward the slope is greater than the lining toward the slope obviously,moreover,the contact force carried by tunnel arch exceeds its sidewall under the excitation of large ground motion. The distribution of peak dynamic stress along the lining is significantly influenced by the flat ratio and the curvature of tunnel lining. The peak dynamic stress in the sidewall backward the slope exceeds than other counterparts under the excitation of large ground motion. The development of lining crack coincides with the distribution of contact force and dynamic stress along the tunnel lining,which provides some reference to the aseismic design of large section with shallow cover and unsymmetrical loading.