穿越软硬围岩隧道设置减震层振动台试验研究

以西部高烈度地震区浅埋公路隧道为依托，通过大型振动台模型试验，研究隧道穿越软硬围岩段在地震荷载作用下设置减震层的动力响应特性，并采用数值模拟方法对试验结果进行验证分析。试验及数值计算结果表明，从洞身段来看，减震层厚度存在最优值；从穿越软硬围岩段来看，增加减震层厚度可降低隧道沿纵向的动力响应差异，但加速度峰值会有所上升；拱顶围岩和隧道衬砌结构加速度响应频谱曲线均表现出“三峰值”现象，设置减震层并不会显著改变围岩频谱特性，衬砌结构也不显著体现自振特性，其响应主要取决所穿越围岩的动力特性；减震层处于最优值时可通过吸收更多的低频组分来降低隧道的动力响应；设置减震层可显著降低二衬动应力，但会使初支动应力呈现不同程度的放大，随减震层厚度的增加，二衬动应力先减小后增大，初支动应力先增大，后呈降低趋势；通过观察衬砌破坏形态，隧道拱顶、拱脚和仰拱易发生开裂，设置减震层后，仰拱相对容易发生破坏，应给予重点关注。研究成果可为西部高烈度地震区浅埋隧道抗震设计提供参考。

Shaking table test on damping layer applied in tunnel crossing #br#soft and hard surrounding rock

A certain case of a shallow road tunnel in high-intensity area of western China is taken as an example, the dynamic response characteristics of tunnel trunk and the segment crossing the hard-soft interface were studied based on the large-scaled shaking table tests and verified by the numerical simulation. The results show that there is an optimal thickness of damping layer for tunnel trunk and the soft-hard rock section. The increase of the thickness of damping layer will reduce the differences in the dynamic response toward the longitudinal direction. The acceleration response spectrum curves of the tunnel crown surrounding rock and lining show the phenomenon of “three peaks”. Spectral features of the surrounding rock can not be changed significantly by installing damping layer. The responses of the lining mainly depend on the dynamic feature of the outside rock without reflecting its self-vibration characteristics distinctly. The dynamic responses of tunnel can be reduced by absorbing low-frequency components with the damping layer of optimal value. The setting of the damping layer can significantly reduce the stress of the second lining with different degrees of amplification in initial support. With the increase of the thickness of the damping layer, the dynamic stress of the second lining decreases first and then increases while that of initial support shows the opposite trend. By observing the damage form of lining, it is found that the crown, arch foot, and arch of the tunnel are easy to crack. After installing the damping layer, he invert arch is relatively easy to crack, so more attention should be paid. The research results can provide a reference for aseismic design of shallow tunnels in the western high-intensity earthquake area.