沉积河谷-衬砌隧道体系对平面P波的散射

沉积河谷对地震动的放大效应已为地震观测和理论研究所证实。现实中有大量隧道穿越河谷情况,而河谷中隧道地震反应规律尚不明确。为此,本文建立沉积河谷-衬砌隧道整体二维平面应变模型,基于一种高精度边界间接积分方程法,对河谷中隧道地震响应及动应力集中进行模拟分析。大量参数计算结果表明:沉积河谷中隧道地震反应更为剧烈,动应力集中更为显著,应力峰值可达到入射波应力幅值的数十倍。随隧道埋深加大,应力频谱振荡加剧且峰值频率发生明显变化。部分频率段,隧道对河谷地表位移同样有较大的扰动。穿越河谷隧道的抗震设计需考虑河谷中地震动放大效应对隧道内力和变形的显著影响。

Scattering of P-waves in Sedimentary Valleys-lining Tunnels

The amplification effect of the alluvial valleys on seismic ground motion has been confirmed by seismic observations and theoretical studies. In reality, a large number of lined tunnels pass through alluvial valley, while the seismic response law of such tunnel in a valley is not yet clear. Therefore, this paper established a two-dimensional plane-strain model of the alluvial valley-lining tunnel system, based on a high-precision boundary indirect-integral equation element method, then simulated and analyzed the seismic response and dynamic stress concentration of the tunnel in an alluvial valley. The calculation results of several key parameters show: the seismic response of the tunnel in an alluvial valley is more intense, the stress concentration is more significant, and the stress peak can reach tens of times of the incident-wave stress amplitude. As the buried depth of tunnel increases, the stress spectrum oscillates more rapidly and the peak frequency also changes. For several frequencies, the tunnel also has a greater disturbance on the valley surface displacement. The anti-seismic design of the tunnel crossing river valley should consider the significant influence induced by the amplification effect of the valley on the seismic motion.