双向地震耦合作用下浅埋偏压黄土隧道共振特性研究

Resonance characteristics of shallow-buried bias loess tunnels under bidirectional coupling earthquake

摘要:

历次震害表明隧道等地下结构受地震影响较大,当地震动的卓越频率与结构的固有频率一致时,引发的共振会对结构产生更严重的破坏。针对共振这一地震中的特殊现象,通过ANSYS分析研究浅埋偏压黄土隧道在双向地震耦合作用下隧道衬砌各处的共振响应和围岩至衬砌段共振响应峰值的变化规律,同时考虑偏压角度和断面最大跨径对共振响应峰值的影响。研究结果表明:浅埋偏压黄土隧道具有多阶固有频率,衬砌的位移和应力均出现了共振现象且共振不表现出结构的自振频率特征;从围岩至衬砌段的共振响应具有放大效应;水平位移峰值随偏压角度的增大而减小;适当增大断面最大跨径对于抵抗共振是有利的;拱腰和拱脚处的主应力受共振影响较大,在隧道的抗震设计中应予以加强。

Abstract:

Previous earthquake damage showed that earthquakes greatly affected underground structures, such as tunnels. When the dominant frequency of ground motion is consistent with the natural frequency of the structure, the resulting resonance will cause serious structural damage. Aiming at the resonance characteristics of shallow-buried bias loess tunnel during earthquakes, harmonic response analysis in ANSYS is conducted to study the resonance response of tunnel lining and variation law of the peak value of resonance response from the surrounding rock to the lining under bidirectional coupling earthquake, and the influence of bias angle and maximum span of section on peak resonance response is discussed. Results indicate the multiorder natural frequencies of the shallow-buried bias loess tunnel. In addition, the displacement and stress of the lining exhibit a resonance phenomenon without the natural frequency characteristics of the structure. The resonance response from the surrounding rock to the lining exhibits an amplification effect. The peak value of horizontal displacement decreases with the increase in bias angle. An appropriate increase in the maximum span of the section is beneficial to seismic resistance. The Arch waist and arch foot should be strengthened in the seismic design of the tunnel because resonance greatly affects principal stress.