Conventional seismic designs are currently inadequate to withstand earthquakes in mountain tunnels, which have historically suffered devastating seismic damage. Seismic buffers made of expanded polystyrene geofoam, which are widely used in aboveground structures, have potential applications in tunnels. However, it is not known what the optimal thickness should be, and the seismic effects on such buffers and their compatibility with tunnel construction require investigation. In this study, the effects of seismic buffer thickness on the tunnel lining are investigated. A novel direction-based displacement approach associated with practical seismic damage forms was devised, and the Mohr–Coulomb criterion was integrated into a meridian space to understand the failure of the lining. The states and forms of lining displacement and stress were probed, and the results were validated through the seismic deformation method, shaking table tests, and on-site investigations. The results indicate that unsafe multiple displacement forms of the lining can be mitigated to a relatively uniform vertical shearing form with a seismic buffer no more than 20 cm thick; moreover, lining failure can be prevented, without changing lining tensile and compression forms. However, adverse effects occur with buffers thicker than 20 cm, leading to the resumption of the multiple lining displacement forms and failure. Buffer thicknesses of 10–20 cm should be considered in future seismic designs of mountain tunnels, combined with a trade-off among the seismic effects, manufacturing, and installation of buffers under specific construction conditions.

中文翻译：

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考虑地震损伤形式和破坏状态的地震缓冲层厚度对圆形岩石隧道的影响


传统的抗震设计目前不足以承受山地隧道中的地震，而山地隧道历来遭受了毁灭性的地震破坏。由发泡聚苯乙烯土工泡沫制成的抗震缓冲器广泛用于地上结构，在隧道中具有潜在的应用。然而，目前尚不清楚最佳厚度应该是多少，并且需要研究这种缓冲器的地震影响及其与隧道施工的兼容性。本研究研究了地震缓冲层厚度对隧道衬砌的影响。设计了一种与实际地震损伤形式相关的新颖的基于方向的位移方法，并将 Mohr-Coulomb 准则集成到子午线空间中以了解衬砌的失效。探究了衬砌位移和应力的状态和形式，并通过地震变形法、振动台试验和现场调查验证了结果。结果表明，衬砌的不安全多重位移形式可以减轻为相对均匀的垂直剪切形式，抗震缓冲区厚度不超过 20 cm;此外，可以防止衬里失效，而无需改变衬里的拉伸和压缩形式。然而，厚度超过 20 厘米的缓冲区会产生不利影响，导致多种衬里位移形式的恢复和失败。在未来的山地隧道抗震设计中，应考虑 10-20 cm 的缓冲层厚度，并结合特定施工条件下缓冲器的地震效应、制造和安装之间的权衡。