Tunnel portals are particularly vulnerable during seismic events due to the influence of adjacent slope geometry and fractured rock formations. This study evaluates the seismic response of tunnel portals and determines an appropriate fortification range. Ray theory is employed to calculate the displacement field of a single-sided slope subjected to incident SH waves, while the tunnel entrance is modeled as an elastic foundation beam. An analytical expression for hoop strain is derived, accounting for the interaction between the tunnel and the surrounding rock, as well as the attenuation of seismic waves. A parametric analysis is also performed to examine the impact of slope angle, seismic wavelength, frequency, and foundation stiffness on the tunnel response. Shaking table tests are conducted to validate the theoretical results and reveal failure patterns in both the slope and tunnel. The findings show that the spandrel and arch foot exhibit the highest hoop strain responses, identifying these positions as critical points of seismic vulnerability. The seismic-affected zones of the tunnel portal are classified into three distinct regions based on the distribution of peak hoop strain. The recommended fortification range for the tunnel portal extends up to 7.5 times the tunnel span, effectively encompassing the areas of peak strain to mitigate potential damage.

中文翻译：

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SH 波入射下隧道空腔段地震影响分区的数学建模和振动台验证


由于相邻斜坡几何形状和裂隙岩层的影响，隧道入口在地震事件期间特别脆弱。本研究评估了隧道入口的地震响应，并确定了合适的设防范围。采用射线理论计算单侧边坡在入射 SH 波作用下的位移场，同时将隧道入口建模为弹性基础梁。推导出了环向应变的解析表达式，考虑了隧道与周围岩石之间的相互作用以及地震波的衰减。此外，还进行了参数分析，以检查坡度角、地震波长、频率和地基刚度对隧道响应的影响。进行振动台测试以验证理论结果并揭示边坡和隧道的破坏模式。研究结果表明，拱肩和弓足表现出最高的环向应变响应，将这些位置确定为地震脆弱性的关键点。隧道入口的地震影响区根据峰值环向应变的分布分为三个不同的区域。隧道入口的推荐防御范围最高可达隧道跨度的 7.5 倍，有效地涵盖了峰值应变区域，以减轻潜在的损害。