受冻融循环影响的寒区隧道洞口段地震响应研究

Study on Seismic Response of Tunnel Entrance Section in Cold Area Affected by Freeze-Thaw Cycle

【目的】我国季冻区交通网在地震带上的占比持续增大,有必要研究冻融循环与地震动双重作用对寒区隧道洞口段的影响。【方法】通过水热力三场耦合控制方程获得衬砌背后冻融圈内随时间变化的冻胀荷载,一并与自重应力近似考虑为初始地应力,将地震荷载等效为各质点的体积力,考虑冻融循环对冻融圈内土体强度与衬砌力学参数的影响,采用拟静力法研究寒区浅埋隧道洞口段地震响应规律。【结果】无论冻结与否,不易察觉的墙脚部位最易进入塑性,仰拱呈现内拉外压的受力特征,顶部拱圈、侧面曲墙等部位受力均匀且较小。地震对衬砌的影响均表现出破坏的可能性随冻融时间(次数)的推移而增大,尤其以墙脚内侧压应力区最为明显。受统计方法约束,冻融前10 a衬砌的地震响应较弱,从冻融第15 a开始洞口段衬砌地震稳定性有了较明显的劣化。【结论】相较于冬令期,融化期发生地震时隧道结构的稳定性更差。在全球气候变暖的背景下,更应深入研究寒区隧道洞口段融化期的地震响应规律。

[Purposes]With the increasing proportion of the traffic network in the earthquake zone,it is necessary to study the influence of freeze-thaw cycle and ground motion on the tunnel entrance section in the cold region.[Methods]The freeze-heaving load in the freeze-thawing ring behind the lining was obtained through the coupled heat-moisture-stress control equation,and the initial ground stress was ap-proximated with the dead weight stress.The seismic load was equivalent to the physical strength of each particle,and the influence of the freeze-thaw cycle on the strength of soil in the freeze-thawing ring and the mechanical parameters of the lining was considered.The quasi-static method is used to investigate the seismic response rule of the entrance section of shallow buried tunnel in cold area.[Findings]No matter frozen or not,the foot of the wall that is not easy to detect is the most easy to enter the plasticity.The invert exhibits the stress characteristics of inner pulling and outer pressing,and the top arch ring and side curved wall have uniform and small forces.The earthquake effect on lining shows that the possi-bility of damage increases with freezing and thawing time(times),especially in the inner compressive stress area of wall foot.Constrained by the statistical method,the seismic response of the lining in the first 10 years of freeze-thaw is weak,and the seismic stability of the lining in the hole section has deterio-rated significantly since the 15th year of freeze-thaw.[Conclusions]Compared with the winter period,the stability of tunnel structure is worse during the earthquake during the melting period.Under the his-torical background of climate warming,it is more necessary to study the seismic response rule of the tun-nel entrance during the melting period in the cold area.