冻融循环条件下寒区隧道衬砌的服役性能

A study of the service performance of tunnel lining in the cold zone when subjected to the freeze-thaw cycle

寒区隧道贯通运营后,衬砌受到周期性变化的洞内气温引起的冻融循环作用,衬砌的物理力学性能随之产生劣化,导致衬砌的服役性能降低。本文通过ANSYS数值模拟,计算研究了冻融循环条件下寒区隧道衬砌的服役性能变化。在不铺设保温层情况下,寒区隧道衬砌服役年数大大降低,隧道运营17 a后衬砌安全系数不满足规范要求;非冻土段运营19 a后拱顶衬砌结构安全系数不满足规范要求。铺设保温层可使衬砌服役性能不下降,多年冻土段铺设2层5 cm保温层,季节冻土段铺设1层5 cm厚保温层,后拱顶处、拱腰处和边墙处衬砌服役性能无减小趋势,而拱脚处和仰拱处衬砌安全系数则不断减小。为保证拱脚和仰拱处衬砌安全,可在表面铺设保温层,并在仰拱和拱脚上加设1层保温层可使衬砌服役性不下降。若要使衬砌服役性能不下降,知亥代隧道多年冻土段保温层铺设厚度至少应为5 cm,非冻土段保温层铺设厚度至少为9 cm。

When subjected to the freeze-thaw cycle and atmospheric temperature, the physical and mechanical properties of lining concrete will deteriorate during the tunnel operation period, which has a considerable effect on the load-bearing capacity. In this thesis, the research results are obtained using the finite element simulation software ANSYS. The service performance of tunnel lining in the cold zone when subjected to the freeze-thaw cycle is investigated. In the absence of an insulation layer, the number of service years of the tunnel lining in the cold zone decreases considerably, and the safety coefficient of the tunnel lining does not meet the requirement of the technical code after 17 years of operation. After 19 years of operation, the safety coefficient of the roof lining of the nonfrozen soil section does not meet the requirement of the technical code. The installation of the insulation layer can keep the service performance of the tunnel lining from deteriorating. When two layers of 5 cm insulation layer are installed in the permafrost zone and one layer of 5 cm insulation layer is installed in the seasonal frozen soil zone, the service performance of the lining at the rear arch crown, arch waist, and side wall does not exhibit a decreasing trend. Meanwhile, the safety coefficient of the lining at the arch foot and inverted arch continuously decreases. To ensure the safety of the lining at the arch foot and inverted arch, we propose that a layer of insulation be installed on the surface and one layer of insulation be added at the inverted arch and arch foot, so that the service performance of the lining does not decrease. To ensure that the service performance of the lining does not decrease in the Zhi Hai Dai Tunnel, the thickness of the insulation layer in the permafrost zone should be approximately 5 cm and that in the nonfrozen soil section should be approximately 9 cm.