盾构隧道双层衬砌横向力学结构参数优化研究

随着水下盾构隧道建设及运营环境日益复杂,安全要求日益提高,盾构隧道双层衬砌有望在工程中得到较为广泛的应用。本文依托武汉轨道交通8号线越江隧道工程,采用双层衬砌盾构隧道三维壳—弹簧力学分析模型,研究了不同工况下二次衬砌强度及厚度对双层衬砌内力及变形的影响,并对二次衬砌是否应当配筋的问题进行了探讨。研究结果表明:二次衬砌强度变化对管片衬砌结构内力影响甚微,但二次衬砌弯矩量值略有提高,同时通过提高二次衬砌强度来抑制隧道竖向变形的效果不明显,考虑到工程造价问题,二次衬砌强度不宜过高,取C40为宜;二次衬砌厚度增加对管片横向内力影响甚微,但对其结构受力有不利影响,综合考虑隧道运营期火灾以及列车撞击等因素,二次衬砌厚度取30~40 cm为宜;在外荷载增大情况下,二次衬砌拉应力量值显著增加,超过混凝土规范容许拉应力值,因此,实际工程中建议对二次衬砌进行配筋设计。研究结论可为盾构隧道双层衬砌的设计及施工提供有益的借鉴。

Optimization Study on Transverse Mechanical Structural Parameters of Shield Tunnel with Double Linings

With the increasingly complex construction and operation environment of underwater shield tunnels and the increasing safety requirements, the double-layer lining of shield tunnels is expected to be widely used in engineering. This paper relied on the Wuhan Metro Line 8 cross-river tunnel project, and adoptedthe three-dimensional shell-spring mechanical analysis model for shield tunnel with double linings. The influence of strength and thickness of secondary lining on internal force and deformation of double-layer lining under different conditions was studied. Whether the secondary lining should be reinforced was also be discussed. The results of the study show that the change of secondary lining strength has little effect on the internal force of segment lining structure, but the moment of secondary lining is slightly increased. At the same time, the effect of restraining tunnel vertical deformation by increasing the strength of secondary lining is not obvious. Considering the cost of construction, the strength of secondary lining should not be too high, and C40 is the appropriate choice; increasing the thickness of secondary lining has little influence on the transverse internal force of segment, but it has adverse effect on the structural stress. Considering the factors such as fire and train impact during tunnel operation, the suitable thickness of secondary lining is 30~40 cm; with the increase of external load, the tensile stress of secondary lining increases significantly, which exceeds the allowable tensile stress in code for design of concrete structures. Therefore, reinforcement design of secondary lining is recommended in practical engineering. The research conclusions can provide useful references for the design and construction of double-layer lining of shield tunnel.