大断面越江地铁盾构隧道衬砌结构方案研究

文章以武汉轨道交通8号线一期工程越江隧道为背景,针对越江隧道断面大、水压高、穿越地层软硬不均,运营期水位涨跌以及河床冲淤变化幅度大的特征,通过建立能较为真实反应接头刚度和不均匀地层影响的地层-管片-内衬模型,研究“单层管片”、“管片+双侧非封闭内衬”、“管片+底部非封闭内衬”以及“管片+全环内衬”结构型式下,管片及内衬的受力变形特性。研究结果表明:水位升高使管片偏心距减小,河床淤积使管片偏心距增大,在地层较弱区域管片弯矩明显增大。施作内衬后,管片受力最大减小16%,拱顶下沉最大减小28%,结构的长期安全和稳定性增强,但会增加施工难度、工期和造价。考虑到内衬能在隧道火灾、撞击时对结构起到较好的保护,并且“底部非封闭内衬”能最大程度的减小结构受力,对工期影响较小,推荐采用“管片+底部非封闭内衬”结构方案。

Research on Structural Types for Construction of Large Section Cross-river Shield Tunnel

This article is based on the cross-river shield tunnel in the first stage of Wuhan Metro Line 8. The cross-river shield tunnel has its own characteristics, such as large cross-section, high water pressure, uneven stratum, great changes of water level and sedimentation of river bed in operation period. Through the stratum-segment-second lining model, stress and deformation of segmental lining and second lining are carried out under structural types, such as single-layered segment ring, segmental lining with unclosed second lining on both sides, segmental lining with unclosed second lining at the bottom and segmental lining with closed second lining. The results show that the eccentricity of segment reduces due to high water pressure, and it increases due to sedimentation of river bed, and bending moment of segment improves in weak stratum. The double-layered lining can lead the stress of segmental lining decrease by 16%, and settlement of vault can decrease by 28%, so security and stability of the structure get enhanced. However, the second lining leads more duration, cost and difficult degree for construction. Taking the perspective of disaster prevention into consideration, such as fire disaster and striking prevention, the structural types of segmental lining with unclosed second lining at the bottom can furthest reduce stress of the structure and the influence of duration. Therefore, the cross-river shield tunnel in the first stage of Wuhan Metro Line 8 has adopted the structural types of segmental lining with unclosed second lining at the bottom.