运用理论分析和数值计算相结合的方法，分别从施工期和运营期角度提出了隧道抗浮稳定合理覆土厚度设定原则和理论计算方法；对于隧道施工期，考虑土体侧向摩阻力和管片环间摩阻力的影响等较为有利因素，同时考虑未凝浆液的影响等不利因素，建立了合理覆土厚度的理论计算公式；对于隧道运营期，建议只考虑隧道上覆土体自重进行抗浮，对于存在洪水冲刷的隧道设计，其上覆土体厚度还要加上设计冲刷深度；为南京某在建隧道的纵断面设计提供了一定的参考，同时也为其他过江海盾构隧道满足抗浮稳定的覆土厚度设定提供理论支持。

The depth of earth cover for tunnel anti-buoyancy security during construction and operation was analyzed in this paper with theoretical and numerical methods. The principles and theoretical analysis methods were proposed for it. The formula of depth of earth cover for anti-buoyancy security of tunnel during construction was given for the first time. It involves the unfavorable factors， such as uncondensed mortar， the favorable factors， such as resistances of soil and segments. The weight of earth cover for tunnel was suggested to consider as unique factor for tunnel security during operation. The eroded depth for design should be considered for tunnel influenced by floods. It has provided some references for longitudinal section design of the tunnel in construction under the Yangzi River in Nanjing. And it also provided theoretical foundation for the set depth of earth cover for anti-buoyancy security of other shield tunnels under river or sea.