为了对盾构下穿既有隧道实现更加准确有效的安全风险评价，提出一套基于模糊贝叶斯和证据理论的安全风险评价方法。在总结大量文献和相关标准的基础上，选取14个主要影响因素建立一套较为完善的盾构下穿既有隧道安全风险评估体系及评价标准，引入可对不确定信息进行有效融合的证据理论，结合模糊贝叶斯网络构建盾构下穿既有隧道安全评价模型，并以武汉某地铁工程为例开展实证分析。得出： 1）基于构建的安全评价模型进行风险推理和敏感性分析，确定工程的安全风险状态为一般，但有向较危险发展的趋势； 2）关键控制因素为新建隧道直径、两隧道的平面夹角、内摩擦角、施工环境的复杂性和施工协调的复杂性。

To achieve accurate and effective safety risk assessment for shield tunneling underneath existing tunnel, a set of safety risk assessment methods based on the fuzzy Bayesian network and evidence theory is proposed. First, by summarizing a large amount of literature and relevant standards, a set of relatively perfect safety risk assessment systems and evaluation standards for shield tunneling underneath existing tunnel is established by selecting 14 main influencing factors. Second, the evidence theory that can effectively fuse uncertain information is introduced, and the safety evaluation model of shield undercrossing existing tunnel is established by combining it with fuzzy Bayesian network. Third, a metro project in Wuhan is taken as an example to conduct an empirical analysis. Conclusions are drawn as follows: (1) based on the risk reasoning and sensitivity analysis of the constructed model, the safety risk state of the project is determined to be general and tends to be more dangerous; and (2) the key control factors are the clear spacing of the tunnel, diameter of the new tunnel, plane angle of the two tunnels, internal friction angle, complexity of the construction environment, and complexity of the construction coordination.