盾构直径过大，其成本和安全风险也将成倍增加。结合佛莞城际铁路狮子洋隧道工程地质特性和工程重难点，分析大直径盾构在高水压、强透水性、复合地层施工过程中设备选型、长距离独头掘进、穿越软硬不均地层与断层破碎带等存在的风险。具体从常压刀盘、泥浆环流系统选型设计以提高设备适应性，制定开挖管理与泥浆管理并重的掘进参数控制方法，针对上软下硬和断层破碎带地层的施工风险控制等方面提出相应对策，规避地质重大风险，确保大直径水下盾构隧道的施工安全。

The cost and risk increase with shield diameter increase. Based on Shiziyang Tunnel on FoshanDongguan Intercity Railway, the risks existed in equipment type selection, longdistance deadend tunneling, uppersoft lowerhard strata and fault and fracture zone during largediameter slurry shield boring in complex strata with high water pressure and strong permeability are analyzed. The equipment adaptability is improved from the selection of atmospheric pressure cutterhead and slurry circulation system; the excavation parameter control method for excavation management and slurry management is determined; and construction countermeasures for uppersoft lowerhard strata and fault fracture zones are proposed to avoid significant geological risks and ensure construction safety of underwater largediameter shield.