为解决4台大直径泥水盾构在临海竖井双向钢套筒始发中所面临的始发空间受限、分体始发施工组织效率低、洞门破除易涌水涌砂、套筒内负环管片易上浮等施工难题，以福州滨海快线滨海新城站—机场站区间盾构隧道工程为依托，通过针对性设计盾构后配套台车功能布局和空间布置、设计分体始发管线延伸装置、制定井下针对性水平运输编组等措施，提高4台泥水盾构分体始发工效。通过对传统始发钢套筒受力与密封系统进行改进，确保始发期间钢套筒受力合理与密封有效。采用三轴搅拌桩端头加固+U型墙辅助降水，为安全破除洞门处地连墙创造条件。采取洞门处增设隔离钢丝刷、优化钢套筒回填料与注浆配比、增设负环预埋件与焊接等技术措施，有效控制大直径泥水盾构始发期间钢套筒内负环管片上浮问题。该系列技术措施实现了临海富水粉细砂地层4台泥水盾构双向钢套筒内快速、安全始发。

During the twoway separate launching of the four largediameter earth pressure balance(EPB) in coastal shaft using steel sleeve, problems, such as limited launching space, low efficiency of separate launching construction organization, easy water and sand gushing when portal breaking, and easy floating of negative ring segment in steel sleeve, exist. Accordingly, a case study is conducted on the shield tunnel project between the Binhaixincheng station and the Airport station of the Binhai express line in Fuzhou, China. Targeted countermeasures, such as functional and spatial layouts of supporting trolley for shield, separate launching pipeline extension device, and downshaft horizontal transportation and marshalling, are designed and formulated to improve the separate launching efficiency of the four EPB shields. By improving the force and sealing system of the traditional launching steel sleeve, the reasonable force and effective sealing of the steel sleeve during the shield launching period can be ensured. The end reinforcement by threeaxis mixing pile + Ushaped wall is adopted to assist the precipitation to create conditions for the safe removal of the connecting wall at the portal. Technical measures, such as adding isolation wire brushes at the tunnel portal, optimizing the ratio of steel sleeve backfill and grouting, and adding negative ring embedded parts and welding, effectively control the floating of the negative ring segment in the steel sleeve. The technical measures recommended ensured the rapid and safe twoway separate launching of the four EPB shields using steel sleeves in the waterrich siltfine sand formation near the sea.