针对我国关于繁华城区大直径泥水盾构施工关键技术研究不足的现状，以杭州环城北路地下通道工程大直径泥水盾构隧道施工为例，结合其工程施工难点，从浅埋地层大直径盾构始发、铁路桥变形预测、泥水分离系统及其适应性改造等方面，对工程中所遇到的难题进行了研究和针对性分析。研究结果表明： 1)端头加固长度以大于盾构主机长度加1环管片的长度为宜； 2)盾构下穿时铁路桥变形实测结果与理论预测结果相吻合，验证了理论预测的重要性； 3)采取增加棒条和改造下层筛板等针对性措施，显著提高了泥水分离效果。

The research of key technologies for largediameter slurry shield under shallowburied strata in flourishing city in China is weak. Study and analysis are made on large diameter shield launching in shallowburied strata, deformation prediction of railway bridge and optimization design and adaptability improvement of slurry separation system by taking underground tunnel on North Huancheng Road in Hangzhou for example. The study results show that: 1) The consolidation length of end soil should be larger than shield body length about 1 ring length. 2) The measured deformation results coincide with the theoretical prediction results, so as to verify the importance of theoretical predictions. 3) The slurry separating effect has been significantly improved by increasing rods and modifying the lower vibration screen, etc.