杭州庆春路过江隧道施工风险控制实例分析

 介绍杭州庆春路过江隧道施工过程中的风险控制，分析盾构出洞时洞门涌泥水及加固区土体坍塌的原因、规避及处理措施；分析两线盾构先后穿越钱塘江大堤时大堤沉降明显不同的原因，结合工程实践提出泥水盾构过堤控制沉降的措施；分析工程中盾尾密封失效的原因，并介绍在江底高承压水地层中采用液氮冻结封堵地下水和修复盾尾刷的方法。工程实践表明，良好的洞门密封可以避免洞门涌水和加固区土体坍塌；持续降雨和泥水压力的剧烈波动会加剧大堤的沉降，而通过优化盾构掘进参数，可以降低盾构施工对大堤的扰动；液氮冻结法可以安全地封堵地下水，更换第一道尾刷并且增设一道尾刷的方案可以成功地消除盾尾漏浆涌水的风险。

ANALYSIS OF ENGINEERING PROJECTS OF RISK CONTROL IN HANGZHOU QING-CHUN ROAD CROSS-RIVER TUNNEL CONSTRUCTION

Engineering projects of risk control in construction of Hangzhou Qingchun road cross-river tunnel are introduced. Contents include：causes of water leakage at the tunnel portal and soil collapse at the reinforced area when the shield setting out are put forward，moreover，avoidance and treatment measures are described. Reasons leading to the differences of settlements of the levee when two shields traversing it respectively are analyzed，and some construction measures for slurry shield to cross the levee are proposed. Reasons to the invalidation of the tail seal are studied，and techniques to shut off the groundwater using liquid nitrogen freezing method and repair the tail seal brushes in the artesian aquifer are presented. Engineering practices show that good tightness of the tunnel portal can avoid water leakage and soil collapse at the reinforced area，and optimization of parameters of shield driving can reduce disturbance to the levee while shield tunneling. On the contrary，sustainable rainfall and severe fluctuation of the chamber pressure lead to larger settlements. It is also shown that liquid nitrogen freezing method can seal off the groundwater safely and the repair of the tail seal brushes eliminates the risk of mud leakage of the shield tail successfully. These results would provide a scientific reference for risk control in similar shield tunnelling in practice.