43m shield machine that is now tunnelling through the Changjiang Estuary for the cross-river link,and is going to offer the tail grease used during its tests,as a rec- ommendatory option for the Contractor s choice.

increasing popularity of ground channels constructed with shield method and deepening of research on sealing technology and grease of shield tail, the article describes mechanism and features of sealing with shield tail grease, focusing on performance index and effectiveness of 3 types of greases typically used in China, Japan and France.

It is introduced the importance of pumpability and water-proof sealing ability of shield tail sealant,high molecular synthetic fluids can improve the pumpability of shield tail sealant, and fibers can evaluate the water-proof sealing ability of shield tail sealant.

Due to the features of the project exhibiting "long distance,large diame- ter,and high water pressure",this article probes into the design of cutterdisc,main bear- ing seals,and shield tail in the aspects of its safety,and reliability for the benefits of pro- viding reference for similar projects hence forth.

Scientific tail selection of the shield machine is pivotal for safe and rapid construction in large-diameter and long-distance tunneling.

Up to now there has been no work example or experience yet on maintenance and repair or replacement of tail brush during shield tunnelling in this country,especially relating to damage prone to fatigue caused by abrasion with segments in a long time run- ning.