Abstract: In order to solve the problems that the thick and large segments are prone to cracks, the appearance quality is poor, and the strength is difficult to control，a series of quality control measures are put forward through the analysis in terms of the selection of mineral admixtures and additives, the optimal design of concrete proportions, the vibrating process, the steam curing technology, and the detailed treatment of bolt holes and concaveconvex grooves. Research and application show that: (1) Adding a large amount of mineral admixtures can improve segment durability and reduce hydration heat; (2) The additive components have a great influence on the appearance; (3) Reasonable setting on the mode and frequency of vibration can effectively ensure the quality of concrete pouring; (4) Reasonable steam curing technology can effectively avoid concrete cracks.

Key words: large diameter shield tunnel, concrete, thick and large segment, precast technology