Abstract: Field casting of air ducts on the top of rails has many challenges, including multiple construction procedures, complex environment, and the difficult control of construction quality. In this study, two techniques for assembled air ducts on the top of the rails of metro stations constructed by different methods are developed, taking a typical doublecolumn islandtype metro station of the Phase 1 project of Beijing metro line No. 19 as a case study. The technical points and force analysis of each scheme are discussed in detail and compared with the traditional ones. The results show that the proposed technical schemes are reliable and construction techniques are rational. They could remarkably reduce onsite environmental pollution and speed up the construction progress. Cost advantage is prominent, especially when the number of stations reaches eight.

Key words: doublecolumn islandtype metro station, air duct at rail top, assembled technology, quality control