Abstract: When a doubleshield tunnel boring machine (TBM) is applied in urban rail transit, there are always several limitations, such as no condition for launching shaft construction, low construction efficiency due to doubletrack smallspacing excavation and frequent station passing, and low economic benefit. Accordingly, a case study is conducted on Qingdao metro line 1. Further, the applicable experience of doubleshield TBM used in Qingdao metro line 2 is studied, and detailed conditions of line 1 and the TBM characteristics are analyzed; thus, a suite of negative ring launching techniques of doubleshield TBM based on tunneling mode, parameters, and attitude control is developed. The techniques include doubletrack smallspacing tunnel excavation realized by a movable support trolley installed in the advance tunnel and Soletanche grouting reinforcement and backup trolley stationpassing technology realized by precast steel support replacement. The application of the techniques shows a good effect in Qingdao metro line 1.

Key words: doubleshield tunnel boring machine, negative ring launching, smallspacing tunnel, precast steel support, station crossing