Abstract:  The geological and environmental conditions of urban metro tunneling are complex, and there is no condition for TBM launching shaft. Hence, it is necessary to develop a new launching method for doubleshield TBM. A case study is conducted on Taidong station on Qingdao metro line 1, and the launching technique with negative ring for doubleshield TBM is studied and implemented. According to the structural characteristics of doubleshield TBM, a negative ring launching scheme is proposed, and its feasibility is demonstrated from the aspects of tunneling mode, tunneling parameters, attitude control, and auxiliary measures. The practical results show that the shield rolling can be effectively controlled by adopting the single[KG2mm]and doubleshield tunneling modes and selecting reasonable tunneling parameters, and the tunneling quality by negative ring launching technique can be guaranteed by employing realtime monitoring, TBM attitude adjustment in time, and necessary auxiliary measures. 

Key words: doubleshield TBM, negative ring launching, Qingdao metro, counterforce frame, single[KG2mm]and doubleshield tunneling modes