Abstract: The shield will encounter many problems when tunneling in extremelysoft fluid plastic stratum, such as difficult posture control, segment fragmentation, water leakage, and over horizontal convergence. As a result, a case study is conducted on a tunnel between Qingling road station and Jianguo road station of Hangzhou metro line 2. The construction difficulties of shield when tunneling in extremelysoft fluid plastic stratum are analyzed, suggestions are provided regarding host selection, opening rate of cutterhead, and relationship between host gravity and the centroid. Techniques such as thrust balance before driving, synchronous grouting, earth pressure and excavation management, secondary grouting, segment assembly and bolt retightening, and pulling plate tensioning, are also introduced. The applicable results of the recommended methods show that the shield has a good adaptability in extremelysoft fluid plastic stratum, and water leakage, vertical posture deviation, and horizontal convergence are reduced. 

Key words: shield tunnel, extremely soft fluid plastic stratum, segment breakage, shield posture, segment floating, horizontal convergence, equipment selection