Mechanical Analysis of a Super-large-diameter Shield Tailskin Under Deep Ground Load

The deformation and stress of a super-large-diameter shield tailskin are analyzed in this paper. Four kinds of structure analysis models, i.e. the perfect solid shell model, the defected solid shell model, the perfect hollow-layered shell model, and the defected hollow-layered shell model are formed to study the effects of initial geometrical defects and the hollow-layered shell formation on the deformation properties of the tailskin. Using the FEM modelling, the defected hollow-layered shell model gets a maximum deformation of 18.8 mm and a maximum Mises-stress of 304 MPa under the ultimate load condition, which indicates plastic deformation; while the perfect solid shell model shows a corresponding result of 3.6 mm and 71.6 MPa. The study shows initial geometrical defects and hollow-layered shell formation lead to much larger deformation and higher stress value, compared with the perfect solid shell model. It is necessary to consider these two factors when designing super-large-diameter shields for deep-buried tunnels.