Face stability analysis of longitudinally inclined shield tunnel considering the effect of tensile strength cut-off and pore water pressure

Abstract

Because of actual requirement, shield machine always excavates with an inclined angle in longitudinal direction. Since many previous studies mainly focus on the face stability of the horizontal shield tunnel, the effects of tensile strength cut-off and pore water pressure on the face stability of the longitudinally inclined shield tunnel are not well investigated. A failure mechanism of a longitudinally inclined shield tunnel face is constructed based on the spatial discretization technique and the tensile strength cut-off criterion is introduced to modify the constructed failure mechanism. The pore water pressure is introduced as an external force into the equation of virtual work and the objective function of the chamber pressure of the shield machine is obtained. Moreover, the critical chamber pressure of the longitudinally inclined shield tunnel is computed by optimal calculation. Parametric analysis indicates that both tensile strength cut-off and pore water pressure have a significant impact on the chamber pressure and the range of the collapse surface block. Finally, the theoretical results are compared with the numerical results calculated by FLAC^3D software which proves that the proposed approach is effective.

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