ABSTRACT
Large torque of cutter disc is partially transferred to the segments inside the shield during tunnelling, inducing the segment to twist. Moreover, the torsion of the segment accumulates continuously when the shield cuts the ground in one direction for a long distance, which causes the tunnel diseases, such as segment cracking, bolt shearing and excessive inclination of operating track. In this paper, a new model is established to investigate the torsional behaviors of segments during tunnelling. The segmental tunnel is regarded as a straight beam with reduced torsional stiffness resting on 3D foundation, based on the longitudinal equivalent continuous model. Besides, the force boundary constrained by shield tail and the effect of tail grouting on the foundation are considered in the model. The determination of key parameters is given. Then, the proposed model is verified by comparison with the FEM results. Finally, the effects of the transferred torque and the length of the unsolidified grout area on the torsional deformation of the segment are analyzed, and the cumulative torsional deformation of the segment considering the long one-way cutting of the shield is given. The proposed model promises a better tunnel torsional design and segment initial stress analysis.
