Torsional Behaviors of Segmental Tunnels Under the Action of Shield Rolling and Jack Thrusting During Tunneling

The large torque generated by the rotary disk potentially causes the rolling of shield/tunnel boring machine (TBM), especially when it cuts rocks with over-excavation or hard obstacles in very soft stratum, which further induces the torsion of assembled segments. In addition, the segment torsion may accumulate due to the unidirectional rotary cutting of shield/TBM over long distances. Excessive torsion of a tunnel induces track inclination, segment cracking, and bolt shearing failure. In the paper, a torsional shield-lining on grouted foundation model was proposed to investigate the torsional behaviors of a segmental tunnel under the action of shield rolling and jack thrusting during tunneling. The segmental tunnel is regarded as a beam with reduced torsional stiffness, subjected to three-dimensional foundation reactions and force boundary constrained by the shield. Besides, a grouted foundation model with longitudinal variable stiffness, accounting for the effect of grout solidification, was applied. The torque transferred from the rotary disk on segments was discussed, and the method to determine the longitudinal torsional stiffness of the segmental tunnel was introduced, considering the effect of shield rolling and jack thrusting. The proposed model was verified by two case studies, and a parametric analysis was conducted to investigate the effects of torque and the characteristics of grout material on structural responses. Additionally, the cumulative torsion of segments subjected to the unidirectional cutting of the shield was discussed. The proposed model and analytical results prove a valuable reference for tunnel anti-torsion design and control measures of segment assembly.