Ground loss model for analyzing shield tunneling-induced surface settlement along curve sections

Abstract

The shield tunneling along the curve section is widespread in cities. This paper proposes a ground loss model for shield tunneling along such sections. A prediction formula for the surface settlement was deduced using the mirror theory and the Mindlin solution, and a finite difference model was constructed based on the Changsha power tunnel engineering project. The law of surface settlement caused by shield tunneling along a curve section was analyzed. The theoretical prediction results and numerical simulation results were found to be in good agreement with the field monitoring data, proving the correctness of the proposed ground loss model and theoretical prediction formula. The over-cutting gap causes the transverse surface settlement to be asymmetrically distributed, whereas the integrative gap at the shield tail causes it to be symmetrically distributed. The transverse surface settlement curve is nonuniformly distributed in a “V” shape when shield tunneling along the curve section. The surface settlement is maximum inside the curve section, and the settlement value inside the curve section is greater than that outside, which is different from the surface settlement law in the straight section. The nonuniform distribution of the ground loss and shield shell friction was found to be the cause of the uneven surface settlement distribution.