Structural Response of Shallow Large-Diameter Shield Tunnel: Experimental Investigation

Extensive research on shield tunnels with modest depths is commonly seen in the literature. Nevertheless, this experimental investigation stands out because it focuses on the challenges posed by shallow-buried large-diameter shield tunnels (11.36 m). The experimental program comprises three precast concrete segmental tunnel lining rings, including two half-rings and one full ring in the middle. The grouting slurry force of cementitious grout during construction and longitudinal force variation have been investigated as their effects on components of precast concrete segmental tunnel linings, e.g., ring convergence, longitudinal joint opening, circumferential joint displacement, and materials strain. To begin with, the convergence of the top ring is more in the crown-invert direction than in the waist of the ring due to the presence of high-impact grouting slurry forces. Further, longitudinal joint opening and circumferential joint displacement showed superior outcomes under grouting slurry forces application at the crown and waist of the ring, respectively. The disparity of longitudinal force application greatly changed the lining behavior, and its minimal presence greatly improved the safety of the lining structures. The outcomes of this research are expected to offer lucidity and support to the shield tunnel community in designing shallow tunnels while also tackling challenges that may arise during the construction phases.