Centrifuge Model Tests on the Effects of Navigable Channel Excavation and Seawall Construction on a Subsea Shield Tunnel Below

Abstract

As subsea shield tunnels are becoming increasingly popular, especially in coastal or river cities, the complicated construction environment poses multiple challenges that need to be addressed to ensure their safety and reliable operation. This study presents the results of centrifuge model tests that aimed to examine the impacts of navigable channel excavation and seawall construction on the deformation and forces acting on a subsea shield tunnel. The symmetry of the tunnel structure, as well as the loading and unloading effects from channel excavation and seawall construction in this engineering project, allow for the simplification of the problem. The centrifuge test model included a novel device to simulate the unloading action of channel excavation and the loading impact from seawall construction. The structural response of the tunnel was monitored using an innovative solution, and various parameters such as vertical displacement, opening of the circumferential joint, circumferential bending moment, and longitudinal stress were analyzed. The results reveal that both channel excavation and seawall construction have significant effects on the stress and deformation of the pre-existing tunnel. While the excavation of the navigable channel reduces the load on the tunnel from the overlying strata, resulting in uplifts in the tunnel structure around the excavation area, and the construction of the seawall causes settlement of the tunnel near the loading zone. The unloading effect of channel excavation leads to the opening tendency of the tunnel circumferential joints, while the loading effect of seawall construction has the opposite effect on the tunnel circumferential joints. The excavation of the channel induces tensile stresses on the tunnel crown around the loading zone, while the seawall construction causes significant compressive stresses on the tunnel crown around the loading zone. It is crucial to prioritize safety and ensure the tunnel’s load-bearing capacity through careful design and construction considerations in practical engineering. The study can guide the design and construction of future projects and help minimize the risk of damage to pre-existing structures.