A Novel Simplified Physical Model Testing Method for Ground Settlement Induced by Shield Tunnel Excavation

In order to investigate the mechanism of ground settlement induced by shield tunnels better, this study proposes a novel simplified physical model testing method. In this physical model, double layer tubes with different materials are used to model the tunnel boring machine (TBM) and tunnel, respectively. When the outer tube in the experimental box is removed, the gap between the two different tubes can be utilized to reflect the ground settlement caused by TMB construction. Meanwhile, 3D image monitoring technology is introduced to collect ground settlement data for research on the mechanism of ground settlement induced by TBM construction. In order to validate the proposed testing method, firstly, the pilot experiment is performed; then, the obtained settlement curve obeys the Gaussian distribution, and the obtained settlement process is similar to that of the practical situation. Furthermore, based on the proposed testing method, an orthogonal experiment is designed to investigate the influences of the ground loss ratio, burial depth, and stratum condition on the ground settlement during the construction process. The results indicate that the ground loss ratio caused by the gap during construction excavation has a more significant impact than the tunnel burial depth and ground conditions. The findings in this study provide a quantitative guide for settlement monitoring during TBM construction, demonstrating that the ground loss ratio has the most significant impact on settlement (up to 28.7% deviation), while the effects of burial depth and stratum conditions are relatively minor (4.4% and 4.2% deviation, respectively). This method offers a practical and efficient approach for predicting and controlling ground settlement in TBM construction, which is of great importance in its practical application.