The deformation caused by tunnel excavation is quite important for safety, especially when it is adjacent to the existing tunnel. Nevertheless, the investigation of deformation characteristics in overlapped curved shield tunneling remains inadequate. The analytical solution for calculating the deformation of the ground and existing tunnel induced by overlapped curved shield tunneling is derived by the Mirror theory, Mindlin solution and Euler-Bernoulli-Pasternak model, subsequently validated through both finite element simulation and field monitoring. It is determined that the overcutting plays a crucial role in the ground settlement resulting from curved shield tunneling compared to straight shield tunneling. The longitudinal settlement distribution can be categorized into five areas, with the area near the tunnel surface experiencing the most dramatic settlement changes. The deformation of the existing tunnel varies most significantly with turning radius compared to tunnel clearance and grouting pressure, especially when the turning radius is less than 30 times the tunnel diameter. The tunnel crown exhibits larger displacement than the tunnel bottom, resulting in a distinctive 'vertical egg' shape. Furthermore, an optimized overcutting mode is proposed, involving precise control of the extension speed and angular velocity of the overcutting cutter, which effectively mitigates ground deformation, ensuring the protection of the existing tunnel during the construction. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Burial depth is a crucial factor affecting the forces and deformation of tunnels during earthquakes. One key issue is a lack of understanding of the effect of a change in the buried depth of a single-side tunnel on the seismic response of a double-tunnel system. In this study, shaking table tests were designed and performed based on a tunnel under construction in Dalian, China. Numerical models were established using the equivalent linear method combined with ABAQUS finite element software to analyze the seismic response of the interacting system. The results showed that the amplification coefficient of the soil acceleration did not change evidently with the burial depth of the new tunnel but decreased as the seismic amplitude increased. In addition, the existing tunnel acceleration, earth pressure, and internal force were hardly affected by the change in the burial depth; for the new tunnel, the acceleration and internal force decreased as the burial depth increased, while the earth pressure increased. This shows that the earth pressure distribution in a double-tunnel system is relatively complex and mainly concentrated on the arch spandrel and arch springing of the relative area. Overall, when the horizontal clearance between the center of the two tunnels was more than twice the sum of the radius of the outer edges of the two tunnels, the change in the burial depth of the new tunnel had little effect on the existing one, and the tunnel structure was deemed safe. These results provide a preliminary understanding and reference for the seismic performance of a double-tunnel system.