The whole freezing process construction of the metro liaison channel is simulated using the indirect method to realize thermal-mechanical coupling by ANSYS to highlight the thaw-settlement characteristics in the freezing structure of the liaison channel on water-rich sandy cobble ground. The discussion of the surface settlement, deformation, and stress characteristics in the thaw-settlement stage of segment structure and liaison channel structure of the double-line tunnel in water-rich sandy cobble ground provides a valuable reference for the construction of the practical project. The results show that the surface settlement increases gradually with the thawing of sandy cobble ground. However, the thaw-settlement effect of sandy cobble ground is small, and the thaw-settlement deformation of the stratum is only 1.85 mm. The settlement value of the segment and the liaison channel structure increases gradually with the thawing of sandy cobble ground. At the same time, the tensile stress of the segment and the liaison channel structure decreases, and the compressive stress increases. The settlement deformation at the top of the connection between the segment structure and the liaison channel structure, the segment’s compressive stress at the bottom of the connection, and the settlement deformation and compressive stress at the floor of the liaison channel should be well-monitored in actual construction.

In order to investigate the influence of external water pressure changes on the mechanical characteristics of prestressed double-layer lining, a three-dimensional finite element model of the prestressed doublelayer lining in a shield tunnel is established based on the Pearl River Delta Water Resources Allocation Project. The structural behavior and deformation of the double-layer lining during the prestressing construction and water flow operation stages are analyzed under different external water head heights (10 m, 20 m, 30 m, 40 m, 50 m). The results indicate the following: during the construction and operation stages, the overall shape of the double-layer lining exhibits an " elliptical" deformation pattern. When the external water head height decreases from 50 m to 10 m, the lateral deformation of the double-layer lining increases by 42.3%, the settlement at the crown decreases by 34.3%, and the uplift at the invert decreases by 42.4%. With the increase of external water pressure, the circumferential stress of the prestressed lining during the construction stage increases, and the tensile area of the segment lining during the operation stage decreases. The maximum circumferential tensile stress decreases by 54.05%. The prestressed double-layer lining tends to be in a hydrostatic pressure state, and the overall deformation pattern transitions from " elliptical deformation " to " overall contraction ". This study contributes to the safety of the double-layer lining structure.