Simulation Study on the Deformation Law of a Shallow-Buried Tunnel with Small Spacing that Passes Under an Existing Highway

The construction process of a portal section of a tunnel was simulated based on an existing shallow-buried tunnel with small spacing that passes under a highway. The research results show that: the left and right tubes tended to move to the left, with the maximum horizontal offset of the right tube being 6 to 8 times greater than that of the left tube; the ground settlement extended toward the left tube from the crown of the right tube and a settlement trough was formed, with the maximum ground settlement occurring at the crown of the right tube; a lining design featuring an asymmetrical geometric structure was most effective for a shallow-buried tunnel with small spacing; and a shear zone was formed from the center pillar to the boundary of the massif and ground, therefore support and monitoring should be strengthened in this area. The obtained deformation law, stress distribution, and deformation characteristics of the center pillar and lining support structure, as well as the settlement law of the existing highway surface, will ensure the safe and smooth construction of the project.