Impact of Short Distance Underpass Construction of Double Line Shield Tunnels on Existing Lines

In order to study the impact of new double-line tunnel underpass construction on existing tunnels, based on the project of Dalian Metro Line 5 underpassing Line 2, a three-dimensional numerical model of shield crossing construction was established by finite element software, and the change law of vertical displacement and additional stress of new tunnel crossing on the vault and arch bottom of existing operating tunnel was studied. The impacts of the new and old tunnel clearances, soil chamber pressure and grouting pressure on the existing line were analyzed. The results showed that: The new double-lane shield tunnel caused different settlement trough curves in the vault and vault bottom of the existing tunnel, the settlement of the vault was smaller than that of the vault bottom, and the impact of the new left line crossing on the existing tunnel was larger than that of the new right line, accounting for about 87% of the final settlement; The additional stress of the existing tunnel was generally tensile, and the value range was expanding as the construction step advances, and the stresses in the vault part continued to increase; The vertical displacement of the existing line displacement increased with the increase of the net distance between the old and new tunnels, and the same trend was shown in the grouting pressure, but the vertical displacement of the existing line did not change significantly with the change of the soil chamber pressure. The research results could provide reference for similar projects.