Simplified Method for Calculating the Settlement of Existing Tunnel Induced by New Tunneling Based on Two Step Method

Abstract

Settlement induced by new tunneling is important in assessing the safety of existing tunnel. A simplified settlement calculation method for the existing tunnel was obtained based on the two-step method. Firstly, ground settlement induced by tunneling was calculated using experimental method and elastic method. Then the entire tunnel deformation can be calculated using elastic-foundation-beam model and the ground settlement obtained in the first step was applied on the existing tunnel as a passive settlement load. Finally, the simplified method was verified by the results from modal test. The results show that the simplified method is available for calculating settlement of existing tunnel induced by new tunneling. Parametric study also studied in the paper, it is found that the tunnel settlement induced by tunneling increases with the increasing ground loss and decreases with the increasing net distance between new tunnel and existing tunnel. The settlement of tunnel with larger depth and harder soil stiffness is larger than the one with lower depth and softer soil when the ground loss is same.