Study on the Stability of Existing Tunnel Influenced By Adjacent Undercrossing Construction

This paper discusses the Dandong overlapping tunnel project in terms of the stability of existing tunnels by the approaching construction of overlapping tunnels. It uses the Peck formula and the theory of the Kinkler elastic foundation beam. The numerical model is established using MIDAS-GTS. The deformation process and the change in settlement and stress increment of the existing tunnel under the influence of the crossing construction were analyzed. Results clearly show the stability of the existing tunnels. The results show that during construction, under the influence of the crossing construction, existing tunnel displacement occurred mainly for vertical settlements, and showed a clear trend in settling tank. As the construction developed, there was a substantial difference between the horizontal and vertical settlements, and the lateral deformation had a strong directionality. The transverse stress increment was shown as a tensile stress increment, whereas the vertical was shown as a compressive stress increment. The safety of the existing tunnel was determined by combining this with the control standard value of the displacement and the stress increment. This method is applied to the construction of Dandong overlapping tunnels, which remedies the shortage in the experience design method, and provides a quantitative method to ensure the safety of the existing tunnel. This yields a reference value for the construction of overlapping tunnels.