Abstract: The new railway subgrade passes through the existing highway bridge in the form of embankment. Aiming at the safety impact of the subgrade on the bridge, this paper presents a case history of a new railway project under passing the highway bridge and effect of the railway embankment on the bridge safety is evaluated. The three-dimensional numerical analysis model is established by using the finite element software Midas GTS. The three types of embankments, namely, slope at both sides, U-shaped structure, U-shaped structure and sheet pile, are compared and analyzed. The results show that the risk control effect and the economy of the U-shaped structure scheme are better. The maximum value of the additional horizontal deformation in the bridge direction is 2.863mm, the maximum value of the additional vertical settlement is 1.189mm, and the maximum value of the additional horizontal deformation in the direction of the bridge is 0.076mm, which meets the requirements of the relevant design codes for the deformation and displacement limits of the existing bridge piers. In addition, the combination of the continuous deformation monitoring during the railway construction and the operation can ensure the operation safety of the existing highway bridges.

Key words: Railway Subgrade, Existing Highway Bridge, Numerical Simulation, U-shaped Structure