To analyze the effect of a void under the track slab on the rail deformation of a ballastless railway caused by tunnel undercrossing,an improved calculation method was proposed to predicate the tunnel undercrossing-induced rail deformation of the ballastless railway.Firstly,the rail of the ballastless railway was simplified as a dual subgrade beam model,and the governing equation was established for the rail deformation of ballastless railway caused by tunnel undercrossing.Then,the ballastless railway was divided into three parts including the middle section above a void and the two sections connecting with the subgrade,and the formulas for the rail deformation of the ballastless railway caused by tunnel undercrossing were derived.The proposed theoretical calculation method was verified by comparing the theoretically calculated and numerically simulated results of rail deformation of the ballastless railway caused by uneven settlement of the subgrade.Finally,the influences of parameters on the rail deformation of the ballastless railway were discussed,including the burial depth of the new tunnel,the ground loss rate caused by tunnel undercrossing construction,and the intersection angle between the railway and the tunnel.The results show that when the undercrossing tunnel is 6 m below the railway,the deformation at the midpoint of the rail reaches the maximum.When the ground loss rate caused by tunnel undercrossing construction increases from 0.25％to 2.50％,the deformation at the midpoint of the rail and the width of the void under the track slab increase by 4.0 and 2.2 times,respectively.
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