When auxiliary tunnels pass through gas-bearing strata, there is a risk of gas explosion, but there is less analysis on the impact of gas explosions on operating railways after the auxiliary tunnels are sealed post-construction. To address the shortcomings of existing research, this paper establishes a numerical model of intersecting tunnels that closely resembles actual conditions. It first studies the law of gas explosion in the closed tunnel, obtaining the overpressure curve of the gas explosion. Based on this, the evolution law of plastic expansion of blocking walls of different thicknesses and at different positions under explosive impact is derived, and the safe thickness of the blocking wall is fitted. The study shows that: in the sealed auxiliary tunnel after construction, the overpressure of the gas explosion initially tends to be stable, then increases rapidly, and finally tends to be stable, with the peak value being up to 0.79 MPa. The duration of the explosion increases with the increase of the tunnel length, and the explosion pressure decreases as the tunnel length increases
under the condition of the highest explosion pressure, the maximum deformation of the blocking wall after the gas explosion is 36.7 mm, the shear strain at the center position of the wall surface is the largest, and the range of tensile shear damage is larger, which is a severely damaged area. The final determination establishes that the minimum safe thickness of the wall is 8.33 m.