Design parameter optimization for protection measures targeting the bridge–subgrade transition section in a wind-blown sand region

Sand disasters can adversely impact on the operational safety of railway projects. To investigate eolian sand movement characteristics in the wind–sand environment around bridge–subgrade transition sections, in this study, we examine vortex and particle motion characteristics in eolian sand flow fields based on the large eddy simulation (LES) technique and discrete phase model (DPM) while proposing corresponding protection measures for this particular railway section. The results reveal that these methods can be employed to simulate turbulent flow fields. The deposition morphology of particles resembles a wavy ribbon, and the presence of horseshoe–shaped and conical vortices in the wind field affects the deposition of particles. Moving particles are deflected toward the side of the passageway under the bridge. Horizontal and vertical retaining walls are designed to control the wind speed and sand movement. The former obstructs particles, creating a low-velocity zone around the wall, while the latter prevents particle deflection. These protection measures can reduce the saltation distance of sand particles by up to 42.9%. The particle velocity is largely reduced to 0 ~ 2.5 m/s, and only a few small-sized particles ( d < 0.35 mm) are transported in suspension. The designed T-shaped retaining wall can effectively prevent sand particles from deviating, achieving a protection rate of 99.85%, with only 0.81% of the sand particles entering the area of the railway operation.