## 3 Results and Discuss
### Analysis of Snow Fences and Snow Cover Distribution  
Using the subgrade model as the basic line, various types of snow fences were introduced to investigate their influence on the snow distribution around the subgrade. By changing the configuration of snow fences, their role in protecting against railway snow-drifts was examined, and different snow fence placement strategies were explored. The initial thickness of the particle layer on the ground remained at 20 mm, the wind speed was set at 6.5 m/s, and the blowing duration was 10 min. Figure 14 shows the snow distribution around the fence before and after the wind tunnel test. Figure 15 illustrates the particle distribution along the central axis of the lower embankment for different snow fence configurations, indicating that the presence of a snow fence did not alter the fundamental pattern of snow distribution around the embankment. Consistent with the previously established model, the test area was divided into five regions. Area I, the upstream zone of the snow fence, is characterized by particle accumulation, with significant accumulation starting approximately 2H upstream of the fence (where H is the height of the snow fence). This accumulation occurs because the fence obstructs the snow flow. Given that the standard snow fence is a free snow fence with a porosity of about 50%, some snow particles pass through and accumulate in this first area due to the fence's impedance. The wind speed is substantially reduced downstream of the snow fence, preventing particles from reaching their initiation speed, thus promoting accumulation. Wind field analysis revealed a \"vortex effect\" at the corners of the snow fence, where reduced ground-level wind speeds allow wind-picked-up snow particles to settle. Consequently, the maximum particle accumulation occurs not immediately upstream or downstream of the fence, but at a certain distance downstream. The snow distribution gradually stabilizes beyond 6H downstream of the snow fence, entering Area V. In this region, as the influence of the snow fence on wind speed diminishes, particle accumulation gradually decreases and becomes relatively uniform across different positions. Both the upstream (Area I) and downstream (Area V) zones relative to the snow fence exhibit a  
Figure 14: Snow fence model. (**a**) Before the experiment; (**b**) After the experiment. \"U\" shaped distribution pattern similar to that observed around an embankment without a snow fence. When comparing the distribution coefficient to the case without a snow fence, a slight, but not substantial, decrease in the snow distribution coefficient on the embankment surface is observed. By comparing the distribution coefficient of snow cover under different snow fence structural configurations, similar overall distribution characteristics can be observed upstream and downstream of the fence, regardless of the specific form. Accumulation patterns are consistent within 2-4 H upstream and 4-6 H downstream of the snow fence. Furthermore, the snow cover distribution coefficient on the subgrade surface does not vary significantly across different snow fence configurations. Comparing snow fences with solid and perforated bottom panels reveals that a solid bottom tends to promote greater particle accumulation upstream of the fence. When the entire snow fence is solid (effectively a snow wall), particle accumulation is maximized upstream, with minimal accumulation downstream. Therefore, by adjusting the structural form of snow fences according to different terrain and landform characteristics, the location of snow accumulation can be controlled to optimize space utilization. However, regardless of the configuration, snow fences should be positioned within a 7 H distance from the foot of the subgrade slope to prevent direct snow accumulation on the embankment.