Study on windbreak effect of road G303 snow wall in pastoral prairie

Abstract: The wind speed on both sides of K1203 of typical road G303 in a pastoral prairie of Inner Mongolia, resulted in problems with the snow wall protecting the road. Systematic research was conducted on the windbreak effect in different distances of concrete, non-ventilated linear snow walls that were 2m high and 0.5m wide. During November 2010, outside wind speed was measured by multichannel automatic anemometer PC-2F. The setting position of wind speed was decided based on the multiple of snow wall height (H, the same as follows). The observation height was 2m and 0.2m and the observation time was 30 minutes. The data were obtained by checking the wind speed every three seconds, and then the observations were repeated three more times. Based on the different height (2.0m~0.2m), different distance (protection region H), and wind speed of the snow wall, interpolations of Point Kriging model and Block Kriging model were applied to discuss the optimal, linear, unbiased estimation by soil statistics software SUFER8.0. Finally, isolines of three-dimensional wind speed flow field were confirmed. Isolines of three-dimensional wind speed were at the height of 0.1h (h was the height of snow wall, 2m)、0.25h、0.5h、0.75h and 1h near surface. They were digitized 5 times. We then obtained five groups and five lists, 200 encryption dates, and analyzed them by the SUFER8.0. After studying the wind speed flow field and section lines of it blowing the snow wall at speed of 6m/s、8m/s and 10m/s, pictures of three-dimensional wind speed flow field and section line of wind speed changing trend projection X-Z plane hatch in different situations were acquired. The results show that: 1) With the wind blowing the snow wall at speed of 6m/s、8m/s and 10m/s, the influence scope ranged from 5H to 6H at the windward side (in front of the snow wall), With an especially more obvious effect at 0.5h high and below on reducing wind speed. In total, it can cut down 26.67%, 43.13% and 45.18%. However, the snow wall has almost no effect on wind speed when the height was over 7H. The protection region at the leeward side could reach -10H to -12H, which has the biggest effect on wind speed. 2) The wind speed projection X-Z plane hatch indicates that when the wind outside with varying speeds blowing the snow wall, it can form an eddy current within 0H~2H and up 0.75h. This will reduce the speed below 0.5h directly and that will weaken the energy of airflow transporting snow grains. As a result, excess snow grains accumulated during transporting near the snow wall. Meanwhile, the wind with varying speeds blowing the non-ventilated linear, the area from 6H to 10H has significant influence in wind speed below 0.5h. According to the study results above, it is suggested that the best setting position of the non-ventilated monolayer linear snow wall in the pastoral prairie could be located within the distance between -10H-12H along the highway at the windward side.