牧区G303公路典型挡雪墙的防风作用

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

    • 摘要: 针对挡雪墙在草原牧区公路风雪流雪害防治过程中与公路之间的设置距离和设计高度存在的问题,该文以对内蒙古境内G303公路两侧2.0 m高典型公路挡雪墙为研究对象,对高2 m,宽0.5 m的浆砌石不透风式公路挡雪墙内外不同距离的防风效果进行系统研究,利用PC-2F多通道自动风速仪对挡雪墙内外的风速进行了野外实测,应用SUFER8.0、Grapher2.03软件对风速流场进行分析。结果表明:不透风式公路挡雪墙迎风侧1~5 m范围对风速的影响最大,特别是0.5 H(H表示防护长度)高度以下削减风速26.67%~45.18%,背风侧有效防护长度可达10~12 m,且旷野风速越大,对作用风速的影响越大;当不同的旷野风速作用于挡雪墙时,在0~2 m范围内0.75 h(h表示挡雪墙的试验测量高度)高度以上形成涡流,因而直接减小0.5 m高度及以下风速,有效的发挥了公路挡雪墙的作用;2 m高不透风式挡雪墙整个的防护范围可达16 m(6~10 m),且对0.5 h高度以下风速具有显著的影响作用;风速剖面线模型研究发现,迎风侧近地表0.5h、1h风速预测趋势线变化与防护长度(H)的关系为3阶多项式函数,其趋势线变化的特点是一个向上倾斜较为平缓变化的"∽"型,在1.5和2.0 h高度的预测趋势线变化为开口向上的2阶多项式函数,变化特点是相对平缓的"U"型。背风侧五组不同高度的风速预测趋势线都为3阶多项式函数,1 H及以下高度的三组风速趋势线变化从挡雪墙迎风侧到背风侧是先小后大的变化过程,而1.5 h和2.0h高度处的趋势线则为先大后小的变化过程。根据研究结果,建议草原牧区公路设置不透风式挡雪墙时,适宜位置应该在距公路上风侧10~12 m之间,该文为牧区公路设置挡雪墙防治风雪流灾害提供参考。

       

      Abstract: 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.

       

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