兰新高铁烟墩风区戈壁近地表风沙流跃移质垂直分布特性
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摘要
跃移质作为风沙流的主体,其近地表垂直分布规律是风沙物理学的重要研究内容,对防沙工程具有重要的指导意义。受研究条件与观测仪器限制,戈壁特别是极端大风区近地表风沙流结构特性研究较为薄弱。利用多梯度风蚀传感器与阶梯式集沙仪对兰新高铁烟墩风区戈壁近地表风沙流跃移质的垂直分布特性进行了观测研究。结果表明:兰新高铁烟墩风区戈壁沙粒发生跃移运动的2 m高临界风速达12 m·s~(-1);戈壁近地表风沙流具有明显的阵性特征,沙粒跃移发生的时间比例在50%以下,与平均风速成正相关关系,与风速脉动强度无显著相关关系; 2 m高阵风7级风速下,戈壁跃移沙粒主要集中于地表50 cm范围内,近地表风沙流结构呈"象鼻效应",跃移质最大质量通量出现在地表2. 5～5 cm高度处,沙粒最大跃移高度可达2 m,且沙粒跃移高度随2 m高风速的增加呈指数规律递增。因此,兰新高铁烟墩风区2 m高阻沙栅栏不足以完全阻截戈壁风沙流,是造成烟墩风区兰新高铁轨道积沙的重要原因之一。
Sand particles in saltation are the main part of wind-blown sand,and features of their vertical distribution is a vital research content in aeolian physics,which is of reference significance for aeolian engineering. Restricted by research condition and observation instruments,the research on features of the saltating sand flux profile over near gobi surface in real time observation is relatively weak,especially in gobi area with strong wind. In this study,wind erosion sensors in five different heights and a gradient sand trap were applied to measure the real-time distribution characteristic of saltating particles in different heights in Yandun Wind District,Xinjiang,China. Results revealed that the threshold velocity for saltation in a height of 2 m in the study area reached 12 m·s~(-1) with a threshold friction velocity of 0. 65 m·s~(-1),and sand transport over gobi was of intermittency,which was below 50% in value during the whole observation period. The intermittency of sand transport was in relation to the average wind speed in the height of 2 m,while it had no significant correlation with the pulsation intensity of wind in a period of 10 min.Also,sand in saltation was mainly transported in a surface layer of 50 cm in a moderate gale,and the curve of the sand flux profile presented an elephant trunk outline,with a maximum mass flux in the heights of 2. 5-5 cm. Besides,the saltation height of sand particles increased exponentially with wind speed in the height of 2 m,and in a moderate gale,sand particles could saltate to a height of 2 m. Thus,the sand fence cannot fully intercept windblown sand over gobi may be one of the main reasons for the sand deposition on rails of the Lanzhou-Xinjiang highspeed railway in Yandun Wind District.
Sand particles in saltation are the main part of wind-blown sand,and features of their vertical distribution is a vital research content in aeolian physics,which is of reference significance for aeolian engineering. Restricted by research condition and observation instruments,the research on features of the saltating sand flux profile over near gobi surface in real time observation is relatively weak,especially in gobi area with strong wind. In this study,wind erosion sensors in five different heights and a gradient sand trap were applied to measure the real-time distribution characteristic of saltating particles in different heights in Yandun Wind District,Xinjiang,China. Results revealed that the threshold velocity for saltation in a height of 2 m in the study area reached 12 m·s~(-1) with a threshold friction velocity of 0. 65 m·s~(-1),and sand transport over gobi was of intermittency,which was below 50% in value during the whole observation period. The intermittency of sand transport was in relation to the average wind speed in the height of 2 m,while it had no significant correlation with the pulsation intensity of wind in a period of 10 min.Also,sand in saltation was mainly transported in a surface layer of 50 cm in a moderate gale,and the curve of the sand flux profile presented an elephant trunk outline,with a maximum mass flux in the heights of 2. 5-5 cm. Besides,the saltation height of sand particles increased exponentially with wind speed in the height of 2 m,and in a moderate gale,sand particles could saltate to a height of 2 m. Thus,the sand fence cannot fully intercept windblown sand over gobi may be one of the main reasons for the sand deposition on rails of the Lanzhou-Xinjiang highspeed railway in Yandun Wind District.
引文
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[13]周晓斯,张洋,王元,等.近床面风沙输移风洞实验的光学测量研究进展[J].科技导报,2017,35(3):43-50.
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[15]钱广强,董治宝,罗万银,等.基于数字图像的中国西北地区戈壁表面砾石形貌特征研究[J].中国沙漠,2014,34(3):625-633.
[16]王锡来,蒋育华.砾漠地段铁路沙害成因及防治[J].中国地质灾害与防治学报,2002,13(1):36-43.
[17] Fryberger S G.Dune forms and wind regime[C]//Mc Kee E D:A Study of Global Sand Seas. Honolulu,USA:University Press of the Pacific,1979,1052:137-169.
[18] Tan L H,Zhang W M,Qu J J,et al.Aeolian sediment transport over gobi:Field studies atop the Mogao Grottoes,China[J].Aeolian Research,2016,21:53-60.
[19] Zhang W M,Tan L H,Zhang G B,et al. Aeolian processes over gravel beds:Field wind tunnel simulation and its application atop the Mogao Grottoes,China[J]. Aeolian Research,2014,15:335-344.
[20] Stout J E,Zobeck T M.Intermittent saltation[J].Sedimentology,1997,44(5):959-970.
[21]谭立海,张伟民,屈建军,等.不同砾石覆盖度戈壁床面风蚀速率定量模拟[J].中国沙漠,2016,36(3):581-588.
[22] Lancaster N,Nickling W G,Gillies J A.Sand transport by wind on complex surfaces:Field studies in the Mc Murdo Dry Valleys,Antarctica[J].Journal of Geophysical Research,2010,115:F03027.
[23] Yang X,Mamtimin A,He Q,et al.Observation of saltation activity at Tazhong area in Taklimakan Desert,China[J]. Journal of Arid Land,2013,5(1):32-41.
[24] Zingg A W.Some characteristics of aeolian sand movement by saltation process[J]. Edition du Centre National de la Recherche Scientifique,1953,7:197-208.
[25] Dong Z B,Liu X P,Wang H T,et al.The flux profile of a blowing sand cloud:a wind tunnel investigation[J].Geomorphology,2003,49(3/4):219-230.
[2] Bagnold R A. The Physics of Wind Blown Sand and Desert Dunes[M].London,UK:M ethuen,1941.
[3]吴正.风沙地貌与治沙工程学[M].北京:科学出版社,2003.
[4]屈建军,黄宁,拓万全,等.戈壁风沙流结构特性及其意义[J].地球科学进展,2005,20(1):19-23.
[5] Tan L H,Zhang W M,Qu J J,et al.Aeolian sand transport over gobi w ith different gravel coverages under limited sand supply:a mobile w ind tunnel investigation[J]. Aeolian Research,2013,11:67-74.
[6] Dong Z B,Wang H T,Liu X P,et al.A wind tunnel investigation of the influences of fetch length on the flux profile of a sand cloud blow ing over a gravel surface[J].Earth Surface Processes and Landforms,2004,29(13):1613-1626.
[7]尹永顺.砾漠大风地区风沙流研究[J].中国沙漠,1989,9(4):27-36.
[8]屈建军,张克存,张伟民,等.几种典型戈壁床面风沙流特性比较[J].中国沙漠,2012,32(2):285-290.
[9]邹学勇,董光荣,王周龙.戈壁风沙流若干特征研究[J].中国沙漠,1995,15(4):368-373.
[10]李凯崇,蒋富强,薛春晓,等.兰新铁路十三间房段的戈壁风沙流特征分析[J].铁道工程学报,2010(3):15-18.
[11] Cheng J J,Jiang F Q,Xue C X,et al.Characteristics of the disastrous w ind-sand environment along railw ays in the Gobi area of Xinjiang,China[J]. Atmospheric Environment,2015,102:344-354.
[12]包慧娟,李振山.风沙流中风速纵向脉动的实验研究[J].中国沙漠,2004,24(2):132-135.
[13]周晓斯,张洋,王元,等.近床面风沙输移风洞实验的光学测量研究进展[J].科技导报,2017,35(3):43-50.
[14]王元,杨斌,王大伟.风沙两相流动光学测量及图像处理技术研究进展[J].实验流体力学,2010,24(1):55-64.
[15]钱广强,董治宝,罗万银,等.基于数字图像的中国西北地区戈壁表面砾石形貌特征研究[J].中国沙漠,2014,34(3):625-633.
[16]王锡来,蒋育华.砾漠地段铁路沙害成因及防治[J].中国地质灾害与防治学报,2002,13(1):36-43.
[17] Fryberger S G.Dune forms and wind regime[C]//Mc Kee E D:A Study of Global Sand Seas. Honolulu,USA:University Press of the Pacific,1979,1052:137-169.
[18] Tan L H,Zhang W M,Qu J J,et al.Aeolian sediment transport over gobi:Field studies atop the Mogao Grottoes,China[J].Aeolian Research,2016,21:53-60.
[19] Zhang W M,Tan L H,Zhang G B,et al. Aeolian processes over gravel beds:Field wind tunnel simulation and its application atop the Mogao Grottoes,China[J]. Aeolian Research,2014,15:335-344.
[20] Stout J E,Zobeck T M.Intermittent saltation[J].Sedimentology,1997,44(5):959-970.
[21]谭立海,张伟民,屈建军,等.不同砾石覆盖度戈壁床面风蚀速率定量模拟[J].中国沙漠,2016,36(3):581-588.
[22] Lancaster N,Nickling W G,Gillies J A.Sand transport by wind on complex surfaces:Field studies in the Mc Murdo Dry Valleys,Antarctica[J].Journal of Geophysical Research,2010,115:F03027.
[23] Yang X,Mamtimin A,He Q,et al.Observation of saltation activity at Tazhong area in Taklimakan Desert,China[J]. Journal of Arid Land,2013,5(1):32-41.
[24] Zingg A W.Some characteristics of aeolian sand movement by saltation process[J]. Edition du Centre National de la Recherche Scientifique,1953,7:197-208.
[25] Dong Z B,Liu X P,Wang H T,et al.The flux profile of a blowing sand cloud:a wind tunnel investigation[J].Geomorphology,2003,49(3/4):219-230.