研究青藏铁路沿线的风沙活动特征,可以为认识高原铁路风沙危害的形成机理、建立完善有效的护路防沙体系提供参考。在实地考察风沙地貌的基础上,架设测风塔获取风况信息,采集了沙丘表层沉积物样品,对铁路沿线察尔汗盐湖段的风动力条件、沙丘沉积物粒度特征和沙丘形态特征进行了分析。结果表明:(1)研究区域年平均风速为3.7 m·s-1,风速最大值出现在春季。起沙风以WNW方向为主,属于中风能环境,低风向变率,宽单峰型风况。合成输沙方向(298.14°)与铁路走向(208.86°)垂直相交。稳定的西北风、风沙流与铁路线路走向垂直的风况特征是青藏铁路沙害形成的动力条件。(2)沉积物以中沙、细沙为主,但细沙组分占优;分选性较好,粒径分布表现出与铁路线越近、颗粒越粗的规律。粒径0.063~0.04 mm的沙粒为青藏铁路风沙危害提供了物质条件。(3)铁路线两侧沙丘分布特征及变化指示该路段风沙活动强烈,现有防沙体系退化严重,风沙危害日益突出。
The research on the characteristics of sand-drift activities along the Qarhan Salt Lake section of Qinghai-Tibet Railway can explore the mechanism of blown sand disaster formation along the railway and provide data for an effective prevention system.We conducted fieldwork to examine the topographic features,and collected sediment samples and wind data.The results are as follow:(1) The annual average wind speed is 3.7 m·s-1 with peak value in spring.The direction of sand-driving wind is mainly WNW.The area belongs to an intermediate wind energy environment.The wind direction variability (RDP/DP) belongs to low ratio and single peak wind regimes.The Resultant Drift Direction (RDD) is 298.14 and intersects vertically with the railway line.The stable wind direction and the intersection of wind to the railway line are dynamic factors contributing to the blown sand disaster.(2) The sediment is mainly composed of middle and fine particles.The closer from the railway,the larger the particle size is.The particles at 0.063-0.04 mm provide material foundation for the sand disaster along the railway.(3) The sand dune form change indicates that sand-drift activities are intensive,and the prevention system severely degraded.
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