植被沙障对近地表风沙流特征影响的风洞实验

植被沙障在一些地区已成为沙害防治的有效手段,其应用也越来越广泛,但对其治沙机理尚不很清楚.在盖度为10%,15%,20%,30%,40%,60%情况下,对植被沙障的防风固沙效益进行了风洞试验.实验风速设置为6,8,11 m/s,测定不同植被盖度的风速廓线特征、风沙流结构特征及其防沙效果.实验结果表明:①积沙总量随盖度增加而逐渐降低,风沙流中的砂粒分布在一定的高度范围内,但分布的高度随盖度的增加呈下降趋势;②植株的茂密程度对风沙流的结构有明显影响,盖度越高,积沙量越集中在下部;③盖度并不是导致积沙量为零的唯一指标,风蚀是否发生,还与植被的疏透度、防护林的高度等有关.

Wind Tunnel Test about the Effect of Vegetation Sand-barrier on Wind-blown Sand Flow near Ground Surface

tively common that road suffers from the impact of wind erosion and sand-burying.Especially,shifting sand movement leads to sand hazard to highway and traffic jam.Furthermore,the traffic and its safety are threatened.At present,the vegetation sand-barrier has become as an effective way for preventing wind-blown sand disasters in some areas,and it will be widely applied in the future,but its mechanism of preventing wind-blown sand disasters is not identified yet.In this paper,a wind tunnel test is made to simulate wind prevention and sand fixation benefits of the vegetation sand-barrier with coverages of 10%,15%,20%,30%,40% and 60%.The testing wind velocities are 6 m/s,8 m/s and 11 m/s.The characteristics of wind speed profile and structure of drifting sand flux,and the effect of sand fixation are revealed.The experimental results are as follows:(1)Total accumulated sand amount is gradually reduced with increasing the coverage,sand particles in wind-blown sand flow are distributed in a certain height range,but the distribution height is in a descending trend with increasing the coverage;(2)Plant luxuriance affects obviously the wind-blown sand flow structure.The higher the coverage is,the more concentrative the sand accumulation in the lower height will be.The coverage is not the only index resulting in the reduction of sand accumulation to zero;(3)Occurrence of wind erosion is not only related to vegetation,but also to the porosity of vegetation,height of shelter forest,etc.