不同组合间距的尼龙阻沙网积沙形态特征对比

Morphological features of sand deposition caught by nylon net windbreak combinations with different intervals

在塔克拉玛干沙漠腹地垄间平沙地,布设了两条尼龙阻沙网水平组合防沙实验,组合间距分别为2H、5H、10H、15H(H为阻沙网高度),一个风季中对实验设置的地形及纵断面蚀积量进行了动态观测。结果表明:(1)各尼龙阻沙网组合形成有规律的地表蚀积空间分布格局:形成以阻沙网为核心的积沙区,其上下风侧分布有较稳定的风蚀区,两条阻沙网之间存在临时的风蚀区。(2)在阻沙网前后形成与阻沙网高度相近的积沙体,在第一条阻沙网上风侧区域,积沙厚度与水平距离呈指数函数关系,在阻沙网背风侧,积沙厚度与水平距离呈二次函数关系。(3)2H和5H积沙体纵断面呈单峰状,风季中后期形似"几"字形,而10H和15H呈双峰状,风季中后期形似"M"字形。(4)阻沙网组合间距越小,积沙分布就越集中,形体越高大,反之则越分散,风季末阻沙网积沙体地形起伏度、平均坡降、积沙体积比、积沙断面面积轮廓比大小排序均为2H>5H>10H>15H。(5)阻沙网积沙体积具有随阻沙网间距增大而降低的趋势,观测断面最大积沙体积5HH>2H>15H>10H,5H、2H、15H分别较10H大13.20%、12.34%、3.78%,可见,5H防沙效果最优。

As one of the most effective sand-controlling measures, nylon net windbreak has an excellent sand-blocking capability, has been applied to lots of transportation projects in desert areas of China. In a practical application, especially in drifting desert, two or more pieces of nylon net windbreaks were always settled togeth- er, however, few studies on its best combinatorial space between two pieces of windbreaks has rarely been report- ed so far. The paper conducted a sand-controlling experiment of two nylon-net-windbreaks combination with dif- ferent space length treatments, which were 2 times （2H）, 5 times （5H）, 10 times （10H）, and 15 times （15H） as broad as windbreak＇ s height on an inter-dune corridor in the hinterland of the Taklimakan Desert, Xinjiang, China. The landforms and erosion-deposition around all nylon-net windbreak combinations were investigated dynamical- ly in a wind season. The results indicate that the intensities of erosion-deposition around the windbreak combina- tions were distributed in a clear spatial pattern including one sand-depositing region around windbreaks, two de- flation regions in its windward and leeward neighborhoods, and one temporary deflation region between the two windbreaks. A sand ridge with similar height like windbreak was formed in the sand-depositing region; in the windward part of the first windbreak, the thickness of sand deposition increased exponentially with the horizontal distance to windbreak shortening; in the leeward part of the windbreaks, the thickness of sand deposition de- creased with the horizontal distance to windbreak increasing, whose relation can be formulated as a standard qua- dratic function. The profiles of sand deposition cross section of 2H and 5H showed as single apex with a shape of Chinese character of＇ 几＇ in the middle and later period of wind season; But the profiles of sand deposition cross section of 1 OH and 15H showed as double peaks with a shape of English character of ＇M＇ in the middle and later period of wind season. The smaller the windbreaks combination spacing, the more concentrated the distribution of sand deposition, the form is tall, the higher the body of sand deposition, conversely, the more dispersed and lower; the sort of the roughness, average grade, sand deposition volume per unit area, ratio between area and pro- file length of sand deposition was 2H, 5H, 10H, 15H in descending order. The volume of sand deposition tends to decrease with increase of windbreaks combination spacing with a descending sort of 5H, 2H, 15H, 1 OH. So the combination mode of 5H has the optimal effect of sand control.