不同沙埋程度下带状沙障的防风固沙效果研究

沙障在防护过程中,易发生沙障沙埋现象。为了对比分析不同沙埋程度下沙障的防风固沙效果差异,该文通过风洞模拟和野外试验相结合的方法,研究了沙袋沙障在裸露、浅埋、深埋3种状态下,防护区近地层风流场、输沙通量等风沙运动规律,并以未设置沙障的流沙区作为对照,明确了沙埋过程中沙障的防风固沙效果变化规律。结果表明,沙障在经历裸露至深埋过程中:1)对过境气流的防护距离、防护高度逐渐减小,近地层风速廓线变化趋势与对照相同,并逐渐服从对数函数;2)沙障防护区输沙分布高度显著降低(P0.01),输沙分布高度由42 cm(裸露)降低至34 cm(浅埋),最终降至28 cm(深埋),而对照的输沙分布高度为24 cm;3)近地层输沙率分布曲线逐渐服从对数函数,0～50 cm高度范围输沙量也呈现递增趋势;4)3种埋设深度野外试验说明,经过两个风季后,裸露、浅埋、深埋的沙袋沙障防护区土壤风蚀呈现降低趋势,风蚀深度分别比对照降低了18.53%、72.97%、80.40%。研究可以为沙障高度优化及应用技术提升提供理论依据。

Effect of wind-preventing and sand fixation of belt sand barrier under different degree of sand burial

Sand barrier is easy to be buried by sand at the beginning of the sand barrier setting and it will lose wind-preventing and sand fixation function when it is buried deeper, but moderate sand bury can improve protect effect while sand burial will help the sand barrier to form a stable protective structure. So it is conducive to understanding the sand burial mechanism and the change law of protective benefits caused by sand burial. In order to study the difference of wind-preventing and sand fixation of different depth sand burial of sand barrier, the research conducted wind tunnel simulation and field experiment. The laws of wind flow field and sediment transport flux in surface layer of the protection zone which was protected by sandbag sand barrier under the condition of bare, shallow and deep sand buried were studied, and the mobile sand dunes without sand barrier was taken as a control. In the wind tunnel test, the variation of the near-surface airflow field, wind speed profile, sediment transport rate and sediment transport height during the sand burial process were analyzed. Sandbag sand barriers were set up in the windward slopes of mobile sand dunes and wind erosion resistance effects of the three sand burial states were tested. The research results showed that with the sand barrier experienced the process of being bare-shallow-deep sand burial, 1) the variation of the airflow field was gradually and steadily in the near-surface layer, and the turbulent flow was reduced significantly, multiple low-speed settlement areas appeared at the right rear when it was bare, and disappeared when it was shallow burial; 2) Both of effective protecting distance and height of transit flow were decreased , that were at least 70 cm and 15 cm of the leeward side of the sand barrier when it was bare, but fell below 50 cm and 7 cm respectively when it was deep burial; 3) The wind speed distribution curve of the near surface layer on the windward and leeward side of the sand barrier did not obey the logarithmic function, and the wind speed profile was volatility change with the height, as the sand barrier was gradually buried by sand, wind speed profile was the same as that of the control and obeyed the law of logarithmic distribution; 4) The height of transporting sediment discharge on protection zone of the sand barriers decreased significantly (P<0.01), height of transporting sediment discharge decreased from 42 cm (bare) to 34 cm (shallow burial) and finally to 28cm (deep burial), and the distribution height of the control was 24 cm; 5) Field experiments of three burial depths showed that wind erosion depth of bare, shallow and deep buried sandbag sand barriers in protection area showed a decreasing trend two years after setting up, the depth of wind erosion decreased by 18.53%, 72.97% and 80.40% respectively compared with the control. The research can provide theoretical support for optimization of sand barrier height and improvement of applied technology.