不同覆盖度沙粒胶结体风蚀抑制效益研究

以塔克拉玛干沙漠腹地的沙粒胶结体(Sand Cemented Bodies,SCB)为研究对象,通过野外自然状态下吹蚀不同沙粒胶结体覆盖度的沙盘,计算沙面风蚀(积)量,并对覆盖度与风蚀率、抗风蚀效率的关系进行分析。结果表明:风蚀量随沙粒胶结体覆盖度的增加而减小,随吹蚀时间的增加而增加;当覆盖度大于30%时,沙面发生风沙堆积,且堆积量随覆盖度和吹蚀时间的增加而增加;沙粒胶结体的抗风蚀效率随覆盖度的增加而线性增大。沙面蚀积转化临界覆盖度为30%左右,且该覆盖度下床面抗风蚀效益最佳。通过对比沙粒胶结体抗风蚀效益的风洞模拟和野外实验,表明风况、风速、沙粒胶结体粒径组合不同可导致沙面蚀积差异和临界覆盖度不同。因此,塔克拉玛干沙漠腹地发育的沙粒胶结体具有很好的风蚀抑制功能,可作为流沙固定新措施继续研究开发。

Field experiment about inhibitory effects on wind erosion of sand cemented bodies with different coverage

Taking the sand cemented bodies (SCB) in thehinterland of Taklimakan Desert, Xinjiang, China, asthe research object, the amounts of wind erosion, accumulationand anti-erosion efficiency on the surface of sand bedswith different SCB coverage were calculated after the field experiment, andthe relation between coverage and wind erosion or anti erosionefficiency was analyzed. The results of thefield experiment and wind tunnel simulation were compared and analyzed at thesame time. The results showed that the amount of erosionwas decreased with the increasing degree of SCB coverage and was increased withthe increasing deflation time. When the coverage was0%-10%, thesurface of sand beds were wind eroded with different deflation time. Thesand blown by the wind accumulated on the sand surface when the coverage isgreater than 30%, and the accumulation was increased with theincrease of coverage and deflation time. Theefficiency of anti wind erosion of SCB was increasedlinearly with the increase of the coverage. Thecritical coverage is about 30% for the sand surface erosion which means thebest effect of anti wind erosion of the sand bed isachieved. The field experimental results were consistentwith the wind tunnel simulation that the SCB can improve the ability of anti wind erosion of sand beds, andSCB can also capture sand from wind drift sand to generate aeolianaccumulation at a given coverage. Thewind erosion rate was increased with the increasing wind speed. Thebigger the wind speed was, the bigger thecritical coverage when erosion was transformed to accumulation will be. However, therewere some differences between the field experiment and wind tunnel simulation. Underthe conditions of field experiment, the critical coveragewas greater than that in the wind tunnel simulation, andfor the erosion rate it was the opposite. Thiswas caused by the different wind conditions, windspeeds and particle sizes of the SCBs as revealed by the comparison between thefield experiment and the wind tunnel simulation. Itwas concretely represented in three aspects: Firstly, thewind speed and direction were kept stable in the wind tunnel simulation, whilethe wind was changeable and complex in the field; secondly, thewind speed in the wind tunnel simulation was higher than the wind velocitythreshold for sand emission in the field; and thirdly in the wind tunnelsimulation, the same coverage experimental sample was usedto place the SCBs of the same particle size range, whilethe SCB of different particle sizes were collected and placed in the fieldexperiment to reflect its true distribution in nature. Inconclusion, the SCB developed in the hinterland of TaklimakanDesert has a good inhibition of wind erosion and can be used as a new measurefor quicksand fixation in the desert.