Comparative Wind Prevention And Sand-fixation Efficiency Of Cotton Haulm Sand Barrier

China's desert area of 712. 900 km² , second only to Australia and Saudi Arabia, is listed third in the world. With global warming, the extent of desertification in China is becoming more worsening, and dust storms also become more frequently, China's desertification area is about 532, 500 km², continues to expand of desertification become the most serious ecological problems. Particularly, in some of Northwest China the desertification becomes even more serious, although the process of China's western development, the establishment of large-scale planting trees and grass in returning farmland to forests as the main measures to combat desertification, which, for improving the ecological environment in west will play a huge promoting role. Because of sand-wind harms in these areas is particularly serious, and extreme worst ecological environment, the use of biological measures is extremely difficult to use in combating sand-wind, mechanical desert controlled as a very necessary measures and can not be replaced by the others. Mechanic Sand-fixing measures is the main works of engineering sand prevention and controlled, by the exert of scientists , the study on specification of sand barrier and sand-effective , and the innovation of using materials, the measures of combating sand-wind and sand-fixation pushed out a way , which is economical and practical, with unique features and be most used widely and effectively.The cotton haulm sand barrier was woven into a cluster-type sand barrier and fence-type sand barrier by wasted cotton haulm in arid areas of China as raw materials, which is based on theoretical studies of mechanic sand barriers, and combined with state of the study area.In this paper, from the observation of wind speed and wind erosion and sand accumulation capacity in fence-type cotton haulm sand barrier with the porosity of 40% and cluster-type cotton haulm sand barriers, and then analyses the wind prevention and sand-fixation efficiency we can draw the following conclusion:1 Setting cotton haulm sand barrier changed the nature of surface, increased the roughness of surface and effectively, reduces the flow rate of sand in transit. By measures of observation, the roughness of checkerboard-style barrier of fence location was 10^1.62-fold, and its coefficient of variation of wind speed and decreased wind speed are 0.48 and 75%.2 The Cotton haulm sand barrier changed the characteristics of turbulent air flow on the surface layer and weakened wind energy, so that a large number of sand deposition, the amount of sand at forefront of the barrier and is more than that of the rear of the plot.3 After long-term role of erosion and accumulation the cotton haulm sand barrier ultimately reach a state of equilibrium corrosion and formed a concave surface, so as to achieve an important function that stabilize the surface and fixed quicksand.4 By the impact of the main wind direction, fence-style cotton haulm sand barrier formed a cross-barrier-type concave surface which different from cluster-style, as a result of accumulating sand barrier is not at the highest point of the sand barrier, the sand barrier cannot be buried by sand easily, thus the using life of sand barrier to be extended and further improve the effectiveness of its anti-desertification.5 After comparative analysis to the efficiency of wind prevention and sand-fixation of three type sand barriers, cluster-type cotton haulm is buried easily by sand, and cavalcade sand barrier fence easy to lodging, checkerboard-style barrier fence is relatively stable.6 After comparative analysis of its sand-fixing effectiveness, confirmed that as a new material sand barrier , the fence-style cotton haulm protective benefits s is very significant, and its setting way is scientific and reliable, in the region of arid area to replace the sand dune-fixing material like nylon net and plastic nets which investment is relatively large is entirely feasible. 7 The fence-type cotton haulm sand barrier has rich raw materials to woven, low cost and easy to construction, no environmental pollution etc, that can be used in mechanical desert control as a new type sand barrier widely.