尼龙网方格沙障防护效应研究
文献类型：学位论文
| 作者 | 黎小娟 |
| 答辩日期 | 2017-05-01 |
| 文献子类 | 硕士 |
| 授予单位 | 中国科学院大学 |
| 授予地点 | 新疆乌鲁木齐 |
| 导师 | 周智彬 |
| 关键词 | 尼龙网方格沙障 流场结构 阻沙 截留沙量 粒度 nylon mesh grid sand barrier flow field structure sand blocking sedimentation capacity intercepted sediment particle |
| 学位专业 | 理学硕士 |
| 英文摘要 | The mechanical sand barrier increases the surface roughness, absorbs and disperses thewind momentum within a certain height above the groundby changing the nature of theunderlying surface to reducethe momentum transfer between the airflow and the groundmaterial. In response to the change of the underlying surface, the effect of airflow onsurface sand, the bed on the airflow and the adjustment of wind speed profile have changed.In this paper, wind tunnel simulation and field observation experiments have been carriedout to study the flow field structure with different sizes of nylon sand barrier. Meanwhile,the morphological characteristics, sand cutoff, sand flow structure with different sizes ofnylon sand barrier and the spatial distribution characteristics of sand grain size in the sandbarrier in the hinterland of Taklimakan Desert were analyzed and explored respectively. Insummary, the reasonable pattern of nylon sand barrier was determined. The paper aim toprovide a basis for rational setting of sand barrier in desert areas and the result will providetheoretical and practical meanings respectively for further understanding the sand preventiontechniques on wind erosion protection. The main conclusions of this paper are as follows:（1）The sand barrier of nylon has a distinct districts feature. The flow field structure ofsand barrier is divided into four flow field area. Which is A（A1.A2.A3）,B,C(C1.C2.C3),D.With the increase of wind speed, the deceleration zone of A1 is reduced, the contours aremore intensive and the vortex is stronger, the area of B has increased and reduced, thedegree of deceleration of C1,C2,C3,C4 has gradually reduced, the wind speed contours atD become straight gradually, respectively. The acceleration rate increased and graduallyrestored to the level before the barrier when the airflow is farther away from the sandbarrier. Apart from 14m·s-1, the greater the experimental wind speed, the more obvious thechange. With the sand barrier specifications gradually increased, the number of zones hasnot changed but the range and the vortex strength.（2）In the form of sand barrier morphology, with the increase in wind speed, Maximum sediment height has reduced. The width of the sand peak is widened. Sediment thickness isalso getting thinner. Contours are becoming more and more intensive. The smaller thespecification, the more smooth the concave surface. Which facilitates the formation ofstable concave surface. In terms of sediment transport rate, the sediment transport rate isdecreasing at the vertical height when the wind speed is small. Sediment transportincreased firstly and then reduced. When the wind speed is great. The greater the windspeed, the more trapped sand material, the greater the fluctuation of the curve, the betterthe retention effect of the nylon sand barrier. The larger the specifications, the less thetrapped sand material, the worse the protective effect.(3)The spatial differentiation characteristics of sand particle size on the surface ofnylon mesh were analyzed by field experiment. 1 m×1 m and 1.5 m×1.5 m sand grainaverage particle size along the main wind gradually increased. 1 m×2 m and 2 m×2 m sandgrain average particle size increases firstly and then decreases. Sorting factor is a goodsorting and sorting better range, the larger the specification, the better the sorting. Theoverall degree of skewness is positive and positive, the larger the specification, the greaterthe skew value. In addition to a few points, the front is a very wide peak. The averageparticle size of the four kinds of sand barrier is not correlated with the sorting coefficient,skewness and kurtosis. The kurtosis of sand grains in sand barrier is positively correlatedwith skewness and separation coefficient. The positive correlation coefficient between theskewness and the sorting coefficient is above 0.92. The vertical distribution of sedimenttransport of coarse-grained sand grains follows the decreasing law of exponential, With thedeepness of the sand barrier, the vertical distribution of sand and the amount of sedimentare affected by sand barrier. The horizontal distribution of sand grains is related to themovement mode of sand and flow field, and it has different distribution characteristics inhorizontal direction. After sand barrier, the horizontal distribution of silver sand is the mostsignificant. In the vertical direction, the degree of separation from L1-L2-L3 is slightlyworse, the skewness is very positive, the skewness coefficient is slightly larger but notsignificant. From wide to narrow, the kurtosis gradually increases. The average particle size increases with height. In the horizontal direction, from the T1-T2-T3 process, theaverage particle size of the sand increased firstly and then decreased; the best sorting at T2,the degree of skewness and kurtosis minimum. In the vertical direction, the average grainsize (Ф) at the L1 and L2 is positively correlated with the sorting coefficient, kurtosis andskewness. In the horizontal orientation, the grain size parameters of the three views (T1, T2and T3) have no significant correlation with the average particle size. |
| 学科主题 | 生态学 |
| 语种 | 中文 |
| 源URL | [http://ir.xjlas.org/handle/365004/14880]  |
| 专题 | 新疆生态与地理研究所_研究系统_荒漠环境研究室 |
| 作者单位 | 中国科学院新疆生态与地理研究所 |
| 推荐引用方式 GB/T 7714 | 黎小娟. 尼龙网方格沙障防护效应研究[D]. 新疆乌鲁木齐. 中国科学院大学. 2017. |
入库方式： OAI收割
来源：新疆生态与地理研究所
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