Numerical simulation on sand sedimentation and erosion characteristics around HDPE sheet sand barrier under different wind angles

For the safety of railroad operations,sand barriers are utilized to mitigate wind-sand disaster effects.These disasters,characterized by multi-directional wind patterns,result in diverse angles among the barriers.In this study,using numerical simulations,we examined the behavior of High Density Polyethylene(HDPE)sheet sand barriers under different wind angles,focusing on flow field distribution,windproof efficiency,and sedimentation erosion dynamics.This study discovered that at a steady wind speed,airflow velocity varies as the angle between the airflow and the HDPE barrier changes.Specifically,a 90°angle results in the widest low-speed airflow area on the barrier’s downwind side.If the airflow is not perpendicular to the barrier,it prompts a lateral airflow movement which decreases as the angle expands.The windproof efficiency correlates directly with this angle but inversely with the wind’s speed.Notably,with a wind angle of 90°,wind speed drops by 81%.The minimum wind speed is found at 5.1H(the sand barrier height)on the barrier’s downwind side.As the angle grows,the barrier’s windproof efficiency improves,extending its protective reach.Sedimentation is most prominent on the barrier’s downwind side,as the wind angle shifts from 30°to 90°,the sand sedimentation area on the barrier’s downwind side enlarges by 14.8H.As the angle grows,sedimentation intensifies,eventually overtakes the forward erosion and enlarges the sedimentation area.

Cost analysis of sand barriers in desertified regions based on the land grid division model

Sand barriers are the most widely used mechanical implements for wind-blown sand control and desertification prevention.However,there is no standard quantitative cost analysis of the sizes and materials required for sand barriers.In this study,based on the original land grid division model for optimal resource utilization,we calculated the total side lengths of square and regular hexagonal sand barriers with the sizes of 1.0 m×1.0 m,2.0 m×2.0 m,and 3.0 m×3.0 m in a desertified region of the Shapotou area on the southeastern edge of the Tengger Desert,China.Then,through literature review and social survey,we obtained the material cost and material utilization amount of sand barriers with different materials and sizes.Finally,we calculated the costs of square and regular hexagonal sand barriers comprised of wheat straw,corn stalk,Salix mongolica,poly lactic acid,magnesium cement,and high-density polyethylene,with the sizes of 1.0 m×1.0 m,2.0 m×2.0 m,and 3.0 m×3.0 m.The results show that the material cost of regular hexagonal corn stalk sand barriers with the size of 3.0 m×3.0 m is the lowest,while the material cost of square magnesium cement sand barriers with the size of 1.0 m×1.0 m is the highest.When using the same material,the cost of regular hexagonal sand barriers is lower than that of square sand barriers with the same size.When using the same size,the cost of sand barriers with corn stalk material is lower than that of sand barriers with other materials.Based on the above analysis,we can conclude that the economic benefits of regular hexagonal sand barriers are greater than those of square sand barriers.This study provides a theoretical basis for accurately calculating the material cost of sand barriers,particularly for the estimated cost of mechanized sand barrier engineering projects.

Progress and Problems of Development Research and Application of Sand Barriers

Due to the restrictions on the conditions for afforestation and sand control,the development research,and application of sand barriers have accelerated in recent years,but some problems that cannot be ignored have emerged in practice. In this paper,the functions of wind prevention,sand blocking and fixation,improving soil physical and chemical properties and increasing plant diversity of sand barriers,accretion coefficient and capacity between sand barriers,and mobile sand barriers were analyzed firstly,and then several issues that should be noted in the development and application of sand barriers were proposed. The results show that sand barriers can fix sand on the spot and maintain the stability of sand surface. As an auxiliary measure before afforestation on a mobile sand surface,they are practical and feasible. The biggest drawback of sand barriers is that they are easy to be saturated. Although they can increase plant diversity and surface roughness,they lose the function of blocking sand flow after being saturated,and their function of in-situ sand fixation also rapidly decreases with the degradation of sand barriers. Mobile sand barriers overcome the disadvantage of sand barriers being easy to be saturated to some extent,but the cost greatly increases. In terms of desertification prevention and control by plants,plants are used as sand barriers to study their functions of sand blocking and sand fixation in many researches and practices,but the more important ecological functions of adjusting temperature on sand surface and achieving surface thermodynamic equilibrium of plants are ignored.

Sand barrier morphological evolution based on time series remote sensing images:a case study of Anhaiao,Pingtan

The morphological evolution of the sand barrier in the Anhaiao coastal zone of Pingtan from 1996 to 2018 was studied.Tidal correction was used to refine the location of the coastline.A standard deviation ellipse method was applied to further analyze the movement of the barrier head with the axis and rotation angle.A natural neighbor interpolation(NNI)method was carried out to calculate the terrain of the intertidal area,and the erosion and deposition characteristics were illustrated based on the terrain.The results showed that the northern part of the sand barrier facing the lagoon area was deposited over the whole studied period,while erosion has always occurred in the southern part of the sand barrier facing the open sea.The erosion and deposition were slightly different on both sides of the barrier head due to hydrodynamic turbulence.The middle sand barrier moved 102.60 m away from its original location in 1996,and the end of the barrier moved 65.45 m.The head of the sand barrier continued moving 379 m to the northwest.Consequently,the preliminary morphological evolution of the sand barrier corresponding to the distance and direction of movement was detected.

Evolution Characteristics and Development Trends of Sand Barriers

Sand barriers are one of the main measures used to prevent desertification and have been widely used in desertification control. Here, we use bibliometric methods and content analysis to summarize sand barrier type, applications and research. Existing problems in research are pointed out and revolution characteristics and development trends of sand barriers are discussed. We conclude that three main driving factors have stimulated sand barrier study： demand, technology and development concept. Developing environmentally friendly technology and promoting industrialization of sand area economies are future directions for sand barrier research.

Damage by wind-blown sand and its control measures along the Taklimakan Desert Highway in China

Desertification is one of the most serious environmental problems in the world,especially in the arid desert regions.Combating desertification,therefore,is an urgent task on a regional or even global scale.The Taklimakan Desert in China is the second largest mobile desert in the world and has been called the''Dead Sea''due to few organisms can exist in such a harsh environment.The Taklimakan Desert Highway,the longest desert highway(a total length of 446 km)across the mobile desert in the world,was built in the 1990s within the Taklimakan Desert.It has an important strategic significance regarding oil and gas resources exploration and plays a vital role in the socio-economic development of southern Xinjiang,China.However,wind-blow sand seriously damages the smoothness of the desert highway and,in this case,mechanical sand control system(including sand barrier fences and straw checkerboards)was used early in the life of the desert highway to protect the road.Unfortunately,more than 70%of the sand barrier fences and straw checkerboards have lost their functions,and the desert highway has often been buried and frequently blocked since 1999.To solve this problem,a long artificial shelterbelt with the length of 437 km was built along the desert highway since 2000.However,some potential problems still exist for the sustainable development of the desert highway,such as water shortage,strong sandstorms,extreme environmental characteristics and large maintenance costs.The study aims to provide an overview of the damages caused by wind-blown sand and the effects of sand control measures along the Taklimakan Desert Highway.Ultimately,we provide some suggestions for the biological sand control system to ensure the sustainable development of the Taklimakan Desert Highway,such as screening drought-resistant species to reduce the irrigation requirement and ensure the sound development of groundwater,screening halophytes to restore vegetation in the case of soil salinization,and planting cash crops,such as Cistanche,Wolfberry,Apocynum and other cash crops to decrease the high cost of maintenance on highways and shelterbelts.

Sand control effect of HDPE sandbreak nets with different porosity structure

Straw checkerboard sand barriers with a porous structure that consists of a pervious upper portion and a dense lower portion are widely used to achieve great sand control effect.Considering this,and resolving the serious earth surface undercutting problem after HDPE sandbreak net checkboard barriers setting,the authors used HDPE(high-density polyethylene)materials to prepare new sandbreak materials with a similar porous structure.Through wind tunnel simulations and field sand control monitoring,we compared the sand control effect of three HDPE sandbreak nets with different porosity structure.Compared to the sandbreak net with uniform porosity structure,the three types of HDPE sandbreak nets with different porosity structure had poorer effect on reducing sand transport rates,but had longer effective protection distance before sandbreak nets at low wind velocity conditions(<12 m/s),longer effective protection distance at high wind velocity(>14 m/s)and longer effective protection distance between sandbreak nets at all experimental wind velocity conditions.Wind and sand control effect characteristics of HDPE sandbreak nets with different porosity structure provide an ideal material on semiburied checkerboard sand barriers for sand stabilization.By contrast,uniform-type sandbreak nets are used as materials on high upright sand fences for sand blocking.These HDPE sandbreak nets can be used to replace traditional sandbreak materials and have a very high potential for widespread and popular application in aeolian sand disaster control.

Pilot Test of the Permeable Reactive Barrier for Removing Uranium from the Flooded Gunnar Pit

This work reports on applying iron oxide coated sand (IOCS) media in an experimental permeable reactive barrier to remove uranium (U) species from uranium containing water. A field study was conducted at the legacy Gunnar uranium mine & mill site that was abandoned in the 1960s with limited to no decommissioning. The flooded Gunnar mine pit presently contains about 3.2 million m3 of water contaminated by dissolved U (1.2 mg/L), Ra-226 (0.4 Bq/L), and minor concentrations of other contaminants (As, Se, etc.). The water is seeping over the pit rim into Lake Athabasca, posing potential environmental and health concerns. IOCS media can be used to immobilize uranium species through an adsorption process. Herein, the preparation of hydrous ferric oxide sorbents and their supported forms onto silica sands is described. Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (pXRD) were used for structural characterization. The adsorption properties of the IOCS sorbent media were modeled by the Langmuir adsorption isotherm, where a maximum uranium uptake capacity was estimated. Bench-scale adsorption kinetic experiments were also performed before moving to a field trial. Based on these lab results and input on field-scale parameters, a pilot permeable reactive barrier was fabricated and a field test conducted near the Gunnar pit in June 2019. This pilot test provided technical data and information needed for designing a full-scale permeable barrier that employs the IOCS media. This approach can be applied for in-situ water treatment at Gunnar and other legacy uranium sites.

纱网沙障研究进展

沙障在流动沙地治理和植被恢复中发挥了重要作用,而纱网沙障具有材质轻、韧性好、抗拉力强、使用寿命长等优点。本文综述了自1989年以来有关纱网沙障材料选择、设置方式、防风固沙作用及植被恢复成效等研究成果,并提出了纱网沙障未来发展趋势。

草方格沙障铺设车输料装置及其拢草机构分析

针对以散草为原料铺设草方格沙障存在空隙的问题,提出了一种草方格沙障铺设车。阐述了该铺设车的整体设计和作业流程,对输料装置进行结构设计和工作过程分析,对该装置的拢草机构进行运动学分析和仿真分析。结果表明:拢草机构的运动满足设计要求,同时给了一组工作参数,以转速为95 r/min为例,水平方向齿尖位置在90 mm左右时,其速度约为310 mm/s,超过传送带输送速度,由此点作为工作切入点,扒齿有效工作距离约为180 mm,在水平位移约为4 mm时,竖直位移大于7 mm,满足预期工作要求。

鄂尔多斯盆地本溪组碎屑障壁海岸砂体微相南北变化

在延长探区近1500口钻井资料的基础上,进行大量岩心和薄片观察以及砂厚和砂地比统计,探究鄂尔多斯盆地本溪组的砂体微相类型、平面形态和分布的沿岸变化及其控制因素。结果表明,延长气田本溪组总体均为中小潮差环境下的陆源碎屑障壁海岸沉积,但南部的甘泉—富县地区波浪作用较弱,形成了典型的障壁砂坝和障壁后沉积。北部延安—靖边南地区波浪作用较强,形成了改造障壁、浅滩和下切谷充填潮道3种主要微相砂体。障壁砂体呈平行岸线的带状或串珠状排列,近源和近岸分布;浅滩砂体呈多个分散的卵圆形远源远岸分布;潮道带砂体充填则受控于古地貌凹槽。该研究结果对延长气田和类似环境的储层识别和评价具有重要的指导意义。

民勤黏土沙障-人工梭梭林物种多样性及土壤水分变化特征

以民勤荒漠区6种不同布设年限(1 a、5 a、10 a、20 a、40 a、60 a)黏土沙障-人工梭梭林样地和流动沙地(对照)为研究对象,对其物种构成、重要值、优势种群特征、物种多样性和土壤水分含量进行调查,探究长时间尺度黏土沙障-人工梭梭林构建对区域植物群落结构、物种多样性和土壤水分的影响。结果表明:民勤荒漠区黏土沙障-人工梭梭林调查样地共记录到植物6科12属12种,以藜科、蒺藜科为主。人工防沙体系的构建能够显著提升区域植物物种数量(从4种增加到5~8种),且随着布设年限的延长,优势种由沙米(Agriophyllum squarrosum)、梭梭(Haloxylon ammodendron)逐步向雾冰藜(Grubovia dasyphylla)、猪毛菜(Kali collinum)、黄花矶松(Limonium aureum)、梭梭(Haloxylon ammodendron)优势种演变,生活型也从以一年生草本为主的单一型向一年生草本+多年生草本+灌木的复合型发生演变。物种丰富度指数、Shannon-Wiener指数、Simpson指数、Pielou指数和Alatalo指数总体呈现出单峰型变化趋势,以布设20 a时物种数最多,物种分布最均匀,对照沙地物种数最少,物种分布均匀度最差。不同样地植物群落的Jaccard指数表现为:对照沙地与布设1 a样地>布设20 a与布设40 a样地>布设1 a与布设5 a样地>布设10 a与布设20 a样地>布设40 a与布设60 a样地>布设5 a与布设10 a样地,相异性指数与Cody指数则表现相反。区域土壤含水率波动态势与植物群落演替趋势保持一致,且相较于较深层土壤(40~60 cm),浅层土壤(10~30 cm)对区域植物自然演替进程所起到的作用更为明显。

高立式芦苇沙障打捆成栅机的设计与试验

针对风沙区铁路安全运行中高立式芦苇沙障生产人工效率低、劳动强度大、制造成本高、操作工序多、工作环境恶劣等问题和对芦苇沙障成栅工艺流程研究的基础上,设计了高立式芦苇沙障打捆成栅机。通过对关键作业部件进行设计选型,确定了喂料机构、铁丝推送机构、打捆拧丝机构的结构,并采用理论分析、Workbench仿真方法对喂料弧片、送丝摇臂与拧丝虎口等关键零件参数进行了设计与分析。为提高作业性能,以芦苇束紧实度、芦苇破损率和单束打捆作业时间为评价指标,以铁丝推送长度、拧丝虎口转速为影响因素,进行了高立式芦苇沙障打捆优化实验,利用Design-Expert V8.0.6.1软件,构建关于评价指标与影响因素间的回归模型,确定最优参数组合为:拧丝虎口转速1297r/min、送丝距离372mm。样机验证试验结果表明:高立式芦苇沙障打捆成栅机具有较强的物料适应性,在优化参数组合下,通过试验验证了设计的正确性和合理性。上述研究成果丰富了高立式芦苇沙障打捆成栅技术,也为整秆打捆成栅机械的设计提供参考依据。

锡林浩特露天煤矿排土场不同恢复措施植被群落特征分析

有效的排土场植被重建会有利于矿区及周边生态功能的恢复,不同措施植被恢复效果不同。以锡林郭勒盟胜利煤田西二号露天煤矿外排土场为研究对象,于2007年开始进行修复工作,本研究对排土场恢复第13年3种不同恢复措施下的植物群落进行调查。其中,3种不同措施分别为生物笆覆盖措施(简称SW)、沙障覆盖措施(简称SZ)和人工条播措施(简称RT)。不同措施坡面同时分为坡上(PS)、坡中(PZ)、坡下(PX)和平台(PT)4个高度。结果表明:(1)覆盖措施恢复效果明显,物种多样性显著高于RT措施,其中SW措施效果较好。(2)同一措施下各高度中,PT恢复效果最好,坡度对于植物生长存在一定影响。(3)一年生草本植物芸薹(Brassica rapa var.oleifera),多年生草本植物披碱草(Elymus dahuricus),灌木植物小叶锦鸡儿(Caragana microphylla)、柠条锦鸡儿(C.korshinskii)对于胜利煤田矿区排土场生态环境适应性较好。

基于慧鱼创意模型的草方格沙障铺设车设计

针对现有沙障铺设机存在的造价高、自动化程度低、适应性差、沙障铺设效果差等问题,该文基于慧鱼创意模型设计了一款自适应强、工作效率高、自动化程度高的草方格沙障铺设车。完成了铺设车机械系统和控制系统方案设计;实现了自动检测、随动控制、草料运转装置三维可调和秸秆精准等功能;搭建了慧鱼创意模型实物样机;开展了模拟样机草方格沙障铺设试验。实验结果表明,该铺设车完全自适应植入秸秆与巩固秸秆,沙障防风固沙质量稳定性、可靠性强,工程应用预期效果显著。

乌珠穆沁沙地聚乳酸纤维沙袋沙障地表蚀积特征

沙障的蚀积特征对其发挥防护作用具有重要影响。为探究聚乳酸纤维(polylactic acid fiber,PLA)沙袋沙障对乌珠穆沁沙地沙化治理的效果,设置0.5 m×0.5 m、1.0 m×1.0 m、2.0 m×2.0 m和3.0 m×3.0 m共4种规格的聚乳酸纤维沙袋沙障,采用悬测法测量障格内部凹曲面形态,并分析不同规格沙障内部凹曲面的形态特征、蚀积效应。结果表明,沙障凹曲面中心风蚀深度随沙障规格的增大由5.17 cm增加到21.23 cm,而堆积强度随沙障规格的增大由3.86 g·cm^(-3)降至0.42 g·cm^(-3),障格内由堆积变为风蚀;蚀积系数稳定在1/9~1/8,随沙障规格的增大蚀积系数逐渐减小;障格内风蚀最深点随主风向偏移,障格内与主风向一致的方位风蚀量更大,剖面曲线开口更大;坡顶处凹曲面拟合效果大于坡中和坡底。综上所述,在乌珠穆沁沙地内,风蚀多发生在西北-东南和西-东方向上,且坡顶处形成的凹曲面较稳定,该地区适合布设2.0 m×2.0 m规格PLA沙障,研究结果为PLA沙障在乌珠穆沁沙地防沙工程中的合理应用提供了科学参考。

高寒沙地不同植被修复措施下土壤水分对降雨响应机制

为探究高寒沙地不同植被修复措施下土壤水分对降雨响应机制,更好地发挥其水土保持作用,以青海共和盆地设置3 a的高立式网笼沙障、麦草方格沙障+花棒、麦草方格沙障+柠条、麦草方格沙障+沙蒿和麦草方格沙障+菊芋种植为研究对象。利用2900ET气象站和ECH 2 O,分别对研究区降雨量和各沙障类型下0~140 cm(10、20、40、60、80、100、120和140 cm)土壤含水量进行连续自动监测,选取3种不同等级降雨事件进行研究,分析其土壤水分响应情况和0~60 cm土壤水分补给特征。结果表明:1)2020年8月—2021年8月,研究区降雨主要集中在4—9月,以低频率小雨为主,<2 mm降雨事件占总降雨事件最高(38.98%),贡献率最小(6.12%),各沙障类型按月土壤总蓄水量变化划为缓慢积累期(1—4月)、消耗期(5—6月)、积累期(7—9月)和稳定期(10—12月)且均在8月达到峰值,其中高立式沙障土壤蓄水量最高(4万7563.54 mm),菊芋沙障最低(2万5564.09 mm),其各土层土壤蓄水量的增加量随着土壤深度增加呈现出“减小—增大—减小—增大”变化。2)降雨量<5 mm时,菊芋沙障0~10 cm、花棒沙障及沙蒿沙障0~20 cm土层水分产生波动;降雨量在5~18 mm时,高立式沙障0~10 cm,柠条沙障、沙蒿沙障及菊芋沙障0~20 cm,花棒沙障0~100 cm土层水分产生波动;降雨量>18 mm时,高立式沙障0~10 cm,柠条沙障、沙蒿沙障及菊芋沙障0~60 cm,花棒沙障0~140 cm土层土壤水分产生波动。综合该地区不同植被修图措施下土壤水分对降雨响应情况,建议在5—6月进行修复。

猫头刺盾状移动式固沙障防沙效应风洞模拟试验研究

[目的]猫头刺盾状移动式固沙障是运用仿生学原理,由盾状铁网筛与上方扎制固沙灌木猫头刺(Oxytropis aciphylla)茎叶构成的一种新型固沙障。对猫头刺盾状移动式固沙障的防风固沙效应进行试验,以确定最佳固沙障类型,并揭示其防风固沙机理,为野外工程防沙措施的选择和制定提供理论依据。[方法]通过风洞模拟试验,在6,10,14,18 m/s 4个风速条件下测量了猫头刺盾状移动式固沙障的风速流场,并在10,14,18 m/s 3个风速条件下对该固沙障进行了携沙风吹蚀试验。对照分析了原位自然型与不同类型,不同大小仿生猫头刺盾状移动式固沙障的防风沙效应。[结果](1)气流在经过猫头刺盾状移动式固沙障时速度均会减弱,形成明显的减速区。在6 m/s时,减速沉降区均达到了20 H(H为沙障高度,H=11 cm);随着风速增加,减速沉降区缩小。风速10与14 m/s时,减速沉降区为15 H;且在风速18 m/s时,也能维持15 H的减速沉降区。(2)3种风速梯度下,猫头刺盾状移动式固沙障的平均输沙量是无沙障的13.8%(10 m/s风速),21.1%(14 m/s风速),23.4%(18 m/s风速)。[结论]结构完整,直径更大的猫头刺盾状移动式固沙障具有最好的防风沙效果。该移动式仿生固沙障防风沙效果好,可移动,可组合并可机械化编制,在防治荒漠化、防风固沙领域有广阔的应用前景。

沙障对石羊河下游人工梭梭林生长及其林下植被物种多样性的影响

通过样地调查的方法,对不同材料、不同布设年限沙障区人工梭梭林的生长状态和林下植被的多样性进行了调查研究,结果表明:1)10a稻草沙障、15a玉米秸秆沙障区梭梭株高、冠幅高于同年限其他沙障类型区,15a尼龙网沙障区树高、冠幅最低;2)不同年限不同材料沙障区梭梭枝条发芽指数存在差异性,5a稻草沙障、10a尼龙网沙障的枝条发芽指数显著高于其他沙障类型,枝条发芽指数5a稻草沙障最高,其次为10a尼龙网沙障,20a黏土沙障最低;3)不同年限不同材料沙障林下植被生物多样性指数和盖度存在差异性,10年黏土沙障区辛普森指数为0.50,Shannon-Wiener指数为0.81;15a黏土沙障区Simpson指数为0.51,Shannon-Wiener指数为0.63;20a黏土沙障区Simpson=0.49,Shannon-Wiener为0.86。不同类型沙障林下植被盖度20a尼龙网沙障、20a黏土沙障最高,15a尼龙网沙障次之,10a尼龙网沙障最低。同一年限不同材料沙障中黏土沙障的盖度相对较高。15~20a沙障类型中稻草沙障的盖度最低,稻草沙障相对其他材料沙障不利于林下物种增加。

机械沙障与治沙植物不同配置防风固沙效益研究

机械沙障与植物治沙对治理荒漠化土地、固定活化沙丘、降低荒漠化危害具有重要作用。为了解机械沙障与治沙植物不同配置防风固沙效益,以吐鲁番市高昌区荒漠化土地为研究对象,在研究区内设置4种不同的治理模式,通过试验分析不同治理模式的植物保存率、防风效能、地表粗糙度、风速廓线、输沙量和地表蚀积深度等防风固沙效益指标,对比不同配置模式活化沙丘的治理效果。结果表明:(1)机械沙障对治沙植物的生长起到了良好的保护作用,植物存活率大于80%;草方格沙障在初期对植物的保护作用大于高立式沙障,梭梭初期的生长情况弱于同等沙障保护下的柽柳。(2)4种治理模式均具有良好的防风效益,草方格沙障在0.4 m以下的防风效能优于高立式沙障,在0.4 m以上,高立式沙障的防风效能更好,同等保护条件下的柽柳防风效能优于梭梭;草方格沙障的地表粗糙度大于高立式沙障,柽柳的防风效能优于梭梭。(3)草方格沙障在0.4 m以下的阻沙效益优于高立式沙障,但总体阻沙效益弱于高立式沙障,在相同沙障中,柽柳的阻沙效益优于梭梭;4种治理模式对地表均具有良好的固定作用,草方格沙障优于高立式沙障,沙面形态更加平稳,柽柳对土壤的固定作用优于梭梭。草方格沙障+柽柳的治理模式防风固沙效益最佳。