沙质地表与砾质戈壁风沙运动对比研究——以敦煌莫高窟窟顶风沙运动为例

通过野外观测资料分析,阐明在沙质地表下,风速相当时不同风向风沙流的结构不同,即含沙量影响风沙流结构.一般随着含沙量的增大,各层的绝对输沙量相应增加,相对输沙量在下层增加,上层减少.但也有不一致的情况,本次野外观测就出现了下层减少上层增加的情况.戈壁风沙流结构与沙质地表显著不同,其风沙流结构呈独特的"象鼻"效应,即在一定高度有一个最大输沙量,且这个高度随风速的增大而增加.西北风作用下,自鸣沙山至窟顶输沙量逐渐减少.戈壁具有一定的阻沙效应,风速为7.7 m/s时,每100 m阻沙率达10%左右.沙山前沿固沙带对输沙量起着重要作用,有防护措施与无防护设施相比较,西北风的输沙量可减少95%左右.偏东北风在缺少沙源的情况下,主要以输送为主,偏南风实际输沙量明显小于偏西北风,输沙量由沙源地到窟区逐渐减少.     

浑善达克沙地公路综合防护技术及其效益分析

浑善达克沙地省际通道综合防护体系包括:公路沙害快速治理和沙源控制技术及耐风沙植被建植技术。阻沙带、固沙带改变了风沙流结构,降低了输沙强度,增加了地表粗糙度,有效的起到了削弱风速,阻截流沙,控制沙丘前移,保持地表稳定的作用;建立稳定的耐风沙植被是持久固沙和生物防护的核心;首次大规模使用“固沙网”专利技术产品用于公路快速固沙保苗,实践证明采用固沙网与柳条立式沙障的组合固沙技术对于快速固沙和植被恢复的作用更加显著;并提出了公路沙害快速治理技术体系与配套的技术措施。项目实施过程中3年投入产出比为1∶2.6,通过公路沙害治理工程的实施,稳定防护10年的经济总收益为4.67亿元;如将挖方路堑段砂质陡坡用植物固沙措施代替传统石砌护面墙技术推广至其它工程,效益更为显著。该项目技术研究与工程建设紧密结合,操作性强,能快速有效治理荒漠化地区公路沙害,总结出了沙区公路、铁路沙害的治理模式,对于我国荒漠化治理有推广应用价值。     

乌兰布和沙漠沿黄段不同治理措施的风沙运移特征及其防护效果

为科学治理黄河乌兰布和沙漠沿岸风沙入黄问题,以该河段沿线流沙为对照,开展了麦草沙障、沙柳沙障、葵花杆沙障和梭梭林为代表的工程与植物固沙实验,对不同治理措施下的风速廓线、粗糙度、风沙流结构、防护效果及其相互关系进行了野外观测与室内分析。结果表明:1)各沙障和梭梭林内风速廓线发生改变,近地表风速显著降低,地表粗糙度和摩阻风速显著增加。2)流沙表面输沙量分布随高度增加呈对数递减,90%集中在0~10cm范围,98%分布在0~30m范围内。3)不同措施的输沙率随风速的增加呈增加趋势,但输沙率仅为流沙的1.07%~38.27%,可很好的控制近地表的流沙活动。4)各类固沙措施的实施效果排序葵花杆沙障>梭梭林>沙柳沙障>麦草沙障,控制流沙效果均达到75%以上,对固定流沙均能起到积极作用。综合考虑固沙效果、成本、运输以及使用寿命等,该地区选择葵花杆沙障和梭梭较为合适。该研究结果可为解决风沙入黄问题、完善黄河沿岸风沙防护体系提供参考。     

沙丘移动速度的观测与计算

在沙漠地区研究沙丘上风沙输运和估算沙丘移动速度对防治沙害有实际意义。文献1,2均给出了计算沙丘移动速度的公式,但必须知道相应的输沙率。由于输沙率和当地风速有关而沿沙丘脊线不同高度处有不同的风速,如何把沙丘上各点的风速与受沙丘扰动的“来流”风速关联起来就成为关键问题。本文对5个不同高度沙丘上的风速和输沙率进行多次观测、在详细分析所得数据的基础上给出了风速之间的关联和计算沙丘移动速度的普遍公式,并与实测结果作了比较。     

戈壁、流沙地表风沙流特性研究

通过对戈壁、流沙地表风沙流特性的风洞模拟实验研究,风沙流中的风速廓线分布满足幂函数的形式,其幂指数在0.20左右。对于戈壁地表,在不同风速下,相同高度层含沙量具有很大的相关性,风沙活动层主要集中在距地表20cm范围内;由于沙粒与戈壁地表的砾石发生碰撞,风沙流不再服从对数关系递减,其极值出现的高度随风速的增加而上移,呈现"象鼻效应"。     

砂粒胶结体盖度与床面风沙活动关系的风洞模拟

塔克拉玛干沙漠腹地部分垄间地表发育了一种由众多砂粒胶结而成的大颗粒物质,称为砂粒胶结体(sand cemented bodies,缩写为SCD),其直径达到粗砂级、极粗砂级和砾石级.为研究其对地表风沙活动的影响,以野外采集SCD颗粒为实验材料,对不同SCD盖度下输沙通量垂直分布及输沙率变化进行了风洞实验.结果表明:风沙通量在SCD盖度沙床面表现为指数变化,主要集中在风沙活动底部.同时,随着SCD盖度的增加,总输沙量降低,部分沙量运移到较高层面,输沙率随SCD盖度变化可分成3个梯度区域,且曲线斜率反映不同风速等级下,SCD盖度对地表沙物质沉积过程的影响.当SCD盖度小于10％时,风沙活动强烈且风速在输沙过程中起主导作用.当SCD盖度在10％ ～ 40％时,随着SCD盖度增加输沙率降低,盖度对地表风沙活动的影响更为明显,特别是对近地表风沙活动的影响.当SCD盖度大于40％时,床面风沙活动趋于稳定,输沙率变化微弱,随SCD盖度变化输沙率保持不变,沙床面不易受侵蚀.因此,砂粒胶结体覆盖沙床面能够有效降低地表风蚀,且在一定盖度下还能捕获流沙颗粒.塔克拉玛干沙漠腹地丘间地天然发育的SCD对于地表风蚀过程具有重要的影响,可作为一种新型固沙材料进行开发.     

塔里木沙漠公路防沙体系建设几个问题的探讨

沙害主要取决于两个系统因素的共同作用 :动力系统—风力和响应系统—下垫面状况。塔里木沙漠公路沿线风沙地貌形态类型复杂多样 ,沙源充足 ;起沙风频数高 ,作用时间长 ,防沙难度极大。已建成的高立式芦苇阻沙栅栏和 1 m× 1 m半隐蔽芦苇草方格固沙沙障结合的“阻固”体系 ,有效控制了沙害 ,但也存在一定问题。定位观测表明 ,沿线起沙风和输沙方向集中于 NE、ENE、E三个方向 ,占 46%～ 68% ,从理论上说 ,应加大风侧 (路东侧 )防护力度 ,而实际上固沙带内部强烈的风蚀与沙埋过程 ,使其有效年限与设置宽度关系不明显 ,宜采取窄宽度勤维修原则 ,上风侧宽度控制在 3 0 m～ 40 m,每 3～ 4年更新一次并及时维修。下风侧可不设置高立式沙障 ,固沙带宽度控制在 1 0 m～ 1 5 m为宜 ;高立式沙障与半隐蔽方格沙障前沿之间空留宽度控制在 8H以内较为适宜。依沙害程度 ,以单一原状芦苇固定沙障、复膜沙袋阻沙体活动沙障及固定沙障与活动沙障有机结合加强前沿阻沙力度 ;不同沙害部位设置不同规格不同高度的半隐蔽方格沙障、固化路肩边坡创造输沙断面等技术 ,形成立体防护体系 ,足以控制沙害。     

巴丹吉林沙漠拐子湖地区贴地层风速廓线和风沙流结构特征

野外监测试验表明：自由风和风沙流廓线拟合虽都以Z=A·exp(-X/T)+Z₁形式分布,但在风沙流中拟合系数更高;风沙流结构中,在20 cm以下随着高度的增加,各高度的输沙率百分比、含沙浓度、运动颗粒能量都呈增大趋势;20 cm以上随高度增加,各高度输沙率百分比变小,输沙率占总输沙率的51%左右,含沙量主要集中在离地面20 cm以内;风沙流在垂直方向上,高度与含沙平均粒径呈负相关,风速与含沙平均粒径变化呈正相关。这些结论对拐子湖地区防风治沙有重要的指导意义。     

塔克拉玛干沙漠北缘荒漠过渡带风沙流结构特征分析

利用多种集沙仪,通过野外实时输沙观测,对塔克拉玛干沙漠北缘荒漠过渡带的地表风沙流特征进行了分析,结果表明：① 100 cm高度范围内,总输沙量的47.3%分布在30 cm高度内,这一比例小于前人的研究结果;输沙量随高度的变化比较符合幂函数分布。② 风沙流输沙的粒径以细砂、极细砂与粉砂为主,各高度层所占比例均达99%以上;风沙流输沙平均粒径随高度增加而减小,沙尘的含量随高度增加呈现“象鼻”状分布。③ 风沙流中贴地层风速廓线受风沙相互作用的影响,不再符合对数分布,更加符合幂函数u=az^b分布。     

阿拉尔-和田沙漠公路机械防沙体系内风沙沉积的粒度特征

对阿拉尔-和田沙漠公路沿线机械防沙体系内外地表风沙沉积物进行了系统采样,运用沉积物的粒度分析方法,以流沙区为对照,对比分析了沙漠公路机械防沙体系中阻沙区和固沙区内风沙沉积物的粒度特征。研究发现:(1)从流沙区到阻沙区,再到固沙区,风沙沉积物的粗砂、中砂含量逐渐降低,极细砂、粉砂含量逐渐增加,阻沙区内风沙沉积物的平均粒径减小了31.0%,固沙区内风沙沉积物的平均粒径减小了47.2%。(2)流沙区、阻沙区和固沙区内蠕-跃截点的平均值分别为1.296Φ、1.647Φ、2.188Φ,跃-悬截点的平均值分别为3.893Φ、4.089Φ、4.292Φ,各运动组分的截点均向细端偏移,并且各运动组分的含量也发生了变化,阻沙区和固沙区内蠕移组分含量分别降低了2.378%、5.837%,悬移组分含量分别增加了4.26%、4.294%。(3)固沙区沙粒的分选性最好,偏度SK的平均值为-0.059,表现为近对称,峰态KG为0.939-0.987,表现为中等峰态。     

塔里木沙漠公路风沙危害形成研究

塔里木沙漠公路南北横贯塔里木盆地 ,全长 5 6 2km ,其中近 80 %的路段穿行于塔克拉玛干沙漠之中 ,是世界上穿越流动沙漠最长的等级公路 ,因而风沙危害是制约沙漠公路正常运行的主要病害。研究表明 ,1)沙漠公路沿线风力强劲 ,沙丘形态各异 ,地表组成物质松散 ,为风沙危害形成提供了动力条件和奠定了物质基础 ;作为风沙危害的受灾对象 ,沙漠公路防沙体系结构以及公路纵横断面也直接作用于风沙危害形成过程 ;2 )沙漠公路风沙危害主要源于防沙体系沙物质的侵入和防沙体系内部因近地面气流变异而产生的风蚀与堆积 ;目前沙漠公路风沙危害的主体是防沙体系 ,危害的形式包括风蚀、风沙流滞留积沙和沙丘前移压埋。     

最近10年来新疆风沙地貌研究进展

最新研究表明,塔克拉玛干沙漠风沙活动与气温变化呈现"风热同步"现象,虽然其风况类型多样,但整个沙漠处于低风能环境。不同沙丘部位上风沙流输沙量的对数与高度之间表现为线性关系。当气流与沙丘走向斜交时,两侧相同部位输沙率的差异不大,这是线形沙丘保持其动力形态平衡的主要原因之一。古尔班通古特沙漠也处于复合型低能风环境之中,冬季积雪和冻土对沙漠地表形成有利的保护,有效植被覆盖和生物结皮是沙面整体处于稳定状态的重要因素,风沙活动仅存在于沙垄顶部和两坡上部。沙漠中生物结皮发育、种类丰富,其类型和分布具有明显的景观异质性特征。天山北坡和昆仑山北坡的黄土研究揭示,新疆两大沙漠从中更新世以来出现明显的干旱化,沙漠逐步扩大至今天规模。此外,塔里木沙漠公路和古尔班通古特沙漠输水明渠沿线的风沙危害具有明显的时空分异特点。因此,根据工程设施所处地形与地貌部位,可定性判断风沙危害类型与强度,进而确定防治方案和措施。今后新疆风沙地貌学研究应注重研究领域的拓展、研究方法的突破和实验手段的创新3个方面。     

Grain size distribution at four developmental stages of crescent dunes in the hinterland of the Taklimakan Desert,China

Although scientists have performed many studies on crescent (barchan) dunes in the Taklimakan Desert,few studies reported the changes in grain size at different development stages of crescent dunes.In order to evaluate the changing trends of surface sediment grain size with dune development,we investigated the grain size characteristics at four developmental stages (oval sand pile,shield dune,incipient crescent dune and mature crescent dune) of crescent dunes by measuring the morphology of sand dune and observing the near-surface wind regime.The dunes have developed in a wide inter-dune corridor between high compound longitudinal ridges in China's Taklimakan Desert.The surface sediments at four developmental stages of the crescent dunes were primarily composed of fine sands,followed by very fine and medium sands.Mean grain sizes ranged from 2.8 to 3.1 φ,with a unimodal distribution.The sands were moderately well-sorted,their distribution varied from platykurtic to very platykurtic,and symmetrical or skewed towards the fine particles.From oval sand piles through shield and incipient crescent dunes to mature crescent dunes,incipient grain size gradually increased,particles became finer,sorting became better,kurtosis and skewness increased.Grain sizes on the surface layer became coarser upwards from the toe of the windward slope and then became finer towards the bottom of the leeward slope.We found that the coarsest particles at different positions at the four developmental stages were different.The coarsest particles were distributed at the top of the oval sand piles and shield dunes,versus at the middle of the windward slope of the incipient and mature crescent dunes.Correlations between the mean grain size and other grain size parameters showed that as mean grain size became finer,sorting became better and kurtosis became wider,but skewness changed only slightly.In addition,grain size variation in the surface sediments correlated with the movement speed of the dunes in the study area.In the open ground among tall-complex longitudinal ridges in the hinterland of the Taklimakan Desert where aeolian environment is characterized by comparatively strong wind and unsaturated sand flow,faster dune movement corresponded to coarser grain size.     

塔克拉玛干沙漠腹地复合纵向沙垄间地沙丘空间分形及稳定性

塔克拉玛干沙漠的大地貌格局是高大复合沙垄和宽广垄间地相间分布,而垄间地是研究简单沙丘发育过程的良好试验场地。基于Google Earth影像,以分形理论为基础,对塔克拉玛干沙漠腹地复合纵向沙垄区垄间地上覆沙丘在主导风方向上的分形特征进行了分析,结果表明：① 垄间地沙丘形状指数（面积-周长关系）的标度-频度双对数关系非常显著,分形关系客观存在,并且不受统计时所用标度的影响;② 垄间地各类沙丘的分维值存在差异,其中,饼状沙堆和沙片分维值最大（1.337）,新月形沙丘次之（1.170）,简单线性沙丘最小（1.087）;③ 垄间地沙丘分维值的空间差异较大,在1.187~1.656,其分维数：背风坡脚（1.24）＜垄间地中部（1.40）＜迎风坡脚（1.50）,变异系数为0.106;④ 垄间地沙丘稳定性指数与分维值的空间分布相反,即背风坡脚（0.26）＞垄间地中部（0.16）＞迎风坡脚（0.10）;⑤ 垄间地沙丘分维值空间差异主要与沙丘发育程度有关,其中,风信是动力基础,沙源是物质基础。在流动沙漠,沙丘分形维数可以作为反映其风沙环境特征的定量指标。     

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.     

Effects of wind guide plates on wind velocity acceleration and dune leveling: a case study in Ulan Buh Desert,China

The areas used to be covered by shifting sand dunes have been reclaimed rapidly in recent years. However, it is a challenge to reclaim high sand dunes because it is rather costly to level the high dunes to gentle arable lands. In this study, a wind guide plate was used to change the characteristics of natural wind to level the sand dunes. The use of wind energy could significantly increase the efficiency of dune leveling and decrease the cost. Low wind velocity is a typical characteristic in Ulan Buh Desert of China where the average wind speed is much lower than the threshold velocity for sand movement. The experiment of this study was conducted to accelerate the wind velocity by a wind guide plate to level a sand dune. Results show that the threshold velocity for sand movement is 3.32 m/s at 10 cm above the sand surface in Ulan Buh Desert. A wind guide plate set at an angle less than 50° could significantly increase the wind velocity. The wind velocity could be accelerated up to the threshold velocity for sand movement behind a plate when the plate is at the angles of 20°, 25°, 35° and 40°. The most significant acceleration of wind velocity appears at 1.5 and 3.0 m behind the plate with an angle of 25°. An obvious wind velocity acceleration zone exists behind the wind guide plate when the angles are at 25°, 35°, 40° and 45°, with the most obvious zone under the angle of 45°. The results also show that the total amount of sand transferred over the experimental period increased by 6.1% under the effects of wind guide plates compared to the sand moved without wind guide plates. The results of the study will provide theoretical and practical supports for desert management in sand dune areas.     

Wind regimes and associated sand dune types in the hinterland of the Badain Jaran Desert,China

Wind controls the formation and development of sand dunes. Therefore, understanding the wind regimes is necessary in sand dune research. In this study, we combined the wind data from 2017 to 2019 at four meteorological stations (Cherigele and Wuertabulage stations in the lake basins, and Yikeri and Sumujilin stations on the top of sand dunes) in the hinterland of the Badain Jaran Desert in China, with high resolution Google Earth images to analyze the correlation between the wind energy environments and dune morphology. The results of data analysis indicated that both the wind direction and sand drift intensity exhibited notable spatial and temporal variations. The highest level of wind activity was observed in spring. Northwesterly and northeasterly winds were the dominant in the Badain Jaran Desert. At the Cherigele, Wuertabulage, and Yikeri stations, the drift potential (DP) was below 200.00 vector units (VU). The wind energy environments in most areas could be classified as low-energy environments. The resultant drift direction differed at different stations and in different seasons, but the overall direction was mainly the southeast. The resultant drift potential (RDP)/DP ratio was greater than 0.30 in most parts of the study area, suggesting that the wind regimes mainly exhibited unimodal or bimodal characteristics. Differences between the thermodynamic properties and the unique landscape settings of lakes and sand dunes could alter the local circulation and intensify the complexity of the wind regimes. The wind regimes were weaker in the lake basins than on the top of sand dunes. Transverse dunes were the most dominant types of sand dunes in the study area, and the wind regimes at most stations were consistent with sand dune types. Wind was thus the main dynamic factor affecting the formation of sand dunes in the Badain Jaran Desert BJD. The results of this study are important for understanding the relationship between the wind regimes and aeolian landforms of the dune field in the deserts.     

塔克拉玛干沙漠南缘策勒县沙丘移动规律的初步研究

关于塔克拉玛干沙漠南缘策勒县的沙丘移动速度,从已经发表的材料来看,存在着两种不同的判断。一种认为“塔克拉玛干沙漠南缘策勒、和田之间……沙丘移动强度也不大”,并且把策勒绿洲西南沙丘移动列为“快速的类型(6—10米/年)”;另一种判断,策勒县“五十年代以来,在县城西北的沙漠,每年前移蔓延80—100米,1957—1980年在策勒乡、     

巴图湾水库风沙入库量的估算

风沙入库给干旱、半干旱地区的水库带来了严重的填淤危害。本文通过对内蒙古乌审旗南部巴图湾水库岸边流动沙丘不同部位风速与风沙流的同步观测,计算出库岸流动沙丘表面的平均输沙率。利用巴图湾水库1986~2005年9月份的5期TM遥感影像统计出水库两岸受不同风向影响的流动沙丘断面的平均长度,结合巴图湾水库附近乌审旗河南乡气象站1985~2004年的气象资料,统计出不同风向大于起沙风的风速年均持续时间,初步计算出巴图湾水库的年均入库风沙量。结果表明:(1)巴图湾水库的年均入库风沙量为3.65万t,其中西岸风沙入库量为3.55万t,东岸为0.10万t。西岸风沙危害最为严重,是治沙工作的重点。(2)巴图湾水库的风沙入库具有明显的时间性和方向性。受季风气候的影响,风沙入库的方向会随着风向的变化而改变。东南风与西北风是造成东西两岸风沙入库的主要风向。西北风对风沙入库量的贡献最大。(3)在大于起沙风的风速中,5~12 m/s风速段是风沙入库的主要风速。当风速中7 m/s以上的风速持续时间有一个较小的增加时,入库风沙量将会有一个巨大的增加。(4)库岸半固定沙丘的风沙入库,降尘和风水复合侵蚀引起的库岸坍塌也是入库风沙量的重要组成部分。因此,巴图湾水库的实际年入库风沙量应该大于3.65万t。