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1.
MAO Donglei LEI Jiaqiang ZENG Fanjiang RAHMUTULLA Zaynulla WANG Cui ZHOU Jie 《中国地理科学(英文版)》2014,(6):658-673
The oasis-desert ecotone is a fragile ecological zone that is affected both by oasis and desert conditions. To understand the impact of the differences in wind power, and the influence of wind erosion and deposition on the ecotone, meteorological data and con- temporaneous wind erosion and deposition data were collected on the southern margin of Tarim Basin with serious sand-blown hazards. The wind velocity, average wind velocity, sand drift potential （DP）, resultant sand drift potential （RDP）, and sand transportation rate decrease significantly and successively across four landscape types with increasing vegetation coverage （VC）. Flat surfaces and areas of shifting sandy ground experience intense wind erosion with fast movement of mobile sand dunes; semi-fixed sand areas experience ex- tensive wind deposition but only slight wind erosion; and fixed sand areas experience only slight wind erosion and deposition. Volume of wind erosion on bare newly reclaimed farmland is up to 6.96 times that of bare shifting sandy ground. Wind erosion volume per unit area and VC follow an exponential function relationship in natural conditions, while wind deposition volume per unit area does not conform to any functions which has close relationship with vary topography and arrangement patterns of vegetation besides for VC. The results indicate that the volume of wind erosion has a close correlation with VC, and different types and distribution patterns of topog- raphy and vegetation also profoundly influence the wind deposition volume in the field, and underground water tables in different land- scape types control the plant community distribution. Keywords： wind erosion; wind deposition; oasis-desert ecotone; vegetation coverage （VC）; topography; Cele County 相似文献
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Field measurements of influence of sand transport rate on structure of wind-sand flow over coastal transverse ridge 总被引：2，自引：0，他引：2
The structure of wind-sand flow under different total sand transport rates was measured with field vertical anemometer and sand trap on the crest of typical coastal transverse ridge in Changli Gold Coast of Hebei Province, which is one of the most typical coastal aeolian distribution regions in China and famous for the tall and typical coastal transverse ridges. The measurement results show that, on the conditions of approximate wind velocities and same surface materials and environments, some changes happen to the structure of wind-sand flow with the increase of total sand transport rate on the crest of coastal transverse ridge. First, the sand transport rates of layers at different heights in the wind-sand flow increase, with the maximum increase at the height layer of 4-8cm. Second, the ratios of sand transport rates of layers at different heights to total sand transport rate decrease at the low height layer （0-4cm）, but increase at the high height layer （4-60cm）. Third, the distribution of the sand transport rate in the wind-sand flow can be expressed by an exponential function at the height layer of 0-40cm, but it changes from power function model to exponential function model in the whole height layer （0-60cm） and changes into polynomial function model at the height layer of 40-60cm with the increase of total sand transport rate. Those changes have a close relationship with the limit of sand grain size of wind flow transporting and composition of sand grain size in the wind-sand flow. 相似文献
4.
中国北方典型农牧交错区的土壤风蚀危险度研究 总被引：1，自引：0，他引：1
土壤风蚀及其引发的土地退化、沙化和沙尘暴是中国北方严重的环境问题之一。通过定量评估中国北方典型农牧交错地区土壤风蚀危险程度,可以为区域生态环境的保护和生态修复提供科学支撑。本文基于文献调研、兼顾数据的可获得性,建立了包括风场强度、植被覆盖率、地形起伏度、土壤干燥度等因子在内的风蚀危险程度评价指标体系。同时,依据遥感参数反演和地面气象观测数据,在地理信息系统技术支持下,形成了上述因子的空间分布数据。另外,利用层次分析方法,构建土壤风蚀危险度评价模型,得到研究区土壤风蚀危险度的空间分布。最后,结合研究区土地利用数据,探讨了风蚀危险度空间分布格局的自然环境和土地利用背景。研究表明:研究区土壤风蚀极险型区域面积为1.47×104km2,强险型区域面积为6.09×104km2,危险型区域面积为3.47×104km2,轻险型区域面积为3.45×104km2,无险型区域面积为2.19×104km2。本区土壤风蚀危险度呈现出从东南到西北逐渐增强的趋势,这与区域的植被、气候,以及土地利用的空间格局具有内在的有机联系。 相似文献
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《中国海洋大学学报(英文版)》2021,20(5)
A flume experiment was conducted to investigate the restratification of liquefied sediment strata under a wave load with the focus on the interbedded strata of coarse and fine sediments formed in estuarine and coastal areas. The aim of this research was to study the characteristics and processes of liquefied sediment strata in terms of wave-induced liquefaction. In the experiment, the bottom bed liquefied under the wave action and the liquefied soil moved in the same period with the overlying waves, and the track of the soil particles in the liquefied soil was an ellipse. The sand layer consisting of coarse particles in the upper part, settled into the lower silt layer. The sinking of coarse particles and upward migration of the fine particles of the lower layer induced by liquefied sediment fluctuations are the likely reasons for sedimentation of the sand layer in liquefied silt. 相似文献
6.
QI Jianhua LI Xianguo FENG Lijuan ZHANG Manping 《中国海洋大学学报(英文版)》2006,5(1):85-90
Total suspended particulate （TSP） samples were collected at three sites along the coast of Qingdao, China, before and during a major dust storm in March, 2002. For comparison, PM10（particulate matter with aerodynamic diameters less than 10μm） samples were collected at one of the three sites. The morphological observation and compositional analysis of bulk and individual particles were performed by using scanning electron microscopy equipped with an energy dispersive X-ray system （SEM/EDX） for the TSP and PM10 samples. The results showed that the particles of different kinds of morphology had different elemental compositions, but the particles of similar morphology did not always have the same elemental composition for non-dust samples. The morphology and composition of non-dust particles were different at different sites. The fractal and spherical particles existed mainly in the coarse fraction for non-dust samples, while in the fine mode （〈 10μm） there were floccules formed by fine particles flocking together and containing crustal elements. Compared with the non-dust particles, the dust particles were more homogeneous in terms of morphology, particle size and composition. Particles with irregular shapes and well-distributed sizes dominated in the dust samples, containing crustal elements such as Mg, A1, Si, Ca, Fe, etc. The high sulfur content indicated that homogeneous and heterogeneous reactions took place on the surfaces of the dust particles in the specific environment of Qingdao. 相似文献
7.
Dambreak-induced bed scouring may undermine the foundation of bridge piers and other structures, and that destruction can
pose a serious threat. Consequently, this paper aims at exploring the mechanisms of scouring and armoring. Firstly, the incipient
velocity for nonuniform sediment particles was studied, and a formula was derived based on the angle of repose of nonuniform
sediment. The results showed that the mechanism of incipient motion for sand and fine gravel differed from that for coarse
gravel and cobbles. Also, comparison between experimental and field data shows that the results from the proposed formula
agree well with those observed for all conditions. Secondly, a birth-death, immigration-emigration Markov process was developed
to describe the bed load transport rate associated with scouring and armoring. The comparison between experimental data and
computed results shows that our model can predict the bed load transport rate, although there may be some limitations, the
chief of which is that there are many variables in the model to be determined through experiment. This makes its application
in river engineering inconvenient. 相似文献
8.
Landslides & debris flows formation from gravelly soil surface erosion and particle losses in Jiangjia Ravine 总被引：1，自引：1，他引：0
Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical properties of the gravelly soils are affected by the content of coarse grain, fine particles, and their adhesive states. These Properties can be verified by laboratory unconsolidated undrained triaxial tests with grain size less than 5 mm and by large scale direct-shear tests with original grain content. Fine particles of the loose gravelly slopes are released under rainfalls, alternated the structures and mechanical properties, even affected the slope stability. There are a series of large scale direct-shear tests with different coarse grain contents to study the influence of fine particles releasing and migration, results showed the strength behavior of the gravelly soils were affected by the coarse grain content （5） and the inflection coarse grain contents. In order to study the erosion features of the gravelly soil slopes on rainfall conditions and the slopes stability alteration, we had carried out one sort of artificial rainfall local and model experiments, the runoff sediment contents were monitored during the experiments. Result showed that the shapes of the slopes surface transformed periodically, runoff sediment contents were divided into five phases according to the experiment phenomena, runoff sediment contents maintained downtrend during the rain time and the downtrend was obviouslyinterpreted by one descend belt no matter the rainfall intensity and the slope angels. Particle size analysis released the deposit on the slope surface lost almost all of the clay, most of the silt and sand after the experiments, this meant the fine particles releasing, migration and accumulation process on condition of rainfall resulted in the instability factor of the slopes even induced landslide or debris flow. 相似文献
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There are two different dust storms in Northeast China, normal dust and alkali dust, from Kerqin sand land and Songnen saline land. As well as visible damages of the dust storms, there are some invisible influences. The authors provide evidences that the bacteria carried by dusts from remote area should not be ignored, but the damages of the alkali dusts are still not clear. 相似文献
10.
Dust storms in Northeast China become more se-rious in recent years due to the global warming and local land use and cover change (LUCC) around the sand lands in western and northwestern Jilin Province. Field investigations and urban testing re-vealed that the amount of dusts brought by dust storm reaches a higher level in the past two years. According to an experiment on the “mud-snow”in April, 2000 and an observation in March, 2002, the dusts coming from the western Jilin and fall… 相似文献
11.
《山地科学学报》2020,17(8):2023-2034
Desert-oasis ecotones are boundary areas between oases and desert ecosystems.Large efforts to control sediment and stabilize these boundaries depend on understanding sedimentary processes,especially aeolian transport and deposition.Previous studies on aeolian sediment deposition have focused primarily on a single land surface type or a single engineering approach.Few studies have considered deposition in a multi-layer oasis protective system.A complete oasis protective system consists of an outer bare sand area,a sand barrier zone,a shrub and herbaceous plant zone,and a farmland shelter zone.This study used sedimentary analysis to quantify grain-size characteristics in samples from the four land surfaces under different types of weather conditions in the Gelintan oasis of the Tengger Desert,the fourth largest desert in China.The results showed that aeolian sediment deposition decreased from the outer bare sand area through the oasis protective system and into the interior.The four land surface types showed significant differences in deposition volume(P 0.05).Deposited sediment showed gradual decrease in dominant grain-size from sand to silt,but sediment deposited during dust weather contained a larger coarse-grained fraction.From the outer desert to the inner oasis,transport mechanisms shifted from saltation(sand) to suspension(silt and smaller) in non-dust weather.During dust weather,deposition primarily occurs from near-surface aeolian sand transport with saltation.Sediment sorting decreased from exterior to interior zones of the protective system while skewness and kurtosis showed no significant change(P 0.05).These results can help inform strategies for stabilizing and protecting desert-oasis ecotones in this region and other localities. 相似文献
12.
《山地科学学报》2019,(11)
Wind and sand control are important factors in combating desertification and protecting oases. An oasis protective system can provide these benefits, but quantitative research on protection effects has been lacking to date. This researchdescribes an oasis protective system in the southeastern border of the Tengger Desert. The system consists of a sand barrier belt, a shrub and herbaceous plant belt, and a farmland shelter belt.The system was compared to a bare dunes area as the control zone. The study investigated windproof effect,sediment transport, and erosion through fieldobservations. Results showed that the roughness of the shrub and herbaceous plant belt, farmland shelter belt, and sand barrier belt were increased compared with bare dunes. The shrub and herbaceous plant belt provided the highest windproof effect values for the same wind velocity measurement height, and the windproof effect values for different protective belts were as follows: shrub and herbaceous plant belt farmland shelter belt sand barrier belt. The sand barrier belt provided effective wind and sand control at heights from 0 to 50 cm above the ground. The total sediment transport for each protective belt is as follows: bare dunes sand barrier belt shrub and herbaceous plant belt farmland shelter belt. The sediment transport decreased exponentially as the height increased. In the bare dunes and protective systems, the sediment transport is mainly within 30 cm of the ground surface. The wind erosion intensity for this protective system was as follows: bare dunes sand barrier belt shrub and herbaceous plant belt farmland shelter belt. This research offers quantitative evidence for how oasis protective systems can effectively intercept sand and prevent erosion in oases. The results of this study can be applied in similar regions. 相似文献
13.
By taking into consideration the effects of ocean surface wave-induced Stokes drift velocity U,w and current velocityU,c on the drag coefficient,the spatial distributions of drag coefficient and wind stress in 2004 are computed over the tropical andnorthern Pacific using an empirical drag coefficient parameterization formula based on wave steepness and wind speed.The globalocean current field is generated from the Hybrid Coordinate Ocean Model (HYCOM) and the wave data are generated from Wave-watch Ⅲ (WW3).The spatial variability of the drag coefficient and wind stress is analyzed.Preliminary results indicate that theocean surface Stokes drift velocity and current velocity exert an important influence on the wind stress.The results also show thatconsideration of the effects of the ocean surface Stokes drift velocity and current velocity on the wind stress can significantly im-prove the modeling of ocean circulation and air-sea interaction processes. 相似文献
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裂缝是断溶体油藏的重要渗流通道,随着地层流体的采出,裂缝将发生闭合,其在地应力作用下的闭合规律对于储层渗透率具有重要影响。采集碳酸盐岩岩样,通过巴西劈裂实验制备裂缝试件,构建基于CT扫描灰度图像的裂缝变形分析方法,通过加压和卸压试验,研究裂缝在被不同填充物填充条件下的闭合规律,裂缝的闭合情况采用岩心渗透率和裂缝开度综合表征,以此研究裂缝填充物性质对裂缝闭合规律的影响。研究结果表明:随着围压的增大,裂缝开度和试件渗透率均逐渐降低;填充物延展性越强,裂缝在压力作用下闭合越明显,渗透率降低幅度越大;对于同样被石英填充的裂缝,不同的填充方式下裂缝闭合规律不同,对于裂缝的支撑效果,单层细砂>厚层细砂>中砂细砂混合（结果）。研究成果可为认识不同矿物填充裂缝在地应力作用下的闭合规律提供参考。 相似文献
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Lee M. Ock Park S. Jin Kang T. Soon 《中国海洋大学学报(英文版)》2006,5(3):219-227
1Introduction GamakBay,anegg shapedseasurfaceareaofap proximately112km2,isasemi enclosedshallowwaterareawithameandepthof9mandhasbotheastandsouthchannelstoreceiveseawaterfromoutside(seeFig.1).Similarscalesoftidalwavesalmostsimultane ouslyenterorexitthrough… 相似文献
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风场反演中距离圈上速度退模糊方法研究 总被引：3，自引：0，他引：3
在深入分析速度模糊的特点后,根据在距离圈上不模糊点到模糊点的不连续性,以及对模糊跳变处风速差和最大不模糊速度间关系的判定,从零方位开始在距离圈上逐点进行速度模糊的判定,并引入模糊标记的形式以确定退模糊处理的区间.然后通过实例分析,证明了方法的可用性和正确性.最后利用经过该方法处理的低仰角基本速度资料成功反演了雷达风场. 相似文献
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本文提出定时观测整数风资料正确地用于大气稳定度分类的1/2计数修正方案,成都、重庆各十年的统计结果表明:该修正方案的统计结果与国家标准规定的自记风统计结果十分吻合,从而使整数风速能替代自记风速用于大气稳定度统计,而不带来多大误差。 相似文献
18.
Serious desertification caused by human activity and climate change, in addition to water loss and soil erosion related to arsenic sandstone in the Mu Us Sandy Land, lead to severe scarcity of soil and water resources, which causes worse local agricultural conditions accordingly. Many physical properties of arsenic sandstone is complementary with that of sand, arsenic sandstone is therefore supposed to be blended to enhance water productivity and arability of sandy land. Container experiments are carried out to study the enhancement of water holding capacity of the mixture, the blending ratio of arsenic sandstone and sand, and the proper size of the arsenic sandstone particles, respectively. The results of the experiments show that particle size of 4 cm with a ratio of 1 ： 2 between arsenic sandstone and sand are the proper parameters on blending. Both water content and fertility increase after blending. Water use efficiency in the mixture is 2.7 times higher than that in sand by the water release curves from experiments. Therefore, a new sand control and development model, including arsenic sandstone blending with sand, efficient water irrigation management and reasonable farming system, is put forward to control and develop sandy land so that water-saving agriculture could be developed. Demonstration of potato planting about 153.1 ha in area in the Mu Us Sandy Land in China indicates that water consumption is 3018 m3/ha in the whole growth period. It means that about 61% of irrigation water can be saved compared with water use in coarse sand without treatment. Recycle economic mode and positive feedback of sand resource-crop planting-soil resource are constructed, which changes sand into arable soil and make it possible to develop water-saving agriculture on it. The proposed model will be helpful for soil-water resources utilization and management in the Mu Us Sandy Land. 相似文献
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沈阳市第四纪沉积物分布广泛，北东薄、南西厚。沉积物类型基本为多层砂土复合结构：地表仅有一层较薄的粘土层，其下为较厚的多层递变的细中砂、粗砂、砾砂、圆砾或卵石层。各土层工程地质性质良好，沈阳市区可适合建筑各种类型的建筑物，选择箱形基础形式及桩基础形式较为合适。 相似文献
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SahelbioclimaticzonecrossNorthAfricabe-tweenl7oNandl3"Nborders,theSaharaDeserttothenorthandtheSudansavannatothesouth,beinganimportantfragileecologicalzoneintheworld.SincethesevereSudano-Saheliandroughtof1968-l973sandydesertificationhasresultedinaverymiserableconse-quencestolocalpeople,asaSahelcountryinwestAhica,theRepublicofMaliisoneofthecountriesmostseverelyaffectedbydroughtanddesertification,AccordingtotheinvestigationsoftheexpertgroupoftheLanzhouInstituteofDesertResearch,theChineseA-… 相似文献