塔克拉玛干沙漠南缘绿洲沙物质粒度特征

运用沉积物的粒度分析方法，研究了塔克拉玛干沙漠南缘绿洲不同类型沙样的粒度参数、粒度频率分布、平均粒径对标准差特性图等粒度特征及其空间关系，为查明沙源物质的性质和风力作用状况，分析风沙运动及风沙地貌形成，建立绿洲防护体系提供依据。     

Transient loading-related settlement of a square foundation on geogrid-reinforced sand

Summary Laboratory model test results are presented that determine the effectiveness of using layers of geogrids as reinforcement in sand to reduce the settlement of square surface foundations subjected to transient loading. The model tests were conducted with only one type of geogrid at one relative density of compaction of sand. The maximum intensity of the transient load applied always exceeded the static ultimate bearing capacity of the foundation when supported by unreinforced sand. The settlement reduction factors for various depths of reinforcement have been determined.     

风沙动力与风沙工程学─—国外发展趋势和我们的任务

风沙动力与风沙工程学当前研究的热点─—主要反映在加深对风沙现象的理解、风沙灾害防治与资源开发三个方面出发，提出了我国在风沙运动力学、土壤风蚀、土地沙漠化的动力机制与过程、风沙地貌形成发育规律、风沙沉积学特征及其形成机制、沙尘暴形成机制以及风沙灾害防护工程技术原理等六个方面的研究建议。     

Dunes on the skeleton coast,Namibia (South West Africa): Geomorphology and grain size relationships

Simple, and locally compound, transverse and barchanoid dunes dominate the 2000 km² Skeleton Coast dunefield in northwestern Namibia/South West Africa. Dune height and spacing are closely correlated (r = 0-89) and decrease across the dunefield from southwest to northeast, with an accompanying change from transverse to barchanoid ridges and ultimately barchans. The dunes are aligned transverse to the dominant strong south and south southwest onshore winds. Alignment patterns indicate that surface roughness changes between coastal plain and dunes cause dune-forming winds to swing to the right over the dunes, but resume their original direction beyond. Grain size and sorting vary at three scales: the dune, the dune landscape and through the dunefield. Overall the sands, derived from three localities by deflation from beaches supplied by vigorous longshore drift, become progressively finer and better sorted across the dunefield paralleling changes in dune height and spacing. A statistically significant relationship (r = ?0?65) was established between dune spacing and the phi grain size of the coarser fraction of the dune sands, demonstrating the importance of the protective effects of coarse grains, and suggesting that the morphometry of simple transverse dunes may be controlled by the scale of turbulence associated with the threshold wind speed required to move the coarsest fraction of the dune sand.     

A test of granulometric control of desert dune geometry

I. G. Wilson's hypothesis of coarse-tail grain-size control of dune spacing was derived from three dunefields in the Sahara and, although it was supplemented by measurements of spacing from other parts of the world, the grain-size data come only from North Africa. In this paper the hypothesis is tested in the Australian dunefields. Australian dunes do not form separate categories on a P₂₀/s (twentieth percentile/spacing) plot and, when placed on Wilson's diagram, the Australian data form a continuum between dunes and draas. Ripples maintain their identity, suggesting that the average saltation length of sand controls ripple wavelength while dunes and Wilson's draas are formed by secondary flow of some kind. In Australia the spread of data on the P₂₀/s diagram indicates that grain-size is not the prime control on s. Data from Australia and the Sahara indicate that direct linear relationships between s and h (dune spacing and height means respectively for blocks of dunes) occur but they have different slopes in different areas. These differences possibly reflect variations in vegetation and substrate as well as differences in wind regime. The separation of dunes from draas in the Sahara reflects the greater role of grain-size in an area where coarse grains frequently occur in dune crests. The relative paucity of coarse grains in Australian dune crests may reflect the fine-grained alluvium from which the dunes are derived. These differences may be ascribed to differing topography in Australia and the Sahara.     

Dune formation on the humid tropical sector of the North Queensland Coast,Australia

Several previous attempts have been made to explain the apparent poor development of coastal dunes in the humid tropics in terms of lack of wind energy, failure of sand supply to the shoreline, excessive climatic wetness, salt crust formation on beaches, and the character of tropical back-beach vegetation. However, recent published reports indicate that coastal dune occurrences are more common in the humid tropics than was formerly thought, throwing suspicion on the idea that environmental conditions militate against dune formation in these areas as a whole. Evidence from the humid tropical sector of the North Queensland coast suggests that the poor development of dunes in this area primarily reflects poor sediment sorting in the beach and nearshore zone and low wind energy at the shoreline due to the nature of the coastal orientation and physiography in relation to the prevailing southeasterly winds. These limiting factors are not unique to humid tropical climates.     

博斯腾湖湖泊沉积物光释光年代测量*

使用光释光年代学的单片再生法测量了博斯腾湖沉积剖面中碳酸盐泥及粉砂质泥底部的浅湖相灰色粉细砂和风成沙的年龄,对剖面上部碳酸盐层中陆生植物残体进行了AMS ¹⁴ C测年。通过不同测片的等效剂量(D_e)值的分布状况评价了样品的晒褪程度,选择不随灵敏度校正后的自然释光信号变化的相对集中的等效剂量(D_e)值计算了样品的埋藏年龄。通过这些年龄结果的对比,发现石英矿物的OSL年龄和AMS ¹⁴ C年龄在地层上是一致的,表明尽管在浅湖相细砂中存在不完全晒褪,但根据相对较小而集中的D_e值计算得到的年龄结果是可靠的。这些年龄结果和地层资料揭示末次冰消期以来至早全新世,博斯腾湖处于无水干盆地向深水湖泊转化的浅水湖泊状态,现代深水博斯腾湖大约形成于距今8ka前后。     

The harmonious character in equilibrium aeolian transport on mixed sand bed

Wind tunnel experiments were carried out to measure the spatial distribution in equilibrium transport of four types of mixed sand. The flux profiles of each grain size group were calculated. It is found that the vertical distribution of mean grain size has a close relation with the grain size distribution in the sand bed. In a log-linear plot, the flux profiles of main grain size groups are all straight lines and their slopes are nearly equal. It is also found that the ratio of transport rate of each size group to the whole transport rate is directly proportional to the mass ratio of each size group in the sand bed and the proportion value is only dependent on the grain size. This harmonious law is applicable to all four types of mixed sand used in the experiment.     

A new criterion for strength of frozen sand under quick triaxial compression considering effect of confining pressure

The strength of frozen soils has been one of the most extensively studied aspects in frozen soil mechanics. When carrying out deep excavations using freezing methods, high stress states are often encountered. Therefore, the strength of frozen soils under high confining pressures is of major concern. This paper first reviews the present failure criteria for frozen soils, especially with regard to the effect of confining pressure on the strength. It is suggested that the strength consists of two components, cohesion and friction, and can be expressed by the Mohr–Coulomb criterion and in the framework of the Drucker–Prager criterion. However, these two components are both dependent on the stress state. Duncan’s equation for the friction angle is extended to frozen soils. A frozen Lanzhou fine sand is taken as study subject. The frozen sand is compressed at a high strain rate under three different temperatures and under a wide range of confining pressure. Experimental results have confirmed the generally recognized principle that the strength increases with the confining pressure up to certain value. Thereafter, it decreases with continued increase in confining pressure. Experimental data from our own tests and literature are fitted to the new criterion, which shows its validity.     

Experimental study of surface texture and resonance mechanism of booming sand

The sound-producing mechanism of booming sand has long been a pending problem in the blown sand physics. Based on the earlier researches, the authors collected some silent sand samples from Teng- ger Desert, Australian Desert, Kuwait Desert, beaches of Hainan Island and Japanese coast as well as the soundless booming sand samples from the Mingsha Mountain in Dunhuang to make washing ex- periments. In the meantime the chemical corrosion experiment of glass micro-spheres, surface coating experiment and SEM examination were also conducted. The experimental results show that the sound production of booming sand seems to have nothing to do with the presence of SiO2 gel on the surface of sand grains and unrelated to the surface chemical composition of sand grains but is related to the resonance cavities formed by porous (pit-like) physical structure resulting from a number of factors such as wind erosion, water erosion, chemical corrosion and SiO2 gel deposition, etc. Its resonance mechanism is similar to that of Hemholz resonance cavity. Under the action of external forces, nu- merous spherical and sand grains with smooth surface and porous surface are set in motion and rub with each other to produce extremely weak vibration sound and then become audible sound by human ears through the magnification of surface cavity resonance. However the booming sands may lose their resonance mechanism and become silent sand due to the damping action caused by the invasion of finer particles such as dust and clay into surface holes of sand grains. Therefore, clearing away fine pollutants on the quartz grain surface is an effective way to make silent sand emit audible sound.