Soil Cover in the Eastern Part of the Dried Bed of the Aral Sea

The greatest environmental disaster in Central Asiathe drying up of the Aral Seahas led to the formation of a new terrain, extending over 2.7 million hectares in Uzbekistan. This newly formed terrain is dynamically developing, with emerging soil formations replacing bottom sediments. This paper analyzes the results of a study on soil formation in the eastern part of the dried-up seabed, focusing on the influence of natural processes occurring there.

Acoustic-Physical Properties of Calcareous Seafloor Soils and Their Significance in Engineering Geology

The basic features and acoustic-physical properties of calcareous seafloor soils in the tropic sea area are obviously different from those of sediments mainly composed of terrigenous materials in the South China Sea. Generally calcareous soils, composed of carbonate particles of marine organism remains. have the characteristics of high water content, high porosity, low wet density, high sound velocity and greatly varied comprehensive strength. Recognizing the differences between calcareous soils and terrigenous sediments and engineering geologic significance of calcareous soils is crucial for seafloor geologic research and geotechnical survey for pile-jacket platform foundation design.

Preliminary studies on methane flux from the ornithogenic soils on Xi-sha atoll, South China Sea

Methane flux from the ornithogenic soils was preliminarily measured by closed chamber method on Xi-sha atoll, South China Sea during March 10 to April 11, 2003 for the first time. The CH4 flux ranged from - 226.7 μg/（m^2 ·h） to 226.3 μg/（m^· h） at the observation sites on Dong Island. High atmospheric CH4 consumption was observed from the ornithogenic soils on sunny days. CH4 uptake rates showed the highest value after the midday and they had a strong positive correlation with soil temperatures. Under the same weather conditions, the CH4 fluxes were also observed from the intact and disturbed soils on Yongxing Island. Results showed that the intact soils with natural vegetation also showed high atmospheric CH4 consumption and the average flux was - 141.8 μg/（ m^2· h）. However, disturbed soils via anthropogenic reclamation showed CH4 emissions and the average flux was 441 .7 μg/（ m^2· h）. Therefore land use changes may have an important effect on the CH4 fluxes from the tropical ornithogenic soils. In addition, different observation sites show a high spatial variation in CH4 fluxes. The wetland in salt marsh showed the CH4 emission on Dong Island, and the dry soil sites all showed high atmospheric CH4 consumption, suggesting that CH4 fluxes were predominantly controlled by soil water regime. The effects of soil chemical properties on CH4 fluxes were also analyzed and discussed in this paper.

Preliminary studies on nitrous oxide emissions from the ornithogenic soils on Xi-sha atoll,South China Sea

The preliminary measurements of nitrous oxide fluxes from the ornithogenic soils on tropical Xi-sha atoll were made using a closed chamber technique for the first time. N_2O fluxes from the ornithogenic soils ranged from 1 8 to 40 3 μg/(m^2\5h) on Dong Island and 3 2 to 20 4 μg/(m^2·h) on Yongxing Island and their flux averaged 11 0 μg/(m^2·h) and 8 3 μg/(m^2·h), respectively. N_2O fluxes from two wetland sites in salt marsh of Dong Island were approximately one order of magnitude lower than those from the ornithogenic soils and averaged 2 1 μg/(m^2·h) and 2 4 μg/(m^2·h). The diurnal variation cycle in the fluxes was obtained at the observation sites; the N_2O flux increased with the increase in soil temperature. The sudden increase in soil moisture greatly stimulated N_2O emission from the ornithogenic soils on Dong Island due to the heavy rainfall. The undisturbed soils showed the lower N_2O fluxes and the average was 4 8 μg/(m^2·h) and the soils via the reclamation showed the higher N_2O fluxes and the average was 16 6 μg/(m^2·h) on Yongxing Island, suggesting that the changes of land use have an important effect on N_2O fluxes from the ornithogenic soils. In addition, the N_2O fluxes at the different sites showed high spatial variations. The fluxes were positively correlated with the concentrations of NO^-_3, PO~ 3- _4 and Mn in the soils. The negative correlation between the fluxes and total S concentration in the ornithogenic soils was also found for the first time. Coastal soils or sediments constitute an important source of global atmospheric N_2O and the increases in nitrogen loading from seabird guanos will lead to significant increases in the flux of this atmospherically active gas.

Composition of the Microorganism Community Found in the Soil Cover on the Dried Seabed of the Aral Sea

As a result of the Aral Sea shrinkage, the unique freshwater body has given place to a huge bitter-saline lake with an area 3.5 times less, volume 6 times less and water salinity 10 times larger than in 1960, and the saline desert at the interface between three sand deserts with an area of more than 5 million ha, being unstable ecological zone. The exposed ground is illustrative of arid salt-accumulation, where was created specific type of soil-costal solonchak. The origination of life in the soil of the dried bed starts long before the occurrence of external characteristics. This process can be traced only by studying the microbiological composition of soil. Research in this direction, was conducted in order to determine the microbiological composition of soil for horizons of one typical profile of solonchak. The research objective was to determine microorganism species in the soil on the dried seabed, identify changes in the microorganism community along the soil profile and dependence on duration of the drying process. Additionally, we paid attention to a vegetation effect on the composition of microorganisms. Soil samples were taken along a transect from the sea to the mainland, selected from the different depth of soil profiles taken under or near plant (saxaul). The method Gas chromatography mass-spectrometry was used. Bacteria of the community of microorganisms in different parts of the soil cover on the dried seabed of the Aral Sea and on the mainland belong to five bacterial phyla: Proteobacteria Actinobacteria Firmicutes Bacteroidetes and Deinococcus-Thermus. In general, 59 bacterial species of 43 genera were reconstructed. The total population varied from 105 cells/g to 108 cells/g of the soil. The association Aeromonas hydrophila-Arthrobacter sp. played the key role at the first stages of the soil formation process on the dried seabed of the Aral Sea. This association is followed by salt-resistant Agrobacterium sp. and humus-accumulating Propionibacterium freudenreichii, activity of which is also very important for the formation of the soil cover. The studying properties of the dried seabed cover of both salt composition and microbiological composition made it possible to trace the formation of primary soil on marine sediments with the subsequent formation of desert-type soil.

Impact of aridization on soil cover transformation of the Aral Sea and the modern Syr-Darya Delta

The effects of human activities on the soil cover transformation in the eastern part of Kazakhstan were investigated during the period of 1956-2008.The results of the research for different soil types in Priaralye indicated that there was 643.3×103 hm2 solonchaks,accounting for 38.5 % of the total area（1670.5×10^3 hm^2） in 2008.Vast areas are occupied with dried lakeshore soil（311.1× 10^3 hm^2）,sandy soils（147.6×10^3 hm^2） and grey-brown desert soils and solonetzes（146.7×10^3 hm^2）.In 2001 the area of solonchak was 755×103 hm2 and decreased to 643.3×10^3 hm^2 in 2008,which due to the shrinkage of the Aral Sea,the areas of marsh and lakeshore solonchaks decreased with the increase of dried bottom of the Aral Sea.The level of soil cover transformation in the modern delta of the Syr-Darya River can be seen from the comparison of the results obtained from the different years in the study area.The area of solonchaks increased by 10×10^3 hm^2 and the area of alluvial-meadow salinizied soils increased by 17.9×10^3 hm^2 during the period of 1956-1969.It means that many non-salinizied soils were transformed into salinizied ones.Striking changes occurred in the structure of soil cover as a result of aridization.So,the researches in1969 significantly determined the areas of hydromorphic soils subjected to desertification（it was not fixed on the map before 1956）.Later,these soils were transformed into takyr-like soils.The area of takyr-like soils increased almost by 3 times for 34 years（from 1956 to 1990）.The long-term soil researches on soil cover transformation in Priaralye have shown that the tendencies of negative processes（salinization and deflation） are being kept and lead to further soil and eco-environment degradation in the region.

An analysis on the error structure and mechanism of soil moisture and ocean salinity remotely sensed sea surface salinity products

For the application of soil moisture and ocean salinity（SMOS） remotely sensed sea surface salinity（SSS） products,SMOS SSS global maps and error characteristics have been investigated based on quality control information.The results show that the errors of SMOS SSS products are distributed zonally,i.e.,relatively small in the tropical oceans,but much greater in the southern oceans in the Southern Hemisphere（negative bias） and along the southern,northern and some other oceanic margins（positive or negative bias）.The physical elements responsible for these errors include wind,temperature,and coastal terrain and so on.Errors in the southern oceans are due to the bias in an SSS retrieval algorithm caused by the coexisting high wind speed and low temperature; errors along the oceanic margins are due to the bias in a brightness temperature（TB） reconstruction caused by the high contrast between L-band emissivities from ice or land and from ocean; in addition,some other systematic errors are due to the bias in TB observation caused by a radio frequency interference and a radiometer receivers drift,etc.The findings will contribute to the scientific correction and appropriate application of the SMOS SSS products.

Experimental research on grouser traction of deep-sea mining machine

The traction characteristics of the grouser, cutting the simulative soil of deepsea sediment, with different tooth widths, tooth heights, and ground pressures are studied with traction characteristic test apparatus. A traction-displacement model is obtained by combining the analysis of the cutting mechanism. The results show that the tractiondisplacement curves of grousers with different tooth widths, tooth heights, and ground pressures have the same changing trend, which matches the Wong traction model. Their sensitivity coefficient and shear modulus are slightly fluctuated. Therefore, the average values can be used as the traction model parameters. The maximum traction of the grouser with a two-side edge and a 10 mm tooth width increment changing with the tooth height and ground pressure can be determined according to the grousers with different tooth widths. By combining the traction model parameters, the traction-displacement curve of the grouser with a certain group values of tooth width, tooth height, and ground pressure can be predicted. Therefore, the slip of the mining machine can be prevented to improve the mining efficiency.

Validation and correction of sea surface salinity retrieval from SMAP

In this study, sea surface salinity(SSS) Level 3(L3) daily product derived from soil moisture active passive(SMAP)during the year 2016, was validated and compared with SSS daily products derived from soil Moisture and ocean salinity(SMOS) and in-situ measurements. Generally, the root mean square error(RMSE) of the daily SSS products is larger along the coastal areas and at high latitudes and is smaller in the tropical regions and open oceans. Comparisons between the two types of daily satellite SSS product revealed that the RMSE was higher in the daily SMOS product than in the SMAP, whereas the bias of the daily SMOS was observed to be less than that of the SMAP when compared with Argo floats data. In addition, the latitude-dependent bias and RMSE of the SMAP SSS were found to be primarily influenced by the precipitation and the sea surface temperature(SST). Then, a regression analysis method which has adopted the precipitation and SST data was used to correct the larger bias of the daily SMAP product. It was confirmed that the corrected daily SMAP product could be used for assimilation in high-resolution forecast models, due to the fact that it was demonstrated to be unbiased and much closer to the in-situ measurements than the original uncorrected SMAP product.

A performance evaluation of remotely sensed sea surface salinity products in combination with other surface measurements in reconstructing three-dimensional salinity fields

Several remotely sensed sea surface salinity（SSS） retrievals with various resolutions from the soil moisture and ocean salinity（SMOS） and Aquarius/SAC-D missions are applied as inputs for retrieving salinity profiles（S） using multilinear regressions. The performance is evaluated using a total root mean square（RMS） error, different error sources, and the feature resolutions of the retrieved S fields. In the mixed layer of the salinity, the SSS-S regression coefficients are uniformly large. The SSS inputs yield smaller RMS errors in the retrieved S with respect to Argo profiles as their spatial or temporal resolution decreases. The projected SSS errors are dominant, and the retrieved S values are more accurate than those of climatology in the tropics except for the tropical Atlantic, where the regression errors are abnormally large. Below that level, because of the influence of a sea level anomaly, the areas of high-accuracy S values shift to higher latitudes except in the high-latitude southern oceans, where the projected SSS errors are abnormally large. A spectral analysis suggests that the CATDS-0.25° results are much noisier and that the BEC-L4-0.25° results are much smoother than those of the other retrievals. Aquarius-CAP-1° generates the smallest RMS errors, and Aquarius-V2-1° performs well in depicting large-scale phenomena. BEC-L3-0.25°,which has small RMS errors and remarkable mesoscale energy, is the best fit for portraying mesoscale features in the SSS and retrieved S fields. The current priority for retrieving S is to improve the reliability of satellite SSS especially at middle and high latitudes, by developing advanced algorithms, combining both sensors, or weighing between accuracy and resolutions.

A new method to retrieve salinity profiles from sea surface salinity observed by SMOS satellite

This paper proposes a new method to retrieve salinity profiles from the sea surface salinity （SSS） observed by the Soil Moisture and Ocean Salinity （SMOS） satellite. The main vertical patterns of the salinity profiles are firstly extracted from the salinity profiles measured by Argo using the empirical orthogonal function. To determine the time coefficients for each vertical pattern, two statistical models are developed. In the linear model, a transfer function is proposed to relate the SSS observed by SMOS （SMOS_SSS） with that measured by Argo, and then a linear relationship between the SMOS_SSS and the time coefficient is established. In the nonlinear model, the neural network is utilized to estimate the time coefficients from SMOS_SSS, months and positions of the salinity profiles. The two models are validated by comparing the salinity profiles retrieved from SMOS with those measured by Argo and the climatological salinities. The root-mean-square error （RMSE） of the linear and nonlinear model are 0.08-0.16 and 0.08-0.14 for the upper 400 m, which are 0.01-0.07 and 0.01-0.09 smaller than the RMSE of climatology. The error sources of the method are also discussed.

极端海况下风力机冲刷效应动力学响应研究

基于有限元方法建立考虑土-构耦合效应的壳单元模型,对不同海况下发生冲刷时的海上风力机进行动力学响应分析。结果表明:在常规和极端海况下,发生较大冲刷时,塔顶和桩基顶部峰值位移均有所增加,且桩基顶部峰值位移增幅更大,随着冲刷深度的增加,塔架水平位移均呈先增大后减小的趋势,桩基水平位移随冲刷深度的增加持续增大,不同冲刷深度下桩基最大加速度位置均发生在桩基顶部,塔架最大应力均出现在塔架底部;与常规海况相比,极端海况下风力机在启动后一直处于不稳定状态,最大加速度位于桩基中上部位置,且随冲刷深度的增加持续增大,桩基应力峰值位置由桩基顶部转移至中部。

深海能源土含气储层边坡稳定性研究

深海能源土开采不当往往会造成含水合物储层的强度劣化,诱发海床失稳问题。为探究深海能源土开采对含气储层边坡稳定性的影响,以深海能源土采挖回填装置的开采工况为实际工程背景,针对3种工况下能源土采挖回填诱发的海底滑坡现象,基于有限元强度折减法建立数值模型,分析不同黏土含量、含气量及回填加固等因素引起的水合物含气储层稳定性问题,得到相应安全系数。研究结果表明:黏土含量越高,海底沉积物边坡的安全系数越低,边坡稳定性越差;含气量对深海能源土含气储层的边坡稳定性呈非线性影响,安全系数随含气量的增加呈先上升后下降的趋势;采用胶结性材料进行回填加固处理可提高海底边坡安全系数,边坡稳定性增强。

循环荷载下深海能源含气土动力特性试验研究

以往对深海能源含气土的研究多以静荷载作用为主,且含气土的气泡尺寸多为不可控的离散小气泡。本研究提出一种能够控制含气量及气泡大小的制样方法,并对含有离散大气泡的深海能源含气土开展固结不排水循环加载动三轴试验,分析深海能源含气土在不同循环应力比(cyclic stress ratio, CSR)、有效围压、饱和度和黏土含量条件下的累积塑性应变、滞回曲线、动孔压和动强度发展规律。结果表明:累积塑性应变分为“稳定增长型”和“失稳破坏型”两类,累积塑性应变增长速率随着CSR增大、饱和度下降、围压增大和黏土含量增加而加快。含气土的滞回圈随振次增加、饱和度下降、围压增大及黏土含量增加,呈现出回弹模量降低、阻尼比增大的现象。含气土动孔压发展模式分为“缓慢增长型”和“孔压骤增型”,孔压增长速率随饱和度下降、CSR增大及黏土含量增加而加快,且在循环荷载作用下,动孔压均未达到有效应力水平,即在轴向应变达到5%前,试样未现液化破坏现象。动强度随饱和度降低而下降,且下降幅度随饱和度的降低,呈现出增大的趋势。

采石场粉尘和海砂混合物力学性能试验和数值研究

越南等发展中国家的道路基础设施建设需要大量天然砂。河砂日益紧缺,其供应量将持续下降。因此,建筑行业必须实施可持续发展战略,将废弃材料与各种可利用资源相结合,以有效应对这一严峻形势。本研究的目的是测试采石场粉尘和海砂混合物的力学性能,并评估其在高速公路路基层中的潜在应用。进行了一系列试验,包括材料的含水率、相对密度、休止角测试和三轴试验,以研究不同配比下混合物的组成。结合Plaxis土工试验中的校准进行了广泛的参数研究,得出了割线模量E_(50)和围压曲线。根据加州承载比CBR对公路路基层所用材料的评估结果,证明海砂和采石场粉尘混合物具有适当性能,可用于公路路基的建设。

考虑深海能源土结构性影响的弹塑性本构模型

深海能源土是指水合物以不同赋存模式填充于孔隙中的海底沉积物。水合物的填充效应会对能源土的密度和孔隙比产生较大影响。水合物的胶结效应会产生随饱和度增大而增大的胶结力,两种效应共同影响着深海能源土的复杂力学特性。同时能源土也是一种特殊的结构性土,其骨架颗粒、孔隙性状和排列方式均会对能源土的强度、应变软化和剪胀剪缩等特性有影响。在CSUH模型的框架下,通过建立与水合物饱和度相关的压硬性参数来反映水合物对能源土压缩特性的影响。其次考虑水合物填充效应的影响,推导出了能源土的实际初始孔隙比计算式,并将其引入至能源土的状态参数中来反映其剪胀特性。最后将用于描述土体损伤效应的结构性参数与水合物饱和度相关的胶结性参数作为硬化规律,建立了一个考虑水合物填充效应的结构性深海能源土的弹塑性本构模型。通过与室内试验结果比较,验证了该模型可有效反映能源土在不同水合物饱和度和围压条件下的应变硬化及软化、体积剪胀剪缩等复杂力学特性。

降压开采条件下胶结型深海能源土力学特性离散元模拟

降压开采会造成影响深海能源土宏观力学特性发生显著变化,而胶结型是天然气水合物赋存于深海能源土储层的主要类型,因此降压开采条件下胶结型深海能源土力学特性研究对于提高天然气水合物开采效率,预防海洋灾害具有重要意义。研究了胶结型深海能源土降压开采时的胶结和损伤影响,构建了三维离散元(Discrete Element Method,DEM)数值模型,并分析了围压、饱和度和损伤对于降压开采条件下胶结型深海能源土力学性能影响。研究结论对于深海能源土储层中天然气水合物开采研究具有较好的借鉴意义。

海域桥梁桩基冲刷固化土防护施工方案比选研究

现依托上海市科委科研项目《工程泥浆制备海域桥梁桩基防冲刷回填材料技术与装备》,首次将固化土技术引入跨海桥梁桩基防护工程中。该技术目前已在单桩形式的海上风电桩基冲刷防护工程中得到了成功应用,但针对海域桥梁群桩基础这一复杂情况下的应用尚需进一步研究。结合东海大桥桥墩桩基固化土防护典型施工试验工程,重点分析研究了工程泥浆固化土用于海域桥梁桩基冲刷防护的施工方案,并比选研究了海上施工与陆上施工方案的优缺点。结果表明,两种施工方案各有长短,可根据工程实际情况择优采用,为固化土防护技术的推广应用提供了参考。

基于自蓄水理论的低渗土壤城市内涝问题研究

针对常规透水铺装难以解决海淤城市内涝问题,通过研制一体成型空腔蓄水-渗透装置,提出了一种消除低渗土壤地区内涝问题的自蓄水理论。对蓄水渗透装置进行了蓄水渗透能力和地基承载力试验研究。研究结果表明,与常规透水铺装相比,蓄水渗透装置在4 cm/h模拟雨强下4 h未产生地表径流,24 h内雨水入渗情况良好;对比天然地基,蓄水渗透装置能够提升地基承载力约40%,具有加固地基土的作用。