A New Approach for Smoothing Soil Grain Size Curve Determined by Hydrometer

In hydrometer analysis for soil grain size distribution, usually, the grains passing sieve No. 200 (<0.074 mm) are used. However, the hydrometer results occasionally give diameters greater than 0.074 mm. This event causes a mismatch in the curve of grain size distribution obtained from sieving and hydrometer methods. Hence, a new approach is proposed for smoothing soil grain size curve determined by hydrometer using Excel-2007 with simple statistical methods. The treatments show that in case of large sizes, there are big differences between the values of soil grain diameters smoothed by Excel-2007 in comparison and the values measured by references. These differences generally decrease with decreasing soil grain size diameters. The statistical treatments also divulge whether the hydrometer results are accurate or not. Furthermore, a general equation has been derived to estimate values of K factor, which is used for calculating the grain diameters in hydrometer analysis. The equation can be applied for any specific gravity of soils and for wide range temperatures.

Experimental study on grain size and soluble salt of saline soil in western Jilin Province, China

Western Jilin Province is a typical seasonal frost region, and is also one of the severest salinization areas of China. In this study, we aim to examine the saline soil in Da＇an and Wukesong areas, western Jilin Province, and mainly analyze the granulometric composition and distribution of salt in soil profiles. Four sampling sites, two in Da＇an and two in Wukesong respectively, are chosen for study. The granulometric composition, especially silt and clay content change in different sites and soil depths are analyzed. Analysis of total and components of soluble salt shows that the surface soil is weak carbonate saline, in which the main cation is Na＋ and the main anion is HCO3-. The total amount of soluble salt presents a decreasing tendency with increasing depth. The comprehensive analysis ofgranulometric composition and soluble salt shows that the clay content and soluble salt content present similar variation tendency with an increase of depth.

The Soil Moisture and Grain Size Characteristics of Micro-area: A Case Study of Minqin Oasis- Desert Ecotone

To elaborate soil moisture and grain size characteristics of 3 typical micro-areas in Minqin oasis-desert ecotone,samples were collected in runoff generation area and accumulated area using soil profile and multi-point sampling method,for soil moisture and physicochemical property analysis. Research results that( i) water accumulation trace of accumulated area is significant and the vegetation coverage is larger than the runoff generation area. The crust development in clay sand barrier + Haloxylon ammodendron forest accumulated is better than runoff generation area,while the situation is contrary in Nitraria tangutorum sand dune lowland and clay flat land.( ii) Moisture of accumulated area in fixed Nitraria tangutorum sand inter-dune lowland is better than the runoff generation area; the moisture of accumulated area in clay flat land topsoil is significantly better than the runoff generation area,while the topsoil moisture of clay sand barrier + Haloxylon ammodendron forest is better in the runoff generation area than in the accumulated area.( iii) Soil moisture of accumulated area in 3 types of micro-areas is in the range of 20- 40 cm; the fixed Nitraria tangutorum sand inter-dune lowland is better than clay flat land and clay sand barrier + Haloxylon ammodendron forest,while the lowest moisture of corresponding runoff generation area is basically consistent with the depth.( iv) The topsoil clay and powder content in accumulated area of fixed Nitraria tangutorum sand inter-dune lowland is lower than the runoff generation area,while the fine sand content in deep layer of runoff generation area is greater than the accumulated area; soil in two areas of clay flat land mainly consists of coarse and fine sand,and clay particles are better in runoff generation area than in accumulated area. Soil in the clay sand barrier + Haloxylon ammodendron forest is mainly coarse sand and the structure is single. In sum,through adjusting allocation of rainfall,micro-areas influence soil moisture and grain size distribution,and further influence spatial- temporal distribution of vegetation in sand micro-areas.

Grain Size and Major Oxide Analyses of Selected Anthill Soils from Winneba Area, Ghana

Termites build their habitat in the form of anthills or termitaria or termite mounds which are characterised by soil of clayey texture. This paper investigated the relative grain size from the base, middle and near the peak of three anthills located 20 km west of Winneba near the Apam-Winneba highway in Ghana and also correlated their elemental compositions. The results showed significant grain size gradation of soils which range from 2O3 (22.18 - 28.88), MnO (0.08 - 0.09), and K2O (0.4 - 0.61). However, as K2O decreased with height on anthill, SiO2, total FeO and Al2O3 increased. Probably soils used to construct these anthills were derived from different rock types and/or the termites were selective in the use of soils rich in silica or iron oxide.

Distribution and characteristics of gravelly soil liquefaction in the Wenchuan M_s 8.0 earthquake

In this paper,a distribution map of gravelly soil liquefaction that was caused by the Wenchuan M8.0 earthquake in China is proposed based on a detailed field investigation and an analysis of geological soil profiles. The geological background of the earthquake disaster region is summarized by compiling geological cross sections and borehole logs. Meanwhile,four typical liquefied sites were selected to conduct sample drillings,dynamic penetration tests (DPT),and shear wave velocity tests,to understand the features of liquefied gravelly soil. One hundred and eighteen (118) liquefied sites were investigated shortly after the earthquake. The field investigation showed:(1) sandboils and waterspouts occurred extensively,involving thousands of miles of farmland,120 villages,eight schools and five factories,which caused damage to some rural houses,schools,manufacturing facilities and wells,etc.; (2) the Chengdu plain is covered by a gravelly soil layer with a thickness of 0 m to 541 m according to the geological cross sections; (3) there were 80 gravelly soil liquefied sites in the Chengdu plain,shaped as five belt areas that varied from 20 km to 40 km in length,and about ten gravelly soil liquefied sites distributed within Mianyang area; and (4) the grain sizes of the sampled soil were relative larger than the ejected soil on the ground,thus the type of liquefied soil cannot be determined by the ejected soil. The gravelly soil liquefied sites are helpful in enriching the global database of gravelly soil liquefaction and developing a corresponding evaluation method in further research efforts.

Environmental and Mineralogical Studies of the Sabkhas Soil at Ismailia—Suez Roadbed, Southern of Suez Canal District, Egypt

Eight surface sabkha soils samples were collected from Ismailia—Suez roadbed, southwestern of Suez Canal district. Sedimentological and mineralogical analyses were conducted using grain size;X-ray diffraction and Scanning Electron Microscopy (SEM). Grain size analysis indicates high contents of fine sand and mud as well as presence of salts. X-ray diffraction;Scanning Electron Microscopy (SEM) and EDAX tool clarified that the sabkha soils are enriched by quartz, sulfate minerals (gypsum, anhydrite), carbonate minerals (calcite-dolomite-aragonite), chlorides (halite and bischofite), and clay minerals. The results elucidate that the appearance of sabkha deposits and their distribution in the study area are controlled mainly by the content of water soluble salts through parent materials;ground water table;subsurface structural;and physiographic features for instance surface relief or topography;and human activity.

激光粒度仪在特殊土颗粒分析试验中的应用

采用激光粒度仪对膨胀土、黄土和红土进行了颗粒分析试验,研究了取样质量和超声波分散时间对试验结果的影响,发现遮光率与取样质量呈现很好的线性正相关,给出了特殊土在激光粒度仪法试验中适宜的遮光率范围(15%~25%)、取样质量(膨胀土取0.1~0.2 g,黄土取0.4~0.8 g,红土取0.2~0.4 g)和超声波分散时间(膨胀土取6 min,黄土和红土取2 min);激光粒度仪法试验结果的离散性,对于黄土和膨胀土较小,但对红土相对较大,红土平行试验中粒组含量极差的最大值为10.1%;与密度计法相比,激光粒度仪法测得的胶粒(0,0.002]mm含量偏小,而黏粒(0.002,0.005]mm或更大粒组的含量则偏大,可能是因为两者试验原理的不同而导致的;2种方法对红土的测试结果差异较大,与红土的特殊性质有一定关系。研究成果为激光粒度仪在特殊土颗粒分析试验中的应用提供了借鉴。

Grain-size features of a Miocene loess-soil sequence at Qinan: Implications on its origin

In this study, grain-size of 507 bulk samples from the QA-I Mioceneloess-soil sequence at Qinan were analyzed, and the grain-size features are compared with those oftypical Quaternary loess and soil samples, representative lacustrine and fluvial samples. Theresults indicate that the grain-size distribution pattern of the Miocene loess is essentiallysimilar to that of Quaternary loess, but greatly differs from the lacustrine and fluvial sediments.Loess layers are regularly coarser than soil layers, indicating cyclical climate changes. Mediangrain-size along the 253.1 m sequence varies from 6 to 13 μm and the 】 63 μm fraction representsonly 5.3% in maximum, 0.9% in average. Long-term grain-size variations are consistent with the loessaccumulation rate at Qinan and with the eolian mass accumulation rate in the North Pacific. Thesefeatures firmly indicate an eolian origin of the studied sequence, and also reveal a coeval changesbetween the long-term changes of eolian grain-size and continental aridity in the dust sourceregions.

Kinetic and thermodynamic studies on partitioning of polychlorinated biphenyls (PCBs) between aqueous solution and modeled individual soil particle grain sizes

The significance of soil mineral properties and secondary environmental conditions such as pH, temperature, ionic strength and time in the partitioning of eight selected polychlorinated biphenyl(PCB) congeners between aqueous solution and soil particles with different grain sizes was studied. The mineral properties of a model soil sample were determined, and Brunauer–Emmett–Teller(BET) adsorption–desorption isotherms were employed to observe the surface characteristics of the individual modeled soil particles.Batch adsorption experiments were conducted to determine the sorption of PCBs onto soil particles of different sizes. The results revealed that the sorption of PCB congeners onto the soil was dependent on the amount of soil organic matter, surface area, and pore size distribution of the various individual soil particles. Low pH favored the sorption of PCBs,with maximum sorption occurring between pH 6.5 and 7.5 with an equilibration period of 8 hr.Changes in the ionic strength were found to be less significant. Low temperature favored the sorption of PCBs onto the soil compared to high temperatures. Thermodynamic studies showed that the partition coefficient(K_d) decreased with increasing temperature, and negative and low values of ΔH° indicated an exothermic physisorption process. The data generated is critical and will help in further understanding remediation and cleanup strategies for polluted water.

Two categories of fractal models of rock and soil expressing volume and size-distribution of pores and grains

Based on the Sierpinski carpet and Menger sponge models, two categories of fractal models of rock and soil which are composed of the volume fractal model of pores, the volume fractal model of grains, pore-size or particle-size distribution fractal models are established and their relations are clarified in this paper. Through comparison and analysis, it is found that previous models can be unified by the two categories of fractal models, so the unified fractal models are formed. Experimental results presented by Katz indicate that the first category of fractal models can be used to express the fractal behavior of sandstone. A scanning electron microscope (SEM) will be used to study the microstructure of soft clay and it will be testified that the fractal behavior of soft clay suits the second category of fractal models.

考虑级配影响的粗粒土−格栅最优网格尺寸试验研究

土工格栅作为土石坝常用的加筋材料,根据颗粒级配采用适合的格栅网格尺寸可显著提高土石坝抗震性能,探究级配影响下最优网格尺寸变化规律具有工程意义。基于连续级配的级配方程,通过改变最大粒径d_(max)和级配面积S,设计15组级配土料,采用4组不同网格尺寸L_(a)对各个土料加筋,做成60组加筋试样。利用大型直剪仪对各个试样进行循环剪切试验,从而定量研究级配与能使加筋粗粒土抗震性能达到最优的土工格栅网格尺寸之间的关系。试验发现,当d_(max)及L_(a)一定时,级配面积存在一个最优值使抗震性能达到最佳,将此定义为最优级配面积S_(opt);当网格尺寸一定时,S_(opt)随d_(max)增大而增大,两者之间呈明显的对数关系;当d_(max)一定时,S_(opt)随L_(a)增大而减小,两者之间也呈明显的对数关系。建立定量描述d_(max)和L_(a)对最优级配面积S_(opt)的耦合影响的计算模型,并结合工程实际,提出基于室内试验结果预测现场粗粒土原级配对应最优网格尺寸的经验公式。

粗粒土缩尺级配的渗透系数规律试验

粗粒土广泛应用于土石坝和软弱地基处理工程,渗透特性对工程设计的安全性具有重要影响。受室内仪器尺寸限制,只能对原级配粗粒土进行缩尺处理才能试验。然而,原级配粗粒土缩尺会改变土颗粒之间的孔隙大小及孔隙通道之间的连通性,导致缩尺后粗粒土室内渗透试验结果与原级配土的渗透系数存在一定差异,这种差异对准确了解原级配土的渗透特性十分重要。因此,如何通过缩尺试样试验结果准确预测原级配土的渗透系数,成为评价工程现场粗粒土渗透特性的关键。本文基于连续级配方程,将颗粒最大粒径d_(max)和级配面积S作为变量,设计16组不同级配试样,利用自制大型常水头渗透仪对各组试样进行室内渗透试验,定量研究缩尺级配的渗透系数变化规律,并找出不同级配土之间渗透系数换算的方法。结果表明:当级配面积S一定时,渗透系数k随d_(max)增大而增大,级配面积越小该规律越明显;当最大粒径d_(max)一定时,渗透系数k随级配面积S增大而减小;d_(max)和S对k的影响规律可分别用特定函数形式定量描述。根据d_(max)和S与k的关系式建立粗粒土不同级配之间的渗透系数换算模型,通过文献计算出该模型对各类粗粒土不同级配下渗透系数预测值与实测值的误差均在6%内,并利用缩尺级配试验结果反推出原级配渗透系数值且误差仅为2.5%,验证了该渗透系数计算模型对粗粒土的适用性。

SWAT分布式流域水文物理模型的改进及应用研究

SWAT(Soil and W ater Assessm ent Tool)模型是一个集成遥感(RS)、地理信息系统(G IS)和数字高程模型(DEM)技术的先进的分布式流域水文物理模型。为了推动该模型在中国的适应性研究及应用,并改进模型以提高水文模拟的精度,针对模型在中国西北寒旱区的黑河流域和中西部温润的汉江流域的水文模拟中发现的问题进行了扩充和改进,增加了土壤粒径转换模块和天气发生器(WGEN)数据预处理模块,改进了模型中的WGEN算法、潜在蒸散量模拟算法以及气象参数的空间离散方法。利用扩充和改进后的模型对汉江褒河上游江口流域的降雨-径流过程进行了系统的研究。结果表明,不仅模型的使用效率有明显提高,而且改进后模型的效率系数和相关系数也比改进前有较大改善。

山东黄河流域下游土壤粒度和深度试验成果

以黄河流域下游野外获得的土壤粒度和深度纵剖面试验资料为基础,分析了黄河流域下游不同土壤类型区、不同地貌单元的土壤粒级组成、元素在各粒级组中的分配特征和元素在土壤纵剖面中的含量、纵向变化规律,探讨了其在生态地球化学调查中的意义。确定了能代表区域内土壤主要物质组成的粒级范围,提出了本区生态地球化学调查的最佳样品筛分加工方案和表层、深层土壤样品采集的有效深度和层位。

浑善达克沙地土地沙漠化过程中土壤粒度与养分变化研究

浑善达克沙地土壤空间异质性大,流动沙丘粒度组成和非沙漠化土地养分含量都存在极显著差异。随着土地沙漠化的发展,土壤表层通常形成粗化层,土壤中的重要养分有机碳(SOC)和全氮(TN)的含量显著下降,且SOC含量比TN含量存在更大的空间差异和随沙漠化土地发展更快的下降速率,致使土壤表层C/N值存在明显下降趋势。沙漠化土地表层土壤中SOC含量和TN含量与土壤粘粒含量和粗粉沙含量之间存在很好的相关性,尤其与土壤粘粒含量的相关性非常高;而且与TN含量的相关性高于与SOC含量的相关性。各种原因引起的土壤风蚀是造成沙漠化发展中土壤过程的主要动力因素,严重影响着土壤的稳定与土壤细物质和养分的迁移。

砂砾土各级颗粒的管涌临界坡降研究

基于渗透力概念在管涌问题研究中的具体应用,按照渗透力与土颗粒浮重间的极限平衡推导出能计算管涌土的砂砾土料各级大小土颗粒的管涌临界坡降公式,并经过国内外大量管涌试验资料的验证是合理可信的。

新疆伊犁河谷新垦荒地土壤粒度特征

在新疆伊犁河谷察布查尔县农业示范区采集17个土壤剖面合汁119个样品，进行土壤粒度分析和综合对比研究．结果表明：1）不同土地类型土壤砂粒（〉50μm）、粉砂（2～50μm）和粘粒（〈2μm）含量差异较明显．多数耕作土壤样本的粉砂含量低于天然荒地，而砂粒含量要高于荒地土壤．2）各种类型土壤剖面粘粒和砂粒组分含量的变异均大于粉砂含量的变化，其中耕作土壤各粒级含量的变异系数要大于荒地土壤，各类土壤表层和下层粒度变异系数也不同．3）不同土地类型土壤的粒度参数存在差异．耕作土壤的平均粒径小于荒地土壤，且前者的分选性要比后者差，这与不同人为耕作方式对土壤粒度组成的扰动密切相关．

江西九江红土堆积的粒度特征及成因研究

在南方红土的研究中,区分不同地区红土地层的成因类型是研究区域古环境演化的关键。以江西九江红土剖面为例,通过系统的粒度分析,并与西峰黄土、古土壤样品及代表性河、湖相沉积的粒度特征进行对比,结果表明,九江红土与西峰黄土、古土壤样品具有相似的粒度分布特征,而与河、湖相沉积有较大区别。其中,九江剖面上部的下蜀土与西峰黄土粒度特征相近,而剖面下部的网纹红土与西峰古土壤样品更为相似,表明江西九江红土堆积与中国北方黄土一样属于风尘堆积。研究成果为古环境信息的进一步提取奠定了基础。

乌兰布和沙漠东北缘5种土地利用类型土壤粒度特征

研究荒漠化发生区域的土壤粒度特征,可为区域荒漠化防治及生态建设提供一定理论依据。通过野外调查、采样及室内分析,对乌兰布和沙漠东北缘5种不同土地利用类型(流动沙丘、草方格沙障固沙区、人工梭梭林、白刺群落和油蒿群落)的土壤粒度特征及分形维数进行了研究。结果表明:(1)5个样地土壤颗粒组成均以细沙为主,含量为66.49%~81.54%;粉沙含量最少,仅为0.58%~1.72%;不同粒级土壤颗粒百分含量由高到低为:细沙>中沙>极细沙>粗沙>粉沙。(2)5个样地土壤颗粒分形维数的差异极显著(p<0.01),油蒿群落(1.72)>白刺群落(1.56)>人工梭梭林(1.44)>流动沙丘(1.40)>草方格沙障>(1.37);土壤颗粒分形维数与粉沙、极细沙百分含量呈极显著正相关(p<0.01),与细沙百分含量呈显著负相关(p<0.05),与中沙和粗沙百分含量关系不显著(p>0.05)。(3)天然植被生长区域,植被盖度较好,风沙土颗粒较细。因此,应加大对区域内天然植被的保护,防止土壤风蚀的发生与发展。

内蒙古典型草原灌丛化与土壤性质的关系研究

本文以内蒙古典型草原区有灌丛入侵及无灌丛入侵现象草地为研究对象,探讨了土壤性质与草原灌丛化现象间的关系。研究结果表明:在围封状态下,无灌丛化草地土壤粉粒、粘粒及养分(有机质、全氮、全磷)含量在0～60cm深度均显著高于灌丛化草地,而土壤容重、砂粒则显著低于灌丛化草地,且二者的差异随着土壤深度的增加而增大;在重度放牧状态下,各指标的变化趋势与围封状态相同,但差异性仅在表层0～10cm显著。草原灌丛化与表层土壤砂粒、容重呈显著正相关性,与土壤粉粒、有机质、全氮、全磷含量呈极显著负相关性。以上结果说明,草原灌丛化的出现与其分布生境的土壤特点有关。相比于草本而言,灌木在粗质贫瘠土壤中更具有竞争性。