检索结果-南通市图书馆

Factors Influencing the soil-water Characteristics of Unsaturated Tropical Silty Sand

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Journal of Geoscience and Environment Protection 2019年第5期7卷 264-273页

作者： B. D. Oluyemi-Ayibiowu T. O. Akinleye Department of Civil Engineering The Federal University of Technology Akure Nigeria

Fine grain soils have a complex engineering behaviour which depends but not limited to moisture content, changes in external pressure and characteristics of the pore medium. Sand often contains a considerable percent of silt which is expected to alter its natural behaviour. This composite matrix is referred to as silty-sand. To understand the behaviour of this matrix under varying moisture conditions, some of the factors influencing the soil-water characteristics of unsaturated silty sands were investigated. Representative samples were collected from a river bank after its index properties were predetermined in the laboratory. The samples were compacted at different moisture conditions and compactive efforts. With the pressure plate extractor device, the soil-water Characteristic (SWC) was obtained and SWC Curves plotted. Compaction at greater compactive effort (modified proctor) and optimum moisture content produced the largest air entry value and reduced air voids. The air entry values of the soils obtained ranged from 21 kPa to 57 kPa. Also changes in the shape of the SWCC were consistent with changes in pore size which occur by varying compaction conditions. Result shows that soil structure, compaction water content, compactive effort and percentage of fine particles are factors affecting the soil-water Characteristics.

关键词： soil-water Characteristics soil-water Characteristics Curve Tropical Silty Sand soil Compaction water Content Compactive Efforts

Conversion relationships between environmental quality criteria of water/air and soil

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Earth Sciences 2018年第12期61卷 1781-1791页

作者： Yong TENG Qixing ZHOU Key Laboratory of Pollution Processes and Environmental Criteria(Ministry of Education)/Tianjin Key Laboratory of Environmental Remediation and Pollution Control College of Environmental Science and Engineering Nankai University

The conversion study on the environmental quality criteria between water/air and soil is the need to carry out research on soil-environmental quality standards in an all-round way, and also the demand for solving emerging problems in this field using the system dynamic and the overall view. Carrying out this study is of practical significance and theoretical values in the face of formulation and revision of soil-environmental quality standards in China. Firstly, the theoretical basis and relative models of soil-water and soil-air systems were expounded, respectively. And on this basis, a preliminary conceptual model about the conversion was constructed. After that, the current worldwide environmental quality criteria/standards for soil, water and air media were introduced based on their types, concerned pollutants and hierarchical classification, and their variation were also analyzed briefly. Particularlly, the key points for the conversion of environmental quality criteria between soil and water and/or between soil and air were discussed, respectively, while combined with the relative researching results. Finally, this conversion study was commented and prospected.

关键词： Environmental quality criteria soil-water system soil-air system Conversion

soil freezing process and different expressions for the soil-freezing characteristic curve

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Research in Cold and Arid Regions 2017年第3期9卷 221-228页

作者： Jun Ping Ren Sai K.Vanapalli Zhong Han Department of Civil Engineering University of Ottawa School of Civil Engineering Wuhan University

The soil-freezing characteristic curve(SFCC),which represents the relationship between unfrozen water content and subfreezing temperature(or suction at ice-water interface)in a freezing soil,can be used for understanding the transportation of heat,water,and solute in frozen *** this paper,the soil freezing process and the similarity between the SFCC of saturated frozen soil and soil-water characteristic curve(SWCC)of unfrozen unsaturated soil are *** on similar characteristics between SWCC and SFCC,a conceptual SFCC is drawn for illustrating the main features of soil freezing and thawing *** SFCC expressions from the literature are *** widely used expressions(i.e.,power relationship,exponential relationship,van Genuchten 1980 equation and Fredlund and Xing 1994 equation)are evaluated using published experimental data on four different soils(i.e.,sandy loam,silt,clay,and saline silt).Results show that the exponential relationship and van Genuchten(1980)equation are more suitable for sandy *** simple power relationship can be used to reasonably best-fit the SFCC for soils with different particle sizes;however,it exhibits limitations when fitting the saline silt *** Fredlund and Xing(1994)equation is suitable for fitting the SFCCs for all soils studied in this paper.

关键词： frozen soil soil-freezing characteristic curve Clapeyron equation soil-water characteristic curve unfrozen water content

A Flexible Model for Moisture-Suction Relationship for Unsaturated soils and Its Application

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

International Journal of Geosciences 2011年第3期2卷 204-213页

作者： Nadarajah Ravichandran Shada H. Krishnapillai Civil Engineering Department Clemson University

The mathematical equation for the moisture-suction relationship also known as soil water characteristic curve (SWCC) is one of the constitutive relations necessary for the computational modeling of deformation and flow problems of unsaturated soil using the finite element method. In this paper, a new empirical equa-tion for the SWCC is developed that incorporates the actual airentry suction and the maximum possible suction of the soil as input parameters. The capability of the new model is investigated by fitting the experimental data for twelve different soils that includes sands, silts, and clays. The model fits the experimental data well including in high suction range which is one of the difficulties observed in other commonly used models such as the Brooks and Corey, van Genuchten, and Fredlund and Xing models. The numerical stability and the performance of the new model at low and high degrees of saturations in finite element simulation are investigated by simulating the dynamic response of a compacted embankment and the results are compared with similar predictions made using widely used SWCC models.

关键词： soil-water Characteristic Curve Unsaturated soils SWCC for Low Degree of Saturation Moisture-Suction Relationship Comparison of soil-water Characteristic Curves

Transfer Factor of Heavy Metals due to Mining Activities in Some Parts of Plateau State,Nigeria(Health Implications on the Inhabitants)

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Oncology Research 2022年第2期4卷 13-26页

作者： J.Waida U.Ibrahim N.G.Goki S.D.Yusuf U.Rilwan Department of Physics Borno State UniversityMaiduguriBorno StateNigeria Department of Physics Nasarawa State UniversityKeffiNasarawa StateNigeria Department of Geology and Mining Nasarawa State UniversityKeffiNasarawa StateNigeria Department of Physics Nigerian Army UniversityBiuBorno StateNigeria

Accumulation of heavy metals in agricultural soils is instigated by industrial and other human activities such as mining,smelting,cement-pollution,energy and fuel production,power transmission,traffic activities,intensive agriculture,sludge dumping and melting *** received heavy metals from soils through ionic exchange,redox reactions,precipitation-dissolution,and so on,which implies that the solubility of trace elements based on factors like minerals in the soil(carbonates,oxide,hydroxide etc.),soil organic matter(humic acids,fulvic acids,polysaccharides and organic acids),soil pH,redox potential,content,nutrient balance,other trace elements concentration in soil,physical and mechanical characteristics of soil,soil temperature and humidity,and so *** this study,the soil-edible plant and soil-water Transfer Factor(TF)for various metals showed that the TF values differed slightly between the *** soil-edible plant transfer,the mean TF for different heavy metals in soil-edible plants decreased in the following order:As(0.6)mg/kg>Cd(0.1)mg/kg>Cr(0.06)mg/kg>Pb(0.003)mg/kg>Ni(0.001)mg/*** total TF for different locations decreases in the following order:Barkin Ladi(1.0)mg/kg>Jos South and Jos East(0.7)mg/kg>Bassa and Mangu(0.6)mg/*** soil-water transfer,the mean TF for different heavy metals in soil-edible plants decreased in the following order:Cd(0.001)mg/L>As(0.0007)mg/L>Cr(0.0005)mg/L>Pb(0.0001)mg/L and Ni(0.0001)mg/*** total TF for different locations decreases in the following order:Jos South(0.003)mg/kg>Barkin Ladi,Bassa,Jos East and Mangu(0.002)mg/*** on the findings of this study,it can be concluded that the water and edible plants in the study area are good for public consumption,even though,regular checking of heavy metals in the study area is recommended.

关键词： Heavy metals soil-Plant soil-water Transfer Factor water soil Edible plan

Factors affecting flocculation performance of synthetic polymer for turbidity control

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Agricultural Chemistry and Environment 2013年第1期2卷 16-21页

作者： Minyoung Kim Seounghee Kim Jinoh Kim Sukwon Kang Sangbong Lee Department of Agricultural Engineering National Academy of Agricultural Science Rural Development Administration (RDA) Suwon Republic of Korea

A multilateral effort into managing nonpoint source pollution from agriculture has gotten much attention for many years. Particularly during the heavy rain season, run-off of turbid water from sloped farmlands, fallow ground and/or unmanaged uplands is deteriorated. Flocculant polymer, commonly used in wastewater treatment facilities, but now exploited to improve control of sediment turbidity by promoting flocculation of particles in construction site. This study used the flocculant polymer to control the discharge of agricultural nonpoint source pollution and focused on the understanding of how soil-water and polymer properties affect flocculation performance. Therefore, a series of flocculation experiments under different conditions was evaluated for better polymer clarification efficiency. Various factors such as flocculant dose, end-over-end inversion of a cylinder, and soil-water properties (pH, NaCl, organic matter) were studied. The effective flocculant dose that fulfilled fast settling rate was 10mg·L-1. Additional findings included that 1) increasing pH decreased the settling rate of soil particle;2) a positive relationship between the percentage of turbidity reduction and a level of salinity in Kaolin suspension was observed, and 3) organic matter in soil solution inhibited PAM adsorption onto soil particles, which caused the reduction of flocculation performance. The findings of this study revealed that flocculant polymer possess good results as a turbidity reducetion measure and couldfurther provide valuable information to make better decision on establishment of Best Management Practice for handling agricultural nonpoint source pollution.

关键词： Agricultural Nonpoint Source Pollution Flocculation Synthetic Polymer Turbidity Control soil-water Properties

A Study on Measurement of Forest soil Redox Potential

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Analytical Sciences, Methods and Instrumentation 2013年第3期3卷 137-151页

作者： Mu Liu Chengde Luo Xiaoyun Liu Gang Wan Bin Dai College of Forestry Sichuan Agricultural University Ya’an China College of Forestry Sichuan Agricultural University Ya’an China&Promotion Center of Forestry Technology Forestry Bureau of Fushun County Fushun China. Promotion Center of Forestry Technology Forestry Bureau of Fushun County Fushun China.

Redox potential has principal influences on formation and attribute of soils and it is necessary to research the measurement of soil redox potential. The self-made potentiometer and two indigenous FJA-5 potentiometers were employed to measure the Eh values of fir forest soils in situ, which lied in Savage Sea Beauty Spot in Sichuan Province. Simultaneously fresh soils in situ were collected and made into suspensions with various soil-water ratios and standing time to measure Eh values. The results demonstrated that the total tendency of Eh values measured by the self-made potentiometer was gradually falling with soil-water ratios increasing and standing time prolonging. There is a great difference between Eh values measured in laboratory and in situ. Only in situ may the measured Eh values show realistic oxidation-reduction conditions and formation characteristics of forest soil. The self-made potentiometer has a preferable performance than indigenous FJA-5 potentiometers and it can be applied to measuring forest soil Eh in situ.

关键词： The Self-Made Potentiometer Redox Conditions Suspensions soil-water Ratios and Standing Time

An Influence of Multiple Drying/Rewetting Cycles upon the Respiration of Organic Forest soil

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of soil Science 2019年第9期9卷 141-154页

作者： Zofia Fischer Institute of Landscape Architecture Catholic University of Lublin Lublin Poland

It is already known that repeating cycles of drying and rewetting decrease the metabolic activity of the soil. The aim of this paper is to explain on the basis of a laboratory experiment how the respiratory processes of organic soil collected from the forest ecosystem typical for a moderate climate are changing during ten consecutive events of watering, and how alters the relationship between changing humidity of the soil and oxygen consumption/carbon dioxide emission. After 10 cycles, the respiration decreases by 2.4 times however amounts of excreted carbon dioxide and consumed oxygen do not differ between cycles 9 and 10. In successive DRW cycles also the relationship between oxygen consumption/carbon dioxide excretion and humidity level changes. This relationship is logarithmic and the analysis of subsequent regressions indicates the direction of those changes. In successive cycles the value of β coefficient (slope) decreases, and both the values of β and coefficient R2 are always higher for oxygen consumption that for carbon dioxide excretion. This indicates that processes involving oxygen consumption are always more sensitive to fluctuations of humidity than processes producing carbon dioxide. The optimum of respiration declines in successive DRW cycles.

关键词： soil-water Relationships Climate Change Carbon Dioxide Excretion

A Statistical Model for the Relative Hydraulic Conductivity of water Phase in Unsaturated soils

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Geosciences 2011年第4期2卷 484-492页

作者： Nadarajah Ravichandran Shada Krishnapillai Civil Engineering Department Clemson University

Permeability coefficients of fluids occupying the pore space of a porous medium have significant influence on the flow of these fluids through the porous medium. In the case of unsaturated soils, in addition to other parameters such as void ratio, void distribution, particle size distribution and initial density the degree of saturation also affects the permeability coefficient of water. The degree of saturation, in unsaturated soil, is directly related to the matric suction of the soil through soil water characteristic curve. Matric suction is one of the two stress state variables widely used to characterize the deformation behavior of unsaturated soils. Therefore, it can be stated that both flow and deformation behaviors of unsaturated soil are affected by the permeability coefficient of water. Numerical modeling of coupled deformation-flow behavior of unsaturated soil requires a mathematical equation that relates the permeability coefficient to the degree of saturation. Since the parameters that affect the permeability coefficient of water in unsaturated soil have similar direct or indirect effects on the soil water characteristic curve, permeability can be effectively predicted using the soil water characteristic curve as done in statistical models. In this paper, a statistical model is proposed for the permeability of water in unsaturated soil using soil water characteristic curve of the soil. The calibrated parameters of the soil water characteristic curve are directly used in the prediction of permeability with- out additional calibration using measured permeability data. The predictive capability of the new equation is verified by matching the measured data of eight different soils found in the literature.

关键词： Unsaturated soils Permeability Function Relative Permeability of Unsaturated soils Relative Permeability Using soil-water Characteristic Curve