Investigating structural stability using the soil water characteristic curve

Soil physical properties, including infiltration, strength, water storage and aeration, affect the productivity of agricultural land. This paper investigated the stability of soil structure to chemical disruption, using the soil water characteristic curve. The soil water characteristic was determined twice on intact soil cores of an acidic mesotrophic, red Ferrosol (Gn4.11) and an acidic, eutrophic, grey Dermosol (Gn4.51). Saturated NaCl or deionised water was used to wet the soil cores between each determination. Despite the variability associated with undisturbed soil cores, significant differences were detected in the soil water characteristic curves both within and between soil types. The ability to detect differences in the soil structure of the Ferrosol and Dermosol, both Emerson class 8, suggests this technique could be used to determine the chemical stability of soils with minimal mechanical disruption of the structure.

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Effects of Temperature Change on the Soil Water Characteristic Curve and a Prediction Model for the Mu Us Bottomland, Northern China

Water ◽

10.3390/w11061235 ◽

2019 ◽

Vol 11 (6) ◽

pp. 1235

Author(s):

Xiaoying Qiao ◽

Shaoyang Ma ◽

Guixing Pan ◽

Guanglu Liu

Keyword(s):

Hydraulic Conductivity ◽

Prediction Model ◽

Soil Water ◽

Direct Measurement ◽

Empirical Formula ◽

Characteristic Curve ◽

Soil Column ◽

Distribution Model ◽

Undisturbed Soil ◽

Soil Water Characteristic Curve

The soil-water characteristic curve (SWCC) is the basis for obtaining the hydraulic conductivity parameters of a soil as well as for using soil water and heat transport models. At present, the curve can be obtained by two methods: by direct measurement and by empirical formula. Direct measurement is both difficult and time-consuming. By contrast, fitting the SWCC with a suitable empirical formula is stable and convenient. The van Genuchten (VG) model has the advantage of universal applicability due to its use of a statistical aperture distribution model for estimating hydraulic conductivity. This study selected the Mu Us Bottomland as a study area. Data on the water content and water potential of undisturbed soil from this site were obtained with a Ku-pF instrument and a self-designed soil column experiment with temperature settings of 13 °C, 18 °C, 23 °C, 27 °C, and 30 °C. The variation of four main parameters in the VG model with temperature was analyzed based on thermodynamic theory and considering the effect of temperature on soil capillary pressure via its effects on surface tension and contact angle. A prediction model for the soil-water characteristic curve of the Mu Us Bottomland was then constructed, and its applicability was further analyzed. The temperature dependence of the SWCC demonstrated here provides an important scientific basis for agricultural production, farmland water conservancy, and the design of soil and water conservation engineering projects.

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Performance Evaluation of Four-Parameter Models of the Soil-Water Characteristic Curve

The Scientific World JOURNAL ◽

10.1155/2014/569851 ◽

2014 ◽

Vol 2014 ◽

pp. 1-12 ◽

Cited By ~ 6

Author(s):

Siti Jahara Matlan ◽

Muhammad Mukhlisin ◽

Mohd Raihan Taha

Keyword(s):

Soil Water ◽

Characteristic Curve ◽

Data Sets ◽

Modified Model ◽

Soil Water Characteristic Curve ◽

Geoenvironmental Engineering ◽

Wide Range ◽

Soil Water Characteristic Curves ◽

Model Equations ◽

Exponential Variable

Soil-water characteristic curves (SWCCs) are important in terms of groundwater recharge, agriculture, and soil chemistry. These relationships are also of considerable value in geotechnical and geoenvironmental engineering. Their measurement, however, is difficult, expensive, and time-consuming. Many empirical models have been developed to describe the SWCC. Statistical assessment of soil-water characteristic curve models found that exponential-based model equations were the most difficult to fit and generally provided the poorest fit to the soil-water characteristic data. In this paper, an exponential-based model is devised to describe the SWCC. The modified equation is similar to those previously reported by Gardner (1956) but includes exponential variable. Verification was performed with 24 independent data sets for a wide range of soil textures. Prediction results were compared with the most widely used models to assess the model’s performance. It was proven that the exponential-based equation of the modified model provided greater flexibility and a better fit to data on various types of soil.

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Experimental Study on Soil Water Characteristic Curve of Compacted Unsaturated Soil

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.168-170.1285 ◽

2010 ◽

Vol 168-170 ◽

pp. 1285-1288

Author(s):

Dong Lin Wang

Keyword(s):

Soil Water ◽

Influencing Factors ◽

Unsaturated Soils ◽

Stress Condition ◽

Characteristic Curve ◽

External Stress ◽

Method Of Least Squares ◽

Soil Water Characteristic Curve ◽

Triaxial Apparatus ◽

Soil Water Characteristic Curves

Soil water characteristic curve is one of important topics of unsaturated soils. Pressure plate extractor and GDS unsaturated triaxial apparatus are used to study influencing factors including types of soils and net mean stress. Through method of least-squares, Fredlund five-parameter model were employed to fit soil-water characteristic curves. The results show that model provided a satisfactory fit to the experimental data. Through an analysis of influencing factors, we find that not only physical condition of samples but also external stress condition can affect the shape of soil water characteristic curve.

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The Development of a One-Parameter Model for the Soil-Water Characteristic Curve in Loess Gully Regions

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.256-259.488 ◽

2012 ◽

Vol 256-259 ◽

pp. 488-493

Author(s):

Xiao Yu Song ◽

Huai You Li ◽

Wen Juan Shi

Keyword(s):

Soil Water ◽

Hydraulic Properties ◽

Characteristic Curve ◽

Soil Samples ◽

Soil Hydraulic Properties ◽

Logarithmic Model ◽

Soil Water Characteristic Curve ◽

Soil Water Characteristic Curves ◽

Best Fit ◽

Gardner Model

It is important to understand soil hydraulic properties in order to predict the movement of water and solutes such as pollutants. To this end, 55 soil samples were collected from different areas of the Nanxiaohegou basin and used to generate soil-water characteristic curves. These were then fitted using the power-, exponential-, and logarithmic versions of the Gardner model; the logarithmic model yielded the best fit overall. The logarithmic model was further simplified to yield a one-parameter model for estimating the soil-water characteristic curve within the basin, and it was demonstrated that the value of the single parameter is dependent on the topography and usage of the land.

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Soil water characteristic curve parameters of collapsible sand in Lambayeque, Peru

MATEC Web of Conferences ◽

10.1051/matecconf/202133701005 ◽

2021 ◽

Vol 337 ◽

pp. 01005

Author(s):

Miguel Isidro ◽

Pablo Trejo ◽

Marko López

Keyword(s):

Soil Water ◽

Filter Paper ◽

Characteristic Curve ◽

Deep Foundations ◽

Soil Behavior ◽

Collapsible Soil ◽

Undisturbed Soil ◽

Soil Water Characteristic Curve ◽

Oil Storage ◽

Collapsible Soils

Several structures are built on collapsible soils in the mining and petroleum industries and on civil sites. In order to analyze the stability of such structures, one must properly study the unsaturated soil behavior. Collapsible soils are frequent sand soil that are susceptible to a significant and sudden reduction in volume upon wetting. An important factor is matric suction, which es related to moisture content through the soil water Characteristic Curve (SWCC), the SWCC is obtained through a filter paper technique and provides a valuable relationship between suction and water content unique to soils. This measures the influence of parameters on the behavior of the structure of collapsible soil. Interactions between structure and soil must be properly evaluated as the bearing capacities of shallow and deep foundations are linked to properties of soil suction, moisture, and grade saturation. This work has experimentally measured the parameters of suction and moisture on the behavior of collapsible sands, where an oil storage tank will be built in the city of Lambayeque in Peru. Undisturbed soil specimens obtained from geotechnical exploration campaigns were used. The filter paper method used in this study was that proposed by models of Brooks-Corey and Van Genuchten. Results show consistent values near reported values from literature.

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Measurement of soil-water characteristic curves for fine-grained soils using a small-scale centrifuge

Canadian Geotechnical Journal ◽

10.1139/t02-060 ◽

2002 ◽

Vol 39 (5) ◽

pp. 1209-1217 ◽

Cited By ~ 41

Author(s):

R M Khanzode ◽

S K Vanapalli ◽

D G Fredlund

Keyword(s):

Water Content ◽

Soil Water ◽

Characteristic Curve ◽

Small Scale ◽

Characteristic Curves ◽

Pressure Plate ◽

Soil Water Characteristic Curve ◽

Fine Grained ◽

Soil Water Characteristic Curves ◽

Plate Apparatus

Considerably long periods of time are required to measure soil-water characteristic curves using conventional equipment such as pressure plate apparatus or a Tempe cell. A commercially available, small-scale medical centrifuge with a swinging type rotor assembly was used to measure the soil-water characteristic curves on statically compacted, fine-grained soil specimens. A specimen holder was specially designed to obtain multiple sets of water content versus suction data for measuring the soil-water characteristic curve at a single speed of rotation of the centrifuge. The soil-water characteristic curves were measured for three different types of fine-grained soils. The three soils used in the study were processed silt (liquid limit, wL = 24%; plasticity index, Ip = 0; and clay = 7%), Indian Head till (wL = 35.5%, Ip = 17%, and clay = 30%), and Regina clay (wL = 75.5%, Ip = 21%, and clay = 70%). The soil-water characteristic curves for the above soils were measured in 0.5, 1, and 2 days, respectively, using the centrifuge technique for suction ranges from 0 to 600 kPa. Time periods of 2, 46, and 16 weeks were required for measuring the soil-water characteristic curves for the same soils using a conventional pressure plate apparatus. There is reasonably good agreement between the experimental results obtained by the centrifuge and the pressure plate methods. The results of this study are encouraging as soil-water characteristic curves can be measured in a reduced time period when using a small-scale centrifuge.Key words: unsaturated soils, soil-water characteristic curve, centrifuge technique, soil suction, matric suction, water content.

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Slope Stability Evaluation of Reservoir Considering Soil-water Characteristic Curve of the Reinforced Ground Including Alginic Acid Sodium Salt

Korean Society of Hazard Mitigation ◽

10.9798/kosham.2020.20.4.231 ◽

2020 ◽

Vol 20 (4) ◽

pp. 231-237

Author(s):

Jaeyong Shin ◽

Sungsu Lee ◽

Jongwon Jung

Keyword(s):

Shear Strength ◽

Capillary Pressure ◽

Soil Water ◽

Sodium Alginate ◽

Alginic Acid ◽

Characteristic Curve ◽

Alginate Solution ◽

Soil Water Characteristic Curve ◽

Acid Sodium Salt ◽

The Stability

Alginic acid sodium salt is a type of biopolymer. It is a polysaccharide obtained from the most widely distributed brown algae among marine plants. Its main characteristics are nontoxicity and biodegradability. It is also considered a natural eco-friendly material because it is completely decomposed by microorganisms using only water and carbon dioxide. Moreover, sodium alginate aqueous solution mixed with water has high viscosity; hence, it is expected to effectively saturate and reinforce the soil. The soil-water characteristic curve shows the properties of the capillary pressure according to the water content of the soil. In other words, this curve can predict the shear strength of the soil. In this study, soil-water characteristic curves of soil reinforced with sodium alginate were studied. The stability of the reservoir slope reinforced with sodium alginate was evaluated using the input values of the numerical analysis, and the change in the shear strength of the soil was calculated. The results show that the increased concentration of sodium alginate solution increased the capillary pressure and residual water content of the soil-water characteristic curve, which increased the stability of the reservoir slope. The shear strength of the soil increased as the concentration and capillary pressure of the sodium alginate solution increased.

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EFFECT OF SAMPLE RE-SATURATION ON SOIL-WATER CHARACTERISTIC CURVE

Revista Caatinga ◽

10.1590/1983-21252018v31n221rc ◽

2018 ◽

Vol 31 (2) ◽

pp. 446-454 ◽

Cited By ~ 2

Author(s):

ÍCARO VASCONCELOS DO NASCIMENTO ◽

THIAGO LEITE DE ALENCAR ◽

CARLOS LEVI ANASTÁCIO DOS SANTOS ◽

RAIMUNDO NONATO DE ASSIS JÚNIOR ◽

JAEDSON CLÁUDIO ANUNCIATO MOTA

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Soil Water ◽

Characteristic Curve ◽

Soil Samples ◽

Similar Process ◽

Undisturbed Soil ◽

Saturation Process ◽

Soil Water Characteristic Curve

ABSTRACT Soil-water characteristic curve (SWCC) is an important tool for water management in irrigated agriculture. However, factors such as texture and structure of soils influence SWCC behavior. According to the literature, wetting and drying cycles alter SWCC. A similar process of re-saturation and drying occurs during SWCC obtainment under laboratory conditions. Based on the hypothesis that re-saturation process alters SWCC due to clay loss in the sample, this study aimed to obtain the SWCC, S index, and pore size distribution from samples submitted to re-saturation cycles, as well as from not re-saturated samples but under higher matric potentials (-2, -4, -6, -8, and -10 kPa). For this, disturbed and undisturbed soil samples, collected from the A (sandy texture) and Btg (sandy clay loam texture) horizons of a Argissolo Acizentado, were used. After obtaining SWCC, each air-dried soil sample was submitted to particle size and clay dispersed in water analyses to verify whether the soil lost clay. The experimental design was a completely randomized design with two methods of SWCC constructing (with and without re-saturation) and eight replications. The re-saturation process generates a loss of clay in the sample, not causing significant changes in SWCC considering the assessed textural soil classes. In addition, sandy soil samples are more sensitive to changes in pore size distribution when submitted to re-saturation.

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Evaluating dual porosity of pelletized diatomaceous earth using bimodal soil-water characteristic curve functions

Canadian Geotechnical Journal ◽

10.1139/t00-084 ◽

2001 ◽

Vol 38 (1) ◽

pp. 53-66 ◽

Cited By ~ 44

Author(s):

Craig A Burger ◽

Charles D Shackelford

Keyword(s):

Soil Water ◽

Diatomaceous Earth ◽

Pore Space ◽

Characteristic Curve ◽

Coarse Grained ◽

Dual Porosity ◽

Scanning Electron Micrographs ◽

Characteristic Curves ◽

Soil Water Characteristic Curve ◽

Soil Water Characteristic Curves

Soil-water characteristic curve data for specimens containing either ~1 mm or ~2 mm diameter pellets of processed diatomaceous earth are measured using a variety of methods (Tempe cell, pressure plate, filter paper, and chilled-mirror psychrometer). The measured soil-water characteristic curve data are bimodal, reflecting both the microscopic porosity region within the individual pellets, or intrapellet porosity, and the macroscopic porosity region between the pellets, or interpellet porosity. The bimodal distributions are consistent with scanning electron micrographs that show the existence of microscopic pores within each pellet, and the relatively high total porosities (0.725 and 0.764) for the coarse-grained diatomaceous earth specimens. The measured soil-water characteristic curve data are fit with modified forms of the BrooksCorey, van Genuchten, and FredlundXing soil-water characteristic curve functions to account for the bimodal shapes of the measured data. The average microscopic porosities resulting from the curve fits represent 45.0 and 47.9% of the total porosities for the two diatomaceous earth materials. These percentages of microscopic pore space are consistent with the product literature value of approximately 50% for the same materials based on mercury intrusion porosimetry. Thus, the results illustrate the application of bimodal soil-water characteristic curve functions for determining the microscopic and macroscopic portions of the total porosity of dual-porosity media, such as pelletized diatomaceous earth.Key words: bimodal soil-water characteristic curves, diatomaceous earth, dual porosity, macroporosity, microporosity, soil-water characteristic curves (SWCC), soil suction.

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