scholarly journals Prediction of Soil Water Characteristic Curve Based on Soil Water Evaporation

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Gaoliang Tao ◽  
Da Lei ◽  
Lisheng Liu ◽  
Yi Li ◽  
Xueliang Zhu
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Experimental Studies ◽  
Water Evaporation ◽  
Natural State ◽  
Good Prediction ◽  
Characteristic Curves ◽  
Ambient Temperatures ◽  
Soil Water Characteristic Curves ◽  
The Relationship

Soil water characteristic curves (SWCC) and soil water evaporation curves both represent the laws of water content variation in the natural state. Aiming to investigate the relationship between them further, Hunan sand with six dry densities were used in this study, and a series of experimental studies were performed. This study developed the application of evaporation curves in geotechnical engineering, reduced the workload of measuring soil water characteristic curves, and explored the relationship between evaporation rate and fractal dimension. Through the indoor tests, we measured soil water characteristic curves of specimens and soil water evaporation curves at different temperatures and explored the relationship between these two curves. In this study, a model was developed that allows the conversion from soil water evaporation curves to soil water characteristic curves, which is an equation about matrix suction ψ versus cumulative time t. Further, two prediction methods are developed, which are derived based on the Fredlund–Xing model and based on the Bird model, respectively. The proposed methods were validated using soil water evaporation tests of Hunan sand with six dry densities at three ambient temperatures, and the results showed that good prediction performances were achieved using these two methods.

Time-domain reflectometry measurements and soil-water characteristic curves of coarse granular materials used in road pavements

2007 ◽  
Vol 44 (7) ◽  
pp. 858-872 ◽  
Author(s):  
Jonas Ekblad ◽  
Ulf Isacsson
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Granular Materials ◽  
Time Domain ◽  
Characteristic Curve ◽  
Road Construction ◽  
Time Domain Reflectometry ◽  
Volumetric Water Content ◽  
Characteristic Curves ◽  
Soil Water Characteristic Curves

Coarse granular materials are used extensively in road construction. Bearing capacity can be affected by the water content in the layers of these materials. The ability to estimate water content and to infer water movements is therefore important. The purpose of the work described herein was to determine soil-water characteristic curves and the relationship between relative apparent permittivity and volumetric water content for coarse (maximum particle size 90 mm) granular materials having various gradations. The relative apparent permittivity was measured with the aid of time-domain reflectometry (TDR), and the concurrent matric suction was measured with a tensiometer. Samples were prepared in a steel box and were heavily compacted, and TDR probes and a tensiometer cup were buried within the matrix. The variation in volumetric water content with apparent relative permittivity was found to deviate from the Topp et al. relationship. Soil-water characteristic curves were described using the Brooks–Corey and van Genuchten models. A pronounced hysteresis between wetting and drying paths was observed. For the low water retention coarse materials, measurements of water content might, in general, require correction because of the nonlinear distribution of water in the sample.Key words: pavement, time-domain reflectometry, soil-water characteristic curve, granular material.

scholarly journals A methodological framework to determine optimum durations for the construction of soil water characteristic curves using centrifugation

2016 ◽  
Vol 55 (2) ◽  
pp. 91-99 ◽  
Author(s):  
Sara E. Vero ◽  
Mark G. Healy ◽  
Tiernan Henry ◽  
Rachel E. Creamer ◽  
Tristan G. Ibrahim ◽  
...  
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Methodological Framework ◽  
Laboratory Assessment ◽  
Characteristic Curves ◽  
Pressure Step ◽  
Significant Difference ◽  
Prolonged Duration ◽  
Soil Water Characteristic Curves ◽  
Grassland Site

Abstract During laboratory assessment of the soil water characteristic curve (SWCC), determining equilibrium at various pressures is challenging. This study establishes a methodological framework to identify appropriate experimental duration at each pressure step for the construction of SWCCs via centrifugation. Three common temporal approaches to equilibrium – 24-, 48- and 72-h – are examined, for a grassland and arable soil. The framework highlights the differences in equilibrium duration between the two soils. For both soils, the 24-h treatment significantly overestimated saturation. For the arable site, no significant difference was observed between the 48- and 72-h treatments. Hence, a 48-h treatment was sufficient to determine ‘effective equilibrium’. For the grassland site, the 48- and 72-h treatments differed significantly. This highlights that a more prolonged duration is necessary for some soils to conclusively determine that effective equilibrium has been reached. This framework can be applied to other soils to determine the optimum centrifuge durations for SWCC construction.

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

2002 ◽  
Vol 39 (5) ◽  
pp. 1209-1217 ◽  
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, 4–6, 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.

scholarly journals A new framework to determine general multimodal soil water characteristic curves

2021 ◽  
Author(s):  
Wei Yan ◽  
Emanuel Birle ◽  
Roberto Cudmani
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Calibration Method ◽  
Soil Suction ◽  
Proposed Model ◽  
Van Genuchten Model ◽  
Soil Water Characteristic Curves ◽  
The Relationship ◽  
New Framework ◽  
Different Soils

AbstractA soil water characteristic curve (SWCC) model named as discrete-continuous multimodal van Genuchten model with a convenient parameter calibration method is developed to describe the relationship between soil suction and the water content of a soil with complex pore structure. The modality number N of the SWCC in the proposed model can be any positive integer (the so-called multimodal or N-modal SWCC). A unique set of parameters is determined by combining curve fitting and a graphical method based on the shape features of the SWCC in the log s–log Se plane. In addition, a modality number reduction method is proposed to minimize the number of parameters and simplify the form of SWCC function. The proposed model is validated using a set of bimodal and trimodal SWCC measurements from different soils, which yield a strong consistency between the fitted curves and the measured SWCC data. The uniqueness in the set of parameters provides the possibility to further improve the proposed model by correlating the parameters to soil properties and state parameters.

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

2001 ◽  
Vol 38 (1) ◽  
pp. 53-66 ◽  
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 Brooks–Corey, van Genuchten, and Fredlund–Xing 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.

Bimodal and multimodal descriptions of soil-water characteristic curves for structural soils

2013 ◽  
Vol 67 (8) ◽  
pp. 1740-1747 ◽  
Author(s):  
Shiyu Liu ◽  
Noriyuki Yasufuku ◽  
Qiang Liu ◽  
Kiyoshi Omine ◽  
Hazarika Hemanta
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Soil Water ◽  
Lognormal Distribution ◽  
Probability Density Functions ◽  
Density Functions ◽  
Characteristic Curves ◽  
Physically Based ◽  
Soil Water Characteristic Curves ◽  
Good Agreement

In the last decades several approaches have been developed to describe bimodal or multimodal soil-water characteristic curves (SWCCs). Unfortunately, most of these models were derived empirically. In the presented study, physically based bimodal and multimodal SWCC functions have been developed for structural soils. The model involved two or more continual pore series; the probability density functions for each pore series were assumed to be lognormal distribution and can be superposed to obtain the overall probability density function of the structural soils. The proposed functions were capable of simulating bimodal or multimodal SWCCs using parameters which can be related to physical properties of the structural soils. The experimental SWCC data were used to verify the proposed method. The fitting results showed that the proposed approaches resulted in good agreement between measurement and simulation. These functions can potentially be used as effective tools for indentifying hydraulic porosities in the structural mediums.

Soil Water Characteristic Curve and its Applications in Tunnel

2011 ◽  
Vol 261-263 ◽  
pp. 1039-1043
Author(s):  
Yu You Yang ◽  
Qin Xi Zhang ◽  
Gui He Wang ◽  
Jia Xing Yu
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Land Subsidence ◽  
Unsaturated Soil ◽  
Characteristic Curve ◽  
Tunnel Construction ◽  
Coupling Theory ◽  
Engineering Analysis ◽  
Soil Water Characteristic Curve ◽  
The Relationship

A soil water characteristic curve (SWCC) can describe the relationship between unsaturated soil matric suction and water content. By analyzing and researching the test data of the soil water characteristic curve researchers can initially establish the SWCC equation and apply this equation to the actual engineering analysis. In another words, this article is based on the fluid-solid coupling theory of unsaturated soil used to analyze and study the problem of land subsidence caused by tunnel construction. Numerical calculations show that the coupling results agree well with the measured curve works.

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