Predicting the pore size distribution curve based on the evolution mechanism of soil–water characteristic curve

The soil-water characteristic curve can be used to estimate various parameters used to describe unsaturated soil behaviour. A general equation for the soil-water characteristic curve is proposed. A nonlinear, least-squares computer program is used to determine the best-fit parameters for experimental data presented in the literature. The equation is based on the assumption that the shape of the soil-water characteristic curve is dependent upon the pore-size distribution of the soil (i.e., the desaturation is a function of the pore-size distribution). The equation has the form of an integrated frequency distribution curve. The equation provides a good fit for sand, silt, and clay soils over the entire suction range from 0 to 106 kPa. Key words : soil-water characteristic curve, pore-size distribution, nonlinear curve fitting, soil suction, water content.

Download Full-text

A simple approach for predicting soil water characteristic curve of clayey soils using pore size distribution data

MATEC Web of Conferences ◽

10.1051/matecconf/202133702012 ◽

2021 ◽

Vol 337 ◽

pp. 02012

Author(s):

Wei Yan ◽

Emanuel Birle ◽

Roberto Cudmani

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Soil Water ◽

Characteristic Curve ◽

Simple Approach ◽

Distribution Data ◽

Clayey Soils ◽

Soil Water Characteristic Curve ◽

Good Consistency

The soil water characteristic curve (SWCC) of soils can be derived from the measured pore size distribution (PSD) data by applying capillary models. This method is limited for clayey soils due to the PSD changes during SWCC testing. In this study, a suction-dependent multimodal PSD model based on probability theory is developed and used to derive SWCC. The model is validated by simulating the drying branches of SWCCs of four compacted Lias Clay samples with different initial states. A good consistency between the measured and predicted SWCC is shown.

Download Full-text

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.

Download Full-text

Measurement and estimation of pore shrinkage and pore distribution in a clayey till during soil-water characteristic curve tests

Canadian Geotechnical Journal ◽

10.1139/t01-014 ◽

2001 ◽

Vol 38 (4) ◽

pp. 741-754 ◽

Cited By ~ 90

Author(s):

Paul H Simms ◽

Ernest K Yanful

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Soil Water ◽

Mine Waste ◽

Characteristic Curve ◽

Landfill Liners ◽

Soil Water Characteristic Curve ◽

Fine Grained ◽

In Series

The soil-water characteristic curve (SWCC) of fine-grained soils is usually determined experimentally. In many applications, such as design of mine waste covers and landfill liners, the unsaturated permeability function, k(h), is often derived theoretically from the measured SWCC. Implicit in these derivations is the transformation of the SWCC to a pore-size distribution (PSD), typically assumed to be constant and mono-modal. PSDs of a clayey till compacted at various water contents were measured after compaction, after flexible-wall permeability testing, and during and after SWCC tests. The measurements show that the PSD changes significantly during permeability and SWCC testing. A method is advanced for predicting the observed changes in PSD during SWCC testing. PSDs are determined for soil samples subjected to the highest and lowest suctions applied during the SWCC test. The measured PSDs are transformed to account for pore trapping; the transform assumes that flow occurs through two sets of randomly distributed pores in series. To model pore shrinkage, the pores are idealized as elastic cylinders. PSDs measured after different suction applications in the SWCC tests are compared with predictions of the shrinkage model. The method can also be used to predict the SWCC. Measured and predicted values are compared.Key words: landfill liners, mine waste covers, soil-water characteristic curve, pore-size distribution.

Download Full-text

Estimation of air permeability function from soil-water characteristic curve

Canadian Geotechnical Journal ◽

10.1139/cgj-2017-0579 ◽

2019 ◽

Vol 56 (4) ◽

pp. 505-513

Author(s):

Qian Zhai ◽

Harianto Rahardjo ◽

Alfrendo Satyanaga

Keyword(s):

Distribution Function ◽

Pore Size Distribution ◽

Pore Size ◽

Soil Water ◽

Unsaturated Soil ◽

Characteristic Curve ◽

Air Permeability ◽

Size Distribution Function ◽

Soil Water Characteristic Curve ◽

Permeability Function

The multiphase flow (including liquid flow and air flow) in unsaturated soil is related to many engineering problems such as contaminant transport, rainwater infiltration, and soil-water evaporation. It is proven that water flow in unsaturated soil can be estimated using the concept of the pore-size distribution function. Many models have been proposed to estimate the water flow or water permeability function, kw, from the soil-water characteristic curve (SWCC). On the other hand, a limited model has been proposed to estimate the air flow or air permeability function, ka, from the SWCC. Most of the models used for the estimation of the air permeability functions are empirical, and they are dependent on the empirical parameters. In this paper, the relative air coefficient of permeability was estimated using the concept of the pore-size distribution function. In the method proposed in this paper, no empirical parameters were adopted, and the estimation results purely depended on the soil-water characteristic curve. The proposed method was verified against experimental data from published literature.

Download Full-text