Abstract
Based on the Tao and Kong (TK) model and the fractal model of the soil–water characteristic curve, a simplified model of the relationship between the saturated permeability coefficient and the air-entry value is established in this study: ks = k0ψa−2. It is shown that the saturated permeability coefficient of soil is determined by its maximum pore size. In order to facilitate the mutual prediction of saturation permeability coefficient and air-entry value, based on the data of five types of soil in the UNSODA database, the comprehensive proportionality constant k0 of the five types of soil were obtained: sand k0 = 0.03051; clay k0 = 0.001878; loam k0 = 0.001426; sandy loam k0 = 0.009301; and silty clay loam k0 = 0.0007055. Based on the obtained comprehensive proportionality constant k0 and the relationship model between saturated permeability coefficient and air intake value, the air-entry value of five kinds of soils in the existing literature and the SoilVision database were calculated. Comparing the calculated air-entry value with the measured one, the results showed that the model simplifies the traditional air-entry value prediction method to some extent and can effectively predict the air-entry value of different types of soil. On the whole, the model better predicts the air-entry value for sandy, clay, and silty clay loam than loam and sandy loam.
Highlights
Soil in nature is a kind of three-phase material, so it is of great significance to study the related characteristics of soil in depth for engineering construction, environmental protection, and energy mining
According to the law of the capillary, the air-entry value is inversely proportional to the maximum pore diameter of the soil, so Formula (8) shows that the saturated permeability coefficient is directly proportional to the maximum pore diameter
In order to verify the accuracy of the obtained comprehensive proportionality constant In order to verify accuracy ofofthe proportionality and the rationality thisobtained method,comprehensive the authors of this paper used aconsimplified relationship stant and the rationality this method, the authors of this paper used a and simplified relamodelofbetween the saturated permeability coefficient air-entry value of soil and the tionship model between the saturated permeabilityconstant coefficient and air-entry value soil the correspondcomprehensive proportionality k0 determined above to of calculate and the comprehensive proportionality constantthe k0 saturated determined above to calculate the coring air-entry value through permeability coefficient; they conducted a comparative analysis with the measured values
Summary
Soil in nature is a kind of three-phase material, so it is of great significance to study the related characteristics of soil in depth for engineering construction, environmental protection, and energy mining. Soils change from the saturated state to the unsaturated state corresponding to the change from the boundary effect zone to the transition zone These two zones are differentiated by their air-entry values. 2021, 5, 180 soil–water characteristic curve, which means that the largest pores in the soil can hardly resist the applied suction and cause water loss At this time, the applied matrix suction is the air-entry value. The method used to test the soil–water characteristic curve usually provides a series of discrete data points between the matrix suction and water content. The authors of this study combined the SWCC fractal model with the existing permeability model and further established a model of constant of proportionality for the permeability coefficient This model was found to simplify the traditional air-entry value prediction method and overcome the limitations of practical measurement methods. The applicability and effectiveness of the model were verified by using the relevant data of existing soil
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