Three-phase Soil Research Articles

Three-phase and gel models of soils in the analysis of experimental results

It is common to consider the results of experiments in soil physics from the position of a three-phase soil model. Along with the three-phase, there is a gel model of soils. The models are based on different principles: in the three–phase model – the constancy of the solid phase and the mobility of the liquid, in the gel model – the ability of soil gels to swell, harden and reduce the mobility of water. The purpose of the work is to assess the applicability of using three–phase and gel soil models to analyze the results of studying some physical properties of soils. The studies were carried out on the soils of the zonal series: sod-podzolic, gray forest, chernozem, chestnut soil. The following methods were used in the work: vibration viscometry, laser diffractometry, electrical resistance of soils. When studying the physical properties of soils, unexpected results were obtained. Firstly, the curve of the influence of the samples moisture content on the viscosity of the pastes prepared from them reached a maximum in the area of the moisture content of the point of limited availability of water (PLAW). Secondly, with increased mechanical action on soil pastes, the particle size in them did not decrease, but increased. Thirdly, the dependence of the electrical resistance of soils on their humidity maintains a uniform course in the area of PLAW. Although at this humidity, the continuous framework of the liquid phase in soils disappears, providing moisture and electrical conductivity. Fourth, moist soils dry out in a desiccator over water. It is not possible to explain these results from the standpoint of the three-phase soil model generally accepted in soil science. Therefore, a gel model of soils was used to analyze the results, which made it possible to explain all the results obtained.

SUBSTANTIVE-GENETIC PRINCIPLES OF SOIL CLASSIFICATION AND DIAGNOSTICS IN THE SCIENTIFIC HERITAGE OF NABOKIKH O.G.

Problem Statement and Purpose. Alexander Nabokikh (1874–1920), who criticized the model of soil classification and diagnostics by V. Dokuchaev and M. Sibirtsev, formulated the original water-mode concept of soil formation. This concept provided for the quantitative assessment of individual soil formation factors, as well as the classification and diagnosis of soils according to their characteristics and properties. Nabokikh ideas and methods were rejected by V. Dokuchaev’s students and have not been improved throughout the history of genetic soil science, but today they are clearly reflected in the «newest» substantive principles of soil diagnosis and classification. The methodological innovations of O. Nabokikh are far-sighted and relevant to this day and require a thorough study. Data & Methods. General scientific and historical methods were used. The research materials are the scientific works of O. Nabokikh, as well as archival materials of the Soil Museum of Odesa State Agrarian University. The maps of «selected major soil properties» of 1914–1916 were analyzed – detailed plans of organic matter content in the soils of the southern region of Ukraine. Results. O. G. Nabokikh proposed the Three-phase soil survey, which was based on methods of soil diagnostics by their properties, as well as the method of mapping the so-called “selected major soil properties”. Nabokikh foresaw the importance of detailed maps of the distribution of soil properties for soil monitoring. A comparative analysis of the data on organic matter content in the early twentieth century and in the early twenty-first century along two (n=94) of O. Nabokikh’s routes in the Odesa region revealed a decrease in organic matter in the surface layer of soils by an average of 0.6%. Nabokikh O. G. remained a supporter of the factor concept of soil formation, but modified it by identifying the “dominant factor” (an inseparable pair of precipitation and relief). In the matter of soil diagnostics and classification, he prefers the substantive principle. When identifying “variants of chernozems,” he cites the following substantive “main features of chernozems and the main modifications of these features”: uniformity of distribution of silicate minerals; accumulation of humus; illuvium of hydrates of one and a half oxides; illuvium of calcium carbonate salts; relict features. Determination of the main features of soils became the basis of the deep-profile method of soil research used by Nabokikh O. G.

Bulk and Rayleigh Waves Propagation in Three-Phase Soil with Flow-Independent Viscosity

The flow-independent viscosity of the soil skeleton has significant influence on the elastic wave propagation in soils. This work studied the bulk and Rayleigh waves propagation in three-phase viscoelastic soil by considering the contribution of the flow-independent viscosity from the soil skeleton. Firstly, the viscoelastic dynamic equations of three-phase unsaturated soil are developed with theoretical derivation. Secondly, the explicit characteristic equations of bulk and Rayleigh waves in three-phase viscoelastic soil are yielded theoretically by implementing Helmholtz resolution for the displacement vectors. Finally, the variations of the motion behavior for bulk and Rayleigh waves with physical parameters such as relaxation time, saturation, frequency, and intrinsic permeability are discussed by utilizing calculation examples and parametric analysis. The results reveal that the influence of soil flow-independent viscosity on the wave speed and attenuation coefficient of bulk and Rayleigh waves is significantly related to physical parameters such as saturation, intrinsic permeability, and frequency.

1D monodirectional or 2D quasi-uniaxial parallel heat fluxes: A discussion on ‘Soil thermal conductivity estimated using a semi-analytical approach’

This letter is a comment to the published paper entitled, ‘‘Soil thermal conductivity estimated using a semi-analytical approach” (by Rubin and Ho, Geothermics, 2021, 92: 102051). In the reviewed article, an enhanced semi-analytical model was proposed to evaluate the effective thermal conductivity of three-phase (solid-liquid-gas) soils by changing the assumption of 1D monodirectional to 2D quasi-uniaxial parallel heat fluxes in pore-scale soil heat conduction process. The significant innovation, some shortcomings and further research directions were discussed in this comment. In addition, some statements, conclusions and misprints occurred in the published version were also mentioned, indicating that more careful proof, necessary corrigendum and some supplementary materials are required to avoid confused presentation and improve the reliability.

Stages and staging of the study of the seabed for earthmoving systems

The development and development of minerals and building materials in water areas, the laying of underwater communications, planning and dredging underwater are preceded by detailed surveys of soil massifs. They establish the lithology and genesis of deposits, bottom surface bathymetry, physicomechanical, acoustic and other properties of underwater soils. These studies are mainly subordinated to the tasks of geology. At the same time, for the development of the deep-water part of the World Ocean, it is planned to use soil development and transport equipment. The kinematic parameters of the equipment used for engineering and geological research do not correspond to the kinematics of existing or planned underwater systems. Despite some progress in the development of engineering-geological methods for studying the ocean, there are currently no reliable data on the mechanical properties of bottom sediments in natural occurrence. Practically the only way to identify the strength properties of deep-water soils is the sampling method (tubes, grabs, dredges). Soil characteristics are determined from samples brought to the surface in a shore or ship laboratory.
 One of the specific features of the tests being carried out is the consideration of hydrostatic pressure, the effect of which on three-phase soils is especially large. Therefore, it should be expected that the measurement errors of the characteristics of bottom sediments in atmospheric conditions due to the violation of their structural relationships during ascent from great depths can differ by an order of magnitude or more from the true values ​​of the parameters of the soil environment. Thus, in order to determine the operating conditions and set external loads on underwater digging machines, it is necessary to measure the strength, deformation and other characteristics of bottom soils in natural conditions under hydrostatic pressure. This paper considers the methods and technical means used for deep-sea exploration of the seabed. Particular attention is paid to engineering-geological methods, which make it possible at the stage of detailed exploration to obtain not only predictive estimates of the mineral resources of the World Ocean but also to determine the physical and mechanical properties of bottom sediments, on which deep-sea digging machines will have to work.

Comments on the paper “New model to evaluate the effective thermal conductivity of three-phase soils, Fabio Gori, Sandra Corasaniti, International Communications in Heat and Mass Transfer, 47(2013)16”

This comment concerns a rightful doubt involved in the above paper. In the reviewed article, a novel model without empirical constants was proposed to evaluate the effective thermal conductivity of three-phase soils, and such a model was claimed to be workable for soils with porosity ranging from 0.0349 to 0.4764 at all saturation degrees. However, sufficient reasons and pictorial explanations were given in this comment to prove its inapplicability for high degrees of saturation. Besides, the inapplicable range is constantly changing, depending on the porosity, i.e. the larger the porosity, the smaller the inapplicable saturation region. Similar issues were further discussed due to its great influence on the follow-up research in this field, i.e. whether can achieve a full coverage of the applicable saturation range [0,1] for a given porosity.

Unsaturated thermal consolidation around a heat source

Thermal loadings in saturated (two-phase) clays induce excess pore water pressure due to the difference in the thermal expansion coefficient of the pore volume and the pore water. The gradual dissipation of the excess pore water pressure causes thermal volume reduction which is known as thermal consolidation. However, thermal consolidation in a three-phase soil system such as unsaturated soil is more sophisticated. In this paper, an analytical model for thermal consolidation around a heat source embedded in unsaturated clay or in calyey soils containing two immiscible fluids is developed based on the effective stress concept. Governing equations, including energy, mass, and momentum balance equations are developed. Coexisting solid and pore fluids are assumed to be in local thermal equilibrium. First, a solution is provided using Fourier-Laplace transformation by considering constant coefficients. The inverse transformation is carried out fully analytically and thus, a closed-form solution is proposed. Then, the variations of soil properties during the thermal consolidation process are considered through a temporal discretization process. The developed model is validated using Green’s function theory and the equations and results are compared with the available models in the literature. Results indicate the capability of the model to accurately predict thermal consolidation in a three-phase clayey soil.

A Spherical Steady-State Method to Measure Soil Thermal Conductivity

The reliable prediction of coupled heat and moisture transfer in three-phase soils involves authentic estimation of soil thermal conductivity. In the current work, a steady-state method was developed to measure soil thermal conductivity. Soil samples for two soils were packed in a plastic of 6.6 cm inner diameter and 3 mm thickness. A 130 Ohm resistor as a heat generator being connected to 5 V electricity source was located in the center of the ball. Three thermocouples were installed at the distances of 0.5, 1.5, and 2.5 cm from the center, respectively. After unpacking the ball, thermal conductivity was measured using the single probe method. The thermal conductivity values measured by both methods were almost the same in air dry soils; overall, the observed differences between the two methods were less than 3%. However, in the intermediate moisture content ranges, the values measured by the steady-state method were slightly lower than those obtained by the single probe method. Considering the effect of convective vapor flux due to thermal expansion of soil air in the single probe method, values measured with the new steady-state method may be more reliable.

Numerical Simulations of Wave-Induced Soil Erosion in Silty Sand Seabeds

Silty sand is a kind of typical marine sediment that is widely distributed in the offshore areas of East China. It has been found that under continuous actions of wave pressure, a mass of fine particles will gradually rise up to the surface of silty sand seabeds, i.e., the phenomenon called wave-induced soil erosion. This is thought to be due to the seepage flow caused by the pore-pressure accumulation within the seabed. In this paper, a kind of three-phase soil model (soil skeleton, pore fluid, and fluidized soil particles) is established to simulate the process of wave-induced soil erosion. In the simulations, the analytical solution for wave-induced pore-pressure accumulation was used, and Darcy flow law, mass conservation, and generation equations were coupled. Then, the time characteristics of wave-induced soil erosion in the seabed were studied, especially for the effects of wave height, wave period, and critical concentration of fluidized particles. It can be concluded that the most significant soil erosion under wave actions appears at the shallow seabed. With the increases of wave height and critical concentration of fluidized particles, the soil erosion rate and erosion degree increase obviously, and there exists a particular wave period that will lead to the most severe and the fastest rate of soil erosion in the seabed.

Microstructure-Based Effective Stress Formulation for Unsaturated Granular Soils

AbstractThe principle of effective stress states that the strength and volume change behaviors of soil are governed by intergranular forces expressed in terms of a continuum quantity called effective stress. Although the principle of effective stress is regarded as one of the most fundamental concepts in soil mechanics, its applicability to unsaturated soil has been questioned. The central issue is whether a measure can be developed for three-phase soils that plays an equivalent role as the effective stress does for two-phase soils. Combining the techniques of microstructural analysis and image processing, this study formulated the effective stress for unsaturated granular soils. A novel suction-controlled experimental setup was integrated with an X-ray computed tomography (CT) scanning system and used to image and model microstructural features. A tensorial quantity, called the fabric tensor of the liquid phase, that characterized the complex fabric resulting from saturated pockets and networks of liquid...

THE INFLUENCE OF VARIOUS MEANS OF TILLAGE SIMPLIFIED MODIFICATION ON SELECTED PHYSICAL AND WATER PROPERTIES OF THE ARABLE-HUMUS HORIZON IN A MINERAL SOIL

This paper presents the results of testing studies of the basic values of physical and water properties of the humus horizon in a typical black earth where three variants of simplified tillage were implemented. The state of a three-phase system of soil after fourteen years of no-til-lage cultivation was compared with the variant of single deep plowing and plowing with manure fertilization. The following properties were marked: texture, specific and bulk density, porosity, moisture, maximal hygroscopic capacity, saturated hydraulic conductivity, water binding potential, total (TAW) and easily (RAW) available water, drainage porosity. It was acknowledged that the systems of most of the physical and water properties in the investigated combinations were very similar. There was no evidence of negative changes of key physical properties in the soil after the 14-year long no-tillage cultivation when compared with the variant of single traditional tillage rotation. Some minor differences were found within hydraulic and water properties and total carbon, however, they cannot practically deteriorate the agrotechnical state of a humus horizon and cannot have a negative effect in the field environment. It was affirmed that within a threephase soil system, the no-tillage cultivation provides plants with almost identical conditions of growth and development as the systems with the tillage rotation.

Riemann solver for irreversibly compressible three-phase porous media

SUMMARY The Riemann problem for an irreversibly compressible three-phase medium has been solved. This solution introduces the maximum medium density that is attained in the process of active loading. The possible wave configurations have been analyzed, and the corresponding equations for the evaluation of the contact pressure and velocity have been obtained. The existence and uniqueness of the solution has been proven. The technique of the Riemann problem's solution for the arbitrary Lagrange–Euler mesh was developed. Examples of the Riemann problem solution for various wave configurations show that neglecting the bulk elastic plastic deformations yields significant errors in the results both quantitatively and qualitatively. The effect of the air volumetric content in a three-phase soil medium on the Riemann problem solution has been investigated. Copyright © 2013 John Wiley & Sons, Ltd.

New model to evaluate the effective thermal conductivity of three-phase soils

The aim of the present paper is to present a new model without empirical constants to evaluate the effective thermal conductivity of three-phase soils. In the model the soil is made of a quasi-spherical solid grain, and is surrounded by two phases, which can be air and water or air and ice. The effective thermal conductivity is obtained theoretically by the integration of the steady-state heat conduction equation under the thermal assumption of parallel heat fluxes. This new model allows to evaluate the effective thermal conductivity of soils with porosity (ratio between the volume of the voids and the total one) in the range between 0.0349 and 0.4734 at all degrees of saturation (ratio between the water volume and the void one) from dryness up to saturation. Comparisons with experimental data of unfrozen and frozen soils confirm that the model can predict the effective thermal conductivity with a fairly good agreement without using any empirical constant.

Thermal conductivity of sands

The thermal properties of soils are important in a variety of applications, including the thermal performance of buried pipelines and geothermal heat pumps. A variety of methods exist for the prediction of thermal conductivity based on empirical fits to databases of soil thermal conductivities. In this paper an analytical model will be developed based on unidirectional heat flow through a three-phase soil element. The performance of this model will be validated against a database of 155 test measurements from the published literature. A variety of alternative prediction methods will be tested against this dataset, with the model derived here being shown to be at least as good as the best empirical model while retaining a physical origin.

Numerical simulation of vertical ground heat exchangers: Intermittent operation in unsaturated soil conditions

The effect of varying the thermal properties of inhomogeneous unsaturated soil on the intermittent operation of a vertical ground heat exchanger (GHE) was simulated by a conjugate heat transfer simulation using a transient conductive heat transfer model. A three-phase soil model was used to introduce soil properties that vary with depth. The performance during the first few hours was significantly different from that of an analytical infinite line source model that assumes steady-state borehole conditions, although relatively good agreement was obtained thereafter. Unsaturated soil conditions afforded a 40% lower mean heat exchange rate than saturated conditions. This demonstrates the importance of considering unsaturated conditions in the design and performance evaluation of GHEs.

Numerical simulation of explosion-induced soil liquefaction and its effect on surface structures

The detonation of high explosives (HE) in soil generates high intensity stress wave, which may induce soil liquefaction and thus cause damage to surface structures in a larger area. A commonly used criterion for the soil liquefaction is the residual excess pore pressure ratio. In order for such a criterion to be applied directly in a numerical analysis, it will be desirable if the soil is modelled as a multi-phase medium such that the stress and pressure in the individual constituents, namely the solid particles, pore water and air, can be resolved. In this paper, a numerical three-phase soil model is employed for the simulation of the effect of blast-induced soil liquefaction on surface structures. The simulation model uses a full coupled modelling approach, where the HE charge, soil medium and the surface structure are all explicitly included. To tackle the large deformation in the area surrounding the charge, the meshfree SPH model is considered, whereas the remaining domain including the surface structure is modelled by Lagrangian finite elements. Numerical case studies are presented to demonstrate the model implementation and examine the characteristic responses. Results indicate that with the proposed modelling methodology it is possible to reproduce the soil liquefaction process and the subsequent effect on surface structure under blast loading.

A nonlinear multi-field coupled model for soils

A nonlinear multi-field coupled model for multi-constituent three-phase soils is derived by using the hybrid mixture theory. The balance equations with three levels (constituents, phases and the whole mixture soil) are set up under the assumption that soil is composed of multi-constituent elastic-plastic solid skeleton (which is different from the linearization method) and viscous liquid and ideal gas. With reasonable constitutive assumptions in such restrictive conditions as the principles of determinism, equipresence, material frame-indifference and the compatible principle in continuum mechanics, a theoretical framework of constitutive relations modeling three-phase soil in both non-equilibrium and equilibrium states is established, thus the closed field equations are formed. In the theoretical framework, the concept of effective generalized thermodynamic forces is introduced, and the nonlinear coupling constitutive relations between generalized dissipation forces and generalized flows within the system at nonequilibrium state are also presented. On such a basis, four special coupling relations, i.e., solid thermal elastic-plastic constitutive relation, liquid visco-elastic-plastic constitutive relation, the generalized Fourier’s law, and the generalized Darcy’s law are put forward. The generalized or nonlinear results mentioned above can degenerate into the linear coupling results given by Bennethum and Singh. Based on a specific dissipation function, the concrete form of generalized Darcy’s law is deduced, which may degenerate into the traditional form of Darcy’s law by neglecting the influence of skeleton deformation and temperature. Without considering temperature and other coupling effects, the nonlinear coupled model in this paper can degenerate into a soil elastic-plastic constitutive model.

A Seepage-Deformation Coupled Analysis of an Unsaturated River Embankment using a Multiphase Elasto-Viscoplastic Theory

ABSTRACT A multiphase deformation analysis of a river embankment was carried out using an air-soil-water coupled finite element method capable of considering unsaturated seepage flow. A numerical model for unsaturated soil was constructed based on the mixture theory and an elasto-viscoplastic constitutive model. The theory used in the analysis is a generalization of Biot's two-phase mixture theory for saturated soil. An air-soil-water coupled finite element method was developed using the governing equations for three-phase soil based on the nonlinear finite deformation theory, i.e., the updated Lagrangian method. Two-dimensional numerical analyses of the river embankment under seepage conditions were conducted, and the deformation associated with the seepage flow was studied. We have found that the occurrence of large deformations corresponds to the large values of the hydraulic gradients at the toe of the embankment, and that the overflow of river water makes the embankment more unstable. It has been confirmed that seepage-deformation coupled three-phase behavior can be simulated well with the proposed method.

Development of an innovative soil remediation: “Cyclodextrin-enhanced combined technology”

This paper introduces an in situ “Cyclodextrin-enhanced soil bioremediation technology” which is a combination of 1. in situ bioventilation for biodegradation in the unsaturated soil zone; 2. physico-chemical treatment of the pumped ground water; 3. impulsive flushing for the three-phase soil. For enhancement of biodegradation and solubilization randomly methylated β-cyclodextrin (RAMEB) was used. An additional aim of this study was to prove the importance of the technology monitoring which was used for characterisation of the soil processes by an integrated methodology. It consists of physico-chemical, biological and ecotoxicological methods specific for the contaminants. For technology monitoring the mobile soil phases – soil gas and ground water – were analysed. Sampling of the whole soil was carried out at the start and end of the technology application. RAMEB resulted in the enhanced removal of pollutants both from the saturated and unsaturated soil zones. Moreover, the biodegradation was more effective than the pump and treat technology, proved by the establishment of the carbon material balance in all soil phases.

Numerical analysis of blast-induced liquefaction of soil

Soil has complicated properties that render the finite element modeling of blast-induced liquefaction very difficult. Recently, a numerical three-phase soil model has been proposed by the authors. This model contains all necessary elements for describing complex responses including the change of pore water pressure and degradation of the soil skeleton when subjected to extreme loading such as an explosion, and hence allows for the analysis and prediction of the liquefaction induced by explosion in the soil. In this paper, the three-phase model is applied to simulate the soil liquefaction. An overview of the three-phase soil model is provided first. The model is then employed to simulate physical experiments on the compressive behaviour of undrained soils under quasi-static and shock loading, respectively. Details about the porewater pressure and the effective stress on the soil skeleton are obtained from the numerical analysis and they compare well with the experimental data. An experimental case involving underwater explosion and liquefaction of a sand bed underneath is also analyzed using a coupled simulation with the three-phase soil model. The results show that the liquefaction zone can be simulated favourably. The effects of different shock loading on soil response and the assessment of the soil liquefaction based on the numerical results are discussed.