scholarly journals One-dimensional large-strain thaw consolidation using nonlinear effective stress – void ratio – hydraulic conductivity relationships

2018 ◽  
Vol 55 (3) ◽  
pp. 414-426 ◽  
Author(s):  
Simon Dumais ◽  
Jean-Marie Konrad
Keyword(s):  
Heat Transfer ◽  
Hydraulic Conductivity ◽  
Effective Stress ◽  
Void Ratio ◽  
Moving Boundary ◽  
Initial Conditions ◽  
Large Strain ◽  
One Dimensional ◽  
Consolidation Theory ◽  
Thaw Consolidation

A one-dimensional model for the consolidation of thawing soils is formulated in terms of large-strain consolidation and heat-transfer equations. The model integrates heat transfer due to conduction, phase change, and advection. The hydromechanical behaviour is modelled by large-strain consolidation theory. The equations are coupled in a moving boundary scheme developed in Lagrangian coordinates. Finite strains are allowed and nonlinear effective stress – void ratio – hydraulic conductivity relationships are proposed to characterize the thawing soil properties. Initial conditions and boundary conditions are presented with special consideration for the moving boundary condition at the thaw front developed in terms of large-strain consolidation. The proposed model is applied and compared with small-strain thaw consolidation theory in a theoretical working example of a thawing fine-grained soil sample. The modelling results are presented in terms of temperature, thaw penetration, settlements, void ratio, and excess pore-water pressures.

Theoretical Study on Thaw Settlement of Saturated Frozen Soil

2012 ◽  
Vol 204-208 ◽  
pp. 155-162
Author(s):  
Feng Ming ◽  
Dong Qing Li ◽  
Kun Zhang
Keyword(s):  
Void Ratio ◽  
Moving Boundary ◽  
Large Strain ◽  
Frozen Soil ◽  
Conductivity Equation ◽  
Consolidation Process ◽  
Thermal Conductivity Equation ◽  
Temperature Boundary ◽  
Thaw Consolidation ◽  
Consolidation Rate

The consolidation of frozen soil is a coupled action of temperature and deformation. Using moving boundary method and taking the void ratio as a variable, the large strain thaw consolidation mathematical model is built according to Gibson’s large strain consolidation theory and thermal conductivity equation with consideration of phase change. In order to verify the model, a simple example is simulated by FEM software. The result shows that the consolidation range and consolidation rate are decided by the temperature boundary; the change of void and deformation are influenced by pore pressure dissipation and the thaw process in permafrost are delayed by consolidation process.

Nonlinear Inverse Heat Conduction With a Moving Boundary: Heat Flux and Surface Recession Estimation

1999 ◽  
Vol 121 (3) ◽  
pp. 708-711 ◽  
Author(s):  
V. Petrushevsky ◽  
S. Cohen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fourier Series ◽  
Heat Conduction ◽  
Moving Boundary ◽  
Heat Conduction Problem ◽  
Inverse Heat Conduction Problem ◽  
Variable Order ◽  
Inverse Heat Conduction ◽  
One Dimensional

A one-dimensional, nonlinear inverse heat conduction problem with surface ablation is considered. In-depth temperature measurements are used to restore the heat flux and the surface recession history. The presented method elaborates a whole domain, parameter estimation approach with the heat flux approximated by Fourier series. Two versions of the method are proposed: with a constant order and with a variable order of the Fourier series. The surface recession is found by a direct heat transfer solution under the estimated heat flux.

One-dimensional Consolidation of Thawing Soils

1971 ◽  
Vol 8 (4) ◽  
pp. 558-565 ◽  
Author(s):  
N. R. Morgenstern ◽  
J. F. Nixon
Keyword(s):  
Moving Boundary ◽  
Practical Interest ◽  
Moving Boundary Problem ◽  
One Dimensional ◽  
Closed Form Solutions ◽  
Pressure Distributions ◽  
Thaw Consolidation ◽  
Degree Of Consolidation ◽  
Compressible Soil ◽  
Excess Pore Pressures

The physics of consolidation of a thawing soil is formulated in terms of the well-known theories of heat conduction and of linear consolidation of a compressible soil. A moving boundary problem results, and closed form solutions have been obtained for several cases of practical interest. The results are presented in terms of normalized pore pressure distributions. It is shown that the excess pore pressures and the degree of consolidation in thawing soils depend primarily on the thaw consolidation ratio.

Predicting the properties of bentonite-sand mixtures

Clay Minerals ◽  
1996 ◽  
Vol 31 (2) ◽  
pp. 243-252 ◽  
Author(s):  
L. H. Mollins ◽  
D. I. Stewart ◽  
T. W. Cousens
Keyword(s):  
Hydraulic Conductivity ◽  
Linear Relationship ◽  
Void Ratio ◽  
Preparation Technique ◽  
Conductivity Data ◽  
Final State ◽  
Waste Containment ◽  
One Dimensional ◽  
Straight Line ◽  
Vertical Effective Stress

AbstractOne-dimensional swelling tests and hydraulic conductivity tests have been performed at vertical effective stresses up to 450 kPa on Na-bentonite powder and compacted sand/Na-bentonite mixtures (5, 10 and 20% bentonite by weight) to investigate the use of bentonite-improved soils for waste containment. It was found that bentonite powder swells to reach a final state described by a single straight line on a plot of void ratio against the logarithm of vertical effective stress, regardless of preparation technique. Swelling of sand/bentonite mixtures expressed in terms of the clay void ratio show a deviation from bentonite behaviour above a stress which depends on the bentonite content. Hydraulic conductivity data for bentonite and sand/bentonite mixtures indicate an approximately linear relationship between logarithm of hydraulic conductivity and logarithm of void ratio. A design model based on the clay void ratio, and the sand porosity and tortuosity is presented enabling the hydraulic conductivity of a mixture to be estimated.

Measurement of hydraulic conductivity in oil sand tailings slurries

1996 ◽  
Vol 33 (4) ◽  
pp. 642-653 ◽  
Author(s):  
Nagula N Suthaker ◽  
J Don Scott
Keyword(s):  
Hydraulic Conductivity ◽  
Oil Sands ◽  
Void Ratio ◽  
Large Strain ◽  
Measurement Techniques ◽  
Hydraulic Gradient ◽  
Oil Sand ◽  
Fines Content ◽  
Acid Lime ◽  
Clamping Device

Fine tails, the resulting fine waste from oil sand processing, undergoes large-strain consolidation in tailings ponds. Its consolidation behaviour must be analyzed using a large-strain consolidation theory, which requires the determination of the relationship between the void ratio and hydraulic conductivity. Conventional measurement techniques are not suitable for fine tails, and a special slurry consolidometer, with a clamping device to prevent seepage-induced consolidation, was designed to determine the hydraulic conductivity of the fine tails and nonsegregating fine tails – sand slurries. The hydraulic conductivity of slurries is not constant but decreases with time to a steady-state value. Hydraulic conductivity is also influenced by the hydraulic gradient and bitumen content. It is shown that a low hydraulic gradient, less than 0.2, is necessary to counteract the effect of the bitumen and to represent tailings pond conditions. The hydraulic conductivity of fine tails – sand mixes is controlled by the fines void ratio, hence, fines content. The hydraulic conductivity of chemically amended nonsegregating tailings can be lower than that of fine tails. However, acid–lime or acid – fly ash amended nonsegregating tailings have similar hydraulic conductivity values in terms of fines void ratio. The hydraulic conductivity of nonsegregating tailings appears to be governed by fines content and by the nature of the fines aggregation caused by the chemical additive. Key words: tailings, slurries, hydraulic conductivity, slurry consolidometer, nonsegregating tailings, oil sands.

scholarly journals One-Dimensional Nonlinear Consolidation Analysis Using Hansbo’s Flow Model and Rebound-Recompression Characteristics of Soil under Cyclic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Banghua Zhu ◽  
Gang Shi ◽  
Zihe Wei
Keyword(s):  
Cyclic Loading ◽  
Effective Stress ◽  
Void Ratio ◽  
Flow Model ◽  
Soft Clay ◽  
Real Life ◽  
Excess Pore Pressure ◽  
One Dimensional ◽  
Consolidation Degree ◽  
Consolidation Analysis

Hansbo’s flow model for one-dimensional consolidation analysis of saturated clay has been widely recognized as being the most representative for soft soils. Many studies have used the model to examine the characteristics of soil under various conditions. However, very few studies have considered soil under cyclic loading. In this study, using a Hansbo’s flow model and assuming known characteristics for soft clay deformation and rebound and recompression of soil, the one-dimensional consolidation model of soft clay under cyclic loading is established. A FlexPDE solution scheme with excess pore pressure u and void ratio e as variables is also given. The reliability of the proposed method is verified by comparing the obtained results with existing results. On this basis, the consolidation characteristics of soft clay foundations under unilateral drainage and cyclic loading are studied. The effects of soil rebound and recompression characteristics, Hansbo’s flow parameters, cyclic loading period, and cyclic loading form on the consolidation characteristics of soft clay foundation are analyzed. The results show that under cyclic loading, the effective stress, void ratio, and average consolidation degree of the foundation all present a cyclic state and gradually enter a stable cyclic state with the increase in cycles. The peak of effective stress lags behind the peak of cyclic load. The rebound and recompression characteristics of soil have little effect on the effective stress of soil but a great effect on the void ratio. In contrast to its characteristic under linear loading, the average consolidation degree of the foundation under cyclic loading finally enters a stable cyclic state. The results of the analysis can be used as a reference in the analysis of real life highways, railways, subway tunnels built on soft soil foundations subjected to periodic cyclic loading.

scholarly journals Influence of Convective and Radiative Cooling on Heat Transfer for a Thin Wire with Temperature-Dependent Thermal Conductivity

2022 ◽  
Vol 17 ◽  
pp. 1-9
Author(s):  
Okey Oseloka Onyejekwe
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Initial Conditions ◽  
Traditional Approach ◽  
Numerical Technique ◽  
System Of Nonlinear Equations ◽  
Thin Wire ◽  
Temperature Dependent ◽  
One Dimensional ◽  
Temperature Dependent Thermal Conductivity

In this study, a numerical prediction of temperature profiles in a thin wire exposed to convective, radiative and temperature-dependent thermal conductivity is carried out using a finite-difference linearization approach. The procedure involves a numerical solution of a one-dimensional nonlinear unsteady heat transfer equation with specified boundary and initial conditions. The resulting system of nonlinear equations is solved with the Newton-Raphson’s technique. However unlike the traditional approach involving an initial discretization in space then in time, a different numerical paradigm involving an Euler scheme temporal discretization is applied followed by a spatial discretization. Appropriate numerical technique involving partial derivatives are devised to handle a squared gradient nonlinear term which plays a key role in the formulation of the Jacobian matrix. Tests on the numerical results obtained herein confirm the validity of the formulation.

Modeling a high-speed pin-on-disk experiment

2021 ◽  
pp. 154851292110403
Author(s):  
Aron Wing ◽  
Tony Liu ◽  
Anthony Palazotto
Keyword(s):  
Heat Transfer ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Spectral Methods ◽  
High Speed ◽  
Moving Boundary ◽  
Frictional Heat ◽  
Element Analysis ◽  
One Dimensional ◽  
Pin On Disk

The purpose of this work is to analyze the heat transfer characteristics of Vascomax®C300 during high-speed sliding. This work extends previous research that is intended to help predict the wear-rate of connecting shoes for a hypersonic rail system at Holloman Air Force Base to prevent critical failure of the system. Solutions were generated using finite element analysis and spectral methods. The frictional heat generated by the pin-on-disk is assumed to flow uniformly and normal to the face of the pin and the pin is assumed to be a perfect cylinder resulting in two-dimensional heat flow. Displacement data obtained from the experiment is used to define the moving boundary. The distribution of temperature resulting from transient finite element analysis is used to justify a one-dimensional model. Spectral methods are then employed to calculate the spatial derivatives improving the approximation of the function which represents the data. It is concluded that a one-dimensional approach with constant heat transfer parameters sufficiently models the high-speed pin-on-disk experiment.

scholarly journals Heat transfer by seepage in sand: Influence of saturated hydraulic conductivity and porosity

2021 ◽  
pp. 61-75
Author(s):  
Yaser Ghafoori ◽  
Matej Maček ◽  
Andrej Vidmar ◽  
Jaromír Říha ◽  
Andrej Kryžanowski
Keyword(s):  
Heat Transfer ◽  
Hydraulic Conductivity ◽  
Initial Conditions ◽  
Numerical Models ◽  
Characteristic Curve ◽  
Experimental Studies ◽  
Seepage Flow ◽  
Heat Transfer Process ◽  
Saturated Hydraulic Conductivity ◽  
Distributed Temperature Sensor

Heat transfer within the soil is a complex process in the presence of seepage flow. In such conditions, the soil’s thermal behavior is influenced by the thermal and hydraulic properties of the medium as well as the initial conditions and boundary conditions to which the medium is subjected. This paper presents the experimental and numerical studies of heat transfer within the sand subjected to the seepage flow. It focuses on the influence of saturated hydraulic conductivity and the porosity of medium on the heat transfer process. The temperature distribution within the sand was monitored by the optical fiber Distributed Temperature Sensor (DTS). The experiment was performed on three types of silica-dominated sands with different saturated hydraulic conductivities and different Soil Water Characteristic Curve (SWCC). In addition to the experimental study, a coupled hydrothermal numerical model was designed in FEFLOW software and validated by comparing its results with the experimental measurements. To determine the influence of porosity and saturated hydraulic conductivity on heat transfer, we analyzed the numerical models for different values of porosity and saturated hydraulic conductivity. The numerical and experimental studies showed that the thermal velocity is higher in sand with higher saturated hydraulic conductivity and temperature declination occurs more quickly due to the heat convection process. Saturated sand with larger porosity has an overall higher heat capacity, wherefore the temperature declination started later in the measuring points but dropped down lower close to the temperature of the upstream water.

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