Simple numerical strategies to model freezing in variably-saturated soil with the standard finite element method

<p>An accurate representation of freezing and thawing in soil covers many applications including simulation of land surface processes, hydrology, and degrading permafrost. Freezing and thawing tightly couple water and heat flow, where temperature and temperature gradients influence the water flow and phase changes, and water content and flow influence the heat transport. In most porous media, the interface between liquid and frozen water is not sharp and a slushy zone is present. A common observation of freezing soil is water accumulation towards the freezing front due to Cryosuction. A mathematical model can be derived using the Clausius-Clapeyron equation, which allows the derivation of a soil freezing curve relating temperature to pressure head. This is based on the assumption that soil freezing is similar to soil drying.</p><p>Many models still lack features such as Cryosuction. We believe that this may be due to numerical issues that model developers face with their current solver and discretization setup. Implementing freezing soil accurately is not straight-forward. Using the Clausius-Clapeyron creates a discontinuity in the freezing rate and latent heat at the freezing point and little attention has been paid to the adequate description of their numerical treatment and computational challenges. Discretizing this discontinuous system with standard finite element methods (standard Galerkin type) can cause spurious oscillations because the standard finite element method uses continuous base/shape functions that are incapable of handling discontinuity of any kind within an element. Similarly, standard finite difference methods are also not capable of handling discontinuities. In this contribution, we present the application of regularization of the discontinuous term, which allows the use of the standard finite element method. We implemented the model in the open-source code base DRUtES (www.drutes.org). We verify this approach on synthetic and various real freezing soil column experiments conducted by Jame (1977) and Mizoguchi (1990).</p><p>Jame, Y.-W., Norum, D.I., 1980. Heat and mass transfer in a freezing unsaturated porous medium. Water Resources Research 16, 811–819. https://doi.org/10.1029/WR016i004p00811</p><p>Mizoguchi, M., 1990. Water, heat and salt transport in freezing soil. sensible and latent heat flow in a partially frozen unsaturated soil. University of Tokyo.</p><p> </p>

Numerical analysis of pile foundations in seasonally freezing soil ground

The article presents the results of numerical analysis for pile foundation in seasonally freezing soil ground. This project uses the static tests of soil by piles at the construction site of Cargo off-loading facilities (Prorva, Atyrau region, Kazakhstan). The project area is located along the east coast of the Caspian Sea, both onshore and offshore, near the Prorva oilfield, Kazakhstan. At present, the North Caspian Sea has a limited water depth (max 8 m). According to the test results have been made design changes in the pile foundation. Static tests (SCLT) were carried out on the piles with 16m in length and precast concrete joint pile foundations with a total length of 22m to 27m. This research is important for an understanding of the interaction mechanism of precast composite joint piles with seasonally freezing soil ground of the Caspian Sea coastal area of the site.

Investigation of the dependence of the thermophysical properties of seasonally freezing soil under the foundations of foundations on their humidity, density and depth of the pit

As a result of the analysis of the current state of the foundation and foundations in the conditions of seasonally freezing soils, the study of thermophysical properties is of great practical importance for the construction of many underground structures. Research in this direction is especially important for local thawing of soil using thermal methods and various chemical reagents. The article presents the results of a scientific - experimental study to establish patterns of change in the physical characteristics of the soil and the coefficient of thermal conductivity of the soil from the dominant factors in the following systems: depth of soil sampling – soil moisture; sampling depth – soil density; soil moisture – coefficient of soil thermal conductivity.

Stress–Strain Model for Freezing Silty Clay under Frost Heave Based on Modified Takashi’s Equation

In analyzing frost heave, researchers often simplify the compressive modulus of freezing soil by considering it as a constant or only as a function of temperature. However, it is a critical parameter characterizing the stress–strain behavior of soil and a variable that is influenced by many other parameters. Hence, herein several one-dimensional freezing experiments are conducted on silty clay in an open system subjected to multistage freezing by considering the compressive modulus as a variable. First, freezing soil under multistage freezing is divided into several layers according to the frozen fringe theory. Then, the correlation between the freezing rate and temperature gradient within each freezing soil layer is investigated. Takashi’s equation for frost heave analysis is modified to extend its application conditions by replacing its freezing rate term with a temperature gradient term. A mechanical model for the stress–strain behavior of freezing soil under the action of frost heave is derived within the theoretical framework of nonlinear elasticity, in which a method for determining the compressive modulus of freezing soil with temperature gradient, overburden pressure, and cooling temperature variables is proposed. This study further enhances our understanding of the typical mechanical behavior of saturated freezing silty clay under frost heave action.