Freezing‐induced stiffness and strength anisotropy in freezing clayey soil: Theory, numerical modeling, and experimental validation

Abstract

This paper presents a combined experimental‐modeling effort to interpret the coupled thermo‐hydro‐mechanical behaviors of the freezing soil, where an unconfined, fully saturated clay is frozen due to a temperature gradient. By leveraging the rich experimental data from the microCT images and the measurements taken during the freezing process, we examine not only how the growth of ice induces volumetric changes of the soil in the fully saturated specimen but also how the presence and propagation of the freezing fringe front may evolve the anisotropy of the effective media of the soil–ice mixture that cannot be otherwise captured phenomenologically in the isotropic saturation‐dependent critical state models for plasticity. The resultant model is not only helpful for providing a qualitative description of how freezing affects the volumetric responses of the clayey material, but also provide a mean to generate more precise predictions for the heaving due to the freezing of the ground.

Analysis on “three-box” model of stress-strain in frozen soil porous media based on representative macroscopic Volume

“…This paper proposes a "three-box" stress-strain model for frozen soil porous media based on RMV, which provides a reference for the study of momentum, energy, and mass transfer characteristics in frozen soil porous media and other porous media, and the conclusions of the study are of guiding significance for the application of frozen soil (Yang et al, 2018;Yin et al, 2022).…”

“…The mechanical properties of the frozen soil are the most important factors that affect its stability. Understanding these factors is very important for the development and construction of frozen soil structures (Yang et al, 2018;Yin et al, 2022).…”

Microstructure‐based effective stress for unsaturated frozen soils

“…40 Besides this morphological difference, ice in micropores has been proven to lead to changes on the soil constitutive behaviors in a way different to ice in macropores. 28,41 In this section, considering these different morphological and mechanical properties that ice may exhibit in micro-and macropores, we assume that the ice in micropores has the consistent deformation with soil particles on their contacts, followed by setting ṽ𝑖1 = 0 and 𝑃 𝑖1 = 𝑃 𝑠 , and that the ice existing in macropores has the relative velocity to the motion of soil particles ṽi2 . The solid matrix for frozen soils is considered to be formed by the mixture of microscopic ice and soil particles, which is also regarded compressible in this study.…”

“…Therefore, we still adopt this additional assumption in the following derivations. As the solid matrix for frozen soils is now regarded as the mixture of the microscopic ice and soil particles, the solid volume fraction 𝜙 𝑠 of unfrozen soils needs to be replaced by 𝜙 𝑠 + 𝜙 𝑖1 for frozen soils, Equation (36) ) div 𝒗 (41) or another form…”

“…Different from the macroscopic ice which can be observed with naked eyes, a network of smaller ice crystals referred to the microscopic ice is aggregated into the soil microstructures, which needs to be captured using the X‐ray tomographic technique 40 . Besides this morphological difference, ice in micropores has been proven to lead to changes on the soil constitutive behaviors in a way different to ice in macropores 28,41 . In this section, considering these different morphological and mechanical properties that ice may exhibit in micro‐ and macropores, we assume that the ice in micropores has the consistent deformation with soil particles on their contacts, followed by setting $${{\bm{\tilde{v}}}}_{i1} = \ 0$$ and $${P}_{i1} = {P}_s$$, and that the ice existing in macropores has the relative velocity to the motion of soil particles $${{\bm{\tilde{v}}}}_{{\rm{i}}2}$$.…”