PSI - Issue 28

A. Prokhorov et al. / Procedia Structural Integrity 28 (2020) 1579–1589 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Nomenclature t – time,

W – moisture, I – ice content, T – temperature, ( ) D D W  – diffusion coefficient, eq eq ( ) W W T  – equilibrium moisture curve, * t – characteristic time of water crystallization, C – effective volumetric heat capacity,  – effective thermal conductivity, L – latent heat of phase transition,

sk  – dry skeleton density, σ – Cauchy stress tensor,  – effective density, g – free fall acceleration vector, C – elastic tensor, ε – strain tensor, T ε – thermal strain tensor, fh ε – frost heave strain tensor, u – displacement vector, I – unit tensor, T  – thermal compression ratio,

0 T – initial temperature 0 W – initial moisture, 0 a – soil-dependent constant, ph T – phase transition temperature, min T – minimum temperature reached during freezing. l  – lateral surface of the cylinder, e,t  , e,b  – cylinder end faces, n – outward normal vector, l k , e k – compliance coefficients of the wall and base of the plastic form, values of functions 1 T , 2 T , 3 T temperature obtained by corresponding thermocouples.

1. Introduction Freezing and frozen soils are actively used as solid foundations and environments for various kinds of engineering structures Tsytovich (1973). Permafrost soils serve as a support for buildings and pipelines Buldovich et al (1999). Artificially frozen soils are used to create temporary barriers during sinking vertical mine shafts and tunnels in weak, unstable, water-saturated rocks Vyalov et al. (1962), Trupak (1974), Andersland et al. (1994). The formation of ice in the soil leads to an increase its strength and stability, and a decrease hydraulic conductivity. At the same time, a change in the temperature of the frozen soil is accompanied by occurrence of significant deformations, which can cause damage to the structures. As a result, during construction, it is necessary to justify the design and engineering decisions, taking into account the mechanical properties and features of freezing and frozen soils. Frost heave during soil freezing is determined by a complex interaction between the processes of heat transfer, mass transfer and an evolution of the stress-strain state of the skeleton. For a detailed study of these processes, laboratory experiments are carried out. In Zhang et al. (2014), Zhang et al. (2017), experimental studies of frost heave deformations and changes in pore pressure in cylindrical samples of moisture-saturated sand and clay were carried out. It was shown that with an increase in the moisture saturation of the sample, the deformations caused by frost heave increase, and the pore pressure decreases with decreasing temperature. At the same time, it is noted that in the