ISSN 0145-8752, Moscow University Geology Bulletin, 2017, Vol. 72, No. 3, pp. 224–229. © Allerton Press, Inc., 2017. Original Russian Text © S.S. Volokhov, I.N. Nikitin, D.S. Lavrov, 2017, published in Vestnik Moskovskogo Universiteta, Seriya 4: Geologiya, 2017, No. 2, pp. 66–71.
Temperature Deformations of Frozen Soils Caused by Rapid Changes in Temperature S. S. Volokhova, *, I. N. Nikitina, **, and D. S. Lavrovb, *** a
Department of Geology, Moscow State University, Moscow, 119991 Russia bLLC GeoProject Survey, Moscow, 111024 Russia *e-mail:
[email protected] **e-mail:
[email protected] ***e-mail:
[email protected] Received March 11, 2017
Abstract⎯The results of the study of the temperature deformations for different types of frozen soils due to rapid temperature variations in cooling–heating cycles have been described. The difference in the patterns of the temperature deformation for step-like and single variations of temperature has been established. The dependence of the temperature deformation of frozen soil on the soil type, the total moisture, and the number of the cooling–heating cycles has been studied. Keywords: frozen soil, temperature, cooling, heating, temperature deformation DOI: 10.3103/S0145875217030103
INTRODUCTION Complex physical and physicochemical processes occur in frozen soils, since they are a complex multicomponent system that is extremely sensitive to changes in ambient conditions. These processes are associated with the phase transition of water, moisture migration, strain and deformation development, fissure formation, etc. Temperature deformation is one of these processes. The study of the temperature deformation of the frozen soils was started by A.E. Fedosov (Fedosov, 1935) and continued by I.N. Votyakov (Votyakov, 1963, 1966; Votyakov and Grechichshev 1969), S.E. Grechichshev (Grechichshev, 1972, 1973, 1983), E.P. Shusherina (Shusherina et al., 1970, 1973), E.D. Ershov (Ershov and Brushkov, 1989; Ershov et al., 2001), A.V. Brushkov (1998), and others. It has been established that frozen soils are characterized by anomalously large coefficients of thermal expansion (α): up to 2 × 10–3°C–1 and higher for clay, 1−4 × 10–4°C–1 for lean clay and silty clay, and 2−5 × 10–5°C–1 for sand. The α coefficient is usually less than 3−10 × 10–6°C–1 for construction materials, rocks, and minerals. For frozen soil-forming components, α is 0.4−8 × 10–6°C–1 for the mineral skeleton, 0.5−5 × 10–5°C–1 for ice, and less than 5 × 10–5°C–1 for unfrozen water. It has been revealed that the coefficient of thermal expansion of frozen soils strongly depends on the temperature and decreases when the temperature decreases. The relationship between the temperature deformation and the tem-
perature is sharply nonlinear, which makes frozen soils stand out from other materials. Moreover, it has been shown that the coefficient α for frozen fine-grained soils increases with an increase in the fine material content, with a decrease in the water content (except for sand), and with an increase in temperature. Using the current concepts on the physics of frozen soils, S.E. Grechichshev (1972, 1973) assumed that the change of the frozen soil volume with respect to the temperature variation is associated with several different internal processes, which are multidirectional: the linear expansion (or contraction) of the soil-forming components, the continuous phase transition at the ice-water phase boundary, and the temperature deformation of the internal microstructures. It was subsequently shown by Grechichshev that the temperature deformations of frozen clayey soils occurred not only due to the water phase transition and the expansion or contraction of ice and the soil skeleton, but is also strongly related to the physicochemical processes associated with the water phase transition (hydration and peptization of aggregates at the thawing; coagulation and aggregation of the skeletal particles at the freezing), the migration of unfrozen water, the structural transformation of frozen soils, and microfissure formation (Grechichshev, 1983). E.P. Shusherina et al. (Shusherina et al., 1973) established that the coefficient of thermal expansion is higher in the samples with a disturbed structure than in samples with a natural structure, which is due to the
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TEMPERATURE DEFORMATIONS OF FROZEN SOILS CAUSED
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Table 1. The particle-size composition of the studied soils Particle content for each fraction, % Soil name
particle size, mm 1−0.5
Lean clay Silty clay Sand
0.5−0.25
0.25−0.1
0.1−0.05 0.05−0.01 0.01−0.005 0.005−0.001
