Dependence of Freezing Soil Heaving Properties on the Degree and Composition of Salinization
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EXPERIMENTAL INVESTIGATIONS DEPENDENCE OF FREEZING SOIL HEAVING PROPERTIES ON THE DEGREE AND COMPOSITION OF SALINIZATION
UDC 626.862 A.G. Alekseev Moscow State University of Civil Engineering, Gersevanov Research Institute of Bases and Underground Structures, Research Centre for Construction JSC, Moscow, Russia, *Corresponding author Email: [email protected].
This research presents the experimental data on physical modeling of cryogenic heaving of saline soils under laboratory conditions in the external mass transfer and isothermal temperature mode. This paper also reports the regularities of frost heaving of sandy and clayey soils salinized with sodium chloride and sodium sulfate. The mechanism of the development of cryogenic heaving of saline soils is presented.
Introduction Freezing of soils, including those at the base of the structures, can lead to cryogenic heaving. The influence of artificial salinization on frost soil heaving in terms of controlling it has been investigated by N. A. Tsytovich, S. B. Ukhov, Ya. A. Kronik, Z. A. Nersesova, B. I. Dalmatov, and V. S. Lastochkin et al. [1-8]. To control frost heaving, artificial soil salinization is performed using water-soluble salts, such as KCl, NaCl, and CaCl2. However, as per previous studies, this process increases the pore solution concentration, changes the physical and chemical properties of the soil, and decreases the ground freezing point [5]. It has been established that an increase in the soil salinity in the high concentration range leads to a decrease in cryogenic heaving. However, despite the available research, this issue of assessing the effect of the concentration of salts contained in the soil on the amount of heaving (particularly when the degree of salinization is up to 0.3%) remains unresolved for various types of soils and freezing conditions. I. A. T'ut'unov and Z. A. Nersesova [1] additionally revealed that the change in the composition of cations from multivalent to monovalent in pore solutions can lead to a decrease in cryogenic heaving during soil freezing, and salinization using chlorides with monovalent cations (KC1 and NaCl) completely eliminates cryogenic water migration and soil heaving. When adding multivalent cations of calcium, iron, or aluminum (Ca2+, Fe3+, and A13+) into nonporous montmorillonite clays, the particles aggregate and the silty fraction content increases, leading to an increase in the intensity of water migration and frost heaving of the soil during freezing. Soils and Equipments The effect of soil salinization on cryogenic heaving was studied using physical modeling under laboratory conditions on silty, heterogeneous sand, free of organic matter (W = 19.5%, ρ = 2.0 g/cm3),
Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 12-15, September-October, 2020. 0038-0741/20/5705-0379
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Fig. 1. Installation IMP 2.3: 1) casing, 2-4) thermostat sectors, 5 and 6) temperature-regulating meters, 7) toggle switch for forced lifting of the pneumatic cy
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