Investigation of salt migration in the ground saturated with a chloride-sulphate sodium-magnesium solution in freezing-thawing cycles

Among the variety of objects in the permafrost zone, soils are encountered, including cryopegs – highly mineralized solutions that have excessive pore pressure. Generally, they have a negative impact, reducing the load-bearing capacity of the ground and causing corrosion of concrete and metal constructions. The study of cryopegs does not receive enough attention from Russian and foreign researchers, not least because of the peculiarities of the thermodynamic state they exist in, therefore detailed investigation of this cryologic object is required in the field and in laboratory conditions. In the presented research the authors study the mechanism of the migration of salt ions in pore water in an enclosed volume of ground during the freezing front movement. To do this, the authors developed an experimental unit and created a measuring unit where the studied moist ground is inserted. Temperature can be set on the opposite sides of the measuring unit. Controlling the extent and speed of temperature change provides a means to regulate freezing front movement (directed from top to bottom). After a number of freezing-thawing cycles salt compositions and concentrations are checked and measured in four intervals of sampling. As a result of the experiments a significant increase in concentration was found at opposite sampling points, and in particular at the beginning of the freezing front movement.