Freezing Point of Saline Soils of Active Layer in Urban Environment of Yakutsk
Torgovkin N.V.
The article provides the results of estimation of important geotechnical parameter which is the freezing point of a saline soil solution – Tbf. Comparison of two calculation methods for the indicator that are applied at absence of experimental data are presented. In this work we considered the saline soils of the active layer of Yakutsk city. The first method is established on the Raoult's law and Van't Hoff factor. It takes into account the salt complex and the temperatures sum is calculated. The second method is based on Code of Practice SP 25.13330.2012 (Bases and Foundations on Permafrost), and Tbf depends on a type of soil pore solution concentration. Our calculations results showed that freezing point being calculated according to the Raoult's law & Van't Hoff factor, in all cases was lower than being determined using the SP. The difference between the calculations results was about 0,2 degrees Celsius for sands, 0,6 degrees Celsius for loamy sands, and about 1,0 degrees Celsius for clay loams. The largest difference is typical for soil pore solutions in chemical composition of which NaCl and Na2SO4 predominate and MgCl2 and CaCl2 are present. For saline sands freezing point calculation both calculation methods are applicable. For saline loamy sands and clay loam in the chemical composition of which sodium chloride and sodium sulphate predominate, and especially when there are magnesium and calcium chlorides, more preferable is to use the Raoult's - Van't Hoff equation.
Key words: salinity, ground, freezing point, Raoult's law & Van't Hoff factor, ground solution.
Science and Education, 2016, No.3, pp.32-36