# Freezing and Thawing Processes of Highways in Kazakhstan
###### Abstract  
This paper presents the results of an experimental study of freezing and thawing patterns of highways in Kazakhstan. Special sensors measure temperature and moisture change every hour in automatic mode. The purpose of this work is to develop a methodology for determining the depth of freezing of subgrade soils of roads of Kazakhstan, and the task is to establish the pattern of cold temperature change (temperature \"0 \"C\") through certain points (sensors) at any time. In the upper part of the pavement (up to 30-40 cm), the temperature changes in annual and daily cycles. As the depth increases, the daily temperature fluctuations disappear, leaving only the annual fluctuation. At a depth of 180 cm and below, temperature fluctuations occur only in the annual cycle. The freezing rate varied from 14 cm/day to 0.33 cm/day. The maximum freezing depth was 227 cm. The descending branch of thawing occurs almost uniformly, with an average rate of 6.25 cm/day to a depth of 220 cm; the average rate of the ascending branch of thawing is 0.9 cm/day. Asphal-concrete layers of the pavement and the upper part of the subgrade were in a frozen state for 151 and 166 days, respectively. In the subgrade at the beginning and end of the cold period, there are abrupt changes in moisture, which are explained by phase transitions of the second order: the transition from the liquid state to the solid (ice) at the beginning of the cold period and the transition of moisture from the solid state to liquid at the end of the cold period.  
Keywords:road; pavement; subgrade; freezing; thawing; temperature; moisture; measuring station +
Footnote †: journal: Medical  
of clay and its plasticity index, climatic, hydrological, and other natural conditions, which vary widely [6; 9; 10; 11]. That is why the depth of freezing varies from year to year, as does the climate on the Earth [12; 13].  
The work [14] also mentions that the temperature field formed on the road surface is determined by climatic factors such as solar radiation, air temperature, wind, etc. An accurate forecast for the temperature field of the road surface is crucial tothe design of the road surface, the winter maintenance of roads, and the formation of a microclimate of the surface environment.  
The influence of precipitation should be considered from different sides, including evaporation (phase transition), convection, and water flow [15]. Water infiltration has a direct effect on the thermal properties of road materials, especially for the porous surface layer of the pavement. This problem becomes severe in winter when freezing or thawing of the road structure occurs.  
All over the world, researchers are dealing with the problems of the influence of environmental factors on the road condition, among which temperature and moisture rank highly. The authors emphasize the need to create databases tomonitor these indicators, recorded in realtime. Information from such monitoring systems allows us to analyze and simulate road properties [16; 17; 18]. When obtaining the necessary parameters in different years, the researchers use various measuring means [16; 19; 20; 21; 22; 23]. At the same time, basically all researchers use sensors based on the principle of thermal resistance to measure temperature, and sensors based on diamagnetic permeability are used to measure moisture.  
In other works [24; 25], the authors investigated the peculiarities of the temperature and moisture distribution at the points of the pavement and the subgrade and their variations over time during different periods of the year, including the winter season.  
The purpose of this paper is to develop a methodology for determining the depth of freezing of subgrade soils in Kazakhstan.  
This paper is a continuation of our earlier works on the study of temperature and moisture in the structural elements of highways [26; 27; 28; 29] and presents the results of an investigation of freezing and thawing on sections of highways located mainly in the northern region of Kazakhstan with a long cold period.