PSI - Issue 28

A. Prokhorov et al. / Procedia Structural Integrity 28 (2020) 1579–1589 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Three main parts can be distinguished on the plots. In the first section a reduce of temperature is observed before the onset of the phase transition. The second section is characterized by a slow temperature change, which is associated with an intense heat dissipation related to the phase transition of water into ice. In the third section, the temperature reduce rate increases again, which is caused by a decrease in the power of the internal heat source, a decrease in the effective volumetric heat capacity, and an increase in the effective thermal conductivity coefficient. In the presented thermo-hydro-mechanical model, the duration of each parts is determined by the freezing temperature, the initial moisture content, the characteristic time of water crystallization and the curve of the equilibrium moisture content. Comparing the numerical and experimental plots, it can be noticed that the maximum deviation is observed at the crossing from the second part to the third one. From this we can conclude that the proposed model does not fully describe the process of the onset of ice formation and predicts a more faster decrease in temperature than its observed in the experiment. In Fig. 5 temperature registered by thermocouples in the one-side freezing experiment are presented. It can be seen that for this type of the freezing the temperature plots have another qualitatively behavior compared to the plots shown in Fig. 4. Here we can see that the second segment related to the onset of the phase transition on the temperature plots given by the thermocouples TC4, TC3 and TC2 slightly pronounce compare to the plots for the thermocouple TC1. The fastest decrease of the temperature is observed in data registered by the thermocouple TC4 that is placed on the freezing side. shows a fast decrease of the temperature. With an increase of the distance from the freezing side the rate of the temperature change rate reduces. It can be related to a consecutive increase of the volume of the soil undergoes to the freezing.

Temperature, C

Figure 5. Temperature measurements by thermocouple ТС1, ТС2, ТС3, TC4 during the one-side freezing experiment.

4.2. Strain measurements and simulation Fig. 6 shows the results of measurements of the deformation sensors BR1, BR2, BR3, BR4 after applying a method of thermal compensation to the readings and deformations obtained as a result of numerical simulation. The thermal compensation procedure was carried out in accordance with the approach proposed in [20], based on the temperature versus time curves taken from the numerical calculation.