PSI - Issue 17

O. Plekhov et al. / Procedia Structural Integrity 17 (2019) 602–609 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

608

7

zones created by different freezing columns. Figure 3 shows a change in ice content during the local closure of the frozen soil barriers. The process of local closure was modeled by two freeze columns designed for a maximum operating temperature of -20 ° C, and located at a distance of 0.2 meters. The distribution of moisture and ice contents along the line connecting the freeze columns is shown in figure 4. The redistribution of moisture takes place in the early stages of the process and leads to a significant drop in humidity at the central point of the line connecting the wells (Fig. 4a). As a result, ice content on the line connecting the wells becomes substantially heterogeneous. At the point of closure of the frozen zones, ice content is 30% less than in the zone near the freeze columns (Fig. 4b).

a)

b)

Fig. 3. Evolution of ice content during the coalescence of two freezing zones.

0 0.05 0.1 0.15 0.2 0.25

0 0.05 0.1 0.15 0.2 0.25 0.3

Ice

Humidity

0

0.05

0.1

0.15

0

0.05

0.1

0.15

x, m

x, m

а)

b) Fig. 4. Distribution of moisture content (a) and ice content (b) as a function of time plotted along the line connecting the freeze wells.

The results of modeling the redistribution of moisture within the closed AGF system are presented in Figure 5. Consideration of the cryogenic flow leads to the non-uniform freezing of the internal space and to an increase in ice content at the freezing front. The humidity at the center of the inner space of the AGF system decreases monotonically during the entire freezing process.

а)

b) Fig. 5. Distribution of ice content during the growth of closed frozen zones (a), distribution of moisture content during the formation of AGF system at different instants of time (b).

4. Conclusions

It is common in engineering practice to use relatively simple phase transition models, which do not describe many of the physical effects and processes involved in the formation of AGF system. The analysis of the state-of-the-art shows that one of the most important effects in describing the filtration processes in porous media is the kinetics of