Issue 63

L. Levin et alii, Frattura ed Integrità Strutturale, 63 (2023) 1-12; DOI: 10.3221/IGF-ESIS.63.01

Figure 6: Time dependencies of the average temperature of the FW (a) and the thickness of the FW (b).

The radial dependencies showed a substantially inhomogeneous form. The temperature of the soils in the frozen zone varied over a wide range (sometimes exceeding 15°C). The average FW temperature during the considered time interval first decreased with time and, after 10 to 12 months, began to increase (see Fig. 6a). The FW thickness for the sand and sandy clay continued to increase throughout the entire time interval, while the FW thickness of the clay increased up to 12 months and decreased in the interval from 12 to 14 months. This was because, for clay, the FW boundaries was considered to be at the lowest temperature of -5°C. This temperature is more difficult to maintain for the freezing system in the passive freezing mode. The model also considered that in the interval between 10 and 12 months, a mine shaft was constructed in the soil layers. This led to the heat inflows from the air space of the shaft. It is important to note that the increase in the average temperature of the FW began much later than the start of the ice holding stage, which was associated with the inertia of the thermal processes in the soil volume and the smoothness regarding the changing of the parameters of the freezing station. Only after the temperature of the brine in the freeze pipes became higher than -20°C, the average temperature of the FW began to increase.

M ECHANICAL CALCULATION OF THE FW BEARING CAPACITY

T

he obtained temperature profiles were used to estimate the temporal change in the ultimate bearing capacity of the FW according to the strength criterion. Under the ultimate bearing capacity of FW, we mean the limiting value of the external lateral load, P, which the FW can withstand (see Fig. 7).

Figure 7: Schematic representation of the external lateral load, P, on the FW.

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