PSI - Issue 17

M. Zhelnin et al. / Procedia Structural Integrity 17 (2019) 316–323 Author nam / Structural Integr ty P o edi 00 (2019) 000 – 000

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Fig. 2. (a) distribution of the mechanical pressure p (blue line) and Mises stress (green line) along the boundary of a freezing well at t = 200 day; (b) distribution of displacement vector field and position of phase transition (blue surface) in the first computational domain at t = 200 day.

The results of the numerical simulation allow one to conclude that in a neighborhood of the wellbores plastic deformation could occur. To estimate plastic deformation of soils surrounding the freezing well, the numerical simulation for the second domain is performed in elasto-plastic formulation. In Fig. 3 distributions of the mechanical pressure and Mises stress in the second domain are shown at t = 200 day. It can be seen that in the sandstone stratum the pressure and the stress are higher compared with other soil stratums, as value of the yield stress of sandstone exceeds the ones of clay and sand. At that in sandstone stratum a rise of the stress is observed in the phase transition zone. The maximal values of the pressure and the stress attain on the well boundary.

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Fig. 3. Distributions of the mechanical pressure (a) and Mises stress (b) in the second computational domain at t = 200 day. White lines denote boundaries of the phase transition zone.

In Fig. 4(a) distributions of the pressure and Mises stress along the well boundaries is presented at t = 200 day. In comparison with the results presented in Fig. 2(a) the distributions are more smoothly that relates to an influence of plastic deformation. In this case values of the pressure and the stress at the interface of soil stratums significantly reduce. The maximum value of the stress attains at interface of the sand and sandstone stratums. In Fig. 4(b) effective plastic strain is presented at t = 200 day. It can be seen that in the sand stratum the plastic strain is higher than in the other soil stratums. This is explained by the yield stress of sand is less than sandstone but thermal diffusivity is higher compared with clay. As a result, in the sand stratum the freezing process proceeds with a high rate and frost-heaving pressure has a more significant impact on stress-strain state. The maximal value of the plastic strain attains on the boundary of the freezing well. At that in the phase transition zone a rise of the strain is