Relevance. The construction of long pipelines in the conditions of the cryolithozone is associated with the problem of soil thawing under them. An effective solution to this problem is the use of two-phase heat stabilizers located next to the piles. To increase the efficiency of the device, it is proposed to fin the inner surface of the aboveground part of the thermosyphon. Aim. To determine the optimal parameters of the finning of the thermosyphon surfaces and the number of segments of the device separating the refrigerant flows. Objects. Heat stabilizer, refrigerant, heat and mass transfer, frozen soil. Methods. The developed model uses the laws of non-isothermal multiphase mechanics. There are five related subtasks: blowing of the above-ground part of the heat stabilizer; condensation of the refrigerant inside the above-ground part of the device; movement of the refrigerant inside the flow-separating device; upward flow of the refrigerant; heat exchange of the heat stabilizer with frozen soil. Results and conclusions. The validation of the proposed model was carried out by comparing the calculated data with measurements of the temperature profile for the Salekhard State Archive building. The work shows that increasing the size of the fins of the outer surface of the underground part of the heat stabilizer and segmenting the device separating the refrigerant flows makes it possible to evenly cool the soil in an area not subject to seasonal thawing. It was found that increasing the contact area of the refrigerant with the inner surface of the aboveground part of the thermosyphon due to the finning of this surface makes it possible to increase the average value of the ambient temperature limit at which the device is effective.