Winners of the “Umnik” program Andrey Boyarintsev (2019) and Aleksandra Zybtseva (2022)

Composite piles are the topic of research by Andrey Boyarintsev, senior lecturer at the SPbGASU Department of Geotechnics. Over five years, four patents on this topic were received, and in March 2024, the fifth invention was patented. Together with Aleksandra Zybtseva, a graduate of our university’s master’s program, the young scientist created a means for measuring ground temperature.

“One of the directions in the study of composite piles was their thermotechnical and thermophysical interaction with the upper part of the soil during freezing and thawing throughout the year. We carried out modeling and experiments where we froze a tray with soil and a pile placed in it. During the work, it was discovered that under certain conditions, the pile material does not affect the increase in the depth of soil freezing. This is very important for construction, because in this case the pile is not a cold bridge and does not aggravate the physical and mechanical processes occurring in the soil when it freezes,” said Andrey Boyarintsev.

The experiments became possible thanks to a grant of 500 thousand rubles received by Aleksandra Zybtseva in the competition of the Foundation for the Promotion of Innovation under the “UMNIK” program for students in educational institutions of higher education in Russia in bachelor’s, specialist’s, master’s or PhD programs. Aleksandra’s project was called “Development of a means for measuring the temperature of permafrost soil based on composite materials”.

• The researchers determined the moment when the pile material begins to influence the increase in freezing depth, or, in other words, at what point the pile becomes a cold bridge. This can be very useful for geotechnical monitoring in the Far North.

The means for measuring frozen soil that are currently used are made of steel pipes. But such a pipe has significant thermal conductivity, which distorts the measurement results. Researchers have proposed using a thermally insulating composite material - fiberglass, which does not allow heat flows from the atmosphere into the ground to pass through its body.

The construction of the device is designed in such a way that its entire length is divided into segments made of composite tubes and connected by steel couplings. The trick is that sensors are attached to the inside of the steel couplings to measure the temperature of the soil. Thus, the coupling very quickly transfers the soil temperature to the temperature measurement sensor, and the fiberglass rods between the couplings eliminate accidental heat flows between the steel couplings. It is these couplings that measure the ground temperature. As a result, it is possible to very accurately measure the soil temperature at a specific point.

“We plan to modify the design so that the sensors can be removed for testing. The design of the tube does not yet provide for this, and it can only be used for two years. We want to supply our thermal tubes as prototypes to companies that conduct geotechnical monitoring in the Far North, so that they can work with them and give feedback on what can be improved,” said Andrey Boyarintsev.

The device received a utility model patent No. 224461.