Scientists of NSTU-NETI study the frozen soils of Siberia and the Russian Arctic

Scientists of NSTU-NETI conducted a multiscale modeling of the stress-strain state of geological media with the participation of the Institute of Petroleum Geology and Geophysics named after A.A. Trofimuk SB RAS (INGG SB RAS). To assess the behavior of the soil in permafrost conditions, the researchers created mathematical models that showed the state of the soil with temperature changes and under the influence of external loads. It turned out that permafrost in the Arctic and Siberia can be called conditionally — in fact, it reacts sensitively to every season and even heat from buildings and pipelines.

According to Anastasia Kutischeva, project manager, Candidate of Physico-Mathematical Sciences, Associate Professor of the Department of Geophysical Systems at NSTU-NETI, in summer the rock can melt to a depth of four meters, but in winter it can freeze again by five meters. According to the modeling data, not only the air temperature is of great importance, but also the snow cover, which works as a natural insulation. "Of course, this is a well-known fact, but it indirectly confirms the correctness of the results obtained. In other words, numerical modeling corresponds to the "physics of the process," the scientist said.

Particularly interesting results were obtained when studying man-made factors, for example, the influence of pile structures. It turned out that a warm concrete pile literally "burns through" the soil around it, creating an area of constant thawing, which makes the rock less durable and poses serious risks to construction, infrastructure and the environment. In addition, the destruction of frozen soils can lead to the release of greenhouse gases such as methane and carbon dioxide, which will accelerate global warming.

"To test these processes, we used special computational methods that allowed us to track permafrost changes in 10-minute increments for daily processes and one day for seasonal processes. All this will help in the future to predict how the soil will behave further, as well as to take into account various factors during the construction of roads, buildings and pipelines in permafrost areas," Anastasia Kutischeva shared.

Using numerical simulations, scientists have tested exactly how frozen soils react to changes in temperature and load. It turned out that even without considering the mobility of groundwater during thawing, but simply under the influence of gravity, the rock sinks by two centimeters per season. The researchers also recorded a consistent melting and freezing of the rock up to 4 m deep, which led to degradation of the rock structure.

According to Anastasia Kutischeva, the work of NSTU-NETI scientists is unique. The technique takes into account several interrelated processes at once — heat transfer, mechanical deformation, and phase transitions of water into soil, which gives more accurate results than other models, which most often focus on only one of these tasks. "In addition, we have optimized the created algorithms for parallel computing. This allowed calculations to be performed faster and at higher resolution. The higher the detail, the better the forecast, and in matters such as building stability or pipeline safety, accuracy decides everything," Anastasia Kutischeva emphasized.

The research will continue. The degradation of frozen rocks requires constant monitoring and refinement of forecasts. In the future, it is planned to adapt the developed models to new climatic conditions, expand the capabilities of the software package, conduct additional computational experiments and analyze how the changing climate will affect the permafrost rocks.