Home – Home – Jornals – Earth’s Cryosphere 2022 number 3

The data on the ground temperature up to the depth of 650 m in a well with a restored thermal regime have been obtained for the first time for the Lena-Aldan interfluve. The abnormal permafrost thickness for this territory (750-780 m) has been determined by geothermal measurements. The change of ground temperature with depth displays the nonstationary contemporary regime of permafrost with the negative geothermal gradient up to a depth of 300 m. The permafrost thickness has been estimated and the possible reasons of its difference in relatively nearby areas are considered.

Temperature monitoring of permafrost near underground oil pipelines allow estimating a permafrost thawing depth under structures, predicting the soil temperature over time and predicting the time of emergency, in case the latter one will occur in the future. Permafrost temperature monitoring is carried out in close proximity to the oil pipeline and at depths below the bottom of the layer of seasonal temperature fluctuations. The results of monitoring are processed according to the methodology described in the article.

The results of experimental studies of the tangential frost heaving forces of clay and sandy soils in laboratory conditions on three installations with different single-plane shear rates at constant normal load are presented. The installations made it possible to perform conditionally instantaneous shift, long-term tests with the application of a stepwise shifting load and a shift at a constant speed. As a result of complex studies, the dependences of shear resistance or equivalent tangential forces of frost heaving of sand and loam on water content (from 10 to 28 %) and temperature (from 0 to -10 °C) on the metal surface have been established. An increase in soil water content and a decrease in soil temperature leads to an increase in the resistance to soil shear. The shear resistance of sand is up to 2 times higher than similar values for loam under identical shear conditions, temperature and water content. An increase in soil moisture leads to an increase in the contact area of soil particles through ice layers with a metal foundation and to an increase in the bonds between the particles as a result of an increase in the volume of ice. It is established that the resistance to conditionally instantaneous shear is up to 3 times higher than the values of extremely long-term shear resistance and shear at a constant speed under similar thermal humidity conditions.

The article provides analytical review of existing approaches and specific models for solving problems of freezing, thawing and frost heaving of soils. The authors analyzed about 100 published works of Russian and 100 works of foreign authors, including articles, monographs, dissertations, patents, conference proceedings, scientific reports. Special attention in the analysis of the physical formulation of mathematical models is paid to taking into account the mechanism of heat and mass transfer, ice segregation, phase transitions of pore water, the formation of deformations and forces of frost heaving of frozen soils.

The analysis of differences in the structure of drifting ice ridges and ice ridges in the landfast ice was carried out on the basis of information obtained during research work done by the Arctic and Antarctic Research Institute in 2007-2019 in the Kara and Laptev Seas. The studies were carried out using thermal water drilling with logger recording of the penetration rate. The main attention was focused on the distribution of ice ridge porosity and the thickness of the consolidated layer. The unconsolidated part of the ice ridge keel and its compaction in the process of ice ridge formation under the action of the Archimedes force were considered. It was revealed that the ice ridges in the landfast ice differed from drifting ice ridges in their somewhat smaller geometric dimensions, but in steeper sail and keel slopes, as well as in a different keel/sail ratio (3.1 versus 3.6). In the landfast ice ridges the porosity of the unconsolidated part of the keel was lower than in drifting ice ridges (by 6 % on average). It was confirmed that the gradual decrease in the porosity of the unconsolidated part of the keel of the ice ridges in the landfast ice was caused by the under-ice currents.

The last catastrophic debris flow disaster took place in Tajikistan in the Barsemdara River valley in 2015. The aim of this study was to apply chain modeling to consider debris flow characteristics of 2015 year. This approach has also been applied to assess potential flood prone zones for future debris flows. To consider the characteristics of debris flow in the source, the transport-shift model, developed by Yu.B. Vinogradov was applied. Based on this model, debris flow hydrographs were obtained and used as input data for valley zoning based on the FLO-2D model. So, for scenario I, the debris flow discharge of the forward wave was used as the input hydrograph (maximum -1630 m³/s), the II scenario - the debris flow discharge at the source outlet (maximum 650 m³/s). The digital elevation model ALOS PALSAR (12.5 m) was used as the relief data. Since there are no rheological data, the modeling was carried out using several sets of parameters. The simulated debris flow discharges based on the most realistic option for I scenario varied from 1494 to 2860 m³/s for individual waves. Additionally, the authors carried out modeling using digital elevation model from an unmanned aerial vehicle obtained during the survey in 2019. The results showed that the considered approach makes it possible to estimate the boundaries of both actual and potential flood prone zones.

This paper has described the role and contribution of P.I. Melnikov, Academician of the USSR Academy of Sciences; N.A. Tsytovich, Corresponding Member of the USSR Academy of Sciences; N.I. Saltykov, Professor, and V.F. Zhukov, Candidate of Technical Sciences, to construction of the Yakutsk Combined Heat and Power Plant. These outstanding figures known for their pioneering researches in different fields of permafrost science and engineering were actively and directly involved in the construction project, including the planning and design, foundation analysis, site investigation, foundation construction, and post-construction monitoring. The foundation condition at the plant site, the causes for talik development and the dynamics of talik distribution during the period of authors’ observations have been discussed. The reasons of the quite stable state of all the plant’s facilities despite the widespread talik occurrence have been adduced.