No 4 (2023)

This paper analyzes a possible impact of scenario earthquakes in the zones of high seismic hazard in order to justify measures for ensuring population safety by the example of the southern Stavropol krai area. Over the past twenty years, the Central CisCaucasus region shows elevated seismicity based on the data recorded by the Geophysical Survey RAS network, reporting the occurrence of seismic events within a wide range of magnitudes, М≥1. One of the last felt events with mb = 4.4 occurred in the studied area on April 1, 2023, producing shaking intensity of 3 to 4 grades on the MSK-64 scale in large resort cities of the region. The parameters for the scenario events are based on the results of detailed seismic zoning (DSZ) and review seismic zoning (RSZ-2016) obtained by the Schmidt Institute of Physics of the Earth RAS. The Extremum system was used to assess felt effects in resort centers located in the southern Stavropol krai. We analyzed the influence of seismic intensity propagation and the parameters of macroseismic field equation on the assessed impact of the scenario earthquakes. Special attention was paid to the depths of strong and moderate events in the considered area of the Northern Caucasus and to the orientation of macroseismic isoseismals. Pre-calibration of the Extremum system loss models is recommended. Estimates of possible simulated damage due to scenario earthquakes with M=6.0 and M = 5.0 for individual large resort cities of the Kavminvody zone are given. The results can be used in the development of both preventive measures and response plans in case of possible events in the region.

To date, there is no comprehensive geotechnical monitoring of pile foundations for residential and industrial buildings in Russian regions located in the permafrost zone and, accordingly, there is no reliable information about which part of them annually undergoes deformations caused by changes in geocryological conditions. This study presents the results of fieldwork on inspection of buildings in Amderma village (Zapolyarny district of the Nenets Autonomous Okrug, the North-East of the European part of Russia, part of the Arctic zone of the Russian Federation). The article presents the main reasons for the deformation of buildings in Amderma. Data were collected on climatic and permafrost conditions and their dynamics, construction features and the current state of engineering structures of Amderma. Based on studies of engineering structures, a general description of the buildings is given. It was identified that in 2021, 59% of the total number of buildings were deformed, of which 80% were wooden, 46% brick and concrete, and 31% buildings made of light structures. Thus, only 40% of the heat-generating facilities in Amderma are not deformed. The main factors of foundation deformations are identified: soil salinity; watering underground or directly near the building; thermokarst in the building area; coastal processes; rise in temperature due to climate change or creep in the base soil. The results of the study made it possible to fill in local information “gaps” for the Arctic coast of the Nenets Autonomous Okrug in the range of works devoted to the problem of buildings and structures deformations. The new results obtained can be integrated with other similar studies.

The paper considers the regional features of the phenomena of timber drifting on mudflow rivers on Sakhalin Island. The regularities of mudflow formation in Sakhalin rivers and their mudflow regime are established and the factors causing timber drifting in the debris flow watercourses of Sakhalin Island are studied. Due to the history of Sakhalin terrain and macrorelief formation, the main mountain structures are composed of marine sediments. This promotes mudflows on rivers, the active development of exogenous processes on river slopes, and the flow of solid phase and woody vegetation into the channel and talvegs. As a result, the density of streams increases, their eroding and abrasive ability rises, which affects significantly channel deformations and involves timber drifting. High-density flows have an elevated transporting capacity, since they increase the pulling force of the flow affecting the midsection of the drifting timber root system, and also raise the timber buoyancy due to an increase in the pushing Archimedean force. Also, regional features include a large amount of liquid precipitation, the annual amounts of which in the valleys and on the coast are 800–1200 mm, and in mountainous areas can reach 1500–2000 mm. The main species of drifting timber drifting include broad-leaved trees (willow and alder), which, unlike coniferous wood, are more prone to form logjams and are most hazardous for culverts.

Correct determination of strength properties is always relevant for the prediction of soil mechanical behavior. This issue in a static formulation of the problem is widely discussed in technical literature. However, the determination of strength properties under dynamic loading remains debatable. This paper discusses a new methodological approach developed to determine the parameters of dynamic shear strength of saturated samples of model clay soils based on a combined analysis of static and dynamic triaxial testing data. It is demonstrated that, other conditions being equal, the value of the angle of internal friction of clay soil samples with predominantly a coagulative structure is the same under static and dynamic conditions; however, cohesion decreases under dynamic loading and this effect is attributed to the thixotropic strength loss in such a soil.

The data are presented on the particle-size distribution, content of hydrocarbons, n-alkanes in their composition and the number of microorganisms in the soils of Dzunbayan oil production area (Mongolia, the Eastern Gobi desert steppe). The soils studied are characterized by the dominance of sand and fluid fraction (99.50–99.8%) with particles of 2–20 μm. The soils show alkaline reaction (pH 8.2–8.7), they are slightly saline in the control areas and highly saline (water extract salinity 0.13–2.34‰) near the production well. The content of petroleum hydrocarbons (HC) in soils of the study area varied from 9 to 60 mg/kg, with a maximum near the well. The study of the molecular composition of n-alkanes revealed the dominance of long-chain homologues (66.3–79.2% of the total n-alkanes), occurring at various stages of physicochemical and microbiological weathering. According to a number of features, the microbial community of soils is characterized by a high degree of adaptation to the conditions of the arid zone, salinity, and high pH values; at the same time, these conditions limit the development of typical representatives of soil microbiocenoses, i.e., actinomycetes and, to a greater extent, microscopic fungi. The total number of heterotrophic bacteria (HBGs) in the studied soil samples varied within 1.22–3.49 million CFU/g of soil. The proportion of oil-oxidizing bacteria (NOB) was 12.6–18.9% OBA, which corresponded to the high adaptive capacity of the community to hydrocarbons. Specific climatic conditions, features of soil composition, as well as oil with a predominance of heavy paraffin fractions of the Dzunbayan deposit, characterize the low potential ability of soils to self-purify under the oil pollution.