No 1 (2023)

Detailed neostructural zoning with typification of tectonic structures should be performed before engineering surveys on the territory of the newest orogens or their large parts. A medium-scale neostructural zoning of the central segment of the Greater Caucasus megavault was carried out. It showed a significantly complex structure of the previously distinguished regional neotectonic bodies. The neotectonic structural plan is less differentiated in the north and east of the segment and it is more differentiated in the southern and western parts. A significant transformation of all local structures and regional suture zones is shown. It is connected with the fact that the newest structures are produced by orogenic uplift, and the older ones were formed under the conditions of horizontal compression. The results of neotectonic zoning are used in engineering, hydrogeological and geoecological surveys for construction design. They are important for paleoecological research, for example, in the study of archaeological sites.

The results of geological and structural-geodynamic research are presented for the territories of several nuclear power plants (NPP) located on the East European Platform. The influence of geological structure, lithology, and the latest tectonic movements are considered as well as the resultant structures and relief, which generally represent the geological environment, on the stability of the NPP areas. Structural and geodynamic conditions, in particular, recent tensile stresses that cause intense rock fracturing and high gas-fluid permeability, suffusion, karst and landslide, are proved to be the main causes of hazardous processes resulting in settling and tilting of some NPP buildings. Tectonic sloping of the sites towards descending depressions, the sand basement of NPP sites, sloping clay aquicludes, fluctuating water levels in the adjacent water reservoirs, the presence of so-called “hydrogeological windows”, the buried relief and modern structural and geodynamic conditions, i.e., tectonic stresses (tensile stresses in many cases) contribute to building deformations. Along with solving practical problems, a number of theoretical issues are considered. Lineaments are associated with rock fracture zones and faults zones; the fault zones in crystalline foundation influence the formation of recent structures; and new platform structures, i.e. gravity-tectonic massifs and pull-apart depressions, are distinguished.

The possibility of sinkhole size prediction in the areas, where soluble rocks are covered by impermeable clay layer is considered. Such sinkholes are named by English-speaking authors as “dropout sinkholes” or “cover collapse sinkholes”, because the process of their formation includes collapse (dropping) of clay covering soluble rocks into a karst cavity. Triggers of this effect are: (1) widening of a cavity below the clay due to dissolution of a soluble rock by groundwater; (2) lowering of hydraulic head in confined karst aquifer, primarily caused by groundwater pumping, which results in decreased support of the overlying clay layer; (3) a dynamic load on the clays, which can have either natural or man-made origin. Fresh dropout sinkholes generally have configuration similar to vertical right circular cylinder, but sometimes their shape can be dome-like with very unstable ground “cantilevers”. The appearance of these forms under foundations can lead to deformation and even to destruction of buildings, structures, and infrastructure facilities. Two concepts exist, which can be used as basis for creating models of soil mechanics to calculate diameter of a dropout sinkhole. The first one is based on a viewpoint that clay collapse into a cavity after a trigger action is displayed immediately at the ground surface as a collapse sink. According to the second concept, the preliminary subsurface collapse of clay occurs as fall of ground block resembling a circular paraboloid. As a result, a dome-like cavity appears in the clay layer and above-lying clay fall into it to form a collapse sink. There are no prediction methods based on the two above-mentioned conceptions. The developed approaches to prediction of a dropout sinkhole diameter are adequately comparable, as they use the same input calculation parameters. The prediction results based on these approaches have been compared to an actual diameter of fresh dropout sinkhole. This verification have allowed us to infer that most adequate is the approach based on concept of initial subsurface clay’s collapse preceding the final collapse sink formation.

The impact of waste dumps on environmental components, i.e., soil, evaporating soil water (condensate) and plants is studied. It has been revealed that industrial and municipal waste dumps continue to affect significantly the environment after their closure. The behavior of heavy metals (Pb, Cu, Zn, Ni, Cd, Co, Sb, Sn, Bi, Hg, and Cr) in soils, plants, and condensate in landfill areas and beyond them (the background) has been studied in detail. It has been found out that soils, plants and condensate at landfills are enriched in heavy metals as compared to the background sites. The degree of soil contamination at waste dumps depends on the reclamation stage of the latter. The landfill soils exceed the norms of maximum permissible concentrations for heavy metals by 1.1–90 times. Concentrations of heavy metals in plants exceed the background values from 1.1 to 104 times at all dumps. The maximum level of heavy metals in plants is exceeded for Zn, Cd, Cr. In the condensate sampled at the dumps, MPC is exceeded for Cu, Zn, and Hg. Based on the analysis results, the geochemical rows of heavy metal distribution in different landfill environments were compiled: in plants – Zn > Cu > Cr >Ni > Pb > Cd > Co > Hg > Sn > Bi; in condensate – Zn > Cu > Ni > Cr > Pb > Sn > Co > > Hg > Sb > Cd > Bi; in the soil – Zn > Cr > Cu > Ni > Pb > Co > Sb = Sn > Cd. The distribution of heavy metals in the condensate and plants is similar. In these environments, contribution of Zn and Cu is more than 80%, contribution of Cr, Ni, Pb varies from 1 to 10%; contribution of Cd, Co, Sb, Sn, Bi, Hg is less than 1%. Heavy metals are distributed in soil according to a different pattern: the main contributors are Zn and Cr (their input is more than 50%), then go Ni, Cu, Co, and Pb (their content in soil varies from 1 to 50%), followed by Sb, Sn, and Cd (their content is less than 1%). Total pollution indices (Zc) of the soil, condensate and plants have been calculated for each landfill. Based on Zc, the landfills were grouped in a ranking series, which can form the basis for assigning the sequence of landfill reclamation measures.

Large-scale experiments on the leaching of pollutants from the products of mechanical and biological treatment of municipal solid waste (MSW) simulating the disposal at a real landfill are considered. These are studies in large reactors and in the experimental section of the MSW landfill, where stabilized waste is placed. The results of these experiments are described and compared with those obtained in the course of various laboratory tests. Recommendations are given for improving laboratory tests and predictive models.

Studies of recent decades have shown that the gas component plays a significant role in the structure and properties of frozen soils. This is indicated by a significant influx of greenhouse gases into the atmosphere from the permafrost; gas emissions leading to accidents at boreholes; the formation of gas emissions craters, etc. These processes are determined by the mutual influence between the characteristics of the gas component and the indicators of the physical and mechanical properties of frozen soils, which have not been studied enough to date. The formation mechanisms of gas-saturated zones are considered; the influence of gas on the physical and mechanical properties of thawed and frozen soils is assessed; and the processes associated with the impact of gas on the soil massif are analyzed.

The article presents the results of studies of technogenous hydrocarbon deposits - Light Non-Aqueous Phase Liquid (LNAPL) bodies in technonatural systems. The specific feature of these bodies is their location in the geological environment beneath operating and abandoned oil industry enterprises. Enterprises are the sources of hydrocarbons in the geological environment. Light non-aqueous phase liquid bodies are interpreted as complex, dynamic, multicomponent systems, which are subject to the influence of flooding and low-water phenomena in the nearby surface water bodies. Based on the study of archive data and the results of field survey of these objects, the integrated system has been developed for assessing the status of technonatural systems containing LNAPL bodies. It is based on the suggested criteria, and includes geometric, technological, geoecological, resource-economic and inertial-oscillatory groups. The scheme of carrying out a complex of works, including research, assessment, modeling, and liquidation of LNAPL bodies is proposed. This scheme takes into account the LNAPL dual nature: on the one hand, LNAPL body contaminate the environment, on the other hand, produce secondary hydrocarbon resources. The proposed integrated assessment system permits us to determine the current state of LNAPL bodies as a part of technonatural systems, to select and justify technological solutions for their liquidation and remediation of contaminated sites.