Vol 278

The paper presents the results of modeling stress fields and analyzing the strength of the rock mass at the Yeniseiskiy site (Krasnoyarsk Region), selected for the construction of an underground research laboratory. Variants of boundary loading conditions along the model boundaries are substantiated, and the results of modeling the distribution of stress tensor components for four loading scenarios are presented, along with an assessment of rock mass stability using well-known strength criteria, including Hoek – Brown, Mohr – Coulomb, von Mises, and others. Regularities in the distribution of stress fields within the rock mass and differences associated with the tectonic conditions of the area are identified. It is established that the localization of zones of stress intensity concentration depends on the ratio of the principal stress components. Orientation of compression in the submeridional direction leads to an increase in stress intensity by 10-15 % relative to other modeling variants. Zones of anomalous stress intensity values are located within blocks as well as in the footwalls of tectonic faults. The models are characterized by high values of the potential energy of distortion in fault zones (as parts of the rock mass most susceptible to deformation) and at their intersections. Three-dimensional modeling makes it possible to identify effects that are weakly expressed in plane strain models. The results of geomechanical modeling are required for planning experiments in the underground research laboratory in order to refine the isolation properties of the rock mass during the disposal of high-level radioactive waste. Methodological approaches of three-dimensional modeling are applied by geomechanical and geotechnical services of industrial enterprises and other hazardous facilities (underground gas storage facilities, mineral deposits, etc.).

More complete extraction of minerals from subsurface by reducing their losses even more actualizes tasks of improving mathematical models of mining objects. Purpose of this work is to create geometric models of typical complex-structured blocks (CSB), which could be extended to real CSB. They are based on mining and geological models of virtual (typical) complex-structured ore blocks of bench, consisting of discontinuous continuous (first type) and dispersed ore bodies (second type). These blocks key parameters are isolated continuous and dispersed ore bodies characteristic points coordinates, ore bodies with host rocks contact line segments length, and ore bodies areas in CSB sections. They determine these objects mining and geological characteristics (ore saturation, block geological and morphological structure complexity). These characteristics are analytically interconnected with disparate ore bodies geometric parameters and admixed rock or lost ore layer size. They are the basis for CSB geometric models numerical values calculation methodology and mining and geological characteristics of ore bodies and whole block. Computer program for automated determination of geometrical characteristics of CSB by given initial key parameters of complex-structured blocks has been created. Example of calculation of these characteristics for typical complex-structured blocks is considered, and significance of research results in CSB development is shown. Proposed methodology of calculation of key characteristics of geometrical models of CSB is an information basis for making decisions on economical and ecological development of CSB of benches. Results of research can be used in exploitation of real complex-structured deposits to significantly reduce loss and dilution of minerals.

The hazard of rock bursts at the Khibiny deposits is largely due to their block structure and the natural gravitational-tectonic stress field in the rock mass. A detailed analysis of documented cases of rock bursts in the fields of the Kola Peninsula allowed to develop a classification of geodynamic events by the mechanism of their occurrence. During the analysis, it was found that in the period 1980-2024, 40 % of all rock bursts were associated with geological disturbances with high strength of the aggregate material. Such geodynamic events occur as a result of activation of a combined mechanism. The cause of the geodynamic event in this case is a combination of structural disturbances of the rock mass with a high level of tectonic stresses. An important criterion of rock burst hazard in the area of geological disturbances in highly stressed rock masses is their relative rigidity, and consequently, the degree of fracturing in relation to the natural conditions of the rock mass. The mechanism of this class of rock bursts can be described within the framework of the theory of rigid-platen theory. Based on the research results, the need to pay serious attention to the development of special measures to prevent or minimize the risk of geodynamic events when approaching tectonic disturbances with high strength of the aggregate material of the stoping and development workings is justified.

Fluorine‑containing wastewater is one of the main problems of the mining and processing industries. Mining, dressing, and sulphuric acid digestion of apatite concentrate – all these processes are accompanied by the generation of vast amounts of wastewater with elevated fluoride content, which pose a serious threat to the environment. Conventional methods do not always allow achieving the required discharge standards, which in turn necessitates the search for alternative reagents. The main objective of this work is to assess the possibility of using waste from the mining and smelting sector (phosphochalk, magnesia scrap, dust from gas cleaning units) as precipitating reagents for the first stage of fluoride ion removal, followed by tertiary treatment with complex titanium‑containing coagulants. We conducted experiments to select reagents and their dosages, the use of which will allow achieving the lowest residual fluoride concentrations in water. We found that using calcium/magnesium hydroxides does not allow meeting the standards for residual fluoride anion content. To achieve maximum precipitation efficiency, a 30 % excess of precipitating reagents is required. The study confirms that large‑volume mineral waste can serve as precipitating reagents for fluoride ion, with treatment efficiencies of 94 % for phosphochalk, 90 % for magnesia refractory scrap, and 99 % for gas cleaning units. We proved the effectiveness of complex titanium‑containing coagulants for water defluorination in comparison with conventional coagulants (aluminium oxychloride/aluminium sulphate). The use of a complex reagent not only significantly reduces coagulant consumption and minimizes residual fluoride anion content, but also substantially intensifies precipitation (by 1.5-1.75 times) and filtration of coagulation sludges (by 1.25-1.5 times). The developed conceptual diagram for wastewater defluorination using large‑volume waste and complex titanium‑containing reagents allows significantly reducing the level of negative environmental impact and taking a step towards implementing the circular economy concept.

The study was conducted on the territory of the Daldyn kimberlite field, within the industrial site of the Udachny Mining and Processing Plant (Yakutia, Russia). The objects of the study were permafrost soils and two types of shrubs – Betula middendorffii T. (Middendorff birch) and Duschekia fruticosa R. (shrubby alder). Soil and plant samples were analyzed using atomic absorption spectrometry for the presence of potentially toxic elements (Pb, Ni, Mn, Cd, Co, Cr, Zn, Cu and As). Bioaccumulation coefficient and potential environmental risk factor were calculated for each element. In the studied plants, the elements of interest were arranged in descending order of content: Mn > Zn > > Cr > Ni > Cu > Pb > As > > Co > Cd, according to the degree of bioaccumulation Betula middendorffii T. characterized by a number of Cr > Zn > Ni > Mn > Pb > Cu > Cd > Co, and Duschekia fruticosa R. – Cr > Zn > Ni > Pb > Cu > Mn > Cd > Co. The research revealed that Betula middendorffiii T. and Duschekia fruticosa R. are resistant to high concentrations of elements, coherent kimberlites – Cr, Ni, Co and dolerites – Cu, Mn and Zn. The consequence of the occurrence of kimberlite magmatism in soils and plants are concentrations of Ni, Cr and Mn that are excessive for plants, which are identified as potential environmental risk factors. Most of the territory of the Daldyn kimberlite field is characterized by low and moderate environmental risk. Impact zones of kimberlite pipe quarries and waste rock dumps are characterized by significant and high potential environmental risk.

The work investigates the influence of seasonal changes in the composition of fresh water on the rheological properties of guar‑borate hydraulic fracturing fluids. Between October 2024 and August 2025, monthly samples were taken from three sources in the Republic of Tatarstan, with analysis of pH (7.3-7.9), alkalinity (73-275 mg/l HCO^-₃), total hardness (180-520 mg/l Ca²⁺+ Mg²⁺), chlorides (42-284 mg/l), sulphates (61-146 mg/l), and iron ions (0.1-0.3 mg/l). Fracturing fluids were prepared using these waters and tested on a Brookfield PVS high‑pressure rheometer at 32 °C in accordance with ISO 3219:1993. The target viscosity range was approximately 400-700 mPa·s. We found that in water with high salinity (source N 2, average hardness ~419 mg/l, Cl^–>180 mg/l), gel viscosity decreased by 10-15 %, the time to recover to operating viscosity increased, and breakdown accelerated, which raised the risk of premature proppant settling. Correlation analysis showed strong positive correlations between hardness, chlorides, sulphates, and alkalinity (r  =  0.53-0.90) for “soft” sources N 1 and 3, whereas in the mineralized water of source N 2 these correlations are weakened (r  =  0.17-0.51). The results demonstrate that the seasonal increase in salinity (winter‑spring period) significantly impairs the rheological stability of hydraulic fracturing fluids and emphasize the need for mandatory monitoring of water composition and adaptation of formulations during periods of peak salinity.

The investigation of bitumen occurrences confined to zones of hydrothermal alteration developed within volcanic rocks of the Late Permian-Early Triassic age, intersected by a well in the upper part of the pre-Jurassic basement section at the Litvakovskoye oil field, is of critical importance for predicting the petroleum potential of the West Siberian basement. The presence of bitumen in metasomatically altered basalts provides evidence of either a destroyed oil accumulation or the existence of hydrocarbon migration pathways within the pre-Jurassic complex. According to mineralogical and petrographic data, hydrocarbon emplacement occurred after the hydrothermal-metasomatic alteration of the volcanic rocks. Based on V.A.Uspensky’s classification, the studied bitumens are identified as pure asphaltites and transitional asphaltite – kerite varieties. Molecular composition and carbon isotope data suggest that the precursor source organic matter of the naphthides was formed under reducing conditions in a shallow basin with elevated water salinity and clay – carbonate sedimentation, which may have received humic material input. The level of thermocatalytic transformation of the bitumens corresponds to the early phase of the oil window. The naphthides have been variably affected by hypergenic and, possibly, migrational processes. In addition to the typical biodegradation markers – C₂₈-C₃₄ 25-norhopanes – the bitumens reveal, for the first time, their lighter homologs: demethylated tricyclic C₁₉ and tetracyclic C₂₃ terpanes, as well as unusual tetracyclic hydrocarbons of the hopanoid type (secohopanes C₂₇, C₂₉, C₃₀). These compounds, along with bicyclic terpanes C₁₇-C₂₄, may be considered a distinctive feature of the solid naphthides from the pre-Jurassic complex of the study area. The bitumens are characterized by low sterane content and exhibit specific compositional features similar to those of crude oils from the Kotyg'yeganskoye and Severo-Khokhryakovskoye oil fields. The distribution of tri- and tetracyclic terpanes indicates a similarity between the bitumens and both crude oils and bitumoids of the Tyumen Formation. The observed sterane and terpane signatures in the bitumens may be attributed to the contribution of humic material to the precursor source organic matter and suggest a possible genetic link between the naphthides and the deposits of the Tyumen Formation.