In GPR (georadar) studies, one of the most popular procedures for determining electromagnetic waves propagation velocity in a rock mass is the selection of theoretical hyperbolic time-distance curves and subsequent comparison with the time-distance curve obtained from a GPR measurement. This procedure is based on the model of homogeneous medium, but nowadays the subject of GPR study is often inhomogeneous media, such as horizontally layered media characteristic of loose permafrost zone sediments. The paper presents the findings of studying the formation of hyperbolic time-distance curves of georadar impulses in a horizontally layered medium without taking into account the dispersion and absorption of electromagnetic waves. On the basis of geometrical optics laws, formulas were derived to calculate the shape of the hyperbolic lineup of georadar impulses reflected from a local feature in a multilayer frozen rock mass. On the example of a permafrost zone rock mass containing a layer of unfrozen rocks, the effect of the thicknesses of rock layers and their relative dielectric permittivity on the apparent dielectric permittivity resulting from the calculation of the theoretical hyperbolic time-distance curve was shown. The conditions under which it is impossible to determine the presence of a layer of unfrozen rocks from a hyperbolic time-distance curve are also presented. The established regularities were tested on synthetic georadar radargrams calculated in the gprMax software program. The findings of the theoretical studies were confirmed by the comparison with the results of the analysis of the georadar measurements computer simulation data in the gprMax system (the relative error was less than 0.5%).

Geotechnical rating classification systems of rock masses are an important tool in the design of underground mining systems. They are especially relevant at the early stages of project development, when primary mining and geological information is available to a limited extent. The presented work shows an approach to the collection of initial information and calculation of RMR (Rock Mass Rating) and Q Index for the rock mass of deep levels of the Udachny underground mine exploiting the kimberlite pipe of the same name. Since the classifications are multi-component systems, they impose heavy demands on the scope and quality of primary data, which can be met by applying an integrated data collection system. The bulk of these were obtained by acoustic televiewer tool (ATV) combined with geologic and structural logging of non-oriented core. Data on physical and mechanical properties of rocks, stress-strain state, and hydrogeological conditions were also used. The ratings were calculated interval by interval along holes, in which acoustic logging was performed. The acoustic wave amplitude parameter, which depends on the physical properties of a rock mass and the degree of its structural disturbance, was proposed as one of the criteria for distinguishing geotechnical intervals. The moderate level of correspondence between Q and RMR systems was established to be due to the different “sensitivity” and structure of the input parameters. Using the calculated ratings, the rock masses of ore bodies and host sediments were evaluated for stability (classes/categories have been assigned), and the optimal method and parameters of workings support were determined. The geotechnical database accumulated during the research process provides the feasibility of calculating alternative ratings such as MRMR, RMi, GSI, etc., without the use of transient equations.

At the moment, the use of digital models in the development of oil and gas fields is an effective tool for making informed tactical and strategic decisions to maximize the extraction of hydrocarbon reserves in a field. At the same time, the permanent increase in the share of hard-to-recover reserves leads to an accelerated increase in the role of simulation of reservoir hydrocarbon systems in the development of oil and gas fields. Many gas-condensate fields in Eastern Siberia can be characterized as reservoirs with low permeability and porosity and difficult thermobaric conditions, and, as a result, the issue of improving the efficiency of the development of such reservoirs to increase the cumulative production of gas and condensate is relevant. If the initial reservoir pressure of a gas-condensate field corresponds to the dewpoint pressure, dropout of a significant amount of retrograde condensate is observed when the pressure in the reservoir decreases. Condensate dropout in the pore space of a reservoir leads to a decrease in both the condensate recovery factor (CRF) and the gas recovery factor (GRF). The predictive calculations of the development of a gas-condensate reservoir by vertical and horizontal wells were carried out with the use of the hydrodynamic simulator T-Navigator of a domestic manufacturer Rock Flow Dynamics. The calculations were performed under various process conditions on the example of a gas-condensate field, which is characterized by complicated thermobaric conditions (the initial reservoir pressure corresponds to the dewpoint pressure), while the target process parameter was the amount of condensate dropout in the reservoir. Based on the results of the study, the main conclusion can be drawn. The development of the reservoir by horizontal wells can significantly reduce the reservoir drawdown pressure compared to vertical wells, while the condensate dropout in the reservoir occurs in a larger volume; the condensate becomes immobile and prevents further gas production, reducing the total production of condensate. An increase in reservoir condensate recovery in the course of the development of a gas-condensate reservoir by vertical wells compared to horizontal wells is observed under certain reservoir conditions corresponding to the simulation performed in this study, namely, at low reservoir permeability and porosity and the presence of a saturated gas-condensate system.

The decrease in the quality of raw materials coming for processing requires involvement of refractory ores in processing, the refractoriness of which is caused by the presence of organic carbonaceous matter sorption-active in relation to dissolved noble metals and impregnation of fine noble metals in mineral-carriers. In this connection, the actual research line is the development of new technological solutions with the use of energy methods of action in order to reduce the losses of valuable components in beneficiation tailings. Treatment with ultra-high frequency electromagnetic radiation has a number of advantages, including rapid and selective heating due to the differences in the ability of minerals to absorb this radiation. Carbon-containing materials represented by carbonaceous flotation concentrate and model samples of activated carbon with adsorbed silver were taken as the research subjects. Using the model samples as an example, the necessity of using magnetite to achieve coarsening fine silver particles during ultra-high frequency treatment was substantiated. The formation of active centers of local heating during the treatment in the points of magnetite addition was confirmed. The necessary content of magnetite of 10% for coarsening fine silver to spherical aggregates, the average size of which was 20–40 microns, was substantiated. Coarsening noble metal particles to sizes of 20–50 microns in treated carbonaceous concentrates containing silver and gold was achieved, when the substantiated amount of magnetite was added. Coarsened particles (aggregates) of noble metals can be recovered using traditional beneficiation methods.

The efficiency of mine rescue operations largely depends on how quickly efforts to localize and mitigate an accident are initiated. Given the remoteness of some mining enterprises, a decision was made to form auxiliary mine rescue teams composed of miners. However, there is ongoing debate regarding the effectiveness of the rescue operations carried out by these auxiliary teams. This paper presents data on the assessment of the readiness of auxiliary mine rescue teams in Russian coal mines. A survey of professional mine rescuers was conducted across all units and platoons, focusing on key aspects of auxiliary team operations. The results, based on expert evaluations, revealed the main challenges in training auxiliary team members and highlighted areas for improving the regulatory and methodological framework for mine rescue tactics. The second part of the paper presents the results of control-tactical exercises held at seven mines. These unannounced exercises took place at the end of a work shift and evaluated a wide range of knowledge, skills, abilities, and physical fitness among the auxiliary teams. Key evaluations included the accuracy of task allocation, tactical training, preparation for mine descent, the use of rescue equipment, first aid skills, theoretical knowledge, and physical fitness.

The study of thermodynamic parameters in the air environment of subway lines is of particular relevance due to the substantial differences in air temperatures between Russian cities and those abroad. These temperature variations influence the formation of aerothermodynamic characteristics, which must be considered when selecting methods to ensure compliance with standard climatic parameters in subway systems. The objective of the study presented in this article was to identify, based on experimental data, the patterns governing aerothermodynamic processes, with the aim of providing recommendations for the standardization of air environment parameters in subway tunnels (both single- and double-track) located at different depths. The primary tasks of the research involved identifying the factors influencing the distribution and variation of temperature and humidity, conducting instrumental measurements of temperature and humidity distribution along the length of the transit tunnel sections under investigation, both in the absence of trains and during varying intensities of train movement. Proposals were then developed to apply the identified patterns in maintaining standard air parameters. The article posits that the selection of technical solutions for improving subway ventilation systems should be based on the unique features of aerothermodynamic processes, which depend on the structural characteristics of the transit tunnels and their depth. Experimental studies revealed the patterns governing the formation of ventilation and thermal regimes in single-track and double-track tunnels, as well as at junction sections, and provided recommendations for optimizing ventilation and thermal regimes to ensure compliance with climatic standards. Specifically, the study found that in deep single-track tunnels, the thermal regime is influenced by the presence of circulation loops between adjacent stations, created by the piston effect and the heat emissions from moving trains. Circulation loops in shallow single-track tunnels, by contrast, are characterized by strong aerodynamic connections with the surface, as surface air enters the stations and tunnels via pedestrian walkways and inclined passages. In double-track underground structures, in the absence of train movement, the variation in air temperature along the length of the transit tunnel is determined by the amount of heat accumulated in the surrounding ground during periods of train operation. When trains are in motion, the heat emitted by trains moving in opposite directions is evenly distributed along the tunnel, due to the near absence of a piston effect, resulting in a stable air temperature throughout the tunnel. However, the sections adjacent to stations experience localized increases in air temperature due to the maximum heat generated during braking and train stops, with tunnel air temperatures in these sections rising by 2–3 °C compared to those in the transit sections. In sections where both single-track and double-track tunnels are present, a potential rise in air temperature at the station adjacent to single-track tunnels is associated with the formation of circulation loops between the junction of different tunnel types and the station itself. Recommendations for normalizing the aerothermodynamic regime in the various tunnel types studied include provisions for mitigating potential summer air temperature increases above the standard levels by either increasing air flow or cooling the air in cross passages adjacent to stations. Methods for increasing air temperature may include organizational, aerodynamic, and heat engineering techniques.

Suspended solids are the predominant pollutants in the wastewater of coal enterprises. The basic wastewater treatment system regulated in BAT No. 15 ITC-37–2017 does not ensure water quality meets the discharge standards for fishery water bodies. The gravitational sedimentation method used in this technology is effective for coarse particles. However, colloidal systems formed from fine insoluble fractions are challenging to separate in a gravitational field. As an effective method for removing suspended solids from wastewater, we recommend filtering through a stationary layer of granular filtering materials. The study investigates the kinetics and dynamics of filtering suspended particles from the wastewater of coal enterprises using various filtering materials. Sedimentation curves of suspended solids from quarry wastewater have been constructed. The dependence of wastewater treatment efficiency on the size of filtering material fractions has been identified. The study provides an evaluation of the effectiveness of using natural filtering materials for treating wastewater from coal enterprises. The experiments demonstrated that the most efficient and cost-effective granular filtering material is quartzite from the Bobrovskoye deposit, which we recommend using in a combination of fractions 20–50 and 0.7–12 mm (in a ratio of 1 : 2). The optimal flow rate of wash water during the regeneration of the granular filter is also determined.

Global challenges (increased consumption of georesources, climatic changes, limited reserves) increase the relevance of the problems of growing waste accumulation and environmentally-sound modernization of mineral extraction. In this regard, the existing approaches to the design of geotechnologies for metal mining need to be improved based on a concept of so-called circulation waste management and ecologization of technological processes. The paper is devoted to the issue of formation of conceptual bases and directions of ecologization of geotechnologies at leaching metals from polymetallic ore processing wastes and wastewater. The study presents recommendations for improving in-situ leaching of ores in blocks, allowing to determine the optimal conditions for increasing the completeness of subsoil use and reducing environmental damage. It was revealed that at metal extraction with solution circulation through brine chambers the content of Na, Cl, SO₄ and Ca ions in dialysate was low, while without circulation through brine, it significantly exceeded corresponding MPCs. This proves the fundamental feasibility of controlling natural leaching processes by enhancing the oxidizing potential of natural solvents through the addition of industrial oxidizing agents. It was found that increasing the duration of agitation leaching (both with and without mechanoactivation) leads to a uniform expansion of the local maximums of Pb yield from the pulp when the minimum NaCl concentration decreases from 11–12 to 7% at H₂SO₄ concentration of 0.6%. One of key results of the study is justifying the expansion of the use of disintegrators to realize targeted activation of tailings. The practical significance of the obtained results lies in the proved feasibility of optimizing the flow sheet of electrochemical extraction of metals from wastewater on the basis of the obtained regularities of the use of brine circulation through brine chambers. In addition, the totality of the obtained results of using a disintegrator for reextraction of lead from geomaterials will allow developing a methodology for calculating the parameters of mechanoactivation action to increase the degree of metal recovery from the tailings of North Ossetia-Alania’s (Zgidskoe, Sadonskoe, Arkhonskoe deposits) polymetallic ores beneficiation. The most promising way for further research is to substantiate methods of using underground space for complete removal of wastes (wastewater and tailings) after their multistage treatment.

In today’s world of rapid urbanization, environmental safety has become a key aspect of urban planning and management. The issue of environmental safety encompasses a wide range of concerns, from pollution reduction and biodiversity conservation to ensuring the sustainable use of natural resources. In this context, metro facilities, as an integral part of urban infrastructure, play a crucial role in providing mobility for urban populations, yet they also pose potential environmental challenges. The operation of metro facilities is associated with noise pollution, emissions of harmful substances due to the use of energy produced from fossil fuels, energy consumption, undesirable impacts on groundwater, and other negative environmental aspects. Equally important is the issue of waste disposal and the use of construction materials during the building and maintenance of metro systems. The aim of this study was to assess the environmental safety of metro facility operations. The consideration of this topic is particularly relevant in light of global efforts towards sustainable development and the need to ensure a high quality of life for urban populations. The assessment of environmental safety in metro operations is proposed to be conducted through a comprehensive approach, involving field studies and modelling the distribution patterns of defects in metro structures under the influence of hydrogeological risks. A systematic approach to evaluating environmental safety in metro operations, based on modelling the development of defects in tunnel structures under the influence of hydrogeological factors, will help organize existing information on potential accidents and develop monitoring methods and measures to minimize risks that compromise the environmental sustainability of underground transport infrastructure. The research results, which include the systematization of environmental safety criteria for metro operations and the analysis of tunnel structure defects caused by hydrogeological factors, provide the basis for further developing methods to ensure environmentally safe operation of urban transport tunnels.

The use of a variable frequency drive (VFD) for sucker-rod pump units (SRPUs), widely employed in oil extraction, enhances the energy and technological efficiency of oil production and reduces equipment wear. However, its application is hindered by unstable operation under insufficient balancing of the SRPU and sensitivity to short-term voltage dips, which frequently occur in the extensive electrical networks of oil fields. Insufficient balancing of the SRPU leads to the occurrence of a period within the pumping cycle where the  motor operates in generator mode, caused by the unevenness and reversal of the resistance torque of the working mechanism. The motor’s transition to generator mode, as well as voltage dips in the power supply, causes the voltage in the DC link of the VFD to exceed the set limits, resulting in the drive being shut down. To investigate the processes during the operation of sucker-rod pump units and to test methods for mitigating the negative impact of generator mode and voltage dips in the power supply network on the VFD, a model of the “power grid – variable frequency SRPU drive” system with a load characteristic of this application was developed in Matlab Simulink. A series of experiments were conducted, and the results were analyzed. The suppression function of the generator mode was examined, and the feasibility of its application to real SRPUs was evaluated. The use of an uninterruptible power supply system based on battery energy storage to prevent operational interruptions during different levels of power supply voltage dips was analyzed. The resulting model can be used for general analysis of operability and stability, as well as for verifying the correct selection of key elements in the design of sucker-rod pump unit systems with variable frequency drives.