TRENDS IN THE DEVELOPMENT OF REACTIVE FIRE PROTECTION (LITERATURE REVIEW)

Purpose. Identification of the main directions of evolution of scientific researches concerning development and improvement of fire protective reactive coatings of intumescent type for steel constructions. Methods. Analysis of literature sources, study and generalization of information, classification and modeling of chemical processes. Results. As a result of the performed researches it has been shown that of all the developed reactive fire protection systems for increasing the fire resistance of steel structures the intumescent composition of ammonium polyphosphate/ pentaerythritol / melamine / polymer is the most widespread and economically justified. To reduce the cost of fire protection measures, it is necessary to improve the coatings of the intumescent type in the following main areas: increasing of fire protection efficiency with a decrease in the thickness of the fire protection layer; prolongation of life time with strengthening of resistance to external factors; reducing the cost of the prescription composition of intumescent paint due to the use of nanomaterials. Scientific novelty. It has been established that nanoclays, nanooxides of metals and silicon, LDH compounds and their analogues should be considered the most promising and multifunctional. The presence of nanomaterials in intumescent compositions allows to increase the environmental parameters of fire-retardant treatment due to the rejection of halogen flame retardants, boron compounds, formaldehyde resins. In addition, the presence of nanocompounds in intumescent coatings significantly reduces smoke in fire. Practical significance. The conclusions obtained from the literature review are of practical importance for the development of new approaches to the design of fire-fighting materials with improved performance through the use of nanomaterials, which provides a strong fire retardant foam char layer and provides rigidity of the insulation frame.

SUBSTANTIATION FOR SIMPLIFICATION OF CALCULATION MODELS FOR ASSESSMENT OF THE STABILITY OF ROOF ROCKS

Purpose. Substantiation of expediency and admissibility of use of the simplified calculation models of a coal seam roof for an estimation of its stability under the action of external loadings. Methods. To achieve this purpose, the studies have been performed using the basic principles of the theory of elasticity and bending of plates, in which the coal seam roof is represented as a model of a rectangular plate or a beam with a symmetrical cross-section with different support conditions. Results. To substantiate and select methods for studying the bending deformations of the roof in the coal massif containing the maingates, the three-dimensional base plate model and the beam model are compared, taking into account the kinematic boundary conditions and the influence of external distributed load. Using the theory of plate bending, the equations for determining the deflections of the coal seam roof in three-dimensional basic models under certain assumptions have a large dimension. After the conditional division of the plate into beams of unit width and symmetrical section, when describing the normal deflections of the middle surface of the studied models, the transition from the partial derivative equation to the usual differential equations is carried out. In this case, the studies of bending deformations of roof rocks are reduced to solving a flat problem in the cross-section of the beam. A comparison of solutions obtained by the methods of the three-dimensional theory of elasticity and strength of materials was performed. For a beam with a symmetrical section, the deflection lies in a plane whose angle of inclination coincides with the direction of the applied load. The calculations did not take into account the difference between the intensity of the surface load applied to the beam. Differences in determining the magnitude of the deflections of the roof in the model of the plate concerning the model of the beam reach 5%, which is acceptable for mining problems. Scientific novelty. To study the bending deformations and determine the magnitude of the roof deflection in models under external uniform distributed load, placed within the simulated plate, a strip of unit width was selected, which has a symmetrical cross-section and is a characteristic component of the plate structure and it is considered as a separate load-bearing element with supports, the cross-sections of this element is remained flat when bending. The deflection of such a linear element is described by the differential equations of the bent axis of the beam without taking into account the integral stiffness of the model, and the vector of its complete displacement coincides with the vector of the force line. Practical significance. In the laboratory, to study the bending deformations and their impact on the stability of the coal seam roof under external loads, it is advisable to use a model of a single width beam with a symmetrical section with supports, the type of which is determined by rock pressure control and secondary support of the maingate at the extraction layout of the coal mine.

JUSTIFICATION OF THE USE OF METALLURGICAL SLAGS AS A BACKFILL MATERIAL FOR QUARRY CAVITIES

Purpose. Experimental studies of the interaction of blast-furnace and steel-making slags with open pit waters during their direct contact and assessment of the volume of filling of the formed man-made cavities during mining of mineral deposits. Methods. Based on the analysis, the current low level of metallurgical slag and the lack of real and effective directions of their large-scale utilization were determined. The laboratory studies of the interaction of metallurgical slags with open pit water at a certain time of interaction, generally accepted methods for studying the chemical composition and concentration of substances in water, computer-aided design software packages and drawings to determine the volumes of the open pit mined-out area were used. Results. The dynamics of changes in the products of interactions of steel-smelting slags with open-pit waters at a certain ratio and period of interaction was investigated. It was found that the concentration of pollutants upon contact of water with steel-making slag changes according to polynomial dependences on the time of their interaction, decreasing by the 30th day, which eliminates the danger for the aquifer. The safest type of metallurgical slag was recommended for the formation of the bottom layer of the backfill massif. The volumes of the mined-out area of the open pit were determined in detail to assess the volumes of placement of the backfill material based on metallurgical slags. Scientific novelty. The safety of the contact of backfill materials based on steelmaking slags with open pit water was scientifically proven, which is confirmed by the established polynomial patterns of changes in concentrations and pollutants from the ratio and time of interaction. Practical significance. The formation of the backfill massif on the basis of blast-furnace dump and steel-smelting slags will allow achieving an environmental effect, such as their safe disposal as a reclamation of technologically disturbed lands by mining and restoration of the economic value of the land plot, as well as preventing the formation of new dumps.

ANALYSIS OF PRODUCTION RISK FROM CRUSHES OF ROCKS AT EXCAVATION SITES, TAKING INTO ACCOUNT WAYS OF PROTECTION

Purpose. To assess the production risk of rock collapse in a deep coal mine to identify hazards in the workplaces of the excavation site, taking into account different methods of protection of workings. Methods. A comprehensive approach was used, which included: analysis and generalization of known research; expert evaluation; use of the basic provisions of probability theory and set algebra (Venn diagrams), the method of estimating the production risk of Fine-Kinney; processing, analysis and interpretation of the obtained results. Results. Problems and sources of industrial risk from rock collapses during maintenance of workings, risk-forming factors that contribute to the threat of dangerous events at the excavation site are analyzed. The decision-making model is considered, which is based on the description of situations when the production risk of the dangerous factor “landslides and collapses” in the maintenance of preparatory workings depends on the result of choosing an alternative method of protection of the retractable lane. For excavation sites under the same mining and geological conditions for all workplaces, the probability of receiving consequences from dangerous events due to uncertain conditions of their implementation has been established. It is fixed that the realization of this production risk is influenced by low reliability and inefficiency of the practiced methods of protection of excavations. Risk analysis is defined as the systematic use of available information to identify hazards in the maintenance of long workings. Novelty. A model for monitoring the production risk of rock collapses in excavations of deep coal mines is proposed, which allows assessing the dynamics of the threat at the stage of technical decisions related to the choice and justification of the method of protection of workings taking into account the interaction of risk factors. Practical significance. When formulating measures to reduce the risk of dangerous events at the excavation site, it is necessary to take into account that the production risk of rock collapse while maintaining the workings depends largely on the method of protection and effectiveness of technological measures.

PHYSICAL PREREQUISITES FOR GAS PERMEABILITY SIMULATION OF MINED ROCK MASS

Purpose. Justification of the gas collectors formation physical model on the basis of research of conformity of permeability of rock mass to the full diagram of rock sample deformation. Methodology consists in sequential analysis of the stages of the complete deformation diagram of the rock specimen under “hard” loading, comparing them with the stages of formation of the high stress zone in front of the lava bottom and statistical analysis of laboratory test results. Results. Based on the rock’s deformation properties analysis and their comparison with the rock sample full deformation diagram, the physical model of formation of gas reservoirs during the development of gas-saturated coal seam is substantiated. Within the solved problem framework, four stages of the complete deformation process are analyzed, namely: elastic, at the limit of strength, out-of-bounds stage and equivoluminal flow zone. The gas collector boundaries, which are the characteristic points of the rock sample deformation diagram in specified deformations mode (the limit of elastic strength and the limit of final strength) are determined. It is proved that the structural and textural features of the coal mass in connection with the course of gas-dynamic processes are manifested in the change in the pores and cracks volume contained in it, which together make the filtration space. Knowledge regarding the transfer of the permeability changes established regularities and free methane accumulation zones formation to the real rock mass, if the process of its forgery is considered as a consistent change of geomechanical states of rocks, is obtained. Scientific novelty lies in the first substantiated possibility of modeling the stress state before the longwall face by equivalent stages of the rock sample destruction in the given deformations mode. Gradual comparative analysis of the internal mechanism of rock samples deformation along the complete deformation diagram allowed establishing causal relationships between geomechanical and gas-dynamic processes in coal mass, and qualitatively characterizing general trends in permeability and volumetric expansion in changes of these samples. Practical value of the work lies in the justification of the principle of construction of a digital geomechanical model for the detection of man-made gas collectors in a mined coal mass.

CALCULATION OF PRODUCTION RISK FROM NOISE POLLUTION FOR THE SAFETY OF WORKERS IN THE OPEN AIR

Purpose. Studying the impact of noise pollution levels at the busiest intersections of Kyiv and determining the exceedances of normative values on the basis of national and international standards. Calculation of the probability of hearing loss under conditions of prolonged exposure to noise on the body of 40-year-old and 50-year-old workers during 30 years of service. Methods. In this paper, based on the obtained field measurement data, noise pollution on the main highways of Kyiv is analyzed. Topicality. The research is aimed at ensuring the safety of operating transport services and construction companies from the constant noise load, which creates traffic flows in the city and leads to occupational diseases. Studies have shown that at an 8-hour exposure in a worker under conditions of constant chronic noise load, there may be a shift in the audibility threshold depending on age and length of service. The method recommended by the international standard ISO1999 / 2013 can be used to determine the corrected level of noise pollution and safety of workers in the open air during the repair of highway overpasses. The scientific novelty lies in the determination of natural data on the noise load on the example of some of the busiest road junctions in Kyiv, where transport mainly moves at low speed and stands in traffic jams. The obtained average data during the working day indicate a noise load that is 18-20% higher than the normative value of workers working outdoors (80 dBA). Based on basic calculations of the probability of hearing loss because of noise pollution at an average level of 90 dBA for workers with 30 years of experience proved the need for enhanced software monitoring in areas of increased noise pollution for production sites and protection of workers for their safety. Practical significance. The research results are aimed at providing safety for workers outdoors during the repair of highways in large cities and on construction sites near major intersections. The importance of the work lies in the need to strengthen the existing dynamic control over working conditions and health of workers in the open air in the conditions of constant noise load of the city and the need to revise the requirements to the employer governing the protection of workers from noise. The research results showed that the maximum value of noise pollution in Kyiv near the main roads during the day is within the range of 87-94dBa, which is on average 11% higher than the normative value for open production sites. The probability of hearing loss of workers due to noise is 11.5% for 50-year-olds and 7% for 40-year-old workers with 30 years of service.

JUSTIFICATION OF PARAMETERS FOR SELECTING EQUIPMENT FOR EXTINGUISHING WASTE COAL

Purpose. Investigation of the choice of parameters of equipment for extinguishing coal mining wastes that go to the formation of waste dumps, the choice of the main components of equipment for the operation of technological units and a schematic diagram of equipment for extinguishing coal mining wastes are proposed. Methods. Analysis of existing approaches to technological solutions to prevent combustion of waste dumps; environmental assessment of alternative options for technological solutions to prevent combustion of waste dumps; creation of an environmentally friendly design technology for the use of coal mining waste. Results. Based on in-depth analysis of the main components of technological units for the operation of the equipment, MFP FullJet irrigation nozzles by Spraying Systems Co. were proposed. – USA, their main advantages are considered. The expediency of using a hydraulic network, which includes pipelines made of polypropylene material produced by “Aquatherm” – Germany, are substantiated; the main component of the pipelines is the material “Fusiolen”, the advantages of which are given in the article. An integral part is pumping equipment, consisting of centrifugal pumps for water supply (1VNS 60-66) and (VNSp 2.5) for supplying limestone suspension to irrigation nozzles of the transporting dump mass. Scientific novelty. Equipment for extinguishing coal mining waste (rock dumps) resistant to spontaneous combustion is proposed, in which the introduction of new structural elements and their interconnection is achieved by the continuous control and management of spraying per unit of the transported surface of the dump rock, dispersed with an inert substance (lime suspension), which prevents the formation of active combustion centers during the operation of waste heaps. Timely coverage of the dump mass with an inert substance reduces the time of contact of the rock with the environment, which is an important stage in the formation of rock dumps, especially of a conical shape, reduces the cost of operation and maintenance due to the formation of fire-resistant dumps, regardless of the influence of environmental conditions. Practical implication. Efficiency from the use of equipment for extinguishing coal waste can be obtained due to the continuous work achieved by covering the dump mass with an inert mixture during transportation, this reduces the contact of the rock with the environment, which is an important stage in the formation of rock dumps of a particularly conical shape, and reduces operating costs and their maintenance due to the formation of fire-resistant waste dumps regardless of the influence of environmental conditions.

RESEARCH OF THE GEOMETRIC PARAMETERS CHANGING DURING SEPARATION THE HIGH-STRENGTH STONES MONOLITES WITH DIAMOND WIRE MACHINES

Aim. Developing the theory of diamond wire cutting of crystalline rocks for separating the facing stone blocks from the array by establishing links between individual geometric parameters of the side and the cutting process. Research methods. To achieve this aim were used the next method: analytical studies of the relationship between the geometric parameters of the process of diamond wire cutting, experimental study of the same geometric parameters of the process of diamond wire cutting of high-strength rocks to confirm or refute previously obtained analytical relationships, and statistical processing of data. Results. The length of contact of the diamond wire with the rock is an important criterion for the process of separating the blocks of facing rocks from the array. Given the unavailability of the diamond wire side in the array for direct measurement methods, there is a need for indirect determination of the contact length. It is proposed to use the length of the free section of the wire, as the total length of the wire remains unchanged during the cutting process. It is assumed that the length of the free section can be estimated by the distance between the diamond wire machine installation and the slope of the ledge. Analytical dependences between the specified sizes are considered. The existence of the obtained dependences and the strength of the correlation connection was confirmed by experimental studies in the conditions of the block quarry of the facing stone. Scientific novelty. At first time, the relationship between the distance of the diamond wire machine installation and the side of the diamond wire and the length of the free section of the diamond edging, which allows to control the length of contact of the diamond wire with rock in the cut. The obtained dependence is analyzed and it is concluded that the geometric parameters of the ledge will affect the length of the cut only in the initial stages of separation of the block of natural stone from the array. In the next stages, the length of the free section of the diamond wire depends only on the distance of the location of the diamond wire machine installation and the side of the diamond rope. Practical significance. The value of the optimal initial distance of the diamond wire machine placement to the slope of the ledge is found. The empirical dependence of the length of the free section of the diamond wire on the location of the diamond wire machine is also obtained

SUBSTANTIATION OF PARAMETERS OF THE EXPERIMENT WITH THREE-DIMENSIONAL COMPUTER MODELING OF THE ROCK MASS AROUND A LONGWALL

Purpose. To substantiate the parameters of computer modeling of the mining area with a step-by-step movement of the working face, as well as taking into account the changing presence of sandstones that lie in the top of the reservoir, to predict the effect of sandstones on the nature of the distribution of convergence in the longwall and the technology of working excavation in the conditions of the mines of Western Donbass. Methods. The work uses a statistical analysis of the geological and technological conditions that are inherent in the coal mining enterprises of the Western Donbass. Also, a comparison was made of the parameters of the experiment of computer modeling of past studies, on the basis of which, a combination of new features was introduced and changed, which is aimed at choosing the optimal modeling parameters. Results. The substantiation of the parameters of the modeling experiment is presented, such as: the choice of the length of the working face, the depth of development of coal seams, the distance of the working face withdrawal from the assembly chamber, the values of the thickness of sandstones that lie in the roof of the coal seams, the choice of values of the distance of occurrence of sandstones above the roof of the coal seam, as well as geometric parameters of the computer model. Based on the justification of the parameters, a plan for conducting experiments was drawn up, the number of which was 225 units. Scientific novelty. As a result of the substantiation of the parameters, an additional combination of new features in existing studies was proposed for the first time, namely, to include in the experiment the presence of coal seams in the top – sandstones with variable thickness, the distance of occurrence above the seam, several standard sizes of the length of the working face were also included, the value of the development depth, the distance of the exit of the working face from the assembly chamber. Changing the above parameters will make it possible to compare the difference in the effect of the results of each experiment separately, depending on the change in each of the parameters, as well as to understand and generalize the idea of ​​the nature and causes of emergency longwall stops associated with the landing of powered support sections “on a hard base”. Practical significance. Substantiated modeling parameters make it possible to most adequately reflect the processes occurring in the rock mass, as well as to clarify the parameters of the reference rock pressure zones, unloading zones, as well as the nature of the change in the distribution of convergence in the longwall. The data obtained as a result of modeling can be used to select and substantiate an effective method for managing the state of the rock mass around the working excavation, which will eliminate the planting of powered support sections “on a hard base”, thereby increasing the efficiency of coal mining in the Western Donbass.

MODELING THE STRESS STATE OF THE BACKFILLING MASS WITH DIFFERENT PHYSICAL AND MECHANICAL PROPERTIES

Purpose. Analytical researches of the stress state of the backfilling stopes with different physical and mechanical properties using numerical modeling to determine possible zones of stability losses and predict their failure. Methods. Numerical modeling of the formation of stresses around a high stopes was carried out for the conditions of mining iron ore reserves in the depth intervals of 740-1040 m of the Pivdenno-Bilozerske deposit, where mining operations are actively carried out using the finite element method in the SolidWorks 2016 software package with reliable substantiation of the parameters of the developed geomechanical model. Results. Numerical simulation of the stress state of the backfilling mass are carried out at variable values of the modulus of its elasticity and the mining depth. It was found that with the existing actual physical and mechanical properties of the backfilling mass during the development of the Pivdenno-Bilozerske deposit, the danger of its failure is predicted at depths of more than 890 m. In the center of the filling array, the stress values change linearly, and at the junction of the roof with the side of the backfilled stopes – polynomial. It was found that an increase in the modulus of elasticity of the backfilling mass allows to reduce the compressive stresses only at the junction of the roof with the side of the backfilled stopes to a value of 800 MPa. Scientific novelty. With an increase in the depth of development, despite an increase in the elastic modulus of the fill, the values of stresses increase, which eliminates the need to increase it with a decrease in the mining depth it was found. Practical significance. The results obtained make it possible to correct the technology of formation of a backfilling mass in the primary stopes, taking into account the formation of stresses on its contour and, with an increase in the mining depth, to form a backfilling mass with viscoplastic properties.