Theoretical basis for the formation of damaging factors during the coal aerosol explosion

Purpose. Assessing the process of damaging factors formation during the coal aerosol explosion in mine workings on the basis of theoretical research of the explosion of coal dust deposits in order to substantiate promising methods of protecting miners from their impact. Methods. An integrated approach is used, which includes a critical analysis of literature data on the occurrence and development of coal aerosol explosions in mine workings; theoretical research into the state of the gaseous medium at the characteristic points of the development diagram of the coal dust deposits explosion as a result of mining operations based on the laws of classical physics and chemistry. Findings. The main aspects of the explosion mechanism of dust in a powdery state, accumulated on the surfaces along the mine working perimeter, and the formation of such negative factors as the effect of gaseous medium accelerated movement, have been revealed; high temperature formed during coal and methane detonative combustion; increased gas pressure. The revealed aspects of the dust explosion mechanism make it possible to determine the main directions for protection of miners caught in the explosion. The diagram of the development of settled coal dust explosion along the mine working with normal ventilation conditions, taking into account the influence of seismic waves, has been improved. Originality. Analytical dependences, reflecting the value of gas energy at characteristic points of the diagram, have been determined, and the dynamics of the formation of negative factors caused by the explosion have been revealed. Practical implications. Possible ways of protecting miners from the impact of negative factors caused by the coal aerosol explosion and reducing the severe consequences of such accidents are proposed.

Assessment of the factors influencing on the formation of energy-oriented modes of electric power consumption by water-drainage installations of the mines

Purpose. Performing the analysis to determine energy-efficient modes and assess the characteristics of the main indicators of electric power consumption by mine water-drainage installations based on the developed research mathematical model. Methods. To achieve the purpose set, a methodology is used to develop the multiple multifactor correlation-regression modeling with respect to the modes of electric power consumption by electrical and mechanical complexes of mine water-drainage installations. The amount of consumed electric power is found as an effective feature. The expediency of using the nonlinear multiple regression analytical ratios has been substantiated during the model development. A comparative analysis of a multiple multifactor regression model, presented in the form of a power and linear function, has been performed. Findings. The research results make it possible to determine that the greatest influence on the electric power consumption is made by water inflow, and the smallest influence – by the depth of water pumping from underground horizons. The expediency of using a multiple multifactor regression model in the form of a power function has been substantiated. The elaborated quantitative values of the factors of electric power consumption by electrical and mechanical complexes of mine water-drainage installations have become the basis for the introduction of innovative technological solutions at the relevant iron ore enterprises to optimize the cost characteristics of the electric power consumption. Originality. For the first time for the analysis and assessment of the operating modes of the main water-drainage installations of mines, the use of mathematical modeling based on the multiple correlation-regression method is proposed. The developed model takes into account a complex of technological parameters of influence on the water-pumping process. The analysis of the proposed model makes it possible to identify significant factors influencing the modes of electric power consumption by electrical and mechanical complexes of water-drainage installations in the mines and to conduct water-drainage assessment for constructing an algorithm for optimal control of this process in the cost-target direction. Practical implications. The research tactics are proposed for determining the energy-efficient operating modes of the main water-drainage installations of the mines by the method of mathematical modeling. The analysis of the obtained results of mathematical and statistical modeling makes it possible to take into account the complex of technological parameters of the influence on the water-pumping process, to identify and assess the modes of electric power consumption by the main water-drainage installations, as well as to obtain the initial data for the development of the structure of the control algorithm for mine stationary installations of this type in the cost-target aspect.

Prediction of the number of consumed disc cutters of tunnel boring machine using intelligent methods

Purpose. Disc cutters are the main cutting tools for the Tunnel Boring Machines (TBMs). Prediction of the number of consumed disc cutters of TBMs is one of the most significant factors in the tunneling projects. Choosing the right model for predicting the number of consumed disc cutters in mechanized tunneling projects has been the most important mechanized tunneling topics in recent years. Methods. In this research, the prediction of the number of consumed disc cutters considering machine and ground conditions such as Power (KW), Revolutions per minute (RPM) (Cycle/Min), Thrust per Cutter (KN), Geological Strength Index (GSI) in the Sabzkooh water conveyance tunnel has been conducted by multiple linear regression analysis and multiple nonlinear regression, Gene Expression Programming (GEP) method and Support Vector Machine (SVM) approaches. Findings. Results showed that the number of consumed disc cutters for linear regression method is R2 = 0.95 and RMSE = 0.83, nonlinear regression method is – R2 = 0.95 and RMSE = 0.84, Gene Expression Programming (GEP) method is – R2 = 0.94 and RMSE = 0.95, Support Vector Machine (SVM) method is – R2 = 0.98 and RMSE = 0.45. Originality. During the analyses, in order to evaluate the accuracy and efficiency of predictive models, the coefficient of determination (R2) and root mean square error (RMSE) have been used. Practical implications. Results demonstrated that all four methods are effective and have high accuracy but the method of support vector machine has a special superiority over other methods.

Application of radio-wave geointoscopy method to study the nature of spreading the solutions in the process of uranium underground leaching

Purpose. Assessment of the effectiveness of using the method of radio-wave geointoscopy of the inter-well space for three-dimensional mapping of the zone of the leaching solution actual propagation in the process of uranium mining by the method of underground leaching. Methods. Experimental-industrial studies of the leaching process are conducted at technological block 68 of the Semizbay deposit (Kazakhstan). In experimental studies, special equipment is used for conducting radio-wave geointoscopy. Inter-well measurements are performed using the RVGI-06 equipment. The observations are conducted in a fan pattern within the filter section. The step between adjacent points along the wellbore is 1 m. At different stages of mining the technological block, maps of geoelectric resistivity have been compiled, with the help of which a comparative analysis is performed. Findings. A tendency to an increase in the area of acidic solutions propagation over time has been revealed by comparing the fragments of RVGI geoelectric map at different stages of mining the block. The influence of a heterogeneous geological structure on the uniformity of the leaching solutions propagation has been proved. It has been determined that the resolving power of the radio-wave geointoscopy method is sufficient to detect changes in geoelectric conditions at small monitoring cycles in time. The spatial-temporal change in the front of the leaching solutions propagation makes it possible to determine the prevailing directions of solutions propagation and to assess the filtration characteristics of rocks. Originality. The patterns have been determined of the leaching solutions propagation over time from the beginning of block acidification to active leaching. The first attempts have been made to use the geophysical well logging method in the practice of uranium mining by In-Situ Leaching (ISL) method. Practical implications. Monitoring studies by radio-wave geointoscopy method at the stage of passive acidification can be re-commended for further experimental and scientific testing at technological blocks of the Semizbay deposit for a quantitative assessment of the filtration characteristics of rocks and the dynamics of the acidification process development, as well as for the development of well-grounded recommendations on the optimal scheme for mining the blocks in specific geotechnical conditions.

Choosing the flow part geometric shape of the dredge pumps for viscous fluids

Purpose. Search for the possibility of increasing the efficiency of dredge pumps for viscous fluids by determining the rational values of the blade-outlet inclination angles in the pump impellers. Methods. During the research, the following is used: theoretical studies of the structure of the viscous fluids flowing through the flow part of dredge pumps; the method of three-dimensional software-simulation modeling of hydrodynamic processes using the Ansys software package; the methods of rational experiment planning for selecting the values of the number of points in the computational grid when optimizing the geometric parameters of the dredge pump impellers; methods of mathematical statistics and correlation analysis. Findings. It has been proven that the main reason for the failure of the flow part components in the dredge pumps is the manifestation of the influence of cavitation processes, which can be eliminated by changing the blade-outlet inclination angles in the pump impellers. A software-simulation complex for the automated design of the flow parts in the dredge pumps has been developed based on the use of optimization algorithms and computational fluid dynamics methods, which makes it possible to design dredge pumps with optimal characteristics that ensure their efficient operation with maximum efficiency values. It has been determined that one of the main factors influencing the head developed by dredge pumps and the efficiency value is the blade-outlet inclination angle in the pump impellers. Originality. Scientific novelty is in the scientific substantiation and development of a simulation-mathematical method for calculating the geometric parameters of the flow part in dredge pumps for viscous fluids at the design stage. Practical implications. The developed method for determining the rational blade-outlet inclination angles of the impellers in the dredge pumps for viscous fluids can be recommended to scientific-research and industrial organizations for use in the improvement, design and operation of the dredge pumps.

Neural simulation-based analysis of the well wall stability while productive seam penetrating

Purpose is the development of mathematical models to evaluate deformation of parameters of the rock mass-well geological and engineering system within the anisotropic media. Methods. Both mathematical and neural modeling of a stress state of the rock mass-well system under conditions of geological uncertainty has been applied for the studies. From the viewpoint of mathematical modeling, analysis of probability of factors, complicating drilling, should involve a number of assumptions for strength and deformation characteristics of rock mass layers corresponding to particular hole-making conditions. Findings. A mathematical model of horizontal wellbore and geological layers, occurring along the structure under the conditions of permanent comprehensive stresses, has been developed. An analytical and graphical form has been applied to implement one of the basic aspects of aggregation principles of strength changes in each particular lithological layer for identification of an ideal value of horizontal/inclined wellbore length relative to the rock mass depths scheduled by mining. Regularities of changes in deformation and spatial well stability within the complex reservoirs depending upon various process duties have been determined. A neural simulation-based model has been proposed to analyze deformation of rock mass layers having different strength characteristics. Originality. Interaction between geomechanical characteristics of rock mass as well as deformation and spatial stability of well design has been evaluated both qualitatively and quantitatively. Practical implications. An opportunity has been presented to forecast deformation of well walls taking into consideration different strength as well as structural and geological rock mass characteristics on the basis of neural simulation. The represented approach has been included on the register of the best scientific-based practices according to “Methods to recover low-pressure gas of Cenomanian producing complex” Project.

Granulometric composition research of mine rocks as a material for backfilling the mined-out area in coal mines

Purpose. Determination of the granulometric characteristics and loosening coefficient of mine rocks formed during stope operations from undercutting the bottom rocks as a potential backfill material based on a set of mine and laboratory research. Methods. To do research, a complex methodology is used, which includes a photographic surveying the mass of destroyed rocks from undercutting the bottom rocks in mine conditions, digital processing and determining the granulometric composition in the software package, sampling the mine rocks at the surface complex, and reconstructing the granulometric composition, similar to the full-scale mine conditions in the laboratory. Sieve analysis, laboratory balance and laboratory container are used to determine the granulometric composition and loosening coefficient. Findings. The dependence between the granulometric composition and loosening coefficient of rocks, which increases by 33% within fractions of 0-50 mm and by 8% within fractions of 50-140 mm, has been revealed. It has been determined that the destroyed rocks in the face within fractions of 0-140 mm have a bulk density of 1.28 g/cm3, loosening coefficient of 1.7, the voidness of and the maximum reserve for the backfill mass compaction with mine rocks is 41.9%. An analytical assessment of the volumes of the formed cavities of the mined-out area in the longwall face and gobed mine workings, as well as the prospects and completeness of their filling with mine rocks have been performed. Originality. It has been determined that the loosening coefficient of mine rocks destroyed in the stope face by KA-200 shearer changes according to the logarithmic dependence on their granulometric composition. This makes it possible to control the granulometric characteristics of the backfill material to achieve the maximum density of the backfill mass. Practical implications. Further research can serve as a basis for determining the rational parameters for the formation and placement of backfill masses during complex-mechanized selective mining of coal seams using various methods of backfilling operations.

Identifying the efficiency decrease factor of motors working under power harmornic in 660V electric mining grids

Purpose. Identify the motors efficiency decrease factor corresponding to various values of load-carrying ratio. Methods. Basing on the onsite measurements of power harmonic in 660V low voltage (LV) grids in Vietnam underground mines, simulations have been done on MATLAB and compared with mathematical models. Verifying data will be implemented in Lab-measurements carried out on pumping system to reveal series of decreasing factors. Findings. Series factors present the relation of the level of power total harmonic distortion (THD) and the decrease in motor efficiency with alternative load-carrying ratio. The factors will help mine operators to have better understanding of the power harmonics impact on 660V motors. Originality. The proposed factors and simulation in MATLAB may be applied to all underground mining grids with diffe-rent input parameters of THD. Practical implications. The research is implemented to identify the factors obtained from the operation of motors which work in high power harmonic environment. The resulting factors could be utilized to recalculate mining efficiency.

A resource efficient and environmentally safe charge structure for mining in an open-pit

Purpose. The purpose is to reduce mineral losses during the explosive destruction of rocks and environmental pollution by harmful gases and fine particulate matter. Methods. To achieve the objectives of the study, methods of physicochemical analysis and mechanics of continuous media have been used. The method of physico-chemical analysis has been used to determine the quantitative and qualitative characteristics of the composition of the well stemming depending on the parameters of the well, the type of explosive, the amount and type of harmful gases formed during the explosion. Methods of solid medium mechanics have been used to establish the patterns of pressure waves during an explosion depending on the characteristics of the gap filler between the charge and the well wall. To solve the problem of the behavior of a two-layer medium during the loading of a cylindrical cavity by a nonstationary load, a numerical method based on the finite-difference McCormack predictor-corrector scheme has been used. Findings. A resource-saving and environmentally friendly charge structure for rock mining by explosion was developed. The design of the charge involves the formation of a gap between the charge and the wall of the borehole, and filling it with a suspension of calcium hydroxide or a suspension of calcium carbonate. Originality. SThe dependences of the volume of harmful gases (NO2, CO2, CO) formed during the explosive destruction of rocks and the magnitude of the pressure peak in the area close to the charge on the chemical composition of the filler of the radial gap between the charge and the well wall have been set. Practical implications. Developed charge design allows to neutralize the harmful gases formed during the explosion, to reduce the pressure peak in the area of the rock massif close to the charge, and can be widely used in non-metallic quarries that extract minerals for the production of crushed stone.

Experimental research on the haulage drifts stability in steeply dipping seams

Purpose. Substantiation of the conditions for haulage drifts stability using different protection methods in steeply dipping seams based on a set of experimental studies. Methods. To achieve the purpose set, mine instrumental observations have been performed to study the rock pressure manifestations in zonal advance workings adjacent to the stope face on the haulage horizon. The conditions for their maintenance, within the mining site, are assessed by the side rocks convergence value on the drift contour and the change in the cross-sectional area, taking into account the deformation properties of the protective structures. Findings. It is recorded that in the zone of the stope works influence, in the most difficult conditions, haulage drifts are maintained, when coal pillars or clumps of prop stays are used for their protection. It has been determined that a decrease in the section of such mine workings up to 50% is the result of the protective structures destruction. When protecting the hau-lage drifts with the rolling-on chocks, a decrease in the mine working section up to 30% occurs in the process of the protective structures compression. It has been revealed that deformation of coal pillars or clumps of prop stays up to 10-20% leads to a loss of their stability, and an increase to 60% leads to a complete loss of their load-bearing capacity, intensification of rock displacements on the mine working contour and deterioration of its stability. It has been determined that in the process of deformation of the rolling-on chocks from sleepers by 20-60%, they are compressed without loss of load-bearing capacity, which ensures a smooth deflection of the overhanging stratum and restriction of rock displacements on the haulage drift contour. Originality. To study the deformation characteristics of protective structures above the drift, the function of the increment is used of side rock displacements on the haulage drift contour along the mining site length dependent on the relative deformations of protective structures, which makes it possible to assess the real dynamics of the process. Practical implications. When mining steep coal seams, using the specificity of geomechanical processes, which are manifested in an anisotropic coal-rock mass during unloading, satisfactory mine workings stability can be ensured by changing the deformation properties of protective structures above the drift.