Home – Home – Jornals – Journal of Mining Sciences 2019 number 4

A method is proposed for solving inverse problems characterized by a set of parameters, which uses a system of singular integral equations connecting the boundary values of stress and displacement components and excluding regularization. The calculation involves specifying the static, kinematic and dynamic aspects and adapting them to the conditions of mining a specific seam. The static aspect is understood as the classical calculation of the stress-strain state in the vicinity of mine opening, the kinematic one accounts for the dead weight of rocks, and the dynamic one considers the process of mining the seam and damage accumulation in enclosing rocks.

A set of geomechanical studies was carried out to justify the angles of stable slopes of the Dzhetygarinsky open-pit mine, including testing the physico-mechanical properties of rocks, studying the structure of adjacent rock mass, determining the values of mining rock mass rating (MRMR) and zoning the open-pit surface according to Professor Laubscher’s classification. The values of slope angles of open-pit benches have been recommended and measures developed to ensure their stability. The factors affecting the adjacent rock mass most negatively were identified in classifying the rocks of open-pit mine surface. It was found that the effect of certain factors can be significantly reduced, which will increase the values of wall control angles while maintaining the proper degree of mining safety.

Synchronized acoustic emission and strain measurements were carried out in rock salt samples subjected simultaneously to different levels of uniaxial mechanical and incrementally increasing temperature effects. Methodological and hardware support of such measurements is described. Experimental dependences are obtained, which reflect changes in shear strains and acoustic emission activity of samples as functions of time and temperature for various axial stresses. As the stresses increase, rock salt transits to the stage of progressive creep at lower temperatures. The transition to each subsequent stage of the temperature effect is accompanied by an increase in the steepness of shear strains and activity-average acoustic emission. The patterns of changes in these parameters at the stages of steady and progressive creep of rock salt are analyzed. The advantages of using acoustic emission measurements to predict rock salt failure due to progressive creep, as well as their importance for solving the problem on estimating salt rocks properties in real thermobaric conditions for the construction and operation of underground gas storages are noted.

The problem of determining the stress-strain state in the vicinity of an opening with an arbitrary shape using the measurements of the Cauchy stress vector and displacement vector has been solved. The states of elasticity, plasticity, and overlimiting deformation are considered. The obtained results allow to determine rapidly the resource capabilities of rock mass resistance to failure on the contour both in a buried opening and in opencast mining.

The interaction of an open pipe with an internal soil plug according to the Coulomb's law of dry friction is investigated. Various soil and pipe models are considered. For all models, finite-difference solutions were obtained, for some-analytical solutions describing the process of elastic interaction of a pipe and a plug. Good agreement between numerical and analytical solutions is shown. The results of numerical calculations for various models are compared and the applicability limits of the models are determined. The effect of Coulomb dry friction on the process of pipe and plug movement was studied.

The preparation mechanism for gas-dynamic failure of outburst-hazardous coal band during an explosive effect on a coal seam is considered. The conditions for crack formation in the zone farthest from the blast hole were studied, as well as modeling of induced cracks filling with methane, which was initially in coal in a dissolved state, and estimation of the time of crack development start due to the pressure of free methane. It has been established that, depending on the mechanical and diffusion parameters of coal, the start time for crack development can vary from tens of seconds to many hours. The study results will be useful in developing a theory of explosive effect on a coal seam in a set of measures to reduce the risk of sudden outbursts of coal and gas.

A model of the longitudinal collision of rods with nonparallel impact ends proposed by V. B. Sokolinskiy, in which the contact characteristic is described by a quadratic dependence, is considered. Longitudinal stresses in rods correspond to experimental data only at the angles of misalignment of impact ends less than 0.5°. At angles greater than 1°, the discrepancy between the theoretical and experimental results reaches 20%. The obtained values of the moment at the ends of the rods do not correspond to the experiment. A model is proposed, where the stress distribution along the radius of the contact surface of the rods obeys a linear law. The dependence of contact forces and the moment at ends of the rods on the angle of misalignment of impact ends and their local contact deformations is obtained. The changes in longitudinal stresses in the rods with time are determined. This model gives results closer to the experiment in comparison with V. B. Sokolinskiy’s model and can be used to estimate the maximum allowable angles of misalignment of the ends when designing and operating percussion systems of drilling and breaking machines.

The purpose of this paper was to observe the generation, development, and extent impact of rock fissures under the blasting process; the failure process of rock under the gases expansion pressure. The latest high-speed camera, producing about 30000 frames per second (each grid was 32 μs, and exposure time 4 μs), was used to capture the failure process of rock in blasting concrete specimens. The types of cracks and the rate of extended development in a quantitative way were recorded for observation, analysis, and verification of the failure mechanism of induced by blasting. The results showed that the gas expansion rate after blasting reached the maximum of about 200 μs and then gradually attenuated. As to the development rate of the fragmentation of rock after blasting, it reached the maximum of about 130 μs, and the attenuation of then became gradual. It is concluded that high-speed photography provides meaningful scientific basis for study of the detonation theory of explosives, rock blasting fracture mechanism, analysis of blast effects, etc. Further improvement and research can be done on the control of the synchronous operation of blasting and photography, and the three-dimensional spatial analysis of the rock blasting process.

The geomechanical conditions of the mined and commissioned ore deposits are determined and systematized based on their typification according to geological and structural features, which are characterized by a commonality of the patterns of stress distribution in an undisturbed rock mass. The area and maximum depth of application of certain geotechnologies in the framework of implementing the geomechanical models of the geological environment are established.

New methods and technical solutions have been developed to intensify the degassing of coal seams based on fixed bridges and formation of impenetrable protective screens in the vicinity of a mine opening. The features of applying local hydraulic fracturing to measure the stresses acting in a rock mass are investigated. Prototypes of devices for the equipment delivery along the horizontal section of the formation hole and implementation of transverse hydraulic fracturing due to the tangential load applied near the isolated interval have been created.

The article presents one of the possibilities of using a bucket wheel excavator technology (with a daily capacity of over 100000 m³) when removing an overburden on the stabilised front in the opencast lignite mine. The influence of excavator manoeuvring movements on the choice of parameters of operational floors is discussed. The assessment of the efficiency of the work process was made, among other things, while maintaining the required safety conditions and geometric parameters of the working front. It has been shown that in the bucket wheel excavator’s over-elevation work with variable variants of vertical and horizontal division (for a given floor height), the length of manoeuvring roads on the operational front is more favourable than the working technology of the entire height of the floor.

A salt block is a regular prism of rock salt containing least undesirable cracks which is mainly used for carving artifacts especiallysalt lamps, tiles and other products. This research work is focused on the comparison of three common and simple dimension stone quarrying techniques including wedges and feathers, expansive cement, and controlled blasting methods for the extraction of rock salt block. The selected techniques were applied at the underground working face of Khewra Salt Mines (Punjab, Pakistan) to extract representative blocks in accordance with a predefined field experimental program. In order to find out the most suitable block extraction technique in terms of the quality of excavated salt blocks, physical and mechanical rock property tests were performed comprising of core recovery, uniaxial compressive strength, Brazilian tensile strength, dynamic Young’s modulus, quality and P-wave velocity. This paper statistically confirms that the rock salt blocks excavated by using wedges and feathers method have higher quality in comparison to the blocks obtained by expansive cement and controlled blasting techniques. Further the results of overall technique wise comparison are also discussed.

The stability of convective air motion in mine shafts after turning off the draft source was investigated. Based on numerical simulation, it was found that the mine ventilation with natural draft was violated by the formation of air vortices extended along the shaft depth. The transverse profiles of motion speed and air temperature were determined in approximation of a plane-parallel laminar flow of an incompressible medium with a vertical temperature gradient in the gravity field. Analytical calculations of the stability of the found flow to plane long-wave perturbations were carried out, as a result of which the value of critical Rayleigh parameter was obtained. A correction to the coefficient of air volume expansion was simulated, allowing to consider the hydrostatic compressibility of air. The dependence of the critical value of air temperature vertical gradient in the shaft was calculated, the excess of which leads to the formation of convective vortices and violation of through ventilation.

Using the methods of X-ray phase analysis, analytical scanning electron microscopy and inductively coupled plasma mass spectrometry, the influence of preliminary energy effects on transformations of eudialyte concentrate base minerals during nitric acid leaching, their micromorphology, and phase composition of the surface was studied. It was established that preliminary mechanical activation of the concentrate provides a 34-45% increase in the extraction of zirconium and the amount of rare-earth metal oxides into pregnant solution. Electrochemical treatment of mineral suspension during nitric acid leaching and, to a greater extent, ultrasonic effects contribute to an additional increase in the extraction of these elements into pregnant solution by 12-23% due to the cleaning of mineral grain surface from amorphous phases and formation of structural inhomogeneities.

A bulk coal sample from the Erkovetsky deposit was studied at Amur experimental and engineering complex. Separate fractions of coal combustion products (slag, fly ash and sludge) were obtained for the first time, in which the morphology, fineness of gold and the composition of inclusions were studied. A consistent decrease in gold size and content was established after coal combustion, transportation in a gas-smoke stream, and subsequent condensation. A comparative analysis of gold in the combustion products of coal and in ore bodies of the fold-mountain framing of the Zeya-Bureinsky basin was carried out, the ways of its migration to peat bogs were considered.

The study results of gold leaching using the samples of humic acids, as well as stage-by-stage fractionation of the initial and gold-containing samples of these acids are presented. The gold content in the product solution was up to 14-30 mg/l. Сhemical analysis of the supernatant obtained by a stage change in pH of the solution and subsequent centrifugation determined that gold-bearing acids contain both organic and dissolved gold, which is stable to precipitation at pH 2. Fractionation of the initial humic acids and subsequent leaching of gold by its individual fractions slows down the dissolution kinetics, and the fractions distinguished at different pH vary significantly in their activity. The most active is the fraction obtained by centrifugation at pH 4.6. The spectrum is presented and the kinetics of gold dissolution by these acids modified by the cyanide complex is shown.

Moroccan Mining Company of Guemassa (MCG) produces from a complex sulphide ore three concentrates using Aerophine 3418A in the flotation circuits of galena and chalcopyrite and potassium amyl xanthate for sphalerite recovery. Water scarcity in the flotation plant area imposes to think of reducing fresh water use by recycling the tailing water process. Substitution of PAX by Aerophine 3418A in the zinc circuit will result in a tailing water process containing one kind of collector which could be easily controlled and recycled in the overall MCG plant.Optimizing and modeling study using experimental design methodology showed that the targeted substitution of PAX in MCG plant is possible: at flotation time of 5 min; 40 g/t of collector; 200 g/t of CuSO₄ and pH of 12, Aerophine 3418A is more selective toward Fe than PAX. Zinc recovery reached 72% when flotation time was extended to 15 minutes.

The moisture-retaining properties of rocks in the massif are considered at ascending capillary leaching. The dependences of the moisture capacity of disperse material of flotation concentration tailings at ascending motion of solutions are found. The dependence of the specific moisture capacity and specific moisture-yielding ability of finely dispersed material at water, pH-neutral and capillary filtration on the grain size and level of feeding aqueous solutions to the massif is revealed. Based on a laboratory experiment, the specific parameters of capillary ascending filtration for the tailing pond are calculated with regard to moisture-capacity properties of the massif.

The processability of industrial waste of the Yaroslavl mining company was studied. The features of processing characteristics of secondary raw materials were estimated. The methods to eliminate the negative effects caused by residues of primary processing reagents and new formations on mineral particles were considered. The effectiveness of ultrasonic slurry treatment aimed at updating the surface of mineral particles and desorption of surface coatings is shown. Experimental data are presented that indicate an increase in the selectivity of fluorite and calcite separation from the head operations of flow chart. A comparative analysis of the flotation kinetics using the standard model and the flow chart with ultrasonic slurry pretreatment indicates an increase in the process speed with a simultaneous selectivity growth. It was found that extraction of fluorite to concentrates with 93.48% of CaF₂ and the use of ultrasonic treatment of flotation feed reaches 60.27-64.43%, and with 95.67% of CaF₂-49.82%.

The software and hardware tools for the instrumental estimation and control of the geomechanical state of engineering structures are presented. A description of the proposed technique for measuring radial and longitudinal displacements of check borehole contour is given. A research methodology and interpretation of experimental data with analysis and control of the stress-strain state of engineering structures are proposed. The results of testing the developed software and hardware in the conditions of industrial enterprises are presented.