Home – Home – Jornals – Journal of Mining Sciences 2020 number 4

The stress-strain behavior of piecewise-homogenous rock mass surrounding a horizontal roadway is defined by the natural stress field and by mechanical constants of rocks and coal. The developed algorithm of successive approximations for the characteristics of rock mass with a roadway integrates all known partial algorithms into a class of difficult problems. The authors propose solving inverse problems by identification of top coal caving parameters from the numerical experiment and using additional information on geomechanical behavior of coal seam ahead of face.

The article presents the model study into determination of block medium structure parameters by the seismic sounding method. The modeling was performed on a fragment of a brick wall. The wall was subjected to impulsive loading, and oscillograms of vibration accelerations in certain bricks were recorded. The velocities and spectral structure of waves were determined from the experimental data. The ratio from the earlier one-dimensional experiments, which connects the velocity of a low-frequency pendulum wave, the frequency limiting the wave spectrum and the longitudinal dimension of a block, holds true on the two-dimensional model of the block medium represented by the brick wall. The research findings allow determination of sizes of characteristic blocks in rock mass by the data of seismic sounding.

The water-blocking action of the clay Cenozoic overburdenlayer is an important factor that affects safety of thin bedrock coal seam mining. The change of thin bedrock thickness has an important influence on the deformation and failure of overlying soil layer. In this work, similarity simulation experiment is used and two indexes of failure height and crack density in soil layer are selected to analyze the influence of thin bedrock thickness on the deformation and failure of overlying soil layer. The experiment results show that the failure height of soil layer increases with the decrease of the bedrock thickness. The change of failure height is small when the bedrock thickness is greater than 30 m (mining thickness is 6 m), while when the bedrock thickness is less than 30 m, the failure height of soil layer increases rapidly with the decrease of the bedrock thickness. The main effect of the decrease of the thin bedrock thickness on the deformation and failure of the overlying soil layer results in the increase of shear/tensile cracks. The shear/tension crack density is 0.04 strip/m when the bedrock thickness is 70 m, while the shear/tension crack density increases to 0.14 strip/m when the bedrock thickness reduced to 20 m.

The article reports the experimental data on brittle rock strength from the bending tests of beams and from diametrical fracture of disk specimens with an axial hole. The author uses the nonlocal fracture approach and compares the strength from the tests with the tensile strength of rocks. It is shown that the different geometry fracture tests allow determining the structural parameter of a medium.

Based on the analysis of the effect of underground closed explosion on geological bodies, a physical model of underground seepage of closed gas explosion is obtained. The model considers the changes of porosity and permeability due to crushing, fragmentation and fracturing of the surrounding body caused in the underground closed explosion zone. The relationship between the proportional radius and porosity, laminar permeability and turbulent permeability are established, respectively, based on the experimental data. The seepage parameters of different zones are obtained accordingly. The law of the pressure field and velocity field of the gas in the geological body and the law of the migration of the explosive gas in the geological body are analyzed using adimensionless finite difference method.

The process flow chart of hydraulic impact on coal and rock mass is examined. The double-sided packer design is presented for the implementation of the chart in uncased wells of large and varied diameters. The laboratory tests of axial displacement of packer seals are described. The DEM-based stress-strain analysis is performed in rock mass in the vicinity of a well subjected to pressure from packer seal. The pressures at the packer seal-well wall interface are calculated.

The authors have developed a procedure for selecting models and number of draglines for overburden removal in direct dumping within the hybrid opencast/underground mining in gently dipping coal seams. The potential opencast production capacity algorithm uses the data on the available workable reserves, life of assets, and geotechnical conditions of mining. The article presents a case study of the procedure in determination of working capacity and number of draglines so that to ensure project capacity of the direct dumping system in certain geotechnical conditions of surface mining in a suite of coal seams.

The influence of jointing on the stability of adjacent rock mass is analyzed using the coefficient of structural weakening and the joint spacing. The gravity-tectonic stress field of ore bodies in Gornaya Shoria, including the azimuth of the principal horizontal stresses is characterized. The laboratory tension tests of combinations of support systems as well as the small-scale extension tests of rock bolts made of different materials are discussed. The framework for a multi-factor digital model of safe and efficient support design for iron ore mines in Gornaya Shoria is based on the stability assessment of adjacent rock mass in terms of jointing and stress state.

The geomechanical conditions of underground gold ore mining in thin steeply dipping ore body under open pit bottom are assessed using the dedicated 3D parameter-oriented model of mine design. The numerical model has produced the forecast stress pattern maps of ore and rock mass disturbed by mining operations. Stability justification is implemented for a sill pillar at a depth of 140 m in case of active stoping two levels above and below the pillar. Safe parameters and conditions are determined for the cut-and-dry fill mining operations.

Ultimate pit limit optimization plays a major role in the mining industry as it serves as the elementary foundation of all the activities in mine planning. This paper reviews and documents some methods used in ultimate pit limit optimization and gives a clear insight of these algorithms, their functionalities and limitations to open up more research opportunities. The algorithms reviewed are classified as rigorous or heuristic. The Lerchs-Grossman algorithm was found to have wider software application as compared to other algorithms. Genetic algorithm, artificial neural network, pseudoflow and stochastic approach also give great insights to focus in the future.

In order to solve the problems of coal pillar loss and relieve the tension of mining replacement in the coalface of a coal mine, this study proposes an adaptive method of retaining roadway along gob with supporting body (pier column) near loading roadway. The supporting technology of pier column retaining roadway along gob is studied through theoretical analysis and numerical simulation. The results show that the roof activity of roadway along gob can be divided into three distinct stages, namely, the stage influenced by primary mining, the stability stage of roadway retention, and the stage influenced by secondary mining. By establishing a roof mechanics model, equations are derived for calculating roof cutting resistance in three stages of gob retaining roadway, and the parameters of the supporting pier are determined. Combined with FLAC^3D numerical simulation, this study develops a numerical model to investigate the surrounding rock stress distribution characteristics and deformation rules, as well as the stress and deformation rules of piers and pillars during the two mining periods of gob retaining roadway. The numerical results demonstrate that the compressible pier column supporting body adopted in this study can not only achieve better retaining effect in the roadway along the goaf, but also reduce the cost and labor.

This paper proposes an approach to select the optimum maintenance policy for mining equipment using risk-based maintenance (RBM). RBM constitutes the process of risk assessment that identifies high-risk components of equipment, and analytic hierarchy process (AHP) that helps selecting an optimum maintenance policy for individual components. By applying RBM, three high-risk components of dragline such as reduction gearbox, bearing, and motor pinion shaft have been identified, and then AHP was used on these three components by considering four criteria, eight sub-criteria and four alternative maintenance policies (such as periodic, preventive, predictive and corrective maintenance). Local and global scores for these three components were calculated from the opinion of three experts of the case study mine. AHP global scores revealed that the optimum maintenance policy for reduction gearbox and motor pinion shaft was preventive maintenance, whereas for bearing it was periodic maintenance policy. Adoption of such maintenance planning is expected to reduce maintenance cost and downtime of the dragline.

The values of pH, temperature and initial concentrations of valuable components have influence on recovery efficiency of zirconium and rare earth elements (REE) from pregnant solutions of nitric-acid leaching of eudialyte concentrate by the chemical deposition method. Zirconium and rare earths exhibit selective recoverability of 99.95% and 87.50%, respectively. The loss of REE is 8.0% with zirconium product and 4.5% with pregnant solution. Micromorphology, structural chemistry and chemical composition of products are analyzed using the scanning electron microscopy, IR spectroscopy and X-ray fluorescence analysis.

The article presents a case-study of thickening and dewatering of tailings slimes from Zhezkazgan Concentrating Plant using UltraflocTester machine and different Kemira’s Superfloc series flocculants. From among the test flocculants containing various polar groups, the anion-type A-150 flocculant has demonstrated the highest efficiency towards tailings slimes. Relatively dense slimes (100 g/l) should be treated at the velocity gradient G = 500-1000 s^-1 for 12 s, while the slimes with the relative average density of 50 g/l should be treated at G = 1000-1500 s^-1 for 6 s. The effect of the hydrodynamic stimulation on the residual suspended matter concentration in overflow and on the moisture content of flocculated precipitate before and after screening under pressure is assessed.

The analytical reagent dithiopyrilmethane (DTM) is investigated in combination with potassium butyl xanthate (PBX) in gold recovery from low-sulphide arsenical gold ore. Thanks to two heterocycling rings in the structure, DTM attaches to nonferrous and noble metals. Adsorption of DTM at arsenopyrite and gold is determined using the electron and laser microscopy, as well as by IR and IV spectroscopy. In flotation of arsenopyrite with nano gold, the PBX-DTM combination increases both the yield of pure arsenopyrite and arsenopyrite with nano gold. The DTM-PBX flotation of Olimpiada ore has improved the quality of the concentrate in terms of the gold content by 3 times at the simultaneous increase of gold recovery and proportional decrease of gold loss with tailings. These results prove advisability of using DTM in integrated gold recovery from arsenical gold ore.

The article reports the studies into surface wetting of sphalerite, chalcopyrite and pyrite after treatment in saltish solution and in artificial sea water with concentration of 2, 8 and 16‰. The collecting agents were potassium isopropyl xanthate and sodium isopropyl dithiophosphate (Aeroflot). The results show that depending on concentration of sea salt and collector as well as on collector type, the surface of sulfide minerals can either be hydrophilic or hydrophobic, which can influence flotation efficiency of such minerals in saltish and sea water.

The vibroacoustic effect on poroperm properties of rock mass in case of directed upward water movement has been studied experimentally. The relationships of percolation velocity and sound load at different pressure gradients are obtained for fine sand. The experiments prove feasibility of multiple increase of percolation velocity in upward capillary movement of water solutions.

In order to recycle valuable elements from solid mine waste, this study took iron-bearing tailings as the research object and involved existing Hanging Vibrating Cone (HVC) concentrator separation technology to explore and determine the most appropriate processing parameters of this equipment for the experiment sample processing. The iron concentrates obtained by the experiment meet the Chinese Steel Industry criterion, within or up to a grade of 61.75 wt. % and the iron element recovery rate of 60.31%. So, a new and feasible way has been found for the reuse of mineral solid waste, which is rich in valuable elements.