Home – Home – Jornals – Journal of Mining Sciences 2021 number 3

The authors propose a dedicated mobile roof support for underground coal mining. Joint deformation of roof rocks and roof support is analyzed using the finite element method. The shapes and sizes of failure zones and the influence of the support on coal and host rocks are determined. The application area for the mobile roof support in underground mining is outlined, and the essentiality of the current prediction method of dynamic events during mining is substantiated. It is feasible to increase the rate of heading by means of reduction of the heading cycle duration.

In uniaxial compression tests of cubic samples, the authors measure displacements in the mid-cross section of the samples at different distances from side faces. The mathematical modeling of deformation of salt rock samples uses the elastoplastic model with linear isotropic strengthening and the associated flow rule. The plasticity condition is the three-dimension strength criterion reflective of shearing and tensile fracturing. The 3D FEM-based mathematical modeling is implemented in terms of displacements with discretization into 8-point isoparametric hexahedral elements. The mathematical model of deformation and failure of salt rock samples is calibrated using the calculation results. The elastoplastic model with linear isotropic strengthening ensures reasonable agreement between the experimental and theoretical data, and is applicable to estimating stability of rib pillars, critical lateral strain rates in the pillars and their remaining life.

The article discusses natural stress field variation with depth. Rocks are assumed to be elastic. Increase in the stress level results in higher principal shear stresses but causes no failure. It is stated that failure is only possible at the increased lateral earth pressure coefficients, which induce hydrostatic stress redistribution at great depths. It is shown that Poisson’s ratio tends to 1/2 in isotropic rock mass.

The presented procedure of slope stability analysis for open pits is based on the comprehensive studies into physical/mechanical properties and structural tectonics of pit wall rock mass with regard to jointing. The procedure is applied to find determine structural weakening and rock quality in Koktaszhal Open Pit Copper Mine in Kazakhstan.

The structural characteristics of expansive soil is susceptible to repeated drying and wetting cycles caused by seasonal periodical changes. In this paper, the characteristics of Nanning expansive soil were studied,and the soil-water characteristic curves of Nanning expansive soil under multiple drying and wetting cycles were obtained by adopt several known equations. Furthermore, a new prediction model considering two factors was proposed basing on the Van Genuchten model. The new model overcomes the shortcomings of the previous model which considers only matrix suction. It can reasonably consider 2 factors including the matrix suction and the number of drying and wetting cycles. The model can establish a general equation for the soil-water characteristic curve with the same fitting parameters in comparison with the previous model, which can greatly reduce workload of the measurement. In addition, the application of the improved model was broadened by comparing the fitting results and test data of expansive soils of Nanyang and volcanic ash soil.

Salt rock is a crystalline material with a particular structure and different mechanical behavior. This inorganic material is a highly deformable rock, which shows creep under constant loads. This study attempts to estimate the properties and mechanical parameters of salt rock, such as uniaxial compressive strength, deformation modulus, Poisson’s ratio, internal friction angle, longitudinal wave propagation speed, and other related parameters by designing and performing the tests in accordance with valid standards in this context. Prismatic specimens were prepared from a salt rock dome, and the complete stress-strain curves in uniaxial compressive tests were determined. Comparison of salt rock strength and deformation characteristics with the brittle rock material shows significant difference between them. The results of tests have demonstrated the effect of the form of samples on their mechanical parameters. The ratio of the strengths under uniaxial loading of cylindrical samples to similar prismatic ones is about 0.83.

The concepts of classification of water solid mineral deposits are discussed. Most classifications are based on hydrogeology, water inflows and water abundance of rock mass. Grouping of mineral deposits without regard to the mining technology disables the integrated evaluation of the potential and attractiveness of mineral resources. The authors propose to classify water solid mineral deposits by grouping the latter with regard to the water flow impact neutralization method and mining technology in open pits.

Hard coal production is a strategic branch of the Polish economy. The exploitation processes at greater depths encounter natural hazards, such as methane hazard. The Mysłowice-Wesoła mine is located in the largest coal basin in Poland-the Upper Silesian Coal Basin (USCB). Methane concentration increases with depth in this area of the studied basin. During the period of gas research, the volume of emitted methane increased over 5 times. This large increase in methane liberation to the mining faces was caused by many factors, including complex tectonic characteristics of the area, permeable nature of the Książ Fault, varied geological structure, higher concentration of coal extraction. The overall study of coal output for the years 1994-2018 follows the entire Polish hard coal production trend, namely, slow, yet constant coal extraction decrease. The total coal output in the Mysłowice-Wesoła mine decreased more than twice with simultaneous increased methane emission.

The authors evaluate the influence exerted by tectonic structure on methane content patterns in QD site in the Qinshui Coal Basin. The gas flow rate versus bottomhole-fault distance and the minimum bottomhole-fault distances for profitable methane production are determined. The obtained results are applicable to methane well patter design in the test site.

The authors address the problem connected with the determination of efficient rotary percussive drilling techniques with DTH hammers and present estimation criteria for their value ranges such that to ensure drilling at minimum energy content and wear of bits. The calculation formulas for drilling techniques are given, and the expediency of maximum destruction at minimum impacts per one complete turn of drill bit is proved. The upper limit of drill bit turn angle between impacts at the maximum drilling capacity and minimum energy content of fracture and wear of tungsten carbide inserts is found. The rotary percussive drilling technique with different DTH hammer models can be optimized suing the energy criterion of volumetric rock destruction and the energy content of fracture.

The authors review the models of dryers, including vibrating machines, for granular minerals after wet separation. The dryer arrangement developed at the Institute of Mining, SB RAS is described. An emphasis is laid on the advantages of the elastic vibrating transporter of the dryer. Dynamics of double-drive elastic vibrating transporter is analyzed using numerical and physical modeling, and the modeling results are presented. It is shown that wobbling of the vibrating transporter ensures the best conditions of granular material conveying during drying.

Potassium butyl xanthate adsorption at galena and chalcopyrite is characterized using the methods of atomic force microscopy and spectroscopy. It is found that layers generated on galena and chalcopyrite surface as a result of agitation in distilled water and interaction with potassium butyl xanthate solution have cardinally different morphology. Observations over adsorption of the reagent in liquid phase reveal different mechanisms of the reagent coating growth on these minerals.

The hydrophobic property generated by chemisorbed agent influences selectivity of flotation but not always governs recovery of minerals. It is suggested to evaluate efficiency of a chemisorbed agent by two criteria. First, free surface energy reduction t the moment of local rupture of the liquid interlayer between particle and bubble. Second, displacement of the contact perimeter of three physical states of particle surface under the action of surface forces at their interface. It is found that physisorption conditions collectability of a flotation agent and recovery of a target mineral in concentrate. A physisorbed collector removes liquid from the particle-bubble interlayer. The definition of the physisorbed collector force is given and its essentiality is proved. The physisorbed collector force is effective at the gas-liquid interface rather than mineral-liquid interface, and is not selective. Selectivity of an agent is governed by the chemisorptions/physisorption activity ratio of a flotation agent.

Acoustic and thermal treatment of zeolite rocks of East Transbaikalia is discussed. The mineralogy and chemistry of the largest natural zeolite deposits in Transbaikalia are described. It is found that quality of zeolite can be affected by iron impurities, montmorillonite, hydromica, quartz, calcite, potash feldspar, crystobalite and pyroxene. The experimental data on efficiency of directional effects on zeolite rocks are presented. The zeolite rock processing technology is developed with regard to the previous research results on effects of accelerated electrons and high-power electromagnetic pulses. Modification of properties of minerals in composition of zeolite rocks is assessed. It is found that magnetic properties of iron-bearing impurities in zeolite change, which improves efficiency of removal of these impurities. The capability of the suggested methods to enhance adsorption capacity of East Transbaikalia natural zeolites within the processing flow charts is illustrated.

The authors test grinding of mining waste material to a preset grain size composition under stagewise increased destructive force and at reduced sliming. The optimized conditions are determined for disintegration of mineral and tin-bearing waste aggregates at minimized micro-size sliming. The quality of the final concentrates can be improved via mechanically activated grinding of roasting stage middlings.

The studies into optimization of rare-metal ore processing using the mineralogical and process characteristics of the ore and by means of controlled combination of ore pre-treatment and gravity separation are presented. Grindabilties of low-grade loparite ore and current production material are compared, general patterns of generation of productive class - 0.63 + 0.07 mm are found. Controlled grinding allows gravity separation of low-grade loparite ore at the level of performance of standard-grade crude ore processing. Regarding promising deposits of rare metals in Eastern Siberia, the authors analyze and select the optimal conditions of gravity separation in combination with spiral separation, table concentration, centrifugal concentration and high-power magnetic separation. The mixed-type gravity/magnetic separation technology with production of columbite and zirconium concentrates is developed.

This paper presents a part of the results from flotation concentration examination of pure chalcopyrite mineral from the deposit of the mine Rudnik in the frothless cell. The examinations were performed in seven series. In the first three series, the conditions under which the recovery of chalcopyrite from the Rudnik mine has the highest value were determined. The examinations was performed as a function of collector (KAX) consumption and pH. In the fourth and fifth series, the possibility of chalcopyrite depression as a function of depressant (NaCN) consumption, collector (KAX) consumption and pH was investigated. In the sixth and seventh series, the possibility of activating previously depressed chalcopyrite as a function of collector (KAX) consumption and pH was investigated.

The authors study the engineering geological characteristics and material constitution of loparite ore mill tailings in the active disposal area and in the dump decommissioned more than 30 years ago. The material constitutions and the contents of valuable components are nonunform in the test tailings. The content of light rare earth elements in fine fraction (- 0.071 mm) is 1.5-2 times higher than in the composite sample. Based on the calculated effective specific activity of natural radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K, the composite sample and the tailings fines belong in waste categories I and II, respectively.