Home – Home – Jornals – Journal of Mining Sciences 2019 number 2

Features of stress state and jointing as well as their effect on hydraulic fracture propagation direction in coal seams are considered. The flow resistance in drainage areas is analyzed depending on hydrofracture orientation, thickness of seams and spacing of holes. The comparison of one-stage and multi-stage hydrofractures created in-plane and orthogonally to hole axes is given. In simulated reservoir conditions, permeability of dense coal is studied without a fracture and with a through propped fracture subjected to confining pressure. The recommendations are developed for improving efficiency of gas drainage in coal seams based on in-seam hydraulic fracturing.

Some kinds of coal in Kuzbass are metalliferous and should be used to the best advantage both as fuel and as a source of valuable components recoverable from ash and slag. It is proposed to initiate a production system composed of a coal mine, heat power plant with multi-stage coal preparation for combustion and a waste treatment plant for: furnace refuses and light-end products in the form of pregnant solution and fly ash.

The studies aimed to evaluate longwall productivity in the Talda-Zapad 1 Mine are carried out with regard to the technological parameters of the drum shearer and capacity of the armored face conveyor in mining thick methane-bearing coal seam. It is found that methane release reduces with increasing output of the shearer, and allowable longwall length and capacity by the gas criterion are determined. The length of longwall 6605 is optimized by the maximum annual profit of the mine.

Overburden dumping in hydraulic fill inside mined-out open pit is discussed. Features of hydraulic filling in an open pit at a gently dipping water-bearing lignite deposit without its drainage are presented. Parameters of hydraulic fill are correlated with hydraulic filling methods. Expediency of hydraulic fill formation without a dike is specified.

Drmno open pit mine with the annual yield of 9 million tons of coal is one of the main providers of the primary energy source in company Elektroprivreda Srbije. Due to the immediate vicinity of two rivers, the Mlava and the Danube, water abundance in the working environment is high and the problem of protecting the open pit from infiltration of underground waters is relevant to the execution of exploitation works. This paper is focused on the multi-attribute check of the preference of one of the two projected variants of the modification of the system for protecting Drmno open pit mine against the infiltration of groundwater. The outcome of the analysis confirms the signification and justification of applying a multi-attribute or multi-criteria analysis for examining such problems.

Air resistances are classified depending on their locality in underground mines. Three groups of local resistances are distinguished: shaft and mining horizon intersections; shaft and air channel intersections; stope and ventilation duct intersections in blind drifts. Influence of each group of the local resistances on the mine depression is evaluated as function of geometry and aerodynamics of underground openings. The criteria are proposed for estimating percentage influence of each group on the total mine depression are proposed. The calculation methods are determined for each group to be advisably used in quantitative analysis of air distribution in underground mine ventilation networks under the ventilation mode change.

Adsorption of IM-50 and tall oil fatty acid (ZHKTM) on cassiterite is for the first time determined using the electron and laser microscopy. The micro images of cassiterite polished sections treated with the collecting agents show newly formed phases of an organic matter, the X-ray spectra of the phases feature the increased carbon content. When cassiterite interacts with IM-50 and ZHKTM, the mineral surface is modified by stable metal-absorbent systems, which promotes efficient tin recovery from tin sulphide ore. By the change in the surface relief parameters of cassiterite, the adsorption layer of IM-50 and ZHKTM agents is qualitatively and quantitatively assessed. The comparative flotation tests of cassiterite and quartz fractions prove high collecting ability of IM-50 and ZHKTM relative to tin. It is found that ZHKTM efficiently floats cassiterite in neutral and alkaline environments while IM-50 is used at higher consumption.

The computing equipment of Computational Fluid Dynamics (CFD) for mathematical modeling of physics and physical chemistry in separation is presented. Completeness and particularization of the initial and boundary conditions in mathematical models condition validation and verification of the algorithm and results of computational experiments presenting the current state and evolution of a heterogeneous medium. There are three possible applications of the computational experiment in studying mineral dressing processes: investigation of operations in mineral processing machines; prediction of technological parameters in variation of separation modes and (or) retrofit installation; prototyping of new design equipment. The computer simulations of centrifugal classification, spiral separation, magnetic-and-gravity separation and flotation are discussed.

The research results on deep concentration of basic mineralogical variety of natural rich ore to obtain high-quality iron ore product for metallization are presented. The main methods of mineral dressing (selective crushing, magnetic separation in weak and strong fields, gravity separation and flotation) are tested in the technological experiments. It is shown that high-quality iron ore product can be obtained from natural rich ore using a simple technology. The simple technology should be applied at the first stage of processing for maximum possible extraction of high-quality product. Wet separation processes should be used at the later stage as they unavoidably result in high loss of marketable product, as well as bring difficulties connected with dewatering and drying.

The process of wet magnetic separation of oxidized ore from the deposit of Abail, Republic of Kazakhstan, is studied. Kinetics of roasted product milling is analyzed, and the optimal size is recommended for the fist stage of milling as -0.071 mm at the content of 55-60%. The accomplished magnetic analysis of different size products shows that the decrease in size causes no increment of iron in the magnetic product and iron is at the level of 63.0 mass%. The scanning electron microscopy reveals that the roasted and magnetic products contain floccules of gangue and magnetite particles which ass into magnetic fraction and worsen its quality. Two schemes are proposed for decomposition of floccules: multistage desliming with regard to sedimentation velocity in liquid medium and attrition with deffloculation agent. It is recommended to apply two two-stage circuit with milling, desliming and wet magnetic separation, which allows production of iron concentrate with iron content of 67% at recovery of 76.5%.

The regular patterns are revealed in the influence exerted by the absorbed dose on the elastic wave velocity in granite after radiation exposure. It is shown that the major change in velocity of P-and S-waves in the treated cores of granite is observed when the absorbed dose is 10 kGy. The energy consumption in breaking and crushing can be estimated in the tests of uniaxial compression up to failure. Radiation exposure of granite cores to the dose of 10 kGy reduces energy consumption from 7.68 to 3.06 J in uniaxial compression up to failure and from 700.4 to 470.88 J in crushing. The obtained result is important for improvement of ore pretreatment processes.

Elastic properties of enclosing rock mass around Botuobinskaya pipe diamond deposit are studied using the standard STO 05282612-001-2913. The Standard is based on an original procedure for determination of static elastic properties of materials under change in temperature or moisture content, which is inprovided by Russian and international standard but is of practical value in mine planning and design in the permafrost zone. A sample is subjected to multiple loading in the range of low irreversible strains, which improves measurement accuracy and enables physically correct estimation of temperature and water content influence on change of properties in a material in transition from thawed to frozen state. Based on the findings, the mechanisms of change in elastic properties of hard rocks are determined in a wide temperature range. It is emphasized that the change in elastic properties exhibits essentially nonlinear dependence on water content.

The methodical basis is given for the macroecological rough-draught mapping of mining and processing industry zones at a local and regional scale by the key indexes and numerical values of geoecological indicators reflecting the real biota response from the results of remote sensing of vegetation cover, with description of contamination sources and production infrastructure. Judged from the functional purpose of maps, the rough-draught maps provide an assessment of current state and quality of the natural environment using the relevant standards and ratings with regard to a human being and the biota as a whole as the principal ecological subject.

An approach is proposed to connecting strength data of different-size rock samples by the linear share-to-normal stress dependence. The data are presented by Mohr’s circles. The key moment is the determination of centroids for uniaxial compression and tensions areas enveloped by Mohr’s semi-circles. Using coordinates of the centroids, the shear stress-normal stress curves are plotted. Thereupon, the model estimate of missing data (ultimate compression and tension strengths) is constructed for rock samples. The missing ultimate strengths are estimated in terms of meta-siltstone.

A rigorous literature review has been carried out on rheological behaviour of hard and soft particle slurries.The rheological characteristics of unimodal and bimodal suspension are presented. From experimentation, it was observed that mineral viscosity increases with solid concentration, while decreases with temperature. Addition of 30% (by weight) proportion of finer particles in coarse particles resulted in significant decrease in apparent viscosity of iron ore suspension. Artificial neural network approach was used for predicting the apparent viscosity of slurry.

Knowledge of the state of stress regime is important to the mine designers for deciding the method of mining and for strategic design in virgin areas. This knowledge helps them in deciding the mining sequence and rock reinforcement for extraction of ores economically and safely. Generally, as excavation progresses to deeper levels, the stress tensors are also equally affected. Elevated stress regime results in concomitant increase in rock fracturing and mining induced deformations. The ambient state of the stress in an element of rock in the ground is determined by the existing loading regime in the rock mass as well as the stress path defined by the cumulative geologic history of the area. Rock failure in the periphery of the excavation is somewhat stress related, and it is therefore important to ascertain the extent of stress levels within a given rock formation. In this paper, the role of stress regime in pre and post mining stages is discussed by referring available and validated data inputs from in-situ stress measurements conducted at deeper levels in mines. Further, the authors also tried to ascertain the redistribution of the stresses due to mining or perturbation due to various other geological factors and any re-orientation of the stresses when compared to pre-mining stress tensor. The generation of post - mining stress data helps in understanding the impact of mining on the stress and could be used for design and sequencing of the mining operations for safe and optimum extraction of the ore/mineral.

The full-scale experiments on acoustic noise recording on the surface of an above-ground pipeline are carried out on operating heating main. The tests were performed in the pipeline branches with different style attachment between pipe and support-rigid (the pipe is welded to the support) and flexible (the freely supported heat-insulated pipe). The experiments show that collection of recorded noise amplitude spectra makes it possible to determine natural frequencies and forms of flexural coincident waves generated by noise in the pipeline spans. Both frequencies and forms of the waves depend on the style of the pipe attachment at the span ends, which may be used in diagnostics of pipeline branches by acoustic noise to detect damaged stiffness of the pipe-support attachment and/or instability of the supports. The computer modeling using the finite element method yields flexural wave frequencies similar to the experiment results. The distributions of nodes and antinodes of flexural coincident waves along pipeline spans at different style pipe-support attachments qualitatively agree with the earlier lab test data.

The monitoring results on earthquake loads from blasting in the Shakhtau open pit mine in 2016-2017 are presented. The integrated model of influence exerted by the parameters of drilling-and-blasting and the environment on the surface earthquake loading is developed, which allows high-precision prediction of the seismic effect value at any point of a study area. The estimates of of the short-blasting initiation errors are given. It is concluded on the promising nature of continuous blasting monitoring in difficult geotechnical conditions when reliability of standard seismic effect valuation procedures is insufficient.

To find out the power source for coal and gas outburst, the experimental instrument ASAP2020M was used for nitrogen adsorption experiment. The experiment was carried out at the temperature of 77 K, in which the activity of nitrogen can be reduced at least and the results of the test were more accurate. The experimental data were fitted by the function of f(x)=ax^b. The total volume of micropores and the degree of micropore volume filled by nitrogen were calculated by the Dubinin-Radushkevich equation. In unexploited coal body, the gas desorption occurs in a unit, it could trigger a desorption of the neighboring units of coal body. When it reaches a certain level that can push the coal body forward, the coal and gas outburst would happen. For the material containing micropores and mesopores like coal, the inflection point was the demarcation point of micropore filling and adsorption of multilayer.

The geomechanical mode, of the powered roof support-top coal-roof rock system is developed. For investigation of disintegration processes in top coal of thick seam, numerical modeling with finite element discretization of a study domain is carried out using the authors’ original code. The computational experiment reveals stress distribution in rock mass, as well as evaluates position, shape and size on uncontrolled caving zones in tope coal.