Home – Home – Jornals – Journal of Mining Sciences 2023 number 2

The author studies stress concentration in wellbore zones during operation of underground gas storages. Numerical modeling yields that at the early stage of high-pressure injection of gas in underground gas storages, near the roof of a productive stratum, in rocks and in the cement lining, destructive shearing stresses arise, comparable with the injection pressure, which can induce the loss of tightness in the annular space. For preventing the loss of gas, it is proposed to ream the wells in the roof of a productive stratum and to install a spring centralizer at a certain place in the casing string. The nominal diameter of the centralizer should exceed the wellbore diameter. This can stop propagation of cement destruction. For decreasing the destructive stress intensity, it is advisable to round off corner zones while reaming within the interval of a productive strata.

Physical modeling of hydraulic fracturing is carried out in cubic blocks with an edge length of 200 mm, made of sand concrete mixed with coal fraction, in the nonuniform stress field. A fracture was created in a vertical branched hole. Computer tomography enabled studying the stress raiser at the mother and daughter hole juncture, the actual diameter of the borehole, the drilling-induced fracturing, the sizes of pores formed in consolidation of the manmade blocks, and the trajectories of the created fractures. It is found how the problem geometry and the compressive stresses affect the direction of the created fracture growth.

A series of laboratory pull-out tests were performed on several types of bolts to investigate the effect of profile geometry of resin grouted bolts on load transfer mechanism. Therefore, three different types of bolts were used to prepare twelve series of specimens with different profiles. To evaluate the effect of bond length, the specimens were made using rebar bolts with two embedment lengths of 75 mm and 150 mm. The results showed that load transfer capacity and displacement at peak load were effectively related to the profile configuration and annulus thickness of resin. The bolt types T1 and G2 had higher peak share stress levels and the bolts with a rib spacing of 12.5, 16, 25 and 8 mm had the highest peak shear strength, respectively. By decreasing the rib spacing and embedment length, the system stiffness increased. In the bolt types T1 and G2, by increasing the embedment length from 75 mm to 150 mm, the shear stress decreased by 7.8% and 10.5% and their stiffness decreased by 60.8% and 75.6%, respectively. As the thickness of the resin annulus increased, the peak load decreased.

This article presents an artificial neural network (ANN)-based mathematical model for the prediction of the intensity of ground vibration at the Veliki Krivelj copper mine. The starting points for the development of the model are the model of ground vibration, the software package Peltarion Synapse, as a basis, using artificial neural networks ANN and input-output data set of blasted patterns at the Veliki Krivelj open pit. The input-output set contains the values of the blasting parameters of individual blasting patterns and the measured peak particle velocities when blasting those patterns. The advantage of the ANN method was confirmed by comparing the results of predicting the particle velocity obtained by different methods.

The behavior of a pillar is examined in the course of mining of a blind ore body in the Southeast site of Tashtagol field. The geomechanics and geodynamics of the field is analyzed. The article gives calculations of stresses and inelastic strains, as well as the possible failure zones nearby the mined-out space during actual mining in the Southeast site and in the period of ground surface sink. The authors present the geophysical survey data on the thickness of the crown pillar between the mined-out area roof and ground surface. The area and parameters of the sink are determined from gravimetric measurements and aerial photography.

The article describes the integrated analytical studies and geotechnical assaying of blasted ore samples with size classification at a gold deposit. The parameters of mixed fractions for processing using different technologies are determined. The ore mining and processing flowsheet is developed for a structurally complex extraction block. An improved technology is proposed for the structurally complex ore deposit. Selective ore extraction is followed with screening and size classification into fractions with high and low contents of useful component. The fractions are blended, the blend with the high content of useful component is subjected to flotation, and the blend with the low content of useful component goes to heap leaching. The fraction with the increased content of useful component from rich ore is treated by two-stage sorption and leaching pre-oxidation, which ensures high metal recovery.

The present article describes the extensive characterization and stabilization of concentrated iron ore suspension having size ≤ 75 µm by various bench-scale tests. The rheological characteristics of iron ore in the concentration range of 60-80% (by wt.) have been investigated with and without the addition of Sapindus Mmukorossi dispersant. The stability of iron ore suspension with saponin is established through rheological properties, dispersant concentration and stabilization mechanism. The nature of experimental rheological data at different shear rates is accomplished by regression analysis and found to be a good fit with Herschel-Bulkley model. The Critical Micellar Concentration of the aqueous extracted dispersant is 0.018 g/cc. The presence of Sapindus Mukorossi saponin greatly improved the slurryability and stability of iron ore suspension. The head loss and specific energy consumption analysis successfully evidence the economic relevance of the surfactants in transporting the slurry through the pipelines.

Crushed rock shear tests are carried out to determine stability of a tailings pond dam. The tests allow finding the rock strength at different grain composition and density of rocks, as well as at different shear ring diameters and normal pressures. It is found that the internal friction angle and cohesion range as 35-40° and 0.0256-0.0293 MPa, respectively, in compacted rocks, and as 25-30° and 0.0163-0.0184 MPa, respectively, in uncompacted rocks.

The authors present the formulation and solution of a problem on the efficient engineering data of multi-drive high-duty belts for bulk coal. The theoretical framework for calculating the belt thrust includes the main equation of the belt conveyor dynamics, and features of calculations in stationary mode and in starting conditions with the regard to horizontal and vertical curvature of the belt route. The rational width and production capacity of a belt conveyor are substantiated. The hauling power and capacity of drives of a multi-drive belt are calculated. The strength test of a selected belt is performed. The calculation using the developed program LENTA 1.0 is presented as a case-study of a multi-drive belt conveyor in Inaglinskaya Mine in the South Yakutia coal field.

The structural layouts of pneumatic percussion machines are reviewed. The use of a pneumatic percussion machines with mixed-type air distribution via elastic valve is substantiated for implementation of adaptive technologies. The authors present the theoretical and experimental studies into dynamics of duty cycle of a pneumatic percussion tool with on-line power adjustability.

A brief literature review on flotation of calcium-bearing minerals is given. It is found that flotation activity of a collector is connected with physisorption of the collector in particle-bubble attachment. The tests prove that physisorption decrease reduces recovery and increases the useful component content /yield ratio in the concentrate. The found correlation is a framework for new approaches to quality improvement of flotation concentrates. The method proposed to select compositions of collectors can enhance selectivity of extraction of useful minerals.

The authors have correlated the fluorescence spectrum with the spectrum and kinetics of X-ray luminescence of organic collectors. The correlations prove applicability of organic collectors with modifying agents. From the integrated evaluation of organic liquids by the criteria of their adhesion capacity relative to diamonds and extraction capacity relative to inorganic luminophores, the selected organic collectors are: diesel, heavy gasoil of catalytic cracking, and their mixture. The spectral functions of organic luminophores contained in organic collectors are replaceable with polyaromatic hydrocarbons which generate intense signals similar to the signals of organic luminophores. Efficiency of modifying agents containing organic collectors and hydrophobic luminophores E-515-115-G5 and FL-530-GZ is high. The test organic collector was heavy gas oil of catalytic cracking and diesel fraction at a ratio of 61-9:1. Recovery of weakly and abnormally fluorescent diamonds was 80-90%, while recovery of kimberlite was not higher than 1%. The results allow recommending the developed modifying agents for the commercial-scale X-ray luminescence separation of diamond-bearing materials.

The article proves the promising nature of using functionalized magnetic nano particles in extraction of metals from process solutions and in treatment of industrial effluents. The experimental copper extraction from solutions using a magnetic nanosorbent made of lipoic acid-functionalized magnetite is described. Sorption efficiency is determined as function of the initial concentration of solutions as compared with non-functionalized nano-size magnetite. The copper-bearing sedimentation mechanism includes chemosorption at active centers of lipoic acid, adsorption at clean magnetite surface and re-crystallization of sorbate in intrinsic copper-bearing phases. The phase composition of copper in the sediments is examined, and the copper extractability is illustrated. The conditioning technology is proposed for copper-bearing solutions. The stage-wise use of the magnetic nanosorbent enables process solution purification up to the maximum allowable concentration at simultaneous production of a concentrate suitable for hydrometallurgical processing.

The test of gold-bearing humic substances aimed to find forms of gold in them. The test results enable estimation of gold compound mobility during sedimentation of humic acids. Re-sedimentation of humic acids shows similar properties of gold after dissolving with and without a selective dissolver. The amino-acid analysis of humic acids before and after their interaction with ammonium hydroxide reveals the increased content of amino acids capable to dissolve gold. Stage-wise spin of gold-bearing liquid humic acids at acceleration from 4000g to 233000g and at pH of 11 nullifies gold-bearing particles in solutions and makes the latter homogenous. The authors describe the impact of destructive effects relative to organic compounds on joint sedimentation of gold and humic acids.

The post-leaching of silver (Ag) from a non-sulfide lead-zinc (Pb-Zn) ore flotation tailing leach residue in a copper-ammonium thiosulfate solution was investigated. Ag (89.7%) was extracted into the leaching solution under the following conditions: 30 g/l ammonium thiosulfate, 0.5 g/l copper sulfate, 25°C leaching temperature and 4 h leaching time. On the basis of the experimental results, a fuzzy logic prediction was made. Ammonium thiosulfate, copper sulfate and leaching period were chosen as predictive criteria in this step. The fuzzy prediction model was found to be very consistent with the experimental data (R²:0.9657). Based on these findings, the application of the fuzzy logic prediction approach to the silver dissolution from the leach residue could be considered.

The authors discuss concentration of chemical elements in underspoil water subject to a season and to climatic conditions. The features of underspoil water composition are analyzed with respect to chemical composition of spoil rocks in water and acid extracts. Majority of the test elements correlate well with their composition in the acid extract and with the spoil rocks composition. The water extract is assumed to be unreliable to predict composition of underspoil water.

The article analyzes the impact of water inflow in a mine on the efficiency of the main mine water drainage system as a case-study of Udachny Mine, ALROSA. It is found that the content of solid particles in mine water grows with the increasing water inflow in the mine. A method is proposed to eliminate excessive water inflow in the mine in warm season in case of a pumping station teardown because of the spoil bank slide. The expected payback time of the proposed engineering solution is calculated.