Home – Home – Jornals – Journal of Mining Sciences 2025 number 5

The applicability of InSAR technique in stress-strain assessment and alteration prediction in rock mass is illustrated as a case-study of the Upper Kama Salt Deposit. The object of research is Berezniki Mine-1 flooded in 2006 after an accidental freshwater inrush. Because of high solubility of salt rocks, velocity of ground subsidence is yet very high within the mine field. Subsidence monitoring is carried out here using benchmark surveying along existing profile lines and TerraSAR-X-base radar survey with a period of 11 days. The InSAR data were interpreted using 3D mathematical modeling of deformation process in undermined rock mass. The computational model displayed a whole set of geological and geotechnical conditions, and a group of factors associated with the freshwater inrush. The numerical calculations used the semi-analytical finite element method. Within the framework of the developed modification of the method for variable-module deformations, InSAR data were a part of the parametric content of the geomechanical model determining deformation of undermined rock mass in time.

The article presents the laboratory studies on cyclic treatment of fine-pore and banded bituminous coal with liquid nitrogen. Permeability of coal cores was determined in the mode of nonstationary flow, and porosity was assessed using the methods of nuclear magnetic resonance and optical microscopy. The procedures and design solutions used in the experiments are described. The change in permeability of coal along and across its banding is examined in the conditions of hydrostatic compression. It is found that permeability of test coal grows by one-two orders of magnitude along its banding and by two-three orders of magnitude across the banding. Anisotropy of permeability decreases. This effect intensifies with the increasing hydrostatic compression and water saturation of coal. It is shown that the effect of the liquid nitrogen treatment is mostly associated with different-scale crack growth in coal at a minor change in open porosity.

The authors have theoretically substantiated and experimentally tested the method of determining permeability of discontinuities as function of stresses in rock masses and reservoirs of quasi-regular layered deformation structure when fluid flows across the strike of the discontinuities. A linear model produces an analytical solution of a problem on stationary fluid flow in media with discontinuities, which allows finding the permeability kJ of the latter by the recorded flow rate. The tests are carried out using samples of sandstone blocks and a dependence is obtained for the interblock space opening h and the normal stress s. A lab-scale testing plant is proposed for the permeability tests with the coincident directions of compression and fluid flow. As a result of the experiments on gas flow in block samples subjected to normal loading, an empirical dependence is found for the specific discontinuity permeability kJ/h and the stress s, which can be approximated by a two-parameter fractional rational function.

Fine particles, when flowing with fluids in the Earth’s crust, can settle on surfaces of pores and fractures, and form colloid barriers which drastically reduce permeability of jointed media. When seismic waves travel in fault zones, which have greatly different stiffness as compared with enclosing rocks, Biot slow-wave diffusion originates, which can cause destruction of the colloid barriers, growth of permeability, redistribution of pore pressure and change in the stress-strain condition of a fault. This article describes the studies into conditions when regular seismic impacts induced by massive blasting can lead to a drastic change in the permeability in the fault zones.

Three calculation models are developed for estimating the cross size of a main crack formed by a blasthole in perimeter blasting: a numerical model for calculating the equilibrium shapes and sizes of a flat crack in 2D elasticity, and two analytical models for estimating the cross size of a flat crack in two-dimensional and axially symmetric problems. The models are used to calculate the sizes of main cracks formed in granite in blasting of ammonite charges of different density. The comparison of the 3D numerical calculations with the 2D and axially symmetric modeling results has allowed finding the conditions when the analytical modeling produces such precision that makes the analytical models applicable in design of perimeter blast patterns.

The article presents the results of the physical modeling of hydraulic fracturing in coarse cement cubes subjected to triaxial loading. The laboratory-scale plant, hardware and software tools, as well as the methods and engineering solutions applied during the experiments are described. The pressures and the trajectories of fractures which intersect the earlier created crack, including propped fractures and fractures filled with an isolating polymer, are investigated. The possibility to control hydraulic fracturing by deformation of a close-spaced hollow cavity which models an underground opening is demonstrated experimentally.

The article reports the experimental data on the effect of sodium laureth sulfate and neonol AF 9-12 on the fracture energy of dolomite at the Internatsionalnaya pipe and limestone at the Mokhsogollokh open pit at temperatures in a range of + 20 … - 30 °C. In the positive temperature range, the fracture energy of dolomite treated with surfactants, lowers by 28% on the average. Under negative temperatures, an increase is observed in the fracture energy of dolomite samples saturated with surfactant solutions. At the temperatures below - 10 °С, the fracture energy of dolomite exceeds its fracture energy at the positive temperatures by 2.3-3.1 times. The indicators of fracture of dolomite samples saturated with surfactants totally agree with the fracture indicators of water-saturated samples. The fracture energy of limestone treated with surfactant solutions decreases by 5-10% under positive temperatures and increases by 8-15% under negative temperatures as compared with the fracture energy of air-dried samples.

Rockburst disaster is a kind of typical dynamic disaster phenomenon. In this work, the risk level of the rockburst disaster was predicted based on the convolutional neural networks and long short-term memory (CNN-LSTM), and particle swarm optimization and general regression neural network (PSO-GRNN) models. A CNN-LSTM deep learning model based on rockburst chaotic time series was proposed to predict the characteristic variables of rockburst state, with a method to quantitatively distinguish and predict the risk level of the rockburst disaster in the future, and thus the dynamic prediction of the rockburst activity was realized. As an example, the microseismic monitoring variables (i.e., indexes of the daily cumulative microseismic energies and daily maximum microseismic energy, angular frequency and concave-convex radius) and electromagnetic radiation signals (i.e., indexes of the daily average amplitude and daily maximum pulse) were used to predict the rockburst. The CNN-LSTM and PSO-GRNN models were confirmed to be the most suitable to predict the risk level of the rockburst. This work provides an important basis for timely mastering the future state of rockburst activities.

The article focuses on placer gold mining as an important factor of social and economic development in the Far Eastern Arctic Zone of Russia. The structure of unmined placer reserves and man-made placers in the permafrost area is examined as these objects are an important source of minerals in the region. The authors point at the expediency of stage-wise evaluation of geological and geotechnical potential of the unmined and man-made placer reserves to develop a resource-saving technology for mining identified clusters. The authors also discuss the approaches applicable in additional exploration and production management at such placers to transfer them to a category of the investment-attractive mineral sources. The database of the mining-altered areas in the Ust-Yana district is collected, the maps of such areas are drawn, and the mining conditions at some of the specified placers are discussed.

The article reports testing results of a hydraulic hammering tool with independently controllable energy and frequency of blows. The blow frequency is adjustable via the fluid flow rate, and the blow energy-via the pressure at the onset of a working cycle. The hydraulic hammering tool and its performance measurement procedures are described, including the pre-blow velocity-using an original piston position sensor composed of two pairs of light-emitting and photo diodes arranged in front of the collision plane of the piston and the breaking tool. The approach allows changing the blow frequency of the tool by 4 times, its blow energy by 5 times and the impact power by 20 times. The authors present the experimental oscillograms of the dynamic characteristics of working cycles and the experimental curves of the integral output characteristics, cycle start pressure, and fluid flow rate. An experimental-and-analytical estimation method is developed for the pre-blow piston velocity using the theorem of a kinetic energy of a material point.

The article offers a substantiation for the simulation model of a pneumatic hammering tool with an elastic element used as an air distributor. The working cycle of the pneumatic hammering tool with the elastic valve is modeled as the fluid-solid interaction. The comparison of these results with the one-dimensional simulation shows that the proposed model is preferable in this multi-physical problem. The parameters of the elastic valve to perform the function of sealing the back-stroke chamber to ensure operation of the hammering tool are determined. The time dependences of the basic physical parameters of air in the hammering tool within its working cycle, as well as the piston travels and velocities are found. The prospects of the proposed method in the design and analysis of hammering machines are assessed.

The authors discuss application conditions of the casing-while-drilling method and present a layout of a compound rock-breaking tool. An advantage of such tool is the coupling of the central and annular bits by spring jaws, owing to which the inner passage section of a casing pipe experiences no reduction. Computer modeling assisted in the strength analysis of the components of the tool during transfer of the impact load from the central to annular bit via the spring jaws. The operational reliability of such components is evaluated, and a method is proposed for enhancing their strength by way of improving quality of their surface finish and optimizing geometry of the surface areas exposed to the highest load. On the basis of the implemented research, a developmental prototype of the compound rock-breaking tool is designed and manufactured.

2D numerical modeling and physical simulation are carried out for a flow of a granular material in an elbow of a pipeline with a view to reducing erosion wear owing to a novel design solution. Protective plate ribs are installed on the inner surface of the elbow at an angle to lines tangent to the fixing points of the ribs. It is found that the optimal choice of the size, number and arrangement of the ribs can reduce the wear of the elbow in the areas of its maximal loading.

Spotlight of the analysis is on bending vibrations of axial fan rotor of main ventilation fans in mines. Their feature is two impellers that act interchangeably as directing and guide vanes, and one impeller only rotates in an active mode. Such design allows attaining high capacity in the reverse mode which preserves 90-95% of the straight flow mode. The presence of two impellers in the rotor influences the frequency behavior of the fan, which can vary in a wide range depending on some parameters that govern the mass and geometry of the rotor. The article describes the analysis of the rotor frequency characteristics obtained from solving a system of differential equations of bend. The curves of free bending vibrations of main shafts and masses of impellers are plotted for different values of added mass of transmission shaft and for different lengths of the main shaft areas. It is shown that in the test range of the main shaft lengths, impeller masses and added masses of the transmission shaft, the operation of rotors of fans with two impellers is safe and reliable in terms of vibrations.

A promising approach to air dedusting in tunnel ventilation in subways is inertia filters which have low air drag and can efficiently catch coarse and medium-size dust particles without addition of sophisticated equipment as dust-laden air flow through the filters is assisted by piston effect in train tunnels. An approach to the numerical modeling of a multi-phase flow in an inertia filter is substantiated. The validation of the approach is proved by the qualitative and quantitative coincidence of the numerical modeling results and lab-scale inertia filter test data. The numerical research findings helped determine the influence exerted by air velocity, dust size and filter surface characteristics on the dust catching efficiency. The design of the filter to be installed at an air connection in a single-track subway tunnel is developed.

The article describes a pilot plant generator of high-voltage nanosecond pulses for energy treatment of ore at the pretreatment stage at the capacity of up to 1 t/h of mineral raw materials. The mineralogical and chemical analyses of ferruginous quartzite are carried out. The distribution of aggregates per size grades is described, and the lab-scale and larger scale bench testing data of the equipment are reported. The experiments have proved efficiency of preliminary treatment of the first and second stage milling sands by strong electromagnetic pulses for the ferruginous quartzite softening and for the magnetic separation intensification. The interconnection is found between the impregnation of ore and rock-forming minerals, efficiency of disintegration of mineral aggregates, their release and the treatment dose. The main effect of treatment of ferruginous quartzite by strong electromagnetic pulses, with the increase in the yield of the final size grade of - 45 µm by 1.4-4.8% at the increased recovery of iron in magnetic concentrate by 2.65%, is conditioned by the decrease in the number of ore and barren rock aggregates and by the increase in the content of free magnetite grains in the size grade of - 0.16 + 0.04 mm after milling by 14.2%.

The authors analyze extra recoverability of zinc from complex ore flotation tailings. The material constitution of the manmade mineral resource is studied and the expediency of its hydrometallurgical processing is substantiated. The influence of the reagent regime on the efficiency of sulfuric-acid leaching of zinc is discussed. The sulfuric acid concentration is optimized, and the efficiency of electric processing of the leaching solution is determined. The efficiency of different oxidizers during leaching is evaluated. Ozonizing of leaching solutions and introduction of sodium chloride in them have a beneficial effect on zinc recovery.

The full-scale testing results of fixed-site recorders of electromagnetic radiation preceding failure in rocks in a mine after installation of the recorders on mobile mining equipment are presented. The threshold values of the recorded signals, coincident with failure of roof areas in mine openings are found, and the frequencies of electromagnetic noise at the totally de-energized electric equipment of working faces, and at the dead and live production equipment are estimated. The recommendations on the improvement of the recorder design and recorded data processing are given.