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The influence of changeability of dry magnetic separation feed characteristics on the separation process efficiency is considered at the fixed operation modes of equipment is examined as a case-study of the Olenegorsk deposit ore. It is found that the major effect is exerted by the content of total iron: its increase in the feed is independent of the maximum linear size in the size grade and of the size modulus, and is accompanied with Fe_tot content growth in the magnetic fraction. The results of dry magnetic separation of a narrow particle size range prove that for - 80 + 2 mm, the correlation of Fe_tot content of the magnetic fraction (at В = 0.16 T) has a high approximation coefficient of 0.9461, which is reflective of a weak contribution of the feed size to separation efficiency. Regarding influence exerted on separation performance by the size modulus, it is found that the absence of ore pretreatment by sifting ensures reduction in loss of Fe_tot with the nonmagnetic fraction in 70% of cases.

The authors analyzed water quality in manmade water bodies at the used and operating tungsten, molybdenum and complex ore mines in eastern and southwestern Transbaikal. The chemical analysis of water used atomic absorption spectrometry and inductively coupled plasma mass spectrometry. The standardized cumulative pollution index is calculated. It is found that the level of the environmental hazard of the test water bodies is abnormally high, which points at the environmental emergency and ecological catastrophe. The greatest threat to surface and underground water is made by the manmade water bodies at the Pervomaiskoe, Sherlova Gora, Bukuka and Bom-Gorkhon deposits. The recreational utilization of such water by people is unhealthy and inadmissible.

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.