Home – Home – Jornals – Journal of Mining Sciences 2015 number 4

Aiming to build up a phenomenological basis for the theory of interaction between geomechanical, thermal and physicochemical processes in methane-bearing coal in Kuzbass, the authors have performed a set of laboratory bench tests on uniaxial stiff loading of various rank coal specimen to failure at a rate of 3.3∙10-6 m/s. The pressure versus temperature dependences are obtained for coal specimens with granite interbeds using high-precision computerized thermal scanner. It is shown that temperature change in coal specimens subjected to loading to failure is connected with volatile yield and internal energy relaxation of methane in Kuzbass coal. Using jointly thermal imaging and laser measuring equipment ALMEC-tv for high-precision and detail control of deformation-wave processes in loaded coal specimens by speckle-method, it has for the first time been proved that nonlinear pendulum-type movements of structural elements are possible in coal specimens under varied temperature field, which is of fundamental importance for actualization of previously ignored mass and gas exchange processes in high-stress different-grade coal seams under mining.

The full-scale measurements of initial stresses and numerical modeling of stresses in rock mass enclosing deep open pit mine Zhelezny under planning at Kovdor Mining-and-Processing Integrated Works are presented in the article. The authors have located hazardous areas in pit wall rock mass and validated stability conditions for pit walls with vertical benches.

In the framework of the developed and implemented nonlinear geomechanical model of a coal seam having block structure to describe gas influx in borehole, the authors propose the method for quantitative estimate of gas content and diffusion and mass exchange coefficients based on solution of inverse problems using pressure measurements taken in shut-in borehole in the “pressure drop” mode. Besides the main function, the set problem had an auxiliary objective function with the less number of arguments. Numerical experiments with synthetic input data show that the auxiliary objective function has a number of local minimums. The authors also put forward a technique of finding global minimum that provides the set problem solution.

The issues of calculation of stresses and strains in the elements of support and in rock mass in stagewise drivage of a production face are under discussion. In order to take into account sequences of mining and support installation, it is required to solve problems on extra stresses due to small cross section drivage. Geomechanical estimation of support and rocks used the method based on single-stage formation of stiffness matrix to describe rock mass prior to mining start. Sequential drivage of excavations and change of mechanical properties in the calculation system are modeled using initial stress procedure. The author calculates two scenarios of mining with stagewise face drivage under conditions of elastic deformation of rocks and support and analyzes behavior of stress redistribution in elements of support being installed in stages. It is shown that mining sequence considerably influences stresses in support elements upon drivage completion. The scenario of mining with initial installation of sideways support elements results in increased tensile stresses in the support as against the scenario when the underroof space is cut and supported in the first place.

The authors describe mathematical model for estimation of cone-type pitwall stability in the framework of rigid-plastic deformation of rocks, with finding safe ultimate pit depth.

The article describes modeling procedure and calculation of wave fields in microseismicity monitoring in anisotropic medium. The research findings are intended for testing of processing algorithms for data of seismic observations in underground mining.

The procedure to estimate growth in load exerted on interchamber pillars with time is based on mathematical modeling of stresses and strains in structural elements of room-and-pillar mining method using roof rock failure criteria. The calculation results illustrate a real time scale of variation in strength of rocks and the associated partial collapse of a parting and failure of edges of interchamber pillars when their height is increased.

The authors analyze mine logs of seismic events in Poland, Finland, Canada, Russia and South Africa. For the analyzed events, induced seismic energy varies by 2-3 orders of magnitude at the same value of seismic moment. The upper and lower limits of the range correspond to “hard” and “tender” sources, respectively. The most probable cause of the wide scatter of the reduced energy values seems to be fluctuating properties of discontinuities due to change in material composition of fracture filler and in water content of rocks.

The authors propose the method to estimate deformation properties of rocks by the data on pressure meter tests in hydrofractured interval, allowing in situ values of Young’s modulus and Poisson’s ratio of rocks. It is shown that integration of pressure meter tests and hydraulic fracturing expands the scope of deformation measurements and improves efficiency of stress assessment in rocks using hydrofracturing method.

The article focuses on ecologically balanced, comprehensive extraction of coal reserves, with minimized impact exerted on human environment by gas emissions. It is found that geometrical design of extraction panels should be based on modeling of oxygen distribution in mined-out stopes followed with the model calibration based on in situ test data.

In the framework of geo-information model of coal deposit and open pit mine, the author derives analytical expressions for calculating work of rock transportation from face to start point of transport incline, considering road characteristics obtained in the course of geo-information modeling. Alternative calculations of freight turnover and transportation work to overcome gravity and road adhesion are analyzed. The example of calculations for the conditions of a particular open pit coal mine contains comparison of one- and two-flank mining schemes.

The theoretical proof is presented for absolute coal bed methane release as a nonlinear extremal function of production face output. The article givers actual and theoretical evidences of reduction in absolute coal bed methane release under high-rate advance of production face.

Using the Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), microscopy and microhardness test methods, the change in the crystalline and chemical properties and in microhardness of rock-forming minerals of kimberlites as a result of exposure to high-power nanosecond electromagnetic pulses (HPEM) has been studied. Based on the data of FTIR and XPS, non-thermal effect of HPEM results in damage of surface microstructure of dielectric minerals due to formation of microcracks, surface breakdowns and other defects, which ensures effective weakening of rock-forming minerals and reduction in their microhardness by 40-66%.

The current technologies of mineral mining, processing and beneficiation require introduction of water circuiting. A common ecological and technological objective is in this case reduction of concentration of copper and commercial-grade fat acid ions that worsen flotation. A promising way of reaching the set objective is preliminary mixing of different waste water flows with maximum concentrations of the specified ions. The thermodynamic calculations justify optimized water treatment modes when engineering-and-economic performance of copper-molybdenum ore dressing remains unaltered, consumption of fresh natural water is lowered, and water supply is enhanced.

Using proprietory method, the authors have obtained flotation agent BO-extract of atomized leaves and stalks of Heracleum sosnowskyi , and analyzed its composition. Qualitative tests, thin-layer chromatography (TLC), ultraviolet spectrophotometry and flotation tests show that aqueous and organic extracts contain substances that differ in chemical and process properties. The article gives test results for aqueous, alcoholic and aqueous-alcoholic extracts BO used as modifiers in chalcopyrite and pyrite flotation. Selective properties of aqueous and aqueous-alcoholic extracts BO are characterized. The highest depression ability relative to pyrite is a characteristic of aqueous BO extract obtained at pH = 3, with heating and treatment in ultrasonic bath. Organic extracts contain mostly furocoumarins, aspic oils and resins, and have no material effect on flotation activity of pyrite.

The article reports tests on studying mechanism of interaction between modified chlorine solutions and gold-bearing sulfides. The change in texture, structural properties and elemental composition of sulfides after electrochemical treatment is analyzed. The authors indicate basic negative factors reducing dissolution velocity of sulfides.

The analysis focuses on collecting ability of easily desorbed (ED-forms) ethyl and butyl xanthates. The authors give visual proof of “dry” spot extension on mineral surface when xanthates that are active relative to air-water interface are desorbed from it. It is shown that ED-forms of agents, being products of interaction between xanthates and heavy metal salts, can remove water from film between mineral particle and air bubble. The main force on water in the film is conditioned by surface tension nonuniformity at the moment of local rupture and by surface pressure of molecules in the film of agent ED-forms. The collecting ability of ED-forms of xanthate is determined as the rate of its influence on water in the film. The forces exerted on water in the film of ED-forms of ethyl and butyl xanthates are estimated numerically. The dependence of volumetric water flow from the film on the surface tension of agent ED-forms active at air-water interface is found. It is shown that collecting ability of an agent is dependent on surface tension of solution of its ED-forms and is governed by structure of hydrocarbon fragment of the collector.

The article describes the integrated method and results of deformation-wave monitoring of temporal lining in rail tunneling in complex geological conditions on the south of Western Siberia. 3D geometric parameters of temporal lining are measured by laser scanning at a span of 3 months, which enables comparing actual 3D models of temporal lining and rocks in reinforced tunnel section. Based on the data obtained at various times of observation, shifting of unmarked points of temporal lining and deformation of tunnel walls and arch was determined. High density scanning allows remote identification of comparatively small zones where structure of rocks and state of lining are changed. The authors analyze seismic vibration of rocks under hammering, which shows that peak spectral densities of elastic wave in rocks are conditioned by low-frequency (pendulum) wave generated at siltstone and coal interface, and are related with dimension of joints and with mechanical properties of rocks.

The article describes engineering designs of dilatometer to measure transverse deformation in borehole subjected to internal pressure exerted through impermeable shell. The device is equipped with the robotized system for advance along the borehole without special sectional barrels. Functionality and capacities of the dilatometer are optimized for surveying in long directional drill holes in mines.