Home – Home – Jornals – Journal of Mining Sciences 2015 number 6

The authors report the numerical modeling data on stress state of rock mass in the vicinity of hydraulic fracturing when two closely-spaced intervals of the well are subjected to shearing and normal load. The article shows applicability of such coupled loading in creation of fracture across an uncased well.

The authors study numerically a problem on vortex flows in bounded domain in granular material using discrete element method. The granular material is composed of spherical particles with the assigned distribution of radii. Dry friction and rolling resistance at particle interfaces are taken into account. The kinematic patterns of granular material specimen deformation are described, and the trajectories of some particles are shown. The article gives values of normal and shear stresses acting at the study domain boundaries from the side of the material.

The authors use physical and DEM modeling to analyze stresses and strains in broken ore discharged from accumulating bins using plate feeder. It is substantiated that the determinant of the peak load on the feeder and the discharge unit is dilatancy. It is shown that the absolute value of the peak load is conditioned by physico-mechanical characteristics of discharged ore, structural design of discharge unit and deformation constraint. The article demonstrates possibility of upgrading one of conventional schemes of discharge unit and shows prospects for new designs.

Variations in strength and stress state of rocks fail to explain the difference observed in efficiency of seismic radiation from separate sources within the limits of the same mine field. The laboratory and numerical experiments show that insignificant variation in ultimate strength of a fracture and, thus, different shear fracture stiffness results in radical change in the seismic event efficiency. The experimentally obtained relations between the key parameters should be taken into account in geomechanical modeling of full-scale objects.

Based on the integrated analysis of micro-strains obtained using speckle-photography method in Brazilian Test of rock specimens and analytically calculated elastic fields of stresses and strains, the authors show that there exist significant correlation dependences between the damage in a certain domain of a rock specimen and the level of the external load. Given a verified geomechanical model describing properly evolution of stresses in a rock specimen, this fact offers pre-requisites for estimation of damage in different areas of a rock specimen by monitoring condition only in one of such areas.

The authors have undertaken experimental and theoretical modeling of fracture growth under the penetration of rigid wedge in brittle rock. The test specimens were made of organic glass to facilitate measurement of size and shape of a fracture. The wedge loading was executed quasi-statically on a testing machine and dynamically by a drop wedge. The scheme developed in the framework of the theory of elasticity for the theoretical description of the fracture growth process accounts for the finite size of the wedge cutting point and the influence of free surface. The theoretical and experimental shapes of fractures are compared.

The authors have determined the causes of drop in performance of induced block caving using fans of blastholes 105 mm in diameter and single blastholes 250 mm in diameter, as well as the sources of increased drilling cost and expansion of start-up time of production blocks in Abakan underground mine. Alternatives of improvement in drilling efficiency under current conditions are discussed.

The article substantiates the need of designing a rotary-percussion drilling tool to drill holes 40-60 mm in diameter and to 50 m long. The drilling rig with a downhole air hammer has been designed and manufactured. The authors have carried out analytical and experimental research to determine drilling velocity in different rocks of varying hardness.

Under consideration is the principal diagram of a percussive tool with a ring-shape elastic valve installed in the air distribution system: the valve closes when contacting the housing and opens under action of elastic forces. The operability conditions and basic design parameters of the valve are determined. The authors characterize contact interaction between the ring-shape valve and the side slide surface when the valve is closing. The balance of forces affecting the ring-shape valve is shown.

The authors determine basic parameters for elements of axial tunnel fan VO-21(t) with direct annular diffuser. The algorithm is proposed for calculating aerodynamic parameters of the axial fan using ANSYS CFX program, which allows modeling, computation and analysis of effect exerted by various parameters of the fan air section on the fan aerodynamics. It is found that it is possible to reduce the fan impeller metal consumption and inertia moment by redistributing normal inertia force of blades from the boss to the disks. The admissible impeller velocity is related with the thickness of the impeller disks.

The authors substantiate new engineering designs for selective heading machines and cutter-loaders fitted with screw-type cutters. It is proposed to use biconical and conical disc tools and their attachment units to polygonal prisms to equip both bits of heading machines and screw cutters of cutter-loaders to cut structurally heterogeneous rock mass. It is recommended to practise reverse-mode operation of universal radial-type drill bits fitted with disk tools mounted on triangular prisms with a view to widen the front of loading to be imposed on sidewalls. The presented data on modeling stress sate of disk tools and variants of their attachments to polygonal prisms show the mechanisms of loading of related parts in the course of rock cutting.

Using numerical modeling of rock mass stress-strain state to estimate and predict stability of structural elements of a mining system in combination with the in situ observation data on deformation of rocks in sidewalls, roofs and floors of underground excavations, the authors perform geomechanical analysis of overcutting scenarios in top-down mining in Internatsionalny Mine, ALROSA. Various overcutting flow sheets are considered, and the optimal sequence of overcutting towards higher stability of stopes is determined.

The article gives the analysis of basic mechanisms in variation of output of production heading versus its length in the cutter-loader and scrape conveyor system in underground mining of flat-lying coal beds. Based on the analysis of interaction between cutter-loader and scrape conveyor, the dependence between the maximum capacity of production heading and the longwall length is determined.

The authors investigate modes and parameters of mining operations with a view to create conditions for transmission of geotechnologically produced kinetic energy of rocks to electric generators. The features of application of energy harvesting equipment in underground mining of hard minerals are discussed. The low-frequency energy trap designed to entrap elastic energy of rock mass oscillations operates in a wide range of amplitudes and frequencies of rock mass vibration, and is composed of three nonlinear oscillators having preset mass and elastic characteristics.

The article presents the applied research on formation of science-and-technology basis for commercial introduction of a technology that ensures cardinal reduction in loss in underground mining at unique Kyshtym quartz deposit. Based on the theoretical analysis of the minimum loss criterion, the authors determine rational variants of combination mining system and quartz breaking pattern of planar charges for in situ experimentation.

Currently coal is extracted from highly gaseous beds using preliminary degassing. To estimate efficiency of measures aimed to reduce residual gas content of coal beds, an original approach is offered based on measuring methane content of coal samples taken directly in mine using deep horizontal holes. The authors describe the purpose-designed core sampler and the methane drainage efficiency estimates obtained using the core sampler.

The article sets methodological basis for selecting support for preparatory drives in copper-nickel ore mining by Transpolar Division of Norilsk Nickel. The authors present a case study of selecting support for preparatory drive in the influence zone of top-down multi-slice breast stoping.

In focus is selection of load-haul-dump machines for hard mineral mines. The authors offer substantiation procedures for tuck-and-shovel systems of mining in difficult ground conditions. In terms of Kyrgaisky Sredni open-cut located in the Erunakovo coal district in Kuzbass, using the Lerchs-Grossman algorithm, the principles and sequence of forming efficient application domains for different specification trucks and shovels within a mine field are presented.

The procedure is proposed for structuring complex coal deposits with respect to quality indexes obtained using ArcGIS with a view to substantiate rational trends in mineral use. The article reports the research on assorting Elginsk black coal reserves in South Yakutia based on volatile content, plastic layer thickness, coal grades, process groups and subgroups.

The article presents new test results on structural and chemical properties of mineral formations on the surface of natural hydrophilic diamonds using Raman, X-ray phase and Auger spectroscopy methods. Analysis of morphological features of nano formations involved scanning electron microscope Jeol-5610 and analyzer INCA. Based on the studies into phase composition of diamonds non-recovered in the circuit of kimberlite ore processing, two types of mineral formations are discovered on their surface: micro-formations as silicate nature globules less than 1 µm in size and silicate nano films more than 5 nm thick. The tests detect also presence of layered talcose silicates that make diamond surface hydrophilic.

The authors have tested effect of type and energy of mechanical impact on selectivity of spodumene ore breakage in a disintegrator and in vibratory and ball mills in terms of pegmatite with lithium content of 0.1%. It is shown that the highest efficiency of mineral dissociation is achieved in disintegration by free impact. Analysis of grain-size distribution and chemical composition and the X-ray study also reveal advantage of the disintegration process, which allows higher content and recovery of lithium in concentrate at reduced sliming.

Under discussion is recoverability of noble and rare metals from caustobioliths (shale, natural bitumen, etc.). The presented mineralogical and technological analyses of samples show higher content of valuable microelements in some of them. All tested samples contain various rank carbon. Depending on the type of the raw material, the research follows one of three lines: stage-wise diagnostic sorption leaching, flotation with pre-milling in amino acetic acid and magnetic concentration. Based on the examination of scattered carbon substance in caustobioliths, it is supposed that concentrations of metals are asphaltene fractions of bitumoids (bitumen-like substance). The research results show prospect of using this nonconventional coal-bearing raw material as a source of noble and rare metals.