Том 54, № 2 (2018)

A new mechanism of rock deformation around underground mine workings is presented. The method is developed for calculating geomechanical state of rock mass; this method takes into account rock weight, the action of which coincides with the directions of tensile stresses on the mine working contour, while these directions differ in the floor. The proposed calculation method for rock deformation includes two additional parameters characterizing the ratio of mine working roof displacements to the floor displacements and the ratio of day surface displacements to roof displacements which are determined experimentally.

The results are presented for uniaxial compression testing of brittle rock samples; their failure occur in the form of columnar cracking along the axis of applying the force. Test results are compared with characteristic quantities determining tensile strength. Sample failure is modeled with regard for grain characteristics, which makes it possible to estimate the ratio of compression strength to tensile strength.

Design development of down-the-hole (DTH) air hammers is discussed with the aim of increasing efficiency of rock drilling. The problem is solved by making hammering piston with curvilinear frees surfaces which are in no contact with the hammer body. This ensures generation of rock-breaking impact at the minimum energy input. New designs of hammering pistons are developed for DTH air hammer models PP110EN and PP110NK designed at the Institute of Mining, Siberian Branch Russian Academy of Sciences. Experiments prove that selection of rational shape of hammering pistons allows improving performance of DTH air hammers by 15% at the average.

The results of the research aimed to substantiate parameters of loose ore and rock mass (protective cushion) formed to protect and isolate underground mines from the open pit mine at Udachnaya kimberlite pipe under mining with the caving methods are presented. The thickness of the cushion is determined based on the effect of an impact of caved rocks and the resultant air blast, and is meant to isolate aerodynamically and thermally the open pit and underground mines. The thickness of the protective cushion is calculated with regard to an increase in the depth of mining down to a level of –680 m.

The results of the experimental research into processes that take place during differently directed controlled trajectory blasting of ore and rock in underground mining of flat-dipping lodes are presented. It is found that methods for designing blast patterns should take into account both linear concentration of energy and dynamics of the increase in resistance to throw of rocks and ore in a narrow stoping area. Based on the modeling data, the throw coefficient and blasting front advance are plotted as functions of geometrical and energy characteristics of the model. It is shown that blasting and throw of ore in the stoping zone is accompanied with the effect of additional fragmentation of ore due to collision with the stope roof.

This study discusses the prediction of penetration rate and specific energy of button bit equipped rotary–percussion drilling machines from drill cuttings and geo-mechanical properties of rocks. The operational parameters of drilling machines measured from selected locations were utilized for the calculation of specific energy of drilling operations. For this purpose three on-going hydropower projects and four active mining quarries of Pakistan were selected. The drill cuttings were further used to determine various descriptors of the chip size distribution including the coarseness index and Rosin–Rammler’s absolute size constant. A complete set of geo-mechanical rock tests were conducted in the laboratory and includes uniaxial compressive strength, Brazilian tensile strength, point load strength, Schmidt rebound hardness, P-wave velocity, dry density, porosity and brittleness indices. Regression analyses were performed to predict the penetration rate and specific energy of drilling from geo-mechanical properties of rocks. The models so developed were also validated by adopting the t-test and the F-test statistical techniques. Moreover, statistical models were also developed to evaluate penetration rate from various descriptors of the chip size distribution. Dependence of bit size on coarseness index and mean particle size was also discussed.

The investigation of influence exerted by ultrasound processing on recovery of zirconium and rare earth elements in pregnant solution of acid leaching of eudialyte concentrate is described. The methods of X-ray photoelectron spectroscopy and analytical scanning electron microscopy are used to study structural, chemical and morphological characteristics as well as elemental composition of minerals in eudialyte concentrate before and after acid leaching.

The results of the thermodynamic modeling are presented for oxidizing roasting of refractory molybdenite (MoS₂) with magnesite (MgCO₃). The phase and chemical compositions of the MoS₂–MgCO₃–O₂ system and its changes are determined depending on the temperature and quantity of the additive agent. The modeling reveals feasibility of thermochemical decomposition of molybdenite with the formation of waterand soda-soluble compounds MgMoO₄ and MgSO₄, which is an evidence of efficiency of magnesium carbonate in the capacity of an additive agent. The optimal conditions of the thermochemical decomposition of molybdenite determined theoretically from thermodynamic calculations are proved experimentally.

Applicability of local and regional scale satellite images in evaluation of vegetation in tundra in the zones of mining in permafrost area is proved. The research results on the environmental impact of the Valkumei Mine, Chukotka Autonomous Region, after its closure are described and analyzed.

The methods of deactivation and reclamation of tailings ponds are studied. The engineeringgeological investigations of apatite–nepheline ore flotation tailings in the sites applied with chemicals at ANOF2 processing plant of Apatit Company are carried out. The monitoring of the bonding surface generated by dust suppression agents Alcotact DS1, Dustbind and Floset S44 is performed. The physical properties and the aggressive action resistance, as well as the effect of suppression agent feed in recycling water on the apatite–nepheline ore flotation performance are tested on a laboratory scale. The Dustbind is recommended as the optimal suppression.

Abstract—Stationary-state combustion of fine dispersed dust–gas–air mixtures in underground workings is considered. Under the assumption that the single source of heat emission is the carbon oxidation reaction, the second-order nonlinear differential equation is obtained for the determination of temperature and the initial conditions are formulated. The analysis of the solution shows that there exist critical values of the dust–gas–air mixture flow velocity, and the excess over these critical values may result in the mixture combustion. The cross-section of mine working is related with the temperature reached in this cross section.

The structure diagram and operation of a combination unit for drilling and initiating slotting are presented. The loads on the cuttier during initiating slotting are calculated, and the rational operating mode of the hybrid unit is determined.