Vol 55, No 1 (2019)

Numerical modeling results are presented for propagating an axially symmetric crack formed due to hydraulic fracturing near the free surface in the isotropic poroelastic medium. The extended finite element method based on phantom nodes and cohesive model of material failure was used to solve this problem. Trajectories of the crack growth are calculated for different distances from the free surface under injection of certain volume of working fluid with regard to its leakage. The influence exerted by impermeable boundary on the hydraulic fracturing propagation is studied.

The results of numerical modeling of intense shock wave propagation after explosion in a mine opening with permeable screen are presented. The problem is solved in the equilibrium non-viscous formulation without regard to chemical reactions and with averaged composition of mine air. It is shown that for a screen composed of four similar permeable barriers arranged as a labyrinth, the incoming shock wave has a strongest impact on the first barrier. As a consequence of weakening of the shock wave front on the first barrier, the rest barriers experience much less loading. In order to decrease peak loads on a load-bearing frame, it is necessary to reduce areas of flat front surfaces of metal structures.

The determination of the grain size distribution of blasted rock exceeds the capability of an analytical sieving machine which only gives reliable results within a range of 63 μm to 125 mm. Other sophisticated methods are often not available for particle size measurement in coarse-grained applications in medium scale mining. Therefore, an alternative low cost method to investigate the grain sizes of blasted rock is introduced which can cover a range from 63 μm at the lower end without an upper limit. Three different options to examine blasted dolomite grains are investigated and combined with sieve analysis to determine a complete sieving equivalent grain size distribution. Comparison with results of a technical sieving shows that this method gives a good approximation of the size distribution, improving the possibilities for design of mineral processing equipment.

In a transportation fleet in open-pit mines, the match factor is defined between loading and dumping vehicles. This factor helps in indicating the number of vehicles that depend on each other. In this study, a new parameter termed the “detailed match factor” is developed to improve the transportation fleet and relationships are deduced to control the production and grade. A transportation fleet model was simulated for a typical iron ore mine and was solved using both the detailed match factor and ant-colony algorithm methods. The detailed match factor helped in increasing the production by 10.6%.

Backfilling mixture preparation technology using a cement-slag binder is developed for the Artem’evsky mine. It is shown that backfill with granulated blast-furnace slag reaches project strength at its fineness 80% of content milled down to -80 urn size. The authors analyze influence of milling fineness of granulated blast-furnace slag from different manufacturers on strength and rheological properties of backfill. The economic analysis of cost of binder in formation of load-bearing layer of backfill prepared using fly ash and milled granulated blast-furnace slag is performed.

Predicting the consequences of changes in limestone exploitation and consumption system is a problem that requires an adequate analytical approach. This paper presents the linear model of location optimization of limestone exploitation and consumption in Macedonia with 29 production entities - open-pit mines, and two options of consumption entities, with 15 and 16 consumers. By changing the number of consumers, the research demonstrates that mathematical model approach with adequate sensitivity to changes in relative parameters is necessary for a complete and reliable overview of system behavior.

Slope stability is “the heart” of open pit mining operations. Pit slope monitoring is an important undertaking requiring collection of structural data for geotechnical characterization and stability analysis. Challenges exist with conventional field data collection methods including time, safety, and data accuracy and reliability. In this paper, 3D laser scanning, photogrammetry and Split FX are integrated to investigate open pit slopes in highly geologically altered materials using a case study from the Melbur Pit slopes in Cornwall, United Kingdom. A 3D laser scanner is applied to scan structures from the slope face and to create a 3D point cloud database. Photogrammetry is applied to capture images for processing. 3D images are draped onto the point cloud to give a visual representation of the slope face. The kinematic analysis indicates that the integrated approach enhances the identification of structural discontinuity sets and their orientations. An integration of emerging digital technologies thus provides a comprehensive and reasonably reliable structural database for slope stability analysis during open pit mining.

The procedure is developed for modification of diamond surface by luminophore-containing organic compositions. The compositions are composed of an organic luminophore—scintillation anthracene, inorganic luminophore K-35 and cetane. Indication compositions are synthesized based on the selected luminophores and organic liquids and tested using pilot separator POLYUS-M. Spectral-kinetic characteristic of luminophopre-containing organic-mineral compositions, treated weakly luminous diamond crystals and kimberlite minerals are determined. The compositions ensuring better spectral-kinetic characteristics and higher extraction of diamonds during H-ray luminescence separation are selected.

The process of fluid mass transfer and formation of concentration zones on evaporation barrier in rock mass are studied. A series of experiments is carried out on a special testing plant in order to examine the process of settling-down on evaporation barrier and to determine parameters of vertical zonality in settling-down of simple and complex water-soluble nonferrous metal salts. The experimentation procedure is described. The regular patterns are found in the change in content in the direction toward the surface across the whole zone of aeration from the groundwater table. The higher salt concentration is observed on the rock mass surface, in the upper salt crust. This distribution law is typical either of simple or complex salts. The main parameters of settling kinetics and evaporation rate on the barrier are revealed and evaluated.

The results of the mineralogical examination of old sulphide and oxidized gold ore tailings of a mining and processing plant in the Krasnoyarsk Territory are presented. Secondary mineral forms of antimony, namely, antimony bloom Sb₂O₃ and tripuhyite FeSBO₄, as well as iron are found. Gypsum in the waste is a newly formed phase, undetected in the initial ore, revealed in sulphide and mixed ore tailings and is absent in oxidized ore tailings. The key valuable component is gold represented by fine accretions in arsenopyrite, free gold size is not more than a few first microns.

Modeling of heat exchange processes in water-saturated rock mass during shafting with artificial freezing is performed. The problem of adjusting thermophysical properties of rock layers by the experimental measurements of temperature in the check thermal wells spaced from the freezing perimeter is analyzed. In terms of the abuilding shafts at Nezhinsky Mining and Processing Plant, significance of adjusting the the thermophysial parameters borrowed from the geological engineering survey data is illustrated. The number of independent adjustment parameters is determined from the analysis of the system of equations in two-dimensional two-phase Stefan problem in the dimensionless form. An inverse Stefan problem is formulated for a horizontal layer of rocks. The numerical algorithm is proposed for the inverse Stefan problem solution based on the gradient descent method. The algorithm minimizes functional of discrepancies between the model and measurement temperatures at the locations of the check wells. The functional of discrepancies in the phase space of the thermophysical properties and the algorithm convergence are analyzed.

A review of various real time temperature monitoring devices available for use in underground coal mines in Queensland was conducted. To investigate the fit-for-purpose of the intrinsically safe (IS) instrument, laboratory experiments were performed. The obtained results were compared to the calibrated reference instrument readings and sling psychrometer data under variation in air flow velocity, moisture content and dust content.