Vol 54, No 6 (2018)

Acoustic emission response of fossil coals being at different stages of metamorphism to cyclic variation of effective thermal stresses is experimentally investigated. The equipment and procedure used in the experiments are described. The features of the response are revealed and analyzed in the samples of anthracite, lignite and bituminous coal with different damage extent governed by the preliminary cyclic freezing and thawing, as well as by water saturation. It is shown that the signature of such features is a thermal analog of the Felicity effect which appears in each cycle of temperature action. The regularities of this effect are found, and their physical explanation is given based on the analysis of defect formation in coals at different stages of thermal treatment. The methodical approaches are proposed and substantiated, which allow structural damage, thermal resistance, oxidation and proneness to frost weathering of coal to be estimated by the Felicity effect in the acoustic emission response of coal to cyclic thermal forces. Possibility of using the found features to predict structural changes in coal products which are in long-term storage under specific climatic conditions, as well as for forecasting risk of self-heating and spontaneous combustion of coal products is discussed.

The results of numerical modeling aimed to evaluate geomechanical behavior of rocks in the vicinity of a fully mechanized longwall face and a gate roadway during gradual narrowing of a coal pillar between them are presented. The variants of longwall face passing of diagonal cut-through are discussed for coal seams of complex structure and various thickness. The regularities of redistribution of stresses, strains, and residual strengths of coal and rocks under variation in coal seam thickness, pillar width and location of dirt bed are determined. The recommendations on the technology for mining coal pillars as their width is decreased and for stability of gate roadways are substantiated to ensure trouble-free operation of fully mechanized longwall faces.

This study is focused on the evaluation of water saturation influence on the mechanical and physical properties of 34 sedimentary rock units selected from different geological formations in Pakistan. The laboratory testing program comprised the determination of physico-mechanical rock properties of both air-dry as well as fully water saturated rock specimens. Further thin section analyses of all rock samples were also performed to explain their petrography. According to the statistical analyses overall reductions of around 40 and 50% were found in UCS_sat and BTS_sat values, respectively, measured on saturated rock samples in comparison to their corresponding dry strength values, i.e. UCS_dry and BTS_dry. Linear correlations were found between ultrasonic wave velocities as well as density of both dry and saturated rock samples. In addition, the dry and saturated UCS values were exponentially related with the rock porosity. Multiple regression technique was also utilized to develop a predictive linear model of UCS_sat with geotechnical rock properties in the dry condition and petrographical characteristics of rock samples. Finally the validity of multiple regression model developed in this study and an existing correlation for the conversion of UCS_dry into UCS_sat was statistically assessed.

Based on the test results and the regression equations, a method for selecting appropriate similar materials to simulate rocks was proposed. A Python script for implementation was developed. A calculation example was given to illustrate the effectiveness and expediency of this method.

Improvability of air-driven pulse-generating mechanisms for operation in mineral mining and construction is discussed. An impact system with two mobile masses incorporated in a common housing is proposed for vibro-percussive driving of structural iron into elastoplastic soil. Experimental prototype of the air hammer with decoupled piston based on the air distribution circuit with elastic valve in the back stroke chamber of the piston is described. The test data of operation cycle of the piston in case of different variants of settings are presented. The possibility to exert influence on the nature and frequency of impacts is demonstrated.

A bolter miner is a mining machinery of coal–rock cutting. In order to study the best pick layout of bolter miner cutting head, three kinds of pick layouts were designed. The performance evaluation of cutting head under the condition of different rotational speeds and pick layouts was intensively studied by simulations and experiments. And the reality of the simulation is verified by cutting experiments. The aim of this research is to provide theoretical guidance for the design of bolter miner cutting head.

The results of the work on the scientific and technical framework of the open pit mine haulage machinery design for the national standard initiated by ALROSA Group in 2015 are presented. The experience of design and operation of haulage systems at open pit diamond mines in the permafrost zone is analyzed. Favorable operating conditions of haulage systems are determined with regard to peculiarities of open pit diamond mines. The sequential shaping of a haulage system all through the life of an open pit mine is substantiated. Application of such approach requires information technologies of transport system design, including computer modeling and multipath analysis under variability of numerous factors.

Specificity of using information technologies to improve safety and efficiency of integrated mineral mining is described. The results of works on creation of information resources for keeping and processing of data on rare earth and rare metal raw materials are presented. The application of the integrated approach to mineral mining under environmental constraints is described in terms of the Partomchorr deposit located in the Russian region of the Arctic. Low-waste technologies are substantiated for ore mining, processing and piling, as well as for mine waste management. The most important avenues of research in the area of automation and robotization of mining are identified.

The paper presents an analysis of experimental data that include space–time distributions of methane concentration at the shearer-exploited longwall. The main objective of the observation was to identify the sources of methane emission and determine the methane distribution along the longwall and the adjacent workings. At present, numerical simulation methods are used more and more extensively while testing the air parameters in mine workings. The conducted analysis was also aimed at preparing input data for verification of numerical models of the longwall area as well as a simulation of the algorithm for controlling the shearer operating at the longwall being exploited in the seam exposed to methane hazards. The object of observation was longwall 841a, seam 405/2 in the Bielszowice mine. In the area of the longwall nine methane detectors (including two in the longwall) were located and used as common protection against methane hazard. As part of the experimental research, 10 additional methane detectors were located in the longwall and the adjacent workings, including 4 in the longwall.

—Using UV-visible spectrophotometry, it is found that old tailings of Solnechny Mining and Processing Plant are characterized with high absorptive capacity relative to sodium dibutyl dithiocarbamate (DBDTC) and require high consumption of collecting agents in flotation. The optical and scanning electron microscopy tools revealed gypsum-cemented finely dispersed fractions (smaller than 20 μm) coating larger mineral particles (60–80 μm). Minerals are represented by chalcopyrite, pyrrhotine, pyrite, sphalerite, jamesonite and cassiterite; rocks are quartz and silicates. A feature of these old tailings is supergene mineralization and sulphide oxidation products. Alongside with cassiterite, varlamovite is present as a typical product of stannite-group tin sulfosalts modification. New experimental data on flotation of Solnechny MPP tailings with DBDTC are obtained. The flotation experiments show that DBDTC addition to butyl xanthate (at ratio of 1: 3) enables increased recovery of copper, lead, zinc and silver in bulk concentrate and reduces loss of these minerals in slime.

Results of research into low-grade rebellious copper-nickel ore are presented. The mineralogical analysis reveals features of material composition, which affect processing properties of the ore—fine primary dissemination, essential serpentinization and substitution of insets by magnetite, as well as considerable fine difficult-to-dissociate epigenetic impregnation. The main causes of insufficient nickel recovery at the accepted modes of processing are determined. With a view to increasing concentration efficiency of this ore, different milling and flotation modes are considered. Ways to improve processing performance of this-type ore are identified.

The modern trends in advance of information support tools for the mining industry call for an integrated solution of technological problems based on a common software platform to ensure prompt development of a novel functional or adaptation of the available one to mining conditions. In this case, of key importance becomes the ideology to develop an information system capable to realize functions of the platform. Relying on more than 20 years experience in evolution of MINEFRAME mining geology information system (MGIS), there are grounds to suggest that the optimal way is to create an object-oriented platform capable to model and to control mining and geological objects in order to grant designers a novel application software for access to the basic MGIS functional. Implementation of this approach allows solving such important problems as higher stabilization of software operation by means of screened access to software tools of the basic level as well as promotion of MGIS functional advance owing to a feasibility to design application programs with the use of the procedures library and the platform functions.