Vol 54, No 3 (2018)

The classical solution of elasticity problem on deformation of a plane weakened by a mathematical cut under wedging by constant forces is analyzed. The ill-posedness of the classical failure mechanics statements for problems with angular points is demonstrated. The approximate solution is constructed for deformation of continuum in the vicinity of a cut under small strains.

A device is developed for loading granular materials by shearing with air flow driven through the material without its pseudo-liquefaction. Internal stresses and dilatancy of a sample are measured depending on shearing angle. It is shown that shear modulus, characterizing material capability to resist shearing as air flow rate is increased, lowers while dilatancy grows.

Interaction between an open-end pipe and a soil plug is studied using Coulomb’s law of friction. The scope of the study embraces different models of soil and pipe. The finite difference solutions obtained for all models and the analytical solutions derived for some models describe the elastic process of the pipe and soil interaction. Agreement of the numerical and analytical solutions is shown. Results of different model calculations are compared, and the validity limits are determined for the models. The influence of Coulomb friction on pipe and soil movement is investigated.

The paper presents two model approaches to life cycle assessment of auxiliary mining machines: one of them is based on reliability theory and the other on the principle of cost-effectiveness. During exploitation of machines, the level of their reliability decreases while operating costs increase. These indicators of opposing trends detect the operating capacity of machines and provide the basis for making a decision on the validity of further operation, maintenance, or replacement of machines. By considering an example of a dozer, as the most frequently used machine for the performance of auxiliary works in the surface coal mines of Electric Power Industry of Serbia, a comparative analysis was made for applying both model approaches including assessment and conclusion.

The problem on oil filtration in the reservoir model with the preset differential pressure harmonically varying in time on its faces is solved. Hysteresis effects of capillary pressure under change in the direction of fluid expulsion are considered. The influence exerted by liquid fluctuations on cleaning the near-well zone from possible capillary blocking of aqueous phase is estimated. The action of alternating pressure pulses on the oil-saturated reservoir model is investigated. It is shown that harmonic change in liquid pressure promotes removal of immobile capillary-blocked water from the near-well zone. The results of in-situ experiments on wave action on the wellbottom zone and oil production stimulation are presented.

Theoretical aspects of studying stability of natural systems depending on investigation purposes are briefly analyzed. Applicability of the watershed/landscape concept of nature management to study transformation of geosystems disturbed by gold placer mining is substantiated. In terms of a model site within the limits of the Ket-Kap cluster of placers, the data on the degree of such transformations are given, and mid- and large-scale landscape mapping is performed using the modern remote sensing techniques. The qualitative indicators of transformation degree under placer mining are given for valley nature systems depending on watershed order. The relevance of the remote sensing in estimating the degree of transformation of natural systems at objects of gold placer mining at regional and local levels is demonstrated.

Airflow disorder in inlet shafts and related crossheadings, caused by local natural ventilation pressure, is a complicated thermodynamic phenomenon. The conception of local natural ventilation pressure is proposed based on a simplified ventilation system. Airflow disorder principle is analyzed theoretically and verified by similar simulation experiment and in-situ study. Research results show that local natural ventilation pressure will form when average temperature difference or density difference of air-column exists among inlet shafts in an underground mine with exhaust ventilation. When changing in a large range, local natural ventilation pressure will cause airflow disorder in inlet shafts or related crossheadings. The research results have guiding significance for promoting the stability of ventilation system and improving the working environment of underground mines.

Organic and inorganic luminophores of similar luminescence parameters as diamonds are selected. Indicators, based on the selected luminophores, are synthesized. Spectral and kinetic characteristics of luminophores are experimentally determined for making a decision on optimal compositions to ensure maximum extraction of diamonds in X-ray luminescence separation owing to extra recovery of non-luminescent diamond crystals. As the components of luminophore-bearing indicators, anthracene and K-35 luminophores are selected as their parameters conform luminescence parameters of diamonds detected using X-ray luminescence separator with standard settings.

The research findings on efficiency of hardly soluble low-hydroxyethylated iso-nonylphenols as regulators of selective flotation are presented. The methods for increasing their solubility are developed, which are based on using unsaturated carboxylic acids as wedding agents for alkaline salts. It is shown that addition of such wedding agents to ethoxylated iso-nonylphenols makes it possible to obtain stable aqueous micellar solutions or emulsions under much lower temperatures, as well as ensures permanence of the process and efficiency of regulating agents in selective flotation of phosphorus-bearing ores with fatty acid collector. Efficiency of the developed methods is proved by in practical application of one of them, which improved ore dressing performance, reduced labor content, energy input and time of solution preparation, and provided considerable economic effect.

Tin-bearing tailings of the Solnechny Mining and Processing Plant (MPP) in the Khabarovsk Territory are studied with a view to producing tin and copper concentrates. The features of the material constitution of tailings and their influence on the process flow diagram (PFD) development are described. Processability of the Solnechny MPP tailings is tested, and PFD is developed using the modern methods of disintegration, including cavitation and ultrasound. The semi-commercial-scale implementation of the proposed PFD has allowed production of copper concentrate at copper content of 18.28% and recovery of 60.48%, tin concentrate at tin content of 11.35% and recovery of 50.88%, and rejects with the tin and copper contents of 0.139 and 0.154%, respectively. The recovery of tin and copper has made 46.66 and 38.45%.

The timely character of using digital satellite observation data at regional and local levels for operational quantitative assessment of nature condition in the areas of mineral mining and processing activities is validated. The qualitative ecological estimates of impacts in time intervals by biota response in the area of location of several mines with different production infrastructure are presented and analyzed.

The mathematical model of heat flow and transfer in roof rocks of underground gas gasifier during coal gasification is developed and tested. In terms of geological conditions in the Olkhovo-Nizhnee site (industrial region in Donbass), in Mathcad environment, convective and conductive components of heat flow from reaction channel to upper-lying aquifer are determined. The change in the heat flow from the reaction channel and in the ground water temperature is estimated depending on impermeable layer thickness and water well yield. It is found that after underground coal gasification, water-bearing sandstones accumulate more than 60% of heat migrating from gasifier to enclosing rock mass. It is shown that withdrawal and use of water heated during underground coal gasification will enhance efficiency of the process by 18–25% subject to thickness of partition layer.

The study is devoted to the methane hazard in hard coal mining. This hazard occurs in almost every coalfield in the world. Ensuring maximum work safety under methane hazard conditions is based, among other things, on reliable, fast and frequent determinations of methane content in a coal seam. The existing methods are time-consuming, and determinations must be performed in laboratories. Indirect methods such as desorbometric methods are burdened with high measurement uncertainties. The study presents a model of methane release from granular coal samples and a device (AMER) developed for measuring methane content in a coal seam under in situ conditions. Measurements are performed in a fully automatic way and preliminary results, based on the approximation of the Crank model, are available within several dozen minutes from the beginning of the measurement. Also, the use of the unipore diffusion equation and a proper software of the device allowed to determine the values of the effective diffusion coefficient. Results of measurements performed with the AMER desorbometer are highly consistent with the results of the measurements performed in the laboratory using a traditional method.

This study was supported by the Russian Foundation for Basic Research, project no. 16-05-00646a.