Home – Home – Jornals – Journal of Mining Sciences 2018 number 5

Physical processes are initiated in rock mass by long-term induced vibration loads which give rise to triggering factors the neglect of which can result in instability of underground structures. The methodical characteristics of the triggering factor monitoring are described for the specific operating conditions of an underground powerhouse hall of a hydroelectric plant in the Kola Peninsula in Russia.

The process of shear of a rigid rough plate in a granular medium is considered. The influence of three factors is analyzed: stiffness of loading, weak shocks and air flow. It is shown that weak shock actions and air flow, either separately or jointly, can act as a trigger of uncontrolled dynamic release of elastic energy in rock mass.

The main objective of this experimental work is to determine the physico-mechanical properties of tuffs used as building stone and to investigate the relationships between basic mechanical properties (compressive strength, flexural tensile strength, loss of volume by abrasion and impact strength) as well as physical and index properties (apparent porosity, dry unit weight, water absorption, P-wave velocity, Brinell hardness and point load index) of tuffs which are relatively easy to implement and low cost. The rock type investigated in this study was tuffs. Statistical analyses were performed to correlate the different properties. The results show that there are good and satisfactory relationships between the mechanical and physical-index properties of tuffs.

The results of investigations for solving the topical problem of geodynamic risk assessment in mining of the Khibiny rockburst-hazardous deposits in the Kola Peninsula are presented. The developed procedures and approaches contribute to minimization of geodynamic risks under large-scale mining of close-spaced apatite ore deposits. The geomechanical model is constructed, which allows analyzing successive development of a system of closely spaced deposits in the Khibiny Massif. Based on the model data on stress-strain state, the optimal sequence and direction of mining in the conditions of rockburst hazard is determined. The nested structure of the rock mass, direction of the tectonic compression, main radial faults, daylight surface relief and the parameters of the ore bodies are taken into account. The complexing of the predicted stress fields and seismicity improves reliability of detection of higher rockburst hazard zones. The examples of stoping sequence justification using a set of in-situ and numerical methods are given. The main lines of development in the support of mining based on geomechanical studies and the variants of process solutions toward regional and local unloading of rock mass are shown.

The influence of surface mining on the initiation of large seismic event is considered. The conditions of shearing-type dynamic events are described. In terms of a surface mine with the similar parameters as the Bachatsky open pit mine in Kuzbass, the mining-induced change in the stress state in the plane of a future rupture as a result of a triggered-type tectonic earthquake nearby a fault plant is quantified. The calculations are performed for different geometrical parameters of the fault zone: the changes are more observable in the zones of gently dipping thrust faulting and less appreciable in the area of steep normal faulting and strike-slip. In case of large surface mines, the zone of positive change in the Coulomb stresses higher than several tenths mega pascals has a considerable dimension and an area markedly larger than the area of nucleation zone of earthquakes of the magnitude . In such conditions, even a small variability at the level of first percentage points of the natural stresses can be sufficient for the initiation of seismicity-generating shearing along the high-stress faults. It is found that, as against underground mining, the surface mining activities have no influence on localization of large earthquake sources but can draw the event nearer.

With the increasing depth of mineral resources exploration, hard rock can have a strong impact on the effect and cost of resource exploration. Due to the particularity of rock, including un-predictable damage such as joints, cracks and holes, the development of mesoscopic defects in the rock under the action of vibration load will lead to the deterioration of its macroscopic mechanical properties. At present, the research about the effect of ultrasonic vibration time on rock crushing is almost blank. In this paper, the method of theoretical analysis, finite element numerical simulation and experimental research is used to explore the damage and the strength degradation law of granite under ultrasonic vibration over time. It is of great significance to improve the effect of rock crushing, and to provide theoretical guidance for the application of ultrasonic vibrators in hard rock drilling and devel-opment of ultrasonic vibration rock drilling. The finite element method is used to establish the practical heterogeneous rock model to analyze the law of rock crack propagation in different time periods, and the ultrasonic vibration time threshold (during 15-20 min) is proposed to provide theoretical guidance for the experiment. The porosity and strength of the rock samples are measured by nuclear magnetic resonance and uniaxial compressive strength after vibration, and the influence of vibration time on rock damage is analyzed.

Practice of rock drilling with tri-cone roller bits, which are extensively used in surface mines, needs proper modes of descriptive statistics for predicting the failure rates of its different sub- assembled components. The statistical models for drilling with tri-cone roller bits are investigated in this article and probability of the non- failure operation is calculated. The interdependency of different component failures is examined by 3D contour plot. The failure rate of the components observed is found not significantly different at 95% contour. In such condition, the reliability is best modelled by Mixed Weibull technique.

The sectoral models are the efficient tools of mathematic simulation and are widely applied in economy. It is inconsistent that the mining industry neglects the sectoral analysis whereas neither industrial sector has ever adopted and implemented operational research methods so promptly as the mining industry. There is no satisfactory explanation of this fact. Aiming to throw light on the dilemma, this article focuses on the characteristics and properties of the sectoral analysis, as well as on the understanding of its applicability in the mining industry. In terms of the sectoral model of the Kolubara mining basin operated by the power industry in Serbia, the implementation and validation of observations and conclusions are demonstrated.

Based on the differentiation of coal ash content into constituents, the procedure is developed for estimating overall (technological and natural) dilution. The accumulated data base on the Elgin coal deposit (South Yakutia) is described. This data base was used to model coal seams for studying variability of their parameters and properties. The estimated ash contents due to mining operations and connected with the discriminated natural groups of mineral admixtures are presented. Higher variability of the overall ash content and its components across the area and in section of coal seams is shown. The percentage of various thickness steaks inside coal seams in the structure of ash content may reach 14-27% and more. Coal mines insufficiently account for this fact, which leads to incomplete utilization of geological potential of complex-structure deposits. It is emphasized that the resource-saving ash content control should not only be focused on processing efficiency. Based on additional appraisal of mineral reserves, it is possible to gain new capabilities of control at the stages of mine planning and design, actual mining and coal pretreatment.

The development of the coal seam long faces with the collapse of the upper packs, characterized by high productivity, due to the presence of powerful coal seams. The study is aimed at predicting the characteristics of the collapse of the upper part of a deep-seated powerful coal seam of the lignite basin in Soma, located in Eastern Turkey. For comparative purposes, the data obtained for active coal mines for long face mining with the collapse of the upper layers, located at a depth of 100 - 400 m. In the future, coal mining in the deep-seated sectors is expected. The upcoming work on coal mining by longwall faces can be attributed to the unique, since the mining will occur at a depth of 700 - 1200 m in layers of different thickness. Empirical and numerical methods are used in this study. Numerical simulation provides a practical basis for constructing soil response curves, with the use of which the results of research at existing and projected mines can be assessed and compared with the subsequent conclusion about the features of the collapse of the upper part of the coal seam.

Slope stability is a critical safety and production issue for mining. Major wall failures can occur seemingly without any visual warning, causing loss of life, damage to equipment, and disruption to the mining process. This study reviews eight different mine operations at different geographical locations. The eight case histories discuss the challenges mining operations have faced regarding instabilities over three decades. Recent rock slope instabilities are also discussed to verify the similarities and differences in past and recent instabilities. The studies show how all the instabilities have been managed, and outline recommendations that will benefit present and future pit operations in managing slope stability issues. The case histories were chosen based on the availability of the data obtained from the mine operations, literature reviews, and consulting reports. At the time this study was conducted, one of the BC mines (Mount Polley) had no records of instabilities in their operation.

Airflow reverse is a severe problem in an underground ventilation system. In addition, the airflow stability and safety production can be seriously affected by the problem of air velocity overrun in the roadways. In this study, the crucial causes of the ventilation problems in a coal mine case study are analyzed and a solution is proposed through an analytical methodology. Measurements indicate high air resistance in the shaft and low values in the maintenance roadway, generating abnormal airflow directional behaviors. Strategies to solve the ventilation-related problems have been proposed and implemented, verifying normal ventilation conditions.

The influence of structural characteristics and interaction parameters of minerals on separation method of lead-bearing complex ore in Russia is analyzed. Based on the studies of deep dissociation of minerals under disintegration using Mineral Liberation Analyzer (MLA), the quantitative distribution of mineral associations in grain-size categories is determined. From the data on mineral dissociation, the series of mineral associations, characteristic of complex ore from some deposits, are defined using milled samples of ore material. It is shown that galena associations with chalcopyrite, fahlore, secondary copper sulphides, sphalerite, pyrite and gangue mostly occur in finely dispersed aggregates with fahlore and, to a lesser degree, with other sulphides. The obtained series of mineral associations make it possible to determine the sequence of dissociation and separation of final-size minerals in the inter-cycle operations during flotation. The primary flotation concentrate contains: fahlore, secondary copper sulphides, gold associations, galena and corroded pyrite.

The results of the research and tests in production of beryllium concentrate of the superior and commercial grades as well as the marketable fluorite concentrate from ore and waste of the Ermakovskoe deposit mining are presented. The ore and waste contain a mineral complex which is hard to separate using fat acids and features an increased content of fluorite. Production of the marketable flotation concentrate is based on fixation of calcium in pulp using sodium carbonate, caustic soda and sodium tripolyphosphate. The autoclave-membrane electrolysis technology is developed for the production of marketable beryllium hydroxide from beryllium concentrates. The technology consists of a set of successive operations: dissociation in autoclave, separation of the suspension after the autoclave dissociation, removal of admixtures from the solutions, membrane electrodyalysis of alkaline solutions, hydrolysis of sodium beryllate and separation of beryllium hydroxide. The processing data of the test beryllium concentrates obtained using the autoclave-membrane electrolysis technology are given.

The influence of the velocity and time of pyrite slurry stirring on the mineralization kinetics of air bubble is studied. The subject of the research was pyrite -0.074 + 0 mm in size, and the collecting agent was sodium ethyl xanthate. The influence of the velocity and time of pyrite slurry stirring on the mineralization kinetics of air bubble is assessed. The conditions, hydrodynamic modes and time of pyrite slurry stirring such that to provide minimum and maximum areas of mineralization of air bubble at the constant concentration of sodium ethyl xanthate are determined.

The urgent nature of the studies into ash and slag from coal combustion in the thermal power sector in Eastern Transbaikalia is governed by the demand for highly efficient and environmentally clean processing technologies aimed at complete utilization of waste. The compositional analysis of the coal-fly ash-ash-and-slag geosystem is given. A special study of processability of ash and slag from combustion of Kharanor, Tataur amd Urtuy coals is carried out, and the main areas of their efficient use in the regional economy are substantiated. The process flow chart is developed for the integrated processing of ash-and-slag waste from thermal power plants in order to obtain marketable products in the form of xenospheres, magnetic fractions, rare and rare earth concentrates, as well as by-products for the building and road construction industries, etc. The proposed complete processing line integrates principles of flotation, magnetic and electrostatic separation as well as leaching, and enables considerable reduction in the environmental impact, improvement in performance and increase in investment attractiveness of thermal power plants.

The purposeful formation of man-made deposits is connected with the creation of such conditions that waste acquires preset process properties while stored. This will enable future environmental clean processing of waste. Aiming to determine general mechanisms of formation of process properties in copper-pyrite mill tailings, the comprehensive analysis of mineralogical composition of tailings from three concentration plants processing ore from six large copper-pyrite deposits in South Ural was performed. The crystal-chemical formulas of the basic ore minerals are studied and systematized. The morphological varieties of ore minerals are identified. It is found that even in case of deposits of the same genetic type, regimes and parameters of processing current mill tailings depend on the initial mineralogical features of waste based on which man-made deposits are formed. These features have influence on the mechanisms and stages of the secondary minerogenesis in the man-made deposits.

The test bench and procedure are proposed for the investigation of methane release from coal samples under wave field treatment, which increases outgassing rate. The ancillary equipment is designed for the shipment of cores from coal mines. Furthermore, the equipment allows measurement of methane emissions.

The variants of application of remote metering technologies, such as laser scanning and airborne imaging, are discussed. Based on the international experience gained in photogrammetry, a technique is proposed for surveying using a camera, quadcopter, electronic tacheometer and an appropriate software support. The sources of errors and the requirements imposed on the survey precision in point positioning in the horizontal and in the vertical are determined. The experimental approval of the technique with the assessment of the obtained data accuracy has been carried out in Sokolovskaya Mine of the Sokolov-Sarbai Mining and Processing Production Association.