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Vaisberg L.A.,Mekhanobr Tekhnika Research and Engineering Corporation | Kameneva E.E.,Petrozavodsk State University
Gornyi Zhurnal | Year: 2014

The article illustrates workability of X-ray computed microtomography (X-ray micro-CT) in the studies of microstructure and physico-mechanical properties of rocks. It is emphasized that the approach to rock disintegration improvement should rest upon the detail analysis of macro- and microstructure of rocks in interconnection with their physicomechanical properties. The authors substantiate that an informative characteristic coupling the properties and structural defects of rocks is the porosity. The prospects offered by the X-ray micro-CT in solving of practical tasks of rock breakage include the quantitative characterization of pore space structure. The advantage of the method is the nondestructive analysis, after which samples can be used in other tests. The authors perform comparative assessment of pore space structure in rocks of different texture and structure: gabbro-diabase, granite and bastard granite. The differences in amount, size, shape, connectivity and distribution of pores in the listed rock types are found. The differential characteristic of distribution of pores by density, size and shape is obtained. It is shown that ultimate compression strength grows if pores are smaller in size, more spherical and have better connectivity. Pores under 40 μm in size do not decrease strength irrespective of their amount. Volumes being the same, bigger and less spherical pores reduce the rock strength.

Vaisberg L.A.,Mekhanobr Tekhnika Research and Engineering Corporation | Kameneva E.E.,Petrozavodsk State University | Pimenov Yu.G.,Gubkin Russian State University of Oil and Gas | Abrosimov A.A.,Gubkin Russian State University of Oil and Gas
Gornyi Zhurnal | Year: 2015

Plenty of theoretical and experimental studies have turned to deformation and strength characteristics of rocks. In accordance with the existing views, the mechanism of rock deformation and failure is associated with generation and growth of damages initiated by structural defects. The studies of rock disintegration reveal the most probable structural elements along which failure develops-pores, microfractures, and interfaces of mineral intergrowth and grains. Deformation results from relative displacement of rock-forming structural elements, the shape, size and properties of which govern the deformation mechanics and kinematics. This study aims at disclosure of processes that run in rocks (granite in the case under discussion) subjected to compressive load that fits with the value of transition from the elastic to plastic deformation. The analysis uses the method of X-Ray Micro-CT. The studies show that under compressive loads fitting with the transition from the elastic to plastic deformation, a failure source forms in a rock specimen - the area with the increased concentration of pores. In undamaged areas, compaction takes place owing to closure of intergrain and intracrystalline pores. The closure of intracrystalline pores causes the change of geometrical characteristics of crystals. The authors validate that effect of dilatancy shows itself in a rock specimen not only as microfracturing but as transformation of volume of rock as a whole and its individual structural elements, i.e. pores and crystals.

Arsentev V.A.,Mekhanobr Tekhnika Research and Engineering Corporation | Vaisberg L.A.,Russian Academy of Sciences | Ustinov I.D.,Mekhanobr Tekhnika Research and Engineering Corporation | Gerasimov A.M.,Mekhanobr Tekhnika Research and Engineering Corporation
Gornyi Zhurnal | Year: 2016

High-ash coal preparation employs mainly "wet" methods with water flow rate of 5-10 t per 1 t of coal. Recycling water supply lowers "fresh" water demand but it is still required to pump considerable volumes of water slurries, which needs much power. On the other hand, dry preparation of low-grade coal using modern technologies is low efficient. This study focuses on the supposition that it is expedient to precede dry preparation of high-ash coal by thermochemical treatment stage and, then, to employ physicomechanical methods aimed to produce low-ash high-energy product. The use of the mentioned chemical transformation opens up new possibilities of processing of heat-treated middlings, namely: · Reduction in energy input of crushing and milling owing to decreased mechanical strength; · Complete removal of ash using "dry" preparation methods only; · Production of agglomeration semicoke using clean hydrocarbon fraction; · Use of roasted mineral fraction to produce special binders, concrete admixtures and building units. It is difficult to separate mineral powders less than 1 mm in size based on their magnetic and electric properties since internal friction forces in powders prevent from efficient separation of particles. It is possible to overcome these forces using the so-called vibro-combustion under certain vibrational impact. The application of this effect has allowed engineering of high-performance separators to recover individual finely dispersed mineral particles based on magnetic and electric properties. These separators have been employed in this study. Efficiency of thermochemical modification of coal and coal preparation products is evaluated using such index as the ash yield per unit calorific capacity. It has been found that cleaned semicoke 3 times exceeds original coal with respect to this index. It is proved that moderate temperature pyrolysis of both black coal and lignite improves disintegration of incombustile mineral fraction, which favors its recovery using dry preparation methods later on - combination of high-rate magnetic and triboelectric separation techniques. After such preparation process, semicoke as solid fuel has higher quality than conventionally dressed coal, and dry preparation tailings are disposable.

Blekhman I.I.,Mekhanobr Tekhnika Research and Engineering Corporation | Vaysberg L.A.,Mekhanobr Tekhnika Research and Engineering Corporation
Obogashchenie Rud | Year: 2014

This paper presents the main physical factors causing bulk material particles segregation under vibration. As a process model, particle motion in vibrating medium, consisting of foreign particles, is studied. Three cases of vibrating medium are considered: horizontal circular vibrations, horizontal rectilinear vibrations and vertical rectilinear vibrations. In each case, formulas are derived for consideration of an effect upon particle average velocity and direction of motion relative to medium (segregation rate), designated, as suggested, «wedge-effect» (in foreign publications certain manifestations of this effect are sometimes described as «Brazil nut effect»). Solution of nonlinear differential equations of particle motion is accomplished through vibratory mechanics approach and direct motion separation method. As a result, relationships are obtained that determine segregation direction and rate. The experimental results are presented. © 2014 John Wiley & Sons, Ltd.

Arsentiev V.A.,Mekhanobr Tekhnika Research and Engineering Corporation | Vaisberg L.A.,Mekhanobr Tekhnika Research and Engineering Corporation | Samukov A.D.,Mekhanobr Tekhnika Research and Engineering Corporation
Gornyi Zhurnal | Year: 2014

The article addresses the problems of reduction and utilization of waste in production of high-quality road metal 5-20 mm in size. The concept of economic utilization of screenings is formulated. A nonwaste technology is offered for volcanic rock processing. The offered nonwaste technology includes a number on intercoupled process flows that enable: 1. Reduction in the amount of screenings after rock crushing (fractions 0-5 mm) by over 10% owing to vibratory crushers as compared with conventional crushing in the standard cone and centrifugal crushers; 2. On-site utilization of screenings (fractions 0-5 mm) and pit-run fines (fractions 0-20(40) mm), which allows production of building materials based on the following engineering solutions: Reshaping of particles in vibratory crushers; Drying and classification of artificial sand into narrow fractions using modified screens; Introduction of classified artificial sand in manufacture of vibro-pressed concrete products; Introduction of dust fraction (0-0.16 mm) in production of granulated light-weight aggregate for concrete. The offered technology is totally in line with the worldwide recognized principle of civilized treatment of any waste material-3R technology where 3R stands for Reduce, i.e. waste reduction, Reuse, i.e. repeated usage, and Recycle, i.e. processing toward production of a new commodity. This work was carried out within the State task in the scientific effort sphere.

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