Formation of synthetic structures and textures of rocks when simulating in COMSOL Multiphysics

Belt conveyors are widely used in mining industry in open-pit and underground mining for moving bulkload in horizontal and inclined directions to the sites of processing. In order to create the best conditions of frictional contact between a belt and a drum, various methods of drive drum lining are used. The main lining material is rubber of different grades, providing proper coefficient of friction of a belt with a drum (within the range of 0.6–0.62). A drive drum lining material must have high wear resistance, thermal resistance, mechanical strength, ability not to accumulate electric charges on the surface and not to generate dangerous concentrations of toxic components (for example, chlorine gases, carbon monoxide) when heated. The use of ceramic lining opens up great opportunities for increasing lining durability and useful life of high capacity heavy-duty conveyors. The paper presents the results of the study of stress-strain state of belt conveyor drive drum ceramic lining plates. We used Solid Work Simulation environment in the study on the basis of the accepted analytical model of plate-belt contact for drive drum with diameter D = 1250 mm, belt width L = 1000 mm, and the belt entering branch tension value Se = 25400 daN with regard to the value, direction, and nature of the acting loads. On the basis of stress-strain analysis of alumina ceramics lining plates, the favorable geometrical parameters of the plate cleats (projections) and the required properties of lining material ensuring the proper load-carrying capacity at the contact with the belt rubber facing were found. It was established that a plate cleat diameter for heavy duty conditions should be not less than 4.5 mm and its end round R should be within the limits of 0.5–0.6 mm, and, in the base, 0.3–0.4 mm at a cleat height of 1.0–1.4 mm in order to prevent stress concentration in hazardous sections. It was also established that alumina ceramics bending strength must be no less than 350 MPa for effective functioning of rubber-ceramic lining. Simulation of a plate stress-strain state on exposure to alternating loads made it possible to identify characteristic areas with maximum stress concentration, which were foci of crack nucleation. Thus, it became possible to predict lining useful life.

Section: методыunclassified

Justification of geometrical parameters of lining plates for a belt conveyor drive drum

Ziborova¹,

Mnatsakanyan

2022

“…Основная идея работы состоит в определении параметров охранных целиков по критерию устойчивости вспомогательной выработки [8], а также с учетом характеристик очистного забоя в условиях наклонных угольных пластов. В качестве инструментария в исследовании используются методы цифрового моделирования напряженно-деформированного состояния массива горных пород на основе конечно-разностных моделей [9,10]. В качестве программной среды использовался комплекс Flac3D.…”

Section: Introductionunclassified

Substantiation of pillar parameters in mining of inclined coal seams in Quang Ninh Province, Vietnam

Nguyen

Pham

Osinski

et al. 2022

Design and operation of auxiliary underground workings in coal mines involves substantiation of parameters of coal pillars and requires development of new approaches to substantiate their geometrics. On the one hand, sufficient stability of a “rock mass – working – coal pillar” system should be ensured. On the other hand, the parameters of “frozen” coal reserves in the pillars should be justified. The joint solution of these two problems requires accurate forecasting based on modern digital models of a rock mass. In this study, a model of rock mass and mine workings with different dimensions of a coal pillar is presented with the use of Flac3D software. The simulation findings showed that when developing sloping coal seams, the volume of coal extraction in a longwall has an effect on the stress-strain state of the enclosing rock mass. During the study different factors having effect on geometrics of a coal pillar were analyzed, and their influence on the field of stresses and shear of inclined layers in a rock mass was studied, and the size of the plastic deformation zone around an auxiliary mine working was also determined. The study findings are also of practical importance in terms of substantiating the parameters of a working support design. The size of coal pillar is also connected with the support type. It should be taken into account that bolts should be of sufficient length to ensure firm fixing and located in the zone of intact rocks. The research showed that a coal pillar should be 10 to 15 m wide in order to ensure optimal mining conditions and safety.

Influence of random parameter joint length on rock electrical conductivity

Sizin

Вознесенский

Kidima-Mbombi

2023

Self Cite

Rock joint hollowness coefficient is an important parameter when resolving practical mining problems. Geophysical methods used to resolve this problem are indirect. Thus the interpretation of their results may cause certain difficulties as a result of the uncertainty of the physical relationships between the parameters of joints and the measurement results. One of the ways to resolve this problem is to combine experimental research methods with analytical and numerical simulation. The studies were aimed at investigating the electrical conductivity of a two-dimensional medium in the presence of thin insulating (non-conducting) joints. This paper proposes an analytical method for assessing the dependence of the specific conductivity of a medium with inclusions in the form of elliptical joints on their half-length. This dependence is show to have the form of an exponent depending on the square of the length of the maximum semi-axis as an argument. The simulation method is based on the assumption of the elliptical shape of a joint when the length of the minor semi-axis of the ellipses tends to zero. A review of publications and their results presented in this paper showed that this method for determining the specific conductivity of the medium with thin joints is one of the best in terms of compliance with experimental data. Its predictions are close to those of the Effective Media Approximation (EMA). However, the proposed method is distinguished by the simplicity of the formulas and their physical visibility essential for the use in interpreting the data of a physical experiment. In two-dimensional formulation, numerical simulation of the specific electrical conductivity of a sample of a medium measuring 1×1 m with elliptical joints of conductivity less than that of the matrix was carried out in the COMSOL Multiphysics environment. A square sample of unit sizes with unit conductivity was considered in which 25 joints with uniform distribution along the length occurred. 40 models were built wherein the maximum length of the joints varied from 0.01 to 0.4 sample size in increments of 0.01 m. The satisfactory concordance of the results of numerical and analytical models, both visual and confirmed by statistical estimates, has been shown. It was noted that when the size of the joints changes to achieve the value of the maximum semi-axis α = 0.15 m, the influence of single joints that do not extend beyond the boundaries of the sample prevails. Above this value, at α > of 0.15 m, the influence of joint coalescence, as well as their extension to and beyond the sample boundaries begins to affect. Comparison of the proposed theoretical model of electrical conductivity, depending on the square of the length of the maximum semi-axis of a joint, with a similar model in the form of an exponent with a linear dependence showed a better concordance of the proposed model with observations at the stage of the lack of joint coalescence and their extension to the sample boundaries at α < 0.15 m. At α > 0.15 m. The proposed model has a lower coefficient of determination compared to the full range including both intervals, but higher than that of the model with a linear dependence in the exponent argument. This indicates the universal nature of the proposed model.