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Mining Innovation

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "H: Geo-Energy".

Deadline for manuscript submissions: closed (31 May 2021) | Viewed by 45980

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Krzysztof Skrzypkowski

E-Mail Website
Guest Editor
Faculty of Civil Engineering and Resource Management, AGH University of Krakow, Mickiewicza 30 Av., 30-059 Kraków, Poland
Interests: underground mining methods; computer-aided design for mining; physical test; numerical modeling; bolting; backfilling
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Contemporary exploitation of natural raw materials by borehole, opencast, underground, seabed, and anthropogenic deposits is closely related to, among others, geomechanics, automation, computer science, and numerical methods. More and more often, individual fields of science coexist and complement each other, contributing to lowering exploitation costs, increasing production, and reduction of the time needed to prepare and exploit the deposit. The continuous development of national economies is related to the increasing demand for energy, metal, rock, and chemical resources. Very often, exploitation is carried out in complex geological and mining conditions, which are accompanied by natural hazards such as rock bursts, methane, coal dust explosion, spontaneous combustion, water, gas, and temperature. In order to conduct a safe and economically justified operation, modern construction materials are being used more and more often in mining to support excavations, both under static and dynamic loads. The individual production stages are supported by specialized computer programs for cutting the deposit as well as for modeling the behavior of the rock mass after excavation in it. Currently, the automation and monitoring of the mining works play a very important role, which will significantly contribute to the improvement of safety conditions.

In this Special Issue of Energies, we intend to focus on innovative laboratory, numerical, and industrial research that has a positive impact on the development of safety and exploitation in mining. We hope that you will consider submitting your original manuscript for peer review to this Special Issue.

Dr. Krzysztof Skrzypkowski
Guest Editor

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Keywords

  • Model tests
  • Numerical modeling
  • Case studies
  • Computer-aided design in mining
  • Automation in mining
  • Rock support
  • Rock mass monitoring

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Published Papers (17 papers)

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Research

18 pages, 2849 KiB  
Article
Open-Pit Mine Dewatering Based on Water Recirculation—Case Study with Numerical Modelling
by Kazimierz Różkowski, Robert Zdechlik and Wojciech Chudzik
Energies 2021, 14(15), 4576; https://doi.org/10.3390/en14154576 - 28 Jul 2021
Cited by 6 | Viewed by 3864
Abstract
The layout of the dewatering system in open-cast mining must be adapted to mining assumptions and to the size of expected inflows, which, in turn, depend on natural conditions and the operation of other mines and groundwater intakes, affecting the arrangement of the [...] Read more.
The layout of the dewatering system in open-cast mining must be adapted to mining assumptions and to the size of expected inflows, which, in turn, depend on natural conditions and the operation of other mines and groundwater intakes, affecting the arrangement of the hydrodynamic field. This case study analyses possible dewatering solutions related to a change in the mining drainage system: decommissioning by flooding of a depleted deposit and dewatering of a new one located in the vicinity. As part of numerical modelling, a solution was sought to minimise the environmental impact of drainage. Forecast calculations for two drainage alternatives were made. One of the solutions follows the classic approach: independent dewatering of the new excavation. The second solution assumes the recirculation of waters from dewatering of the new mine through their discharge into a closed and flooded pit located in the vicinity. The results of the forecasts for both variants point to the modification of the hydrodynamic field resulting from expected volumes of inflows and different environmental effects. The use of numerical simulations assisted the selection of the optimal dewatering solution. Full article
(This article belongs to the Special Issue Mining Innovation)
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10 pages, 490 KiB  
Article
Innovative Method for Calculating the Break-Even for Multi-Assortment Production
by Dariusz Fuksa
Energies 2021, 14(14), 4213; https://doi.org/10.3390/en14144213 - 12 Jul 2021
Cited by 2 | Viewed by 2040
Abstract
The subject of the article is a new method that I have developed for calculating a multi-asset break-even for multi-assortment production, extended by a percentage threshold and a current sales ratio (which was missing in previously published methods). The percentage threshold provides unambiguous [...] Read more.
The subject of the article is a new method that I have developed for calculating a multi-asset break-even for multi-assortment production, extended by a percentage threshold and a current sales ratio (which was missing in previously published methods). The percentage threshold provides unambiguous information about the economic health of a company. As a result, it became possible to use it in practice to evaluate the activities of economic entities (mines) and to perform modelling and optimisation of production plans based on different variants of customer demand scenarios. The publication addresses the complexity of the problem of determining the break-even in multi-assortment production. Moreover, it discusses the practical limitations of previous methods and demonstrates the usefulness of the proposed method on the example of hard coal mines. Full article
(This article belongs to the Special Issue Mining Innovation)
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21 pages, 21441 KiB  
Article
Design and Research on Power Systems and Algorithms for Controlling Electric Underground Mining Machines Powered by Batteries
by Artur Kozłowski and Łukasz Bołoz
Energies 2021, 14(13), 4060; https://doi.org/10.3390/en14134060 - 5 Jul 2021
Cited by 9 | Viewed by 3216
Abstract
This article discusses the work that resulted in the development of two battery-powered self-propelled electric mining machines intended for operation in the conditions of a Polish copper ore mine. Currently, the global mining industry is seeing a growing interest in battery-powered electric machines, [...] Read more.
This article discusses the work that resulted in the development of two battery-powered self-propelled electric mining machines intended for operation in the conditions of a Polish copper ore mine. Currently, the global mining industry is seeing a growing interest in battery-powered electric machines, which are replacing solutions powered by internal combustion engines. The cooperation of Mine Master, Łukasiewicz Research Network—Institute of Innovative Technologies EMAG and AGH University of Science and Technology allowed carrying out a number of works that resulted in the production of two completely new machines. In order to develop the requirements and assumptions for the designed battery-powered propulsion systems, underground tests of the existing combustion machines were carried out. Based on the results of these tests, power supply systems and control algorithms were developed and verified in a virtual environment. Next, a laboratory test stand for validating power supply systems and control algorithms was developed and constructed. The tests were aimed at checking all possible situations in which the battery gets discharged as a result of the machine’s ride or operation and when it is charged from the mine’s mains or with energy recovered during braking. Simulations of undesirable situations, such as fluctuations in the supply voltage or charging power limitation, were also carried out at the test stand. Positive test results were obtained. Finally, the power supply systems along with control algorithms were implemented and tested in the produced battery-powered machines during operational trials. The power systems and control algorithms are universal enough to be implemented in two different types of machines. Both machines were specially designed to substitute diesel machines in the conditions of a Polish ore mine. They are the lowest underground battery-powered drilling and bolting rigs with onboard chargers. The machines can also be charged by external fast battery chargers. Full article
(This article belongs to the Special Issue Mining Innovation)
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14 pages, 2266 KiB  
Article
Method for Determining the Utilization Rate of Thin-Deck Shearers Based on Recorded Electromotor Loads
by Marek Kęsek and Romuald Ogrodnik
Energies 2021, 14(13), 4059; https://doi.org/10.3390/en14134059 - 5 Jul 2021
Cited by 1 | Viewed by 1864
Abstract
Mining machinery and equipment used in modern mining are equipped with sensors and measurement systems at the stage of their production. Measuring devices are most often components of a control system or a machine performance monitoring system. In the case of headers, the [...] Read more.
Mining machinery and equipment used in modern mining are equipped with sensors and measurement systems at the stage of their production. Measuring devices are most often components of a control system or a machine performance monitoring system. In the case of headers, the primary task of these systems is to ensure safe operation and to monitor its correctness. It is customary to collect information in very large databases and analyze it when a failure occurs. Data mining methods allow for analysis to be made during the operation of machinery and mining equipment, thanks to which it is possible to determine not only their technical condition but also the causes of any changes that have occurred. The purpose of this work is to present a method for discovering missing information based on other available parameters, which facilitates the subsequent analysis of machine performance. The primary data used in this paper are the currents flowing through the windings of four header motors. In the method, the original reconstruction of the data layout was performed using the R language function, and then the analysis of the operating states of the header was performed based on these data. Based on the rules used and determined in the analysis, the percentage structure of machine operation states was obtained, which allows for additional reporting and verification of parts of the process. Full article
(This article belongs to the Special Issue Mining Innovation)
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17 pages, 6239 KiB  
Article
Application of Hydraulic Backfill for Rockburst Prevention in the Mining Field with Remnant in the Polish Underground Copper Mines
by Karolina Adach-Pawelus and Daniel Pawelus
Energies 2021, 14(13), 3869; https://doi.org/10.3390/en14133869 - 27 Jun 2021
Cited by 6 | Viewed by 2019
Abstract
In the polish underground copper mines owned by KGHM Polska Miedz S.A, various types of room and pillar mining systems are used, mainly with roof deflection, but also with dry and hydraulic backfill. One of the basic problems associated with the exploitation of [...] Read more.
In the polish underground copper mines owned by KGHM Polska Miedz S.A, various types of room and pillar mining systems are used, mainly with roof deflection, but also with dry and hydraulic backfill. One of the basic problems associated with the exploitation of copper deposits is rockburst hazard. Aa high level of rockburst hazard is caused by mining the ore at great depth in difficult geological and mining conditions, among others, in the vicinity of remnants. The main goal of this study is to investigate how hydraulic backfill improves the geomechanical situation in the mining filed and reduce rockburst risk in the vicinity of remnants. Numerical modeling was conducted for the case study of a mining field where undisturbed ore remnant, 40 m in width, was left behind. To compare the results, simulations were performed for a room and pillar mining system with roof deflection and for a room and pillar mining system with hydraulic backfill. Results of numerical analysis demonstrate that hydraulic backfill can limit rock mass deformation and disintegration in the mining field where remnants have been left. It may also reduce stress concentration inside or in the vicinity of a remnant, increase its stability, as well as prevent and reduce seismic and rockburst hazards. Hydraulic backfill as a local support stabilizes the geomechanical situation in the mining field. Full article
(This article belongs to the Special Issue Mining Innovation)
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20 pages, 3817 KiB  
Article
Gate Road Support Deformation Forecasting Based on Multivariate Singular Spectrum Analysis and Fuzzy Time Series
by Luka Crnogorac, Rade Tokalić, Zoran Gligorić, Aleksandar Milutinović, Suzana Lutovac and Aleksandar Ganić
Energies 2021, 14(12), 3710; https://doi.org/10.3390/en14123710 - 21 Jun 2021
Cited by 2 | Viewed by 1856
Abstract
Underground mining engineers and planners in our country are faced with extremely difficult working conditions and a continuous shortage of money. Production disruptions are frequent and can sometimes last more than a week. During this time, gate road support is additionally exposed to [...] Read more.
Underground mining engineers and planners in our country are faced with extremely difficult working conditions and a continuous shortage of money. Production disruptions are frequent and can sometimes last more than a week. During this time, gate road support is additionally exposed to rock stress and the result is its progressive deformation and the loss of functionality of gate roads. In such an environment, it is necessary to develop a low-cost methodology to maintain a gate road support system. For this purpose, we have developed a model consisting of two main phases. The first phase is related to support deformation monitoring, while the second phase is related to data analysis. To record support deformations over a defined time horizon we use laser scanning technology together with multivariate singular spectrum analysis to conduct data processing and forecasting. Fuzzy time series is applied to classify the intensity of displacements into several independent groups (clusters). Full article
(This article belongs to the Special Issue Mining Innovation)
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19 pages, 4406 KiB  
Article
Enhancement of Machinery Activity Recognition in a Mining Environment with GPS Data
by Paulina Gackowiec, Edyta Brzychczy and Marek Kęsek
Energies 2021, 14(12), 3422; https://doi.org/10.3390/en14123422 - 10 Jun 2021
Cited by 6 | Viewed by 2196
Abstract
Fast-growing methods of automatic data acquisition allow for collecting various types of data from the production process. This entails developing methods that are able to process vast amounts of data, providing generalised knowledge about the analysed process. Appropriate use of this knowledge can [...] Read more.
Fast-growing methods of automatic data acquisition allow for collecting various types of data from the production process. This entails developing methods that are able to process vast amounts of data, providing generalised knowledge about the analysed process. Appropriate use of this knowledge can be the basis for decision-making, leading to more effective use of the company’s resources. This article presents the approach for data analysis aimed at determining the operating states of a wheel loader and the place where it operates based on the recorded data. For this purpose, we have used several methods, e.g., for clustering and classification, namely: DBSCAN, CART, C5.0. Our approach has allowed for the creation of decision rules that recognise the operating states of the machine. In this study, we have taken into account the GPS signal readings, and thanks to this, we have indicated the differences in machine operation within the designated states in the open pit and at the mine base area. In this paper, we present the characteristics of the selected clusters corresponding to the machine operation states and emphasise the differences in the context of the operation area. The knowledge obtained in this study allows for determining the states based on only a few selected most essential parameters, even without consideration of the coordinates of the machine’s workplace. Our approach enables a significant acceleration of subsequent analyses, e.g., analysis of the machine states structure, which may be helpful in the optimisation of its use. Full article
(This article belongs to the Special Issue Mining Innovation)
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19 pages, 5714 KiB  
Article
Determination of the Backfilling Time for the Zinc and Lead Ore Deposits with Application of the BackfillCAD Model
by Krzysztof Skrzypkowski
Energies 2021, 14(11), 3186; https://doi.org/10.3390/en14113186 - 29 May 2021
Cited by 15 | Viewed by 2326
Abstract
This article introduces a BackfillCAD model that relates to the determination of the backfilling time. The relationship of the individual model modules using a flow chart are characterized and presented. The main aim of the research was to determine the time of backfilling [...] Read more.
This article introduces a BackfillCAD model that relates to the determination of the backfilling time. The relationship of the individual model modules using a flow chart are characterized and presented. The main aim of the research was to determine the time of backfilling for the prospective deposits of zinc and lead ores in the Olkusz region in Poland. In the first stage of the research, laboratory tests were carried out on the backfilling mixture consisting of sand and water in a 1:1 volume ratio. In the laboratory tests, the content of grains below 0.1 mm, the washability, water permeability, and compressibility of the backfilling mixture were determined. After the standard requirements were met by the backfilling mixture, the arrangement of one-way and bidirectional strip excavations was designed. In the next stages, by means of computer aided-design MineScape software, maximum thicknesses of the ore-bearing dolomite layer (T21_VI) for four geological cross-sections were determined. The height of the first backfilled layer with a thickness of 5 m was analyzed. Taking into account the geometrical parameters of the strip—the maximum length and its width and height, as well as the capacity of the backfilling installation—this study calculated the backfilling times for the future strip excavations. Full article
(This article belongs to the Special Issue Mining Innovation)
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14 pages, 6646 KiB  
Article
Application of a New Semi-Automatic Algorithm for the Detection of Subsidence Areas in SAR Images on the Example of the Upper Silesian Coal Basin
by Maciej Dwornik, Justyna Bała and Anna Franczyk
Energies 2021, 14(11), 3051; https://doi.org/10.3390/en14113051 - 24 May 2021
Cited by 3 | Viewed by 1765
Abstract
The article presents a new method of automatic detection of subsidence troughs caused by underground coal mining. Land subsidence that results from mining leads to considerable damage to subsurface and surface infrastructure such as walls of buildings, road surfaces, and water relations in [...] Read more.
The article presents a new method of automatic detection of subsidence troughs caused by underground coal mining. Land subsidence that results from mining leads to considerable damage to subsurface and surface infrastructure such as walls of buildings, road surfaces, and water relations in built-up areas. Within next 30 years, all coal mines are to be closed as part of the transformation of the mining industry in Poland. However, this is not going to solve the problem of subsidence in those areas. Thus, it is necessary to detect and constantly monitor such hazards. One of the techniques used for that purpose is DInSAR (differential interferometry synthetic aperture radar). It makes it possible to monitor land deformation over large areas with high accuracy and very good spatial and temporal resolution. Subsidence, particularly related to mining, usually manifests itself in interferograms in the form of elliptical interferometric fringes. An important issue here is partial or full automation of the subsidence detection process, as manual analysis is time-consuming and unreliable. Most of the proposed trough detection methods (i.e., Hough transform, circlet transform, circular Gabor filters, template recognition) focus on the shape of the troughs. They fail, however, when the interferometric fringes do not have distinct elliptical shapes or are very noisy. The method presented in this article is based on the analysis of the variability of the phase value in a micro-area of a relatively high entropy. The algorithm was tested for differential interferograms form the Upper Silesian Coal Basin (southern Poland). Due to mining, the studied area is particularly prone to various types of subsidence. Full article
(This article belongs to the Special Issue Mining Innovation)
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22 pages, 9670 KiB  
Article
Microgravity Survey to Detect Voids and Loosening Zones in the Vicinity of the Mine Shaft
by Slawomir Porzucek and Monika Loj
Energies 2021, 14(11), 3021; https://doi.org/10.3390/en14113021 - 23 May 2021
Cited by 8 | Viewed by 2927
Abstract
In mining and post-mining areas, the assessment of the risks to the surface and its infrastructure from the opening or closed mine is of the utmost importance; particular attention should be paid to mine shafts. The risks include the occurrence of undetected voids [...] Read more.
In mining and post-mining areas, the assessment of the risks to the surface and its infrastructure from the opening or closed mine is of the utmost importance; particular attention should be paid to mine shafts. The risks include the occurrence of undetected voids or loosening zones in the rock mass. Their detection makes it possible to prevent their impact on a mine shaft and surface infrastructure. Geophysical methods, and in particular, a microgravity method lend themselves for the detection of changes in the distribution of masses (i.e., the density) due to voids and loosening zones. The paper presents the results of surface microgravity surveys in the vicinity of three mine shafts: under construction, working, and a liquidated one. Based on the gravity anomalies, the density distribution of the rock mass for all three cases was recognized. The properties of the anomalies allowed to determine which of the identified decreased density zones may pose a threat to the surface infrastructure or a mine shaft. The microgravity survey made inside the working mining shaft provided information on the density of rocks outside the shaft lining, regardless of the type of lining. No significant decrease of density was found, which means that there are no larger voids outside the shaft lining. Nevertheless, at a depth of 42 m in running sands layer, the decreasing density zone was located, which should be controlled. Additionally, measurements in two vertical profiles gave the possibility of directional tracking of density changes outside shaft lining. Such changes were observed on three boundaries of geological layers, with two of them being on the boundary of gypsum and other rocks. Full article
(This article belongs to the Special Issue Mining Innovation)
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23 pages, 36356 KiB  
Article
P-Wave-Only Inversion of Challenging Walkaway VSP Data for Detailed Estimation of Local Anisotropy and Reservoir Parameters: A Case Study of Seismic Processing in Northern Poland
by Mateusz Zaręba, Tomasz Danek and Michał Stefaniuk
Energies 2021, 14(8), 2061; https://doi.org/10.3390/en14082061 - 8 Apr 2021
Cited by 1 | Viewed by 2669
Abstract
In this paper, we present a detailed analysis of walkaway vertical seismic profiling (VSP) data, which can be used to obtain Thomsen parameters using P-wave-only inversion. Data acquisition took place in difficult field conditions, which influenced the quality of the data. Therefore, this [...] Read more.
In this paper, we present a detailed analysis of walkaway vertical seismic profiling (VSP) data, which can be used to obtain Thomsen parameters using P-wave-only inversion. Data acquisition took place in difficult field conditions, which influenced the quality of the data. Therefore, this paper also shows a seismic data processing scheme that allows the estimation of correct polarization angles despite poor input data quality. Moreover, we showed that it is possible to obtain reliable and detailed values of Thomsen’s anisotropy parameters for data that are challenging due to extremely difficult field conditions during acquisition and the presence of an overburden of salt and anhydrite (Zechstein formation). This complex is known for its strong seismic signal-attenuating properties. We designed a special processing workflow with a signal-matching procedure that allows reliable estimation of polarization angles for low-quality data. Additionally, we showed that P-wave-only inversion for the estimation of local anisotropy parameters can be used as valuable additional input for detailed interpretation of geological media, even if anisotropy is relatively low. Full article
(This article belongs to the Special Issue Mining Innovation)
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14 pages, 4667 KiB  
Article
Influence of Hydrogeological Investigation’s Accuracy on Technology of Shaft Sinking and Design of Shaft Lining—Case Study from Southern Poland
by Kajetan d’Obyrn, Paweł Kamiński and Jacek Motyka
Energies 2021, 14(8), 2050; https://doi.org/10.3390/en14082050 - 7 Apr 2021
Cited by 6 | Viewed by 2028
Abstract
Accuracy of hydrogeological and geotechnical investigation in place of shaft sinking is a key factor for selection of sinking method and design of the shaft lining. The following work presents the influence of the rising level of accuracy of geological data gathered in [...] Read more.
Accuracy of hydrogeological and geotechnical investigation in place of shaft sinking is a key factor for selection of sinking method and design of the shaft lining. The following work presents the influence of the rising level of accuracy of geological data gathered in the area of shaft sinking in the Silesian Coal Basin and technical projects of shaft lining and technology of its sinking, which have been changing over the years. The initial project of the shaft was repeatedly modified. Each modification eventuated in rising requirements for the shaft lining, such as increasing its thickness or changing concrete class. It has become necessary to use additional methods of reinforcing rock mass around the shaft. Full article
(This article belongs to the Special Issue Mining Innovation)
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17 pages, 5263 KiB  
Article
An Experimental Investigation into the Stress-Strain Characteristic under Static and Quasi-Static Loading for Partially Embedded Rock Bolts
by Krzysztof Skrzypkowski
Energies 2021, 14(5), 1483; https://doi.org/10.3390/en14051483 - 9 Mar 2021
Cited by 29 | Viewed by 2532
Abstract
This article deals with a static and quasi-static load using the maximum power of a hydraulic pump. Additionally, quasi-static coefficients for the partially embedded rock bolts were determined. The laboratory tests included 2.2 m long bolts, which were embedded segmentally on the lengths [...] Read more.
This article deals with a static and quasi-static load using the maximum power of a hydraulic pump. Additionally, quasi-static coefficients for the partially embedded rock bolts were determined. The laboratory tests included 2.2 m long bolts, which were embedded segmentally on the lengths of 0.05 m, 0.3 m and 0.9 m and were tested. To fix the ribbed bolt rods in the steel cylinders, resin cartridges with a length of 0.45 m long were used. The main aim of the research was to determine the load-displacement characteristics. Knowing the bolt rod tensile mechanism, the points of failure in the material continuity were identified, on the basis of which stress-strain characteristics are made. Particular attention was paid to the definition of: tensile stress for the yield point (σ1), maximum stress (σ2), stress at failure (σ3), strain in the elastic range (ε1), strain for maximum stress (ε2) and strain corresponding to the failure (ε3). Full article
(This article belongs to the Special Issue Mining Innovation)
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20 pages, 13031 KiB  
Article
Fault Sealing Evaluation of a Strike-Slip Fault Based on Normal Stress: A Case Study from Eastern Junggar Basin, NW China
by Jie Ji, Kongyou Wu, Yangwen Pei, Wenjian Guo, Yin Liu and Tianran Li
Energies 2021, 14(5), 1468; https://doi.org/10.3390/en14051468 - 8 Mar 2021
Cited by 5 | Viewed by 2446
Abstract
The sealing of a fault zone has been a focus for geological studies in the past decades. The majority of previous studies have focused on the extensional regimes, where the displacement pressure difference between fault rock and reservoir was used to evaluate the [...] Read more.
The sealing of a fault zone has been a focus for geological studies in the past decades. The majority of previous studies have focused on the extensional regimes, where the displacement pressure difference between fault rock and reservoir was used to evaluate the fault-sealing property from the basic principle of fault sealing. When considering the displacement pressure difference, the impact of gravity on the fault rock was considered, whereas the impact of horizontal stress was ignored. In this study, we utilize the displacement pressure difference as an index to evaluate the sealing capacity of strike-slip faults, in which both the impacts of gravity and horizontal stress on the fault rocks are all integrated. By calculating the values of σH/σV and σh/σV in the vicinity of fault planes, the coefficient K of compaction impacts on fault rocks between normal stress to fault planes and gravity was then determined. By revealing the quantitative relationship between the displacement pressure of rocks, burial depth and clay content, the displacement pressure difference between fault rocks and reservoirs were calculated. The results suggest that the sealing capacity of a strike-slip fault is not only related to the magnitude of normal stress to the fault plane, but also to the stress regime. The clay content is also an important factor controlling the sealing capacity of strike-slip faults. Full article
(This article belongs to the Special Issue Mining Innovation)
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18 pages, 6065 KiB  
Article
Experimental Study on Shear Mechanism of Rock-Like Material Containing a Single Non-Persistent Rough Joint
by Sayedalireza Fereshtenejad, Jineon Kim and Jae-Joon Song
Energies 2021, 14(4), 987; https://doi.org/10.3390/en14040987 - 13 Feb 2021
Cited by 1 | Viewed by 2845
Abstract
The geometrical and mechanical properties of non-persistent joints as well as the mechanical behavior of intact rock (rock bridges) are significantly effective in the shear strength of weakness planes containing non-persistent joints. Therefore, comprehensive knowledge of the shear mechanism of both joints and [...] Read more.
The geometrical and mechanical properties of non-persistent joints as well as the mechanical behavior of intact rock (rock bridges) are significantly effective in the shear strength of weakness planes containing non-persistent joints. Therefore, comprehensive knowledge of the shear mechanism of both joints and rock bridges is required to assess the shear strength of the planes. In this study, the shear behavior of specimens containing a single non-persistent rough joint is investigated. A novel procedure was used to prepare cast specimens embedding a non-persistent (disc-shaped) rough joint using 3D printing and casting technology, and the shear strength of the specimens was examined through an extensive direct shear testing program under constant normal load (CNL) condition. Three levels for three different variables of the joint roughness, rock bridge ratio, and normal stress were considered, and the effects of these factors on the shear behavior of prepared samples were tested. The experimental results show a clear influence of the three variables on the shear strength of the specimens. The results show that the normal stress applied to the jointed zone of weakness planes is considerable, and thus joint friction contribution should be taken into account during shear strength evaluation. Furthermore, the dilation mechanism of the specimens before and after failure was investigated through a digital image correlation analysis. Finally, a camcorder was used to analyze the location and sequence of the initiated cracks. Full article
(This article belongs to the Special Issue Mining Innovation)
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24 pages, 2498 KiB  
Article
Estimation of Damage Induced by Single-Hole Rock Blasting: A Review on Analytical, Numerical, and Experimental Solutions
by Mahdi Shadabfar, Cagri Gokdemir, Mingliang Zhou, Hadi Kordestani and Edmond V. Muho
Energies 2021, 14(1), 29; https://doi.org/10.3390/en14010029 - 23 Dec 2020
Cited by 25 | Viewed by 5165
Abstract
This paper presents a review of the existing models for the estimation of explosion-induced crushed and cracked zones. The control of these zones is of utmost importance in the rock explosion design, since it aims at optimizing the fragmentation and, as a result, [...] Read more.
This paper presents a review of the existing models for the estimation of explosion-induced crushed and cracked zones. The control of these zones is of utmost importance in the rock explosion design, since it aims at optimizing the fragmentation and, as a result, minimizing the fine grain production and recovery cycle. Moreover, this optimization can reduce the damage beyond the set border and align the excavation plan with the geometric design. The models are categorized into three groups based on the approach, i.e., analytical, numerical, and experimental approaches, and for each group, the relevant studies are classified and presented in a comprehensive manner. More specifically, in the analytical methods, the assumptions and results are described and discussed in order to provide a useful reference to judge the applicability of each model. Considering the numerical models, all commonly-used algorithms along with the simulation details and the influential parameters are reported and discussed. Finally, considering the experimental models, the emphasis is given here on presenting the most practical and widely employed laboratory models. The empirical equations derived from the models and their applications are examined in detail. In the Discussion section, the most common methods are selected and used to estimate the damage size of 13 case study problems. The results are then utilized to compare the accuracy and applicability of each selected method. Furthermore, the probabilistic analysis of the explosion-induced failure is reviewed using several structural reliability models. The selection, classification, and discussion of the models presented in this paper can be used as a reference in real engineering projects. Full article
(This article belongs to the Special Issue Mining Innovation)
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17 pages, 8191 KiB  
Article
Failure Analysis of a Pre-Excavation Double Equipment Withdrawal Channel and Its Control Techniques
by Chen Li, Xiaofei Guo, Xiaoyong Lian and Nianjie Ma
Energies 2020, 13(23), 6368; https://doi.org/10.3390/en13236368 - 2 Dec 2020
Cited by 13 | Viewed by 1981
Abstract
The use of pre-excavation equipment withdrawal channels (EWCs) at the stop-production line is important for the rapid withdrawal of coal mining equipment. However, during the final mining period, the dynamic pressure of a pre-excavated double EWC is severe, which leads to instability of [...] Read more.
The use of pre-excavation equipment withdrawal channels (EWCs) at the stop-production line is important for the rapid withdrawal of coal mining equipment. However, during the final mining period, the dynamic pressure of a pre-excavated double EWC is severe, which leads to instability of the surrounding rock around the EWCs. Therefore, in this paper, the methods of field monitoring, theoretical analysis, and numerical simulation were used to systematically study the stress and plastic zone evolution of a double EWC during the final mining period. Firstly, the distribution characteristics of mining abutment pressure and roadway failure modes under the action of mining abutment pressure were analyzed theoretically. Afterward, a FLAC3D mining numerical model was established according to the distribution of rock strata obtained from roof detection. Finally, the evolution laws of the stress fields and plastic zones of the EWCs during final mining were obtained by numerical simulation. The present study suggests that asymmetric stress distribution dominates asymmetric failure of the surrounding rock around the EWCs during the final mining period, and deformation failure within 10 m from the working face to the main EWC (MEWC) accounted for most of the roadway deformation. Based on the research results combined with actual production experience, the stability control technique of the surrounding rock with reinforcement of anchor cables and double-row buttress hydraulic support for the MEWC was put forward. After the field application, the ideal result was obtained. Full article
(This article belongs to the Special Issue Mining Innovation)
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