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Abrasiveness as an intrinsic property of rocks defines the extent of wear or loss when interacting with other materials. In engineering sectors like hard rock mining and tunnelling, comprehending rock abrasiveness holds paramount importance due to its direct effect on tool wear during excavation. Among the diverse methods for assessing rock abrasiveness, the Cerchar abrasivity test emerges as the most widely used approach. Over time, the Cerchar test has garnered substantial attention from scholars, who have delved into the factors influencing test results due to testing conditions and examined the connection between the physical-mechanical parameters of rocks and their abrasiveness. Recent advancements in testing instrument have expanded our ability to measure additional parameters during rock cutting or drilling, yielding fresh insights for abrasiveness assessment, tool wear prediction, tool performance evaluation and rock excavatability estimation. The Cerchar abrasivity test, coupled with recent developments in testing instrument and parameter measurement, holds promising potential for enhancing our comprehension of rock abrasiveness and its practical implications. This review systematically traces the evolution of the test. It commences with an overview of the test origin and progression, emphasizing its pivotal role in assessing rock abrasiveness. Furthermore, it consolidates and categorizes the research contributions from various scholars regarding the test. This includes enhancements and refinements of the testing apparatus, as well as investigations into various testing orientations and their effects on different types of rocks. Moreover, this review illuminates the broader applications and interdisciplinary possibilities of this test, not only in material science but also in tribology. It underscores how the insights gleaned from the Cerchar test can be extrapolated to diverse areas of research beyond the scope of rock engineering. Article Highlights: A comprehensive review on the Cerchar abrasivity test was performed Testing condition-based factors affecting the Cerchar values were studied Correlations of abrasive with physical-mechanical-mineralogical-petrographical properties of rocks were investigated Applications of Cerchar test in material science, tribology and rock engineering were discussed [ABSTRACT FROM AUTHOR]

The rapid increase in lithium demand has recently drawn attention to the environmental impacts of conventional mining processes. Pyrometallurgical extraction from hard rock is associated with high energy consumption, greenhouse gas (GHG) emissions, and land degradation. Extraction from brines involves the depletion of water resources and risks to local ecosystems. In response to these environmental challenges, this study explores innovative pathways for more sustainable primary lithium extraction for a truly green energy transition across the entire supply chain. This paper provides a comprehensive examination of novel technologies designed to mitigate these impacts, with particular emphasis on direct lithium extraction (DLE) technologies, which offer promising solutions for water savings, CO2e emissions reduction, and improved lithium recovery. A comprehensive review of the scientific literature, along with an analysis of data and information from various pilot projects and demonstration plants, have been conducted. The main conclusion is that, despite considerable efforts by mining companies, two primary obstacles remain to the implementation of novel technology: scalability and operational costs. To address these challenges, it is essential to sustain consistent investments in R&D (Research and Development) initiatives and continue testing the implementation of the most sustainable experimental practices on an industrial scale. [ABSTRACT FROM AUTHOR]

Three hundred and twenty-four data points on the saturated hydraulic conductivity (k) of various hard rock mine tailings are collected from previous publications. The applicability of existing empirical equations for hard rock mine tailings is assessed based on this database collected. Results show that with a greater exponent of d10, the correlation between the measured and predicted k is greatly improved. An empirically modified version of the Kozeny–Carman equation is then proposed for predicting the saturated k of tailings and compared with the database. The proposed equation gives the best fit with a varying exponent greater than 2 for d10. Finally, the impact of particle shape on k is discussed. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article delves into the debates, both in print and digital media, surrounding copper mining and its associated concerns, particularly those related to hardrock mining. Guided by agenda-building, pragma-dialectics, and stakeholder theories, this research employs topic modeling to scrutinize the media strategies and arguments employed by key stakeholders involved in an environmental movement. The aim is to unveil implicit communication activities that contribute to the emergence of public debates, shedding light on the nuanced dynamics within stakeholder discourses. The analysis shows that by referring to authoritative arguments, the local press distributes the places of power while representing conflicting standpoints and arguments. With digital media, the opponents build a pro-environmentalist network to publicize the issues relative to the mining project and the importance of defending southwestern habitats and landscape. Mining proponents similarly rely on business communities to underscore the importance of hardrock mining for things like decarbonized energy and modern living. Across groups, stakeholder communication situates differing conceptions of the relationship between humans and their natural environment. Our findings reveal that, consistently across various groups, the discourse maintains a degree of stability as topics and arguments persist over time. On one side, discussions highlight the destructive impacts of mining, while the opposing perspective underscores the significance of sustainable and resilient mining practices. This analysis of stakeholder discourses in the media helps uncover the various ways primary actors maintain their positionality and power in this particular case. [ABSTRACT FROM AUTHOR]

The article discusses the potential for decarbonization in the global steel industry through the use of green steel technologies. It highlights the energy-intensive steps involved in steel production and the various technologies, such as blast furnaces and electric smelting furnaces, that can help reduce carbon emissions. The text emphasizes the importance of integrating decarbonization efforts from mining to steel production and explores innovative technologies like carbon capture and storage, hydrogen injection, and the use of low-carbon energy sources. Additionally, it addresses the need for increased energy efficiency, waste reduction, and technological innovation in the steel industry to achieve low-carbon steel production. [Extracted from the article]

Introduction: The research concerns how making cut cavities improves drilling and blasting operations as well as the optimum parameters to arrange both snubber and auxiliary blastholes. Methods: The research methods include experimental and industrial activities to identify the optimum depth of the first-section snubber blastholes relative to the second-section blastholes. It also identifies optimum parameters of the snubber blastholes while driving mine workings and ore breaking in stopes with different mine working sections and different rock mass strengths broken using the technique of cut-cavity formation. Results and Discussion: Experimental explosions executed in a production environment have proved the efficiency of the proposed technique of sectional formation of a cut cavity, which helped increase the blasthole use coefficient (BUC) from 0.88 to 0.97. The depth of the first-section boreholes should be determined relative to the length of the second-section boreholes and the broken rock mass strength. The higher the strength of the broken formation, the larger the ratio between the first and the second-section blasthole lengths should be. The results of the experimental explosions indicate that the depth of first-section snubber blastholes varies from 0.5 and more of the second-section boreholes, depending upon the depth of the latter and the broken rock mass strength. If the strength of the broken rock mass is 12 on the Protodyakonov scale, and the second-section blasthole depth increases from 1.6 m to 2.6 m, then the depth of the second-section boreholes should be increased from 0.9 m to 1.54 m so as to be 0.55-0.56 of the second section blasthole length. If the strength of the broken rock mass is 18, and the length of the second section increases from 1.8 m to 2.82 m, then the first-section length varies from 0.9 m to 1.75 m, being 0.5-0.62 of the second section blasthole length. Applying the novel proposed procedure for a cut-cavity formation will increase the blasthole use coefficient and reduce the cost of drilling and blasting operations. Moreover, the procedure may also be practical for driving underground mine workings and for ore breaking within stopes. [ABSTRACT FROM AUTHOR]

Pillar stability is of paramount importance in ensuring the safety of underground rock engineering structures. The stability of pillars directly influences the structural integrity of the mine and mitigates the risk of collapses or accidents. Therefore, assessing pillar stability is crucial for safe, productive, reliable, and profitable underground mining engineering processes. This study developed the application of decision intelligence-based predictive modelling of hard rock pillar stability in underground engineering structures using K-Nearest Neighbour coupled with the grey wolf optimization algorithm (KNN-GWO). Initially, a substantial dataset consisting of 236 different pillar cases was collected from seven underground hard rock mining engineering projects. This dataset was gathered by considering five significant input variables, namely pillar width, pillar height, pillar width/height ratio, uniaxial compressive strength, and average pillar stress. Secondly, the original hard rock pillar stability level has been classified into three types: failed, unstable, and stable, based on the pillar's instability mechanism and failure process. Thirdly, several visual relationships were established in order to ascertain the correlation between input variables and the corresponding pillar stability level. Fourthly, the entire pillar database was randomly divided into a training dataset and testing dataset with a 70:30 sampling method. Moreover, the (KNN-GWO) model was developed to predict the stability of pillars in hard rock mining. Lastly, the performance of the suggested predictive model was evaluated using accuracy, precision, recall, F1-score, and a confusion matrix. The findings of the proposed model offer a superior benchmark for accurately predicting the stability of hard rock pillars. Therefore, it is recommended to employ decision intelligence models in mining engineering in order to effectively prioritise safety measures and improve the efficiency of operational processes, risk management, and decision-making related to underground engineering structures. [ABSTRACT FROM AUTHOR]

To investigate the influence of non-singular terms (T stress) in the stress field on the composite fractures of hard rock Type I–II, such as rock splitting failure and hydraulic fracture propagation, this study focused on hard rocks in metallic mines. Through splitting tests and hydraulic fracturing experiments, the impact of T stress on the characteristics of Type I–II composite fractures in hard rocks was analyzed. Utilizing the generalized maximum tangential (GMTS) stress criterion considering T stress, the stress intensity factors of hard rock Type I–II composite fractures with different pre-existing crack angles were predicted. The critical fracture pressure expression for hard rocks was derived based on the maximum tangential stress (MTS) criterion. The results indicate that the GMTS criterion, considering T stress, is more suitable for describing the characteristics of Type I–II composite fractures under rock-splitting loads. However, under hydraulic fracturing, T stress has a minor influence on the fracture characteristics of hard rock hydraulic fractures. Therefore, when predicting the critical fracture pressure of hydraulic fractures, T stress can be disregarded. This study provides a scientific basis and guidance for hard rock hydraulic fracturing engineering. [ABSTRACT FROM AUTHOR]

Introduction: Cavability issues often arise in hard rock mines employing the block caving mining method. Hydraulic fracturing stands out as a promising preconditioning technology for hard rock masses, with its pre-conditioning effects dependent on variable parameters. Methods: The impact of cluster number, injection rate, and liquid volume on fracture propagation was investigated through on-site hydraulic fracturing practices. Fracturability was initially verified via true triaxial fracturing tests, and preconditioning parameters were subsequently optimized using numerical simulations. The optimized on-site construction was monitored using electromagnetic methods. Results: The study revealed a negative correlation between fracture radius and the number of clusters, gradually decreasing with an increase in cluster number. However, the fracture weakening area increased with the rise in the number of clusters. The fracture weakening area also increased with the injection rate. Additionally, the fracture radius initially increased and then decreased. Both fracture weakening area and radius increased with an increase in liquid volume. The optimized parameters were identified as four clusters, an injection rate of 4 m3/min, and a liquid volume of 500 m3. Discussion: Building upon these findings, on-site experiments were conducted and monitored using electromagnetic methods. The monitored results demonstrated that the optimized parameters effectively achieved hydraulic fracturing expansion, accomplishing the goal of weakening hard rock. [ABSTRACT FROM AUTHOR]

Numerical modelling is an important instrument for rock engineering; it can assist in the design and prediction of failure in rock masses. Dependable results can be obtained from the models if, and only if, the underlying assumptions, strengths, and weaknesses of the model are known. A set of guidelines to implement a numerical modelling program can also be used to obtain high-quality and reliable results. The importance of a well-structured numerical modelling program to attain practically reasonable results cannot be overstated. This paper presents an analysis of the results of modelling a rock engineering problem involving deep mining excavations prone to high-stress challenges. The study used Lamodel and Examine 2D. The results obtained show that the two software programs can be used together to complement each other in attaining a deeper understanding of the influence of high stresses on mining excavations at depth. Lamodel and Examine 2D are both boundary element code-based software and are quick and easy to use. More advanced numerical modelling tools could be used, but these two were found to be suitable for the problem at hand. Many diagrams and results can be obtained from the numerical modelling of any rock engineering challenge; in this paper, only those diagrams and results deemed to be most relevant and appropriate to demonstrate the capabilities, limitations, and validity of the numerical modelling of the problem have been presented. [ABSTRACT FROM AUTHOR]

Declines and extirpations of American pika (Ochotona princeps) populations at historically occupied sites started being documented in the literature during the early 2000s. Commensurate with global climate change, many of these losses at peripheral and lower elevation sites have been associated with changes in ambient air temperature and precipitation regimes. Here, we report on a decline in available genetic resources for an iconic American pika metapopulation, located at the southwestern edge of the species distribution in the Bodie Hills of eastern California, USA. Composed of highly fragmented habitat created by hard rock mining, the ore dumps at this site were likely colonized by pikas around the end of the 19th century from nearby natural talus outcrops. Genetic data extracted from both contemporary samples and archived natural history collections allowed us to track population and patch-level genetic diversity for Bodie pikas across three distinct sampling points during the last half-century (1948-1949, 1988-1991, 2013-2015). Reductions in within-population allelic diversity and expected heterozygosity were observed across the full time period. More extensive sampling of extant patches during the 1988-1991 and 2013-2015 periods revealed an increase in population structure and a reduction in effective population size. Furthermore, census records from the last 51 years as well as archived museum samples collected in 1947 from a nearby pika population in the Wassuk range (Nevada, USA) provide further support of the increasing isolation and genetic coalescence occurring in this region. This study highlights the importance of museum samples and long-term monitoring in contextualizing our understanding of population viability. [ABSTRACT FROM AUTHOR]

The dominant technology in hard rock mining is drilling and blasting; therefore, the importance of fragment size estimation is an essential problem in the mining industry. By using a theoretical foundation that explains rock-fracturing mechanisms by blasting, a 3D fragmentation model with general applicability was developed. The main capabilities of the model are the ability to consider different and complex blasting patterns, both with parallel and non-parallel boreholes, and different explosive and rock properties. The geological input of the model is defined by generating the primary blocks within rock mass using discrete fracture networks. The model handles different, complex geological setups and blasting scenarios that include bench, ring, and tunneling blasting. Also, it considers borehole deviation, misfires, and the influence of previous blasts. Full-scale ring blasts were carried out to validate the model against real-world data, and the results showed a high level of agreement between model predictions and in situ data. In situ data were collected using image processing methodology and WipFrag v4 software. X50 and X80 size values showed a maximum error in prediction of around 15%, while R2 values between fragmentation curves were approximately 90% without a detailed model calibration to the obtained data. [ABSTRACT FROM AUTHOR]

Rock blasting with explosives is the first stage of rock fragmentation and plays a key role in the results of the mining chain. Fragmentation optimization is achieved by considering the energy efficiency of the explosive, the optimal distribution of explosive energy in the rocky mass, and the programmed and controlled release of explosive energy during blasting. The quality of fragmentation is usually performed using tools that estimate the sizes of fragments via the analysis of two- or three-dimensional images. This article presents a study of the rock fragmentation optimization of very compact itabirites, based on four blasting tests, performed in a different way from the conventional blasting design. The fragmentation analysis was performed using the P o r t a M e t r i c s T M tool, and compared with the Kuznetsov and Rosin–Rammler particle size distribution model, to compare the reliability of this tool. Finally, the mine productivity after blasting was estimated from the particle size distribution obtained in the tests. The model presented idealistic results considering the technical parameters used in the equations. However, the P o r t a M e t r i c s T M tool suggests good performance for the preliminary evaluation of blast design. [ABSTRACT FROM AUTHOR]

10.3390/en14165005 23 Wu J., Fu Q., Zhang J., Sun B. A Fast Calculation Method for Improving the Steering Arm of Mining Trucks with Macpherson Suspension. The study area is made up of thick quaternary alluvium deposited on top of older basement rock, and previous studies, including drilling and geo-electrical resistivity surveys, have been conducted in the area, but none of them managed to conclusively precisely determine the basement rock type and depth. Pilecka et al. [[4]] investigated the impact of high energy mining-induced tremors on building damage in the Upper Silesian Coal Basin (USCB), Poland, by analyzing one of the highest energy tremors (E = 4.0 × 10 SP 8 sp J). Mining is an essential sector for economic development, as it provides valuable resources that are crucial for modern living. [Extracted from the article]

Rockbursts occur as a direct consequence of underground mining or civil excavation. The general scale of their seismic disturbance and consequences depend upon known factors. However, uncertainty remains as to exactly when and where rockbursts will occur, as well as the effectiveness of ground support measures to fully mitigate their consequences. While the uncertainty in when and where is a dilemma shared with earthquake prediction, that associated with ground support capability is both a design and a management concern. Following a brief review of the known mechanisms that produce rockbursts, the paper explores the sources and scales of energy demands that characterize the risk of their damaging consequences upon underground excavations. We note that some of this risk continues to be associated with uncertainty with respect to rockmass properties and in situ stress, particularly in the context of deep mining. A review is presented of all available yielding ground support systems and their necessary design requirements, identifying practical weaknesses and limitations where these are known. The paper concludes with some suggested areas where further study and development could provide the ways and means to reduce the design uncertainty in managing rockbursts. [ABSTRACT FROM AUTHOR]

With the increase in mining depth and the deterioration of mining conditions, thick and hard overburden movement frequently induces mine earthquakes and rock bursts. Some mines are expected to prevent and control super thick hard rock mine earthquakes through vertical ground well water fracturing technology. However, the dynamic underground disaster appears more intense. Taking the '11.30' mine earthquake in a mine in Shandong Province as the engineering background, the dynamic disaster mechanism of an extraordinarily thick and hard roof induced by hydraulic fracturing of vertical wells on the ground was studied utilizing field investigation, accident case analysis, similar material simulation test, and theoretical analysis. The main conclusions are as follows: (1) After hydraulic fracturing vertical wells on the ground, the movement mode of thick and hard roofs changed from layer-by-layer to overall sliding movement; (2) The influence range of the advanced abutment pressure of the working face is reduced by the hydraulic fracturing of the vertical shaft, and the peak value of the advanced abutment pressure increases. Furthermore, the advanced abutment pressure's peak is far from the coal wall; (3) The hydraulic fracturing technology of cross-arranged vertical surface deep and shallow wells and the hydraulic fracturing technology of cross-perforated surface multi-branch horizontal wells are proposed to avoid the dynamic disaster of overall sliding movement of an extremely thick hard roof induced by surface hydraulic fracturing. Therefore, these research results provide significance for preventing and controlling mine earthquakes and rock bursts in super thick hard roof mines. [ABSTRACT FROM AUTHOR]

The blasting operation considerably influences the overall productivity of opencast mines, especially when blasting results in oversized fragments that impact the operations ranging from excavation to milling. In this work, a numerical analysis of blasting performance was implemented to optimize the blasting parameters and improve the fragmentation of the hard rock in a copper open pit mine site in Brazil. In this paper, the methodology comprised data collection, 3D numerical model construction for blasting optimization using Blo-Up software, calibration with historical data, and predictive analysis, including testing two different blast designs. With the objective of achieving a desired P80 size of the blasting fragmentation, the results indicate an optimized calibrated model with an overall error equal to 4.0% using a Swebrec distribution fitted to the model data. The optimal P80 size of the resulting muckpile was equivalent to ~0.53 m for the hard rock copper fragments, which was close to the desired P80 size. [ABSTRACT FROM AUTHOR]

The use of post-mining wastes in the reclamation of an open pit may act as a source of pollution that has a very strong impact on the groundwater environment. One such facility in Poland is the CTL Maczki-Bór S.A. sand mine filled with waste rock from hard coal mines. The current hydrodynamic conditions in the Quaternary aquifer causes that the wastes are in the bottom part of the open pit under the constant influence of groundwater. Due to the sub-level nature of the pollution source, the author of the study modified the classic rank-weight method of assessing the groundwater vulnerability to pollution in order to adapt it to the atypical type of the pollutant emitter. An individual approach was proposed by modifying the range of parameters as well as the assigned ranks and weights. Six key parameters were indicated, i.e. the thickness of the aeration zone, the thickness of the saturation zone, the filtration coefficients of the deposits in both of these zones, the recharge of the aquifer and the surface topography. The correctness of weight selection was verified by sensitivity analysis in the sensitivity variant of one parameter. It has been proposed to classify the groundwater vulnerability to 5 classes from moderately high to extremely high. For theoretical and effective weights, the obtained values of the index of groundwater vulnerability to pollution allowed to divide the area of the reclaimed open pit into two zones with high and very high groundwater vulnerability to pollution. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In underground mines, stability problems can cause unplanned dilution, increasing the costs of mining operations, such as loading, transport, crushing and grinding. This is usually dealt with by simply increasing investments with support. However, the design geometry of stopes and drifts also has a great effect on a stope's stability. The use of empirical stability methods is a very common practice, however because of their few input parameters, it cannot predict the actual performance related to each stope and drift design. This study has as main goals a back analysis of the actual dilution, using the Equivalent Linear Overbreak Slough (ELOS) method and analysis in the drift developments at the hanging wall contact, using numerical models. The case study is an underground hard rock gold mine, with a pillar-less Transversal Stope method. The hanging wall failure was quantified using a database from 19 stopes measured by the Cavity Monitoring System (CMS). Numerical finite elements models (FEM) were used, and 5 primary stopes were selected to calibrate models. The volumes of actual dilution showed a good correlation with the volumes of the relaxation zones produced by the models. Then, new optimized drift geometry layouts at the hanging wall contact were proposed, showing a decrease in 2.35 times in the relaxation zone of the numerical models, therefore justifying the use of these models as a dilution optimization tool. This methodology also proved to be useful in the definition of cable bolt length. [ABSTRACT FROM AUTHOR]

Underground mining operations are a very problematic task, especially in poor geotechnical conditions. The right choice of excavation and support techniques leads to adequate and secure mining operations. This should ensure the overall stability of the underground mine with the best productivity and stability performance. In this paper, an empirical model for obtaining support systems for underground galleries was applied. Then, a numerical model for the evaluation of the performance of support measures for rock masses in the Boukhadra iron mine was introduced. Extensive field and laboratory tests were performed to obtain geological, geotechnical, and mechanical data on the entire geologic formations of the (1105 m) level. The performance of the design is supported by the selection of a common support plan between RMR, Q, and UBC systems for each geotechnical unit. Therefore, the rock masses classification based on the geo-mechanical model has determined the suitable support systems. The finite element model (FEM) was used for the analysis of rock mass behaviour, displacements, stress, and plastic point distribution. The results permit the optimization of the plastic zone thickness around the gallery. The outcomes of this study could improve the stability of the mine by choosing the right direction of excavation in consideration to the direction of the discontinuity planes. In order to choose between the current and the recommended mining operations, an equivalent calculation sequence was verified. Our study demonstrated that the consideration of discontinuity sets in the orientation of excavation highly improves the mining conditions with or without support. [ABSTRACT FROM AUTHOR]

Considering the low efficiency of cutting blasting in hard rock mine tunnels, a novel solution of increasing the charge diameter of the cutting holes was put forward. To investigate the influence of the charge diameter on the cutting blasting results, three different working conditions of Φ 32 mm, Φ 42 mm, and Φ 50 mm blasting holes combined with Φ 27 mm, Φ 35 mm, and Φ 45 mm cartridges, respectively, were taken as the investigation objects. At first, the theoretical destruction ranges of single cutting holes under the three different charge diameters were computed. The computed results showed that the destruction range of the cutting holes could be expanded by increasing the charge diameter, which would be beneficial to the destruction of the rock far away from the cutting holes in the cutting cavity. Subsequently, numerical simulations of cutting blasting under the three different charge diameters were performed to display the dynamic propagation process of the blasting stress wave. Importantly, the stress field intensity in the cutting cavity was enhanced significantly with the charge diameter. The stronger stress field intensities generated by the larger diameter charges were more conducive to breaking the rock in the cutting cavity into small fragments that were easy to be discarded. Ultimately, a hard rock vertical slope was used instead of the driving face to carry out the cutting blasting experiments, and the hole utilizations of the cutting blasting were 70.4%, 82.0%, and 94.0%, respectively, under the three different charge diameters, from small to large. The experimental results forcefully substantiated that a higher cutting blasting efficiency could be achieved by increasing the charge diameter of cutting holes in hard rock mine tunnels. [ABSTRACT FROM AUTHOR]

Rock bursts are often encountered in coal mines worldwide. (10) Li, L. et al., Study on Overburden Movement and Fissure Evolution Law of Protective Layer Mining in Shallow Coal Seam [[10]]. 10.3390/en15051803 10 Li L., Wu G., Liu Q. Study on Overburden Movement and Fissure Evolution Law of Protective Layer Mining in Shallow Coal Seam. 10.3390/en14164832 3 Xiong Y., Kong D., Cheng Z., Wen Z., Ma Z., Wu G., Liu Y. Instability control of roadway surrounding rock in close-distance coal seam groups under repeated mining. [Extracted from the article]

In this study hardfacing by flux-cored arc welding with Fe-Mo-Mn-B-C-based alloy as an alternative technique for improving wear resistance of mining machines conical picks was investigated. The microstructure of hardfaced layer consists of the uniformly distributed faceted grains of binary (Fe,Mn)Mo2B2 boride phase with average size of 25 μm and austenite-based eutectic. The hardness measured by microindentation and microscratching techniques across the interfaces between deposited layer and base steel was within 2.2 -- 18 GPa. No welding defects such as cracks, pores or non-metal inclusions in the hardfaced layer and heat affected zones were detected. Comparative studies of the developed hardfacing alloy with commercially available Capilla HR MAG hardfacing and heat treated 35HGS steel were carried out using testing machine developed at the department of machinery engineering and transport of AGH university of science and technology for semi-industrial wear tests of mining machines conical picks. Wear measurement results show that using hardfacing with proposed alloy of Fe-Mo-Mn-B-C system leads to decreasing of impact-abrasion wear rate in approximately 3 times than that for tested commercial materials. This allows to recommend hardfacing by FCAW with proposed material in form of flux-cored wire for conical picks insert holders' surfaces during mining of hard rocks. [ABSTRACT FROM AUTHOR]

In Canada, many mines have adopted the sublevel stoping method, such a blasthole stoping (BHS), to extract steeply deposited minerals. Sill pillars are usually kept in place in this mining method to support the weight of the overburden in underground mining. To prolong the mine's life, sill pillars will be recovered, and sill pillar recovery could cause failures, fatality, and equipment loss in the stopes. In this paper, three sill pillar recovery schemes—SBS, SS1, and SS2—were proposed and conducted to assess the feasibility of recovering two sill pillars in a hard rock mine by developing a full-sized three-dimensional (3D) analysis model employing the finite element method (FEM). The numerical model was calibrated by comparing the model computed ground settlement with the in situ monitored ground settlement data. The rockburst tendency of the stope accesses caused by the sill pillar recovery was assessed by employing the tangential stress (Ts) criterion and burst potential index (BPI) criterion. All three proposed sill pillar recovery schemes were feasible and safe to recover the sill pillars in this hard rock mine, and the scheme SBS was the optimum one among the three schemes. [ABSTRACT FROM AUTHOR]

In case of extra-thick Carboniferous coal seam mining, the hard rock strata of 50-100 m existing above the coal seam roof in upper layer, simple roof caving controlling technology can hardly achieve the engineering needs. To solve the strong abutment pressure in mining induced by multiple hard rocks overlying strata in coal mine, the structure and lithology of the overbeding hard rock strata were explored. Based on the engineering background of fully mechanized caving coal mine in Datong coalfield of China, a technical scheme of strata control of multiple hard roof fracturing was formulated. A ground and underground combined hydraulic fracturing technology was carried out. Results show that the deformational behavior of lower strata is closely related to the movements of the upper hard rock strata. The development and expansion of the cracks within upper hard rock strata is the dominant factor to the abutment pressure of the working face according to microseismic monitoring data. The working resistance of the hydraulic supports, deformation of the roadway and the pressure of the advanced support in tailgate were used to verify the effectiveness of the proposed controlling technology. The conclusions obtained in this study provide a novel method for the joint control of the multilayer of rigid roof and provides a means of precise control of hard rock strata. [ABSTRACT FROM AUTHOR]

The demand for minerals has never been so high and is expected to increase in the coming decades. Karlsson et al. adapted the commonly used hydrogen peroxide-ammonium citrate extraction method from ore exploration practices to the characterization of mine waste rocks, and demonstrated that it can be efficient in the evaluation of the risks of sulphide-related element mobilities from waste rock material during the preliminary phase of a mining project [[11]]. 10.3390/min11050495 11 Karlsson T., Räisänen M., Myöhänen T., Alakangas L., Lehtonen M., Kauppila P. Hydrogen Peroxide Ammonium Citrate Extraction: Mineral Decomposition and Preliminary Waste Rock Characterization. [Extracted from the article]

In this study, based on the example of the ground vibration damage response of a thick and hard rock layer fracture type mine quake, and by applying the theories of mine pressure, rock mechanics and vibration energy principle, the concept of "vibration damage boundary" of mine quake ground, which uses particle vibration velocity to evaluate the vibration damage, is proposed. In addition, the quantitative prediction method of the ground vibration damage boundary is preliminarily established. The research results reveal that the elastic deformation of the fixed support end of the thick and hard rock layer structure in the stope is the main energy source for the formation of mine quakes, and that the particle vibration velocity caused by the propagation of focal energy to the ground can reasonably reflect the response degree of vibration damage. The proposed prediction method considers the "instantaneous" motion characteristics of mining thick and hard rock layer and the dynamic load effect of "mine quakes." The method can deepen our understanding of mining ground damage prediction, and increase the reliability of ground damage boundary prediction. Finally, the results are used to predict the ground vibration damage boundary of limestone primary fracture in the longwall 16101 face of the Fuping Coal Mine. [ABSTRACT FROM AUTHOR]

A methodology using three-dimensional elasto-plastic analysis has been formulated to assess the required strength parameters for a stable backfill wall for various dimensions of a stope. The numerical modelling results show linearly increasing trend for the required backfill cohesion with respect to stope height for longer stopes and curvilinear with flattening trend for shorter stopes. Comparison of the numerical modelling results with those of a popular theoretical equation shows that the theoretical equation fails to represent the interface friction and tension. The numerical modelling methodology is a better tool which can capture a gamut of aspects. The developed methodology has been used to estimate the required pastefill strength and binder percentage for a hard rock mine in North India, where it has been successfully implemented in over 50 stopes without any significant case of backfill failure. [ABSTRACT FROM AUTHOR]

Fires in underground mines may pose a challenge to fire and rescue personnel where the complex environment and multiple influences of a fire are poorly considered during pre-incident planning. A better knowledge of pre-incident planning in underground mines would improve the safety of personnel. This study on pre-incident planning in underground mines applied data from experiments, inventories and design fire studies. A number of questions were considered related to information sources, fire modelling, capturing complexity and using fire scenarios. When performing fire modelling, empirical models could be used to complement other modelling tools. The study found that for modelling of spatially extensive mine sections, the use of ventilation network-based mine fire simulations could be a better option. Using an analytical toolbox, an iterative testing of plans and an ongoing planning process, the pre-planning challenges for a mine can be mitigated. The purpose of this study was to examine existing pre-incident planning and propose information sources, tools and specific actions for future plans. [ABSTRACT FROM AUTHOR]

The selection of mining equipment is one of the most important parts for decision-makers, which can affect the mine and the entire planning. Underground mines are usually divided into two categories; hard rock and soft rock, each of which has its equipment according to the type of exploitation method used. There are different ways to make decisions and choose mining equipment. One of the practical approaches can be the use of the Multi-Criteria-Decision-Making models (MCDM). The main aim of this research is to develop a decision support system based on MCDM methods and use FUZZY logic to resolve uncertainties in the Underground-Hard Rock Mining Equipment Selection (U-HRMES). In this paper, the U-HRMES model has been used in Anguran underground lead and zinc mine as a case study. At present, the drilling and loading-hauling equipment of the Angoran mine does not perform properly. Therefore, to improve the performance and speed up the mining operation, it was tried to suggest suitable equipment using the U-HRMES. For this purpose, effective criteria were obtained based on a literature review, and according to the conditions of the Anguran underground lead and zinc mine, these criteria were filtered, and then, Twenty-two subcriteria with four groups of main criteria; technical specifications of the machine, economic and environmental issues, stope conditions and finally management and operational issues were obtained. It should be noted that the types of preference functions in the selection process of underground hard rock mining equipment were determined based on expert groups. Using the U-HRMES, two series of decisions were evaluated for the options of drilling equipment and loading and hauling equipment for the Anguran underground stopes. Finally, single-arm drilling with a score of 0.870 was chosen as the appropriate choice for drilling equipment, and LHD WX04 with a score of 0.252 was selected for loading and hauling equipment. Also, by analyzing the sensibility of the model results based on the change of criteria weights from ±10 % to ±20 %, there was no change in the results. The observations were that the drilling equipment selection has more sensitivity and reaction to changes in weight of the stope conditions. At the same time, the loading and transport equipment selection has this reaction and this sensitivity to changes in the weight of technical specifications of the machine. [ABSTRACT FROM AUTHOR]

The use of waste rock inclusions in tailings impoundments is a recent technique that offers many advantages, but it also raises a few technical issues that must be addressed to optimize their design. A laboratory physical modelling study was conducted to assess the effect of waste rock inclusion on the behavior of initially saturated hard rock mine tailings in terms of drainage and consolidation. The evolution of pore-water pressures and settlements after hydraulic deposition of the fine-grained tailings (slurry), with and without a drainage inclusion, has been monitored and analysed. This investigation also focused on the evolution of the tailings void ratio and volumetric water content, the amount of water transferred to the waste rock, and the movement of fine particles at the interface between the two materials. The experimental results are used to demonstrate how such waste rock inclusion can affect tailings consolidation by reducing pore-water pressures with accelerated water drainage, for various imposed conditions. The experimental data are also analysed with numerical models to better understand the coupled processes involved. A discussion follows on practical implications of the use of waste rock inclusions in tailings impoundments. [ABSTRACT FROM AUTHOR]