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By Li Zhang, Jing Zhao, Chuanwei Zang, Shuanlin Wang

The application of gob-side entry retaining (GER) in steeply pitching seam longwall mining with a hard roof has always been a difficult problem. Based on the simplified roof beam mechanical model, the traditional gob-side entry retaining by packing (GERP) roof structure evolution process and its problems with use in steeply pitching seams are analyzed. Therefore, based on the unique characteristics of the gangue rolling and accumulating in the steeply pitching seam, this contribution proposes an innovative method of gob-side entry retaining by roof cutting (GERRC) in steeply pitching seam and details its technical process. The roof structures of the GERRC and the GERP are compared. Taking the Chang Gouyu Coal Mine as a case study, field experiments were carried out. This research finds that the GERRC can both overcome the impact of rolling gangue on roadside support and make the rolling and stacking gangue become a roadside support. The roof structure of the GERRC is in a one-time statically indeterminate state, which is conducive to the stability of the roadway. In the field test, the total displacement of the roadway roof and floor is 97 mm, the supporting pressure of the serried single props is less than 28 MPa, and the props have no obvious bending phenomenon.

May 6, 2020

By A. M. Anthony, A. Y. Atta, S. S. Magaji, U. Abubakar-Zaria

There are two major gold recovery methods: the hydrometallurgical technique, which employs cyanide solutions, and amalgamation method, which involves mercury (Hg). These methods present considerable health, safety, and environmental concerns. Past applications of alpha-cyclodextrin (α-CD) on gold scraps show that α-CD is not only inexpensive, but is also environmentally friendly. This research work used α-CD to recover gold from gold ores instead of gold scraps. The gold ore was sourced from Shanono gold deposit site Kano State,Nigeria. The gold ore was characterized by fire assay (FA) for the precious metal. The concentrate was digested with aqua regia (AR) for 24 h. Modified AR, where hydrochloric acid was replaced with hydrobromic acid, was used for the gold digestion due to the good match in molecular recognition between gold bromide ion (AuBr)− and α- CD in a second sphere coordination complex. The digestate was characterized using atomic absorption spectroscopy (AAS). Gold recovery using this technique is pH sensitive, and five pH values (2.0, 3.6, 4.0, 5.4, and 6.0) were investigated. FA analysis showed the Shanono gold ore deposit contains an average of 4.71 ppm of gold, AAS analysis showed highest gold recovery of 69% at pH 4.0, which is lower than recoveries from the metal scraps. This could be due to the presence of other gangue minerals closely associated with the ore. However, gold recovery using α-CD on Shanono gold ore has shown to have a higher yield of 69% compared to 35.5% yield obtainable by Artisan Small Scale Miners using mercury.

May 5, 2020

By Kallam V. K. Reddy, VADAPALLI SANJANA, Veerendra Singh, Gajanan Kapure

This work describes a leaching process for the conversion of high-magnesium peridotite rock, which is a chromite ore overburden, into two valuable products: magnesium salts and micro silica. Under normal leaching conditions, residue remaining after leaching is of a gelatinous nature and thus hinders the filtration process. To address this issue, oxidative leaching with the addition of H2O2 was employed, and it significantly improved the filtration kinetics. Four different approaches for H2O2 addition were tried, and they all proved effective in controlling gelation. The optimum oxidative leaching condition was 70 °C, 2 h time, 2 M H2SO4, 0.5MH2O2 and 400 RPM; under these conditions, 92% magnesium leaching efficiency was achieved. After leaching, the leach liquor obtained was purified and dried into Mg(OH)2 and MgSO4 salts. The leach residue contained mainly silica particles, with size in the 10–30 μm range. This material thus represents an attractive candidate for the production of highperformance concrete for the construction industry. The oxidative leaching process described here enabled the complete conversion of peridotite into valuable products, magnesium salts and micro silica.

May 5, 2020

By XUEWEN WANG, Changda Zhang, Huaguang Wang, Mingyu Wang, Bin Hu

The copper smelting process produces plenty of copper slag every year, which is a hazardous solid waste, but a secondary resource. In the present study, the extraction of copper, nickel, and cobalt from copper slag was investigated through the process of sulfation roasting–water leaching and the process of sulfation roasting–sulfate decomposition roasting–water leaching respectively. Compared with the process of sulfation roasting–water leaching, the process of sulfation roasting–sulfate decomposition roasting–water leaching is a better choice, which could not only get almost the same leaching of copper, nickel, and cobalt as the former process, but has a lower leaching of iron and aluminum. For the process of sulfation roasting–sulfate decomposition roasting–water leaching, the leaching of Cu, Ni, and Co reached up to 74.2%, 71.1%, and 69.6% respectively, under the optimal conditions including sulfation roasted with 80 wt% sulfuric acid addition at 200 °C for 60 min and sulfate decomposition roasted at 650 °C for 60 min, followed by water leached at 90 °C for 30min with a liquid–solid ratio of 2 ml/g. The leaching of Fe and Al was only 4.9% and 17.6%.

May 4, 2020

By Nikhil Dhawan, Débora Moreira, Yogendra Pratap, Himanshu Tanvar

A glauconitic siltstone sample with a potash content of 10% is investigated as a potential potash source. The fine grain structure comprises potash bearing phases of glauconite, muscovite, and microcline. The as-received samples showed poor dissolution ~ 5%. Planetary ball milling was attempted for the dissociation of the underlying silicate structure for the potash release, and ~ 60% potash was obtained after 12-h milling. Mechanical activation (8 h, 60% NaOH) prior to heat treatment (600 °C, 30 min) was found successful in recovering more than 95%K values from glauconite. The final residue consists mainly of quartz, indicating a complete breakdown of the silicate matrix. The mechanical activation process followed is simple, adaptable, and less energyintensive compared to existing methods.

May 4, 2020

By Simón Díaz-Quezada, HUMBERTO ESTAY

The heap leaching process has been widely used for recovering different metals since its first application at the end of the 1960s. In Chile, copper production via heap leaching has accounted for between 30 and 40% of annual copper production over the past 10 years. This level of production has been achieved through and supported by the use of a mathematical relation, known as the leaching ratio (LR) or irrigation ratio (IR), which relates operational parameters with metal extraction in a heap leaching operation. This ratio has been used to develop leaching column tests, to scale up results from the laboratory to industrial operations, to design new heap leaching plants, and in metallurgical control and production estimation. In spite of the widespread industrial use of this relation, few scientific studies mention it. This is due to its simplicity and basic theoretical foundations. This disparity between industrial practice and scientific research could lead to operational decisions which lack substantial theoretical support, and to scientific studies which have limited industrial impact. Against this background, several questions arise about the use of the LR: What are the constraints on the use of the LR? Are there practical advantages with respect to reported kinetic models? What is the main reason that industry prefers the use of the LR over kinetic models, which enjoy greater theoretical support? In order to guide its future use, this paper describes the leaching ratio and its current uses and limitations, through a literature review and case studies.

May 2, 2020

By Juan Francisco Mori, Miguel Ángel Aucapoma, Pablo Zevallos

En este artículo se describe el prototipo de un equipamiento instrumentado digital cuya función es monitorear la condición de los techos de los socavones para evitar que se produzcan accidentes por desprendimientos generados por el debilitamiento de las estructuras que sostienen los techos, debido al corrimiento de las estructuras del macizo rocoso. Básicamente el sistema informa mediante la activación de alarmas pre-configuradas al interior de mina, con el propósito de prevenir y evacuar al personal.

Apr 30, 2020

By Sihua Lei, Hong Zhong, Shuai Wang, Yu Gan, Zhanfang Cao

High purity MgO is widely used in various fields as an important magnesiumcompound. The separation of Mg and Ca is of great importance for the preparation of high purity MgO from dolomite. In this study, the key effects of carbonization temperature and nano-calcium carbonate agglomeration on the separation mechanism of calcium and magnesium have been investigated. The results indicated that the reaction in the carbonization process was stepwise. Precise control of the carbonization temperature was essential for the formation of Mg(HCO3)2 due to its low reaction efficiency at lower temperatures or decomposition markedly at higher temperatures. Meanwhile, there was a common-ion effect in solutions containing Mg2+ and Ca2+. Nano-CaCO3 particles were formed during carbonization and agglomerated with the prolongation of static time. A product with a purity of 99.56% MgO and 0.16% CaO was obtained under the optimized conditions: ratio of liquid–solid 30 L/g, carbonization temperature 22–25 °C, carbonization time 1 h, and refining time 4 h. This work has important guiding significance for the preparation of high purity magnesium oxide from dolomite.

Apr 21, 2020

By VÍCTOR VÁZQUEZ-VÁZQUEZ, GUILLERMO TIBURCIO-MUNIVE, María M. Salazar-Campoy, JESÚS L. VALENZUELA-GARCÍA, OFELIA HERNÁNDEZ-NEGRETE

The present study examined a process for precious metal recovery (silver and gold) from difficult minerals which exhibit refractory characteristics to cyanidation and ammonium thiosulfate leaching (low extraction and high consumption of leaching agent). It is well known that mangano-argentiferous minerals are mainly composed of manganese, silver, gold, and iron. In this research, a mineral sample from Monte del Favor mine, located in Hostotipaquillo, Jalisco, Mexico, was physically and chemically characterized by X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), fire assay, and atomic absorption spectroscopy (AAS). Two-stage leaching was carried out: first to eliminate manganese from the sample using sodium sulfite (Na2SO3) as a reductive reagent and sulfuric acid (H2SO4) and a second stage to dissolve silver and gold with sodium hypochlorite (NaClO) and hydrochloric acid (HCl); the results show extraction around 96% for Mn and 98.73% and 83%of Ag and Au, respectively. The usefulness of high acidity and Na2SO3 to obtain good results in Mn and Ag leaching is discussed along with the roles that HCl and NaClO play in the dissolution of Ag and Au values.

Apr 15, 2020

By Jon A. Hummer, MICHAEL R. SHAHAN, Aleksandar D. Bugarski, Shawn Vanderslice

A study was conducted in an undergroundminewith the objective to identify, characterize, and source apportion airborne aerosols at the setup face and recovery room during longwall move operations. The focus was on contributions of diesel- and battery-powered heavy-duty vehicles used to transfer equipment between the depleted and new longwall panels and diesel-powered light-duty vehicles used to transport personnel and materials to various locations within the mine. Aerosols at the setup face were found to be distributed among diesel combustion-generated submicrometer and mechanically generated coarse aerosols. According to the data, the submicrometer aerosols downstream of the setup face were sourced to diesel exhaust emitted by vehicles operated inside and outside of the panel. Depending on the intensity of the activities on the panel, the outby sources contributed between 12.5 and 99.6% to the average elemental carbon mass flow at the setup face and recovery room. Extensively used light-duty vehicles contributedmeasurably to the elemental carbon concentrations at the setup face. The number concentrations of aerosols downstream of the setup face were associated with aerosols generated by combustion in diesel engines operated in the shield haulage loop and/or outside of the longwall panels. Entrainment of road dust by diesel or battery-powered load-haul-dump vehicles operated near the measurement site appears to be the primary source of mass concentrations of aerosols. The findings of this study should help the underground mining industry in its efforts to reduce exposures of miners to diesel and coarse aerosols.

Apr 14, 2020

By Justin R. Patts, Andrew B. Cecala, A. KYLE LOUK, Emily J. Haas

The National Institute for Occupational Safety and Health (NIOSH) and the former U.S. Bureau ofMines (USBM) have given a significant effort over the past four decades in researching and developing engineering controls and interventions to reduce mine workers’ dust exposures during the bagging and palletizing of industrial minerals. Workers performing manual bagging and palletizing of 50- to 100-pound bags typically have some of the highest dust exposures of all workers at mining and mineral processing operations. This paper will provide an overview of available dust control technologies for bagging operations and present the findings of a recent case study that was conducted at four different industrial sand operations to identify the current types of bagging and palletizing technologies being used and to evaluate their effectiveness in reducing workers’ exposures to respirable crystalline silica dust. An evaluation will also be performed to determine if further reductions in respirable dust levels can be achieved by incorporating additional modifications or improvements into the existing technology.

Apr 3, 2020

By H. Maleki, B. Jaramillo

La importancia de los diseños de pilares de acceso y de barrera, para el control del estrés y la sismicidad se demuestra utilizando datos geotécnicos y el monitoreo del estrés en tres estudios de casos. Los esfuerzos para eliminar los pilares de barrera fracasan en el primer estudio, mientras que una barrera de tamaño marginal contribuye a un evento sísmico de 4.2 en la segunda mina estudiada, la cual se ubica a una profundidad de 760 m. Por el contrario, la efectividad de un pilar de barrera de 150 m de ancho se muestra en el tercer caso, en las condiciones litológicas rígidas que caracterizan a Utah. El estudio confirma una reducción notable en el número de eventos por kilómetro (un factor de 4 a 8), en comparación con el distrito minero inicial en el que se usa la extracción de carbón por el método de pared larga de lado a lado (Long Wall).

Mar 30, 2020

By Zetti Gavelan, Eric Ruiz, Emilio Delgado, Ely Loayza, Jesús Cruces

Debido a la variabilidad de la competitividad del yacimiento que está formado por skarn y pórfidos, para mejorar el concepto de conminución en Las Bambas el proceso de reducción de tamaño se inició en el manejo de los factores de carga, diseño de mallas de perforación y diseño de voladura del macizo rocoso. La maximización del sistema de molienda SAG se consiguió de manera sostenible con la integración del equipo de voladura en las optimizaciones realizadas en la planta. De este modo, se logró incrementar el procesamiento a 150 Kton/día.

Mar 30, 2020

By Zhiguo Chang, QINGXIANG CAI, Ebelia Manda, IZHAR MITHAL JISKANI, XIANG LU, Wei Zhou, Saleem Raza Chalgri

The concept of mine safety is highlighted in the literature of sustainable mining but not extensively discussed. This study analyzes various aspects of underground and surface mine safety and emphasizes its importance in the context of sustainable mining. More specifically, this research attempts to find the relationship between mine hazards and demographic characteristics, examine and compare the perceptual difference among miners, and determine the impact of mine hazards on workplace safety and safety climate. Descriptive analysis, chi-square test, independent samples t test, and linear regression modeling were conducted to achieve study objectives. Results confirmed that mine hazards were significantly associated with age and experience. Miners perceived lower levels of management safety practices, followed by supervisor safety, coworker safety, and job safety. The analysis showed that underground miners reported lower safety scores than surface miners. There was a statistically significant difference between miners’ perception of safety climate (p < 0.05). The results showed that the higher prevalence of mine hazards predicts poor workplace safety and a low safety climate. The regression models revealed that mine hazards have a significant effect on workplace safety (p < 0.05) and safety climate (p < 0.05). In conclusion, the distinctive model of mine safety presented here contributes to the monitoring and design of comprehensive safety interventions and helps to better understand how certain factors interact on multiple levels to influence the overall safety of the industry. In this study, some suggestions are put forward to provide directions to develop a sustainable mine safety system.

Mar 27, 2020

By Aruna Mangalpady, Sandeep Kumar Jeripotula, Govinda Raj Mandela

Injuries due to work-related musculoskeletal disorders (WMSDs) are not uncommon in heavy industry like mining. Researchers acknowledged that occupational exposure to ergonomic risk factors is the chief causative factor in the development ofWMSDs. The aim of this study was to perform an ergonomic assessment of musculoskeletal disorders among surface mine workers in India. Standardized Nordic Questionnaire was used to collect subjective response from 500 workers. A stratified random sampling method according to surface mining work activity type was used to obtain the sample. Data was collected by means of a structured questionnaire, and the Statistical Package for Social Sciences (SPSS) was used to analyze data using descriptive and inferential statistical methods. A response rate of 85% was obtained out of 500 targeted groups. TheWMSDs prevalence for the 12-month period was estimated to be 44.23%. The mean and standard deviation of workers’ age were 41.31and 8.927, respectively. The study has shown that the operators of dumpers, dozers, and graders along with electricians were found to be the most susceptible to developWMSD problems. Among the most affected body parts, back disorder reported the highest. Further, it was found that working with static posture over the longer duration has a significant association with the lower back disorder (with p = 0.020) and bouncing and jarring has also significantly associated with the lower back disorder (with p = 0.023). Similarly, a significant association was found between repetitive work and neck pain (with p = 0.016). The study depicted a significant association between ergonomic hazards and WMSDs, like working with prolonged static posture, bouncing and jarring, and repetitive work.

Mar 13, 2020

By Maybee Vásquez, Robert Santos, Marco Antonio Jáuregui

El estudio surge de la necesidad de ubicar los sectores más importantes para la realización de sondajes diamantinos, los cuales ayudarían a la confirmación y/o adición de nuevos recursos para el proyecto Chaquicocha Subterráneo. Tras analizar y detallar los riesgos identificados, así como los controles a tener en cuenta al realizar excavaciones mineras en ambientes con alto contenido de azufre nativo, se confirmó la viabilidad del proyecto, preservando la integridad de trabajadores y equipos.

Feb 28, 2020

By Mirian Mamani

Luego de revisar la data ofrecida por estudios de magmatismo y geoquímica para varios yacimientos epitermales relacionados con grandes complejos volcánicos en el sur y norte de Perú, además de analizar dos grandes complejos volcánicos con varios depósitos epitermales; el presente estudio destaca la importancia de estimar el volumen emitido y los tipos de erupciones de los aparatos volcánicos en tiempo y espacio, así como de conocer la geoquímica y arquitectura de todas las rocas emitidas y de caja. Los resultados de este estudio pueden orientar la toma de decisiones y la exploración por Au-Ag en vetas y diseminados en la región andina.

Feb 28, 2020

By Dirección General de Promoción y Sostenibilidad Minera del Ministerio de Energía y Minas

El artículo da cuenta de la situación del sector al 2019, año en el que pese al panorama adverso se superó la meta de inversiones con más de US$ 6 100 millones ejecutados. Se reportan asimismo las importantes mejoras efectuadas en la normativa minera para actividades de exploración, como son —entre otras— la ampliación por 3 años de la vigencia de la Ley N° 27623 y el adelanto de inicio del proceso de consulta previa para actividades de exploración. El artículo incluye la nueva cartera y el Mapa de Proyectos de Exploración Minera, actualizados a febrero 2020.

Feb 28, 2020

By Felipe França Sitonio

Parameter’s control of explosives used in blasting operations have become more relevant over the years, bringing a better understanding of detonation performance. Giving into consideration that bulk emulsion density’s variation reflects directly on blasting results due to its importance in product sensitivity and velocity of detonation (VOD), blast designs are conducted assuming that cup density measurements are reliable and explosives gassing agents will perform as per specifications. Nevertheless, confinement conditions in boreholes like temperature, presence of water and surrounding circumstances of rock mass are often neglected on predictive modelling and off-site measurements. This paper describes the assembly of a device equipped with pressure sensors and its utilization in confined boreholes of an open pit mining operation, aiming to obtain in situ monitoring of density variation in several explosive columns. After we developed a software to get and process data of a hardware prototype and the device functionality was validated in water, oil and quarry mining experimental trials, 7 of 291 boreholes in a gold mine operation were chosen to be monitored with two probes each, placed at the top and at the bottom of the explosive column profile. The results obtained enabled a comparison between the bulk emulsion density variation when acting in different environments, since we selected boreholes with diameter of 101.6 mm (4 in) and 139.7 mm (5.5 in) and some with presence of water. Besides the increase of explosive density with depth related to hydrostatic pressure increase, we found an overall error of 6% in cup density measurements when compared with sensors placed at the bottom of boreholes and 2% when compared with sensors placed at the top of explosive column. These findings provide detailed insights into how bulk emulsion explosives behave in different circumstances including depth and borehole diameter, giving the opportunity to re-evaluate blast design parameters such as its geometry, sequence pattern, charging profile and explosive composition.

Feb 2, 2020

By Catherine Johnson, Kelly Williams

Advances in high-speed video imaging make it possible to see the refraction of light due to the high-density gradient at the shock front without the need for parabolic mirrors or additional light sources necessary for Schlieren or shadowgraph imaging. The average shock front velocity between two points can be calculated by dividing the change in position by the elapsed time between the images. Using the Rankine-Hugoniot relationship demonstrated by Swisdak the peak overpressure of the shock wave can be calculated from its velocity eliminating the interference of the gage and mount

Feb 1, 2020