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By Corby G. Anderson

Since 1985, the Sunshine Mining Company has used a patented nitric-sulfuric acid pressure leaching system for production of silver and copper from a refractory sulfide ore body. To better understand this novel process, a program of lab scale testing was undertaken to quantify the effect of system variables on silver recovery. Some of the factors studied include temperature, agitation, acidity, vessel pressure, particle size, percent solids and oxidizer amount. In turn, this knowledge will be applied in actual plant practice to upgrade reaction time, increase concentrate throughput, raise silver recovery and lower reagent costs. A discussion of plant process changes resulting from lab scale testing is included.

Jan 1, 1991

Thallium is an uncommon heavy metal that may be found in concentrations that exceed regulatory limits in mining influenced water associated with processing cadmium, copper, gold, lead, and zinc ores. This study evaluated cost-effective modifications to lime precipitation treatment to reduce thallium concentrations to below the EPA drinking water MCL of 2 ppb. The oxidative precipitation of Tl+ to Tlß+ by potassium permanganate was explored for thallium removal at low concentrations (1 ppm initial thallium). Laboratory batch tests were performed to evaluate the removal of thallium from synthetic solutions. Three ratios of potassium permanganate to oxidizable metals in solution were used (one-half, one and two times stoichiometry). Thallium was removed to less than 1 ppb for all stoichiometric ratios evaluated within 10 minutes of reaction. The efficacy of oxidative precipitation for thallium removal is presented.

Jan 1, 2011

By B. Swarbrick

Today’s mining occurs in a dynamic world of conflicting objectives. Mining companies have to look further than a traditional cash flow analysis to determine the potential value of developing a mine. In particular, proposals for new mine developments undergo rigorous scrutiny by a variety of stakeholders including regulators, NGO’s, and the local communities. From a business risk perspective, how mining companies address stakeholder concerns can have a dramatic impact on the success of the project. In today’s mining environment mining companies must continue to ‘walk the talk’ to stay in business, particularly during downturns in the business cycle. Falconbridge’s Raglan Mine is an example of a project that was successfully developed in a region that is sensitive from many perspectives, including environmental, socio economic, and regulatory. Close working relationships with local stakeholders along with strong environmental management systems are necessary elements of continued success for the project.

Jan 1, 2000

By Anthony Harding

In a world of technology and electronic communication, it is easy to forget what engineers do best with a problem: sitting around a table, exchanging views and ideas with sketches and respecting everyone?s view. This was the approach adopted in the project to arrive at a solution for the cross passage opening sup-port for the Seattle University Link Extension. Schedule and space constraints usually impede concurrent cross passage excavation and tunnel boring machine (TBM) operation. And where the space is constrained, opening support solutions that maximize available cross sections are of great benefit. While there are a number of solutions that minimize space, some of these solutions can require expensive steelwork and extensive drilling and fixing. However, following a detailed round-the-table discussion of the options and constraints, it was identified that a shotcrete shell would not only limit obstruction of the space during installation, but also permit easy installation, particularly around services, and avoid costly steelwork and drilling and fixing.

By Mikael Ramström, Mark Board, Clayr Alexander, Wes Johnson

"The Coeur d’Alene mining district in northern Idaho was first discovered more than 130 years ago and has been the most prolific silver producer in the United States. The Lucky Friday Mine of Hecla Mining Co. (Fig. 1) is the oldest (76 years) and deepest mine in the district, producing approximately 725 t/day (800 stpd) from narrow, vertical lead-zinc-silver veins. Cut-and-fill stoping is currently employed at depths to about 2.3 km (7,500 ft) below ground surface, making it one of the three deepest mines in the western hemisphere. The #4 Shaft, a winze collared at approximately 1.8 km (5,900 ft) below surface and extending to a depth of nearly 2.9 km (9,600 ft), was recently completed to exploit the high-grade 30 Vein, whose resource has been identified to at least 3 km (9,700 ft) in depth.As with other deep mines worldwide, a number of challenging engineering issues occur, including: high in situ rock stress, squeezing ground, seismicity, high in situ rock temperature that requires refrigeration, diesel equipment that generates diesel particulate matter (DPM) requiring high ventilation airflow rates and long travel times for worker transport to mining areas.This article describes the methods that Hecla Mining Co. has employed during the past 50 years to combat these issues, with emphasis on the current efforts to implement continuous, mechanical mining with automated or teleremote operation and to introduce electric and battery-powered equipment to minimize refrigeration and ventilation requirements for the removal of DPMs.Geology and in situ stressThe host rock mass is an extremely thick sedimentary sequence (the Belt Series) that has been tilted vertically by mountain building. The rock mass in the current section of the mine consists of weak, heavily foliated argillites and stronger, bedded silty-argillites termed siltite. The vertical veins (80° to 85° dip) are parallel to the foliation with an approximate width of around 3 m (10 ft). There are two regional, vertical faults that parallel the vein; one forming the hangingwall of the orebody and one approximately 90 m (300 ft) in the footwall. Additionally, there are several thin, rough northdipping faults that occur in the footwall of the vein which terminate on the major vertical faults.Both the argillite and vein package rock have moderate strength, with uniaxial compressive strength averaging about 100 MPa (14,700 psi with a range from about 70 to 125 MPa), and are moderately abrasive, with CERCHAR abrasivity index of 2 to 3. The major in situ stress is horizontal and oriented in a northwest direction with magnitude about 1.5 times the vertical stress. Consequently, the Lucky Friday stress magnitude at depth is analogous to significantly deeper South African gold operations."

Jan 12, 2017

By Arman Hazrathosseini, Ali Moradi Afrapoli

Fleet management systems (FMSs) as the pivotal part of any surface mining operation find it essential to evolve from conventional into intelligent systems because of both Mining 4.0 requirements and some shortcomings inherent in conventional methods. However, this novel transformation needs to be investigated technically and strategically. To this end, the previously published research works on intelligent FMSs are explored to track the latest status of these third generation frameworks within the surface mining context. Following that, their underlying models are compared in terms of five categories of allocation and dispatching features to pinpoint the technical gaps ignored. Having drawn the future lines of research, the present article then leverages the popular SWOT analysis method to outline the strengths, weaknesses, opportunities, and threats associated with the advent of these intelligent FMSs in mines of future. By and large, the analysis indicates that advantages outweigh disadvantages. Solutions are offered to address the existing weaknesses and threats.

Nov 10, 2023

By L. Yan, B. Lambie, J. Srednicki, J. Carr

Electromagnetic emissions from electrical devices may interfere with electronic safety systems or other devices in the mining environment. This electromagnetic interference (EMI) may cause unwanted changes in the performance of the affected devices and may cause safety issues for miners. To minimize the risk of EMI, the National Institute for Occupational Safety and Health (NIOSH) has conducted research quantifying the electromagnetic emissions of several types of equipment that might be used in the mining environment. Previous research has shown that welding arcs can give off ultraviolet (UV) emissions, visible light, and infrared (IR) emissions that can cause health problem on skin and eyes. In this study, the electromagnetic emissions of the shielded metal arc welding (SMAW) process were monitored and measured. Several factors including operating mode (AC, DC positive or DC+, DC negative or DC-), current setting (low, medium, high, maximum), and electrode type were investigated to compare their effect on emission level. The test shows that the emission level from the welding process can be affected by those factors. The test data also shows that, among those factors, the operating mode has more influence on emission level than do current setting and electrode type. The information in this paper can be useful for the mining industry to better understand the emission in the 9-kHz to 500-MHz frequency range from a SMAW welder.

Feb 1, 2023

By W. Miles

Introduction From a historical perspective, bentonite is the common rock term for various uses and applications. Its name originates from water-based muds near Fort Benton used for lubrication of wagon wheels during the 19th century migration to western territories (which are presently part of the United States) when the pioneers ran out of axle grease. From a clay mineralogy perspective, bentonite is composed primarily of montmorillonite, an expandable magnesium aluminum silicate clay mineral. When magnesium occupies an octahedral structural site that usually contains an aluminum atom, a negative charge is created. In order to neutralize negative charges, cations are drawn to the interlayer surfaces between clay mineral sheet structures. Modern applications for bentonite depend on the sodium or calcium cation populations and other characteristics of the clay mineral. When sodium is the dominant cation, the material is also called sodium bentonite, also known as swelling bentonite, western bentonite or Wyoming bentonite. When calcium or magnesium is the dominant cation, the material is called calcium bentonite, also known as nonswelling bentonite or southern bentonite. Swelling bentonite is recognized for its rapid hydration of interlayer sodium and subsequent dramatic expansion up to more than 20 times its original volume. Low shear can then disperse the hydrated sodium bentonite to form suspensions that increase viscosity and suspend solids. However, when shear is subsequently eliminated a sodium bentonite slurry gels. Characteristically, nonswelling calcium bentonite has relatively poor hydration properties and thus low expansion of the clay mineral. When subjected to low shear, calcium bentonite exhibits very little viscosity and poor suspension. Additionally, when shear is subsequently eliminated no more than minimal gelling takes place. The domestic and export markets related to both swelling and nonswelling bentonite are discussed below.

Jan 1, 2007

By C. L. Kosmoski

In recent years, coal mining safety has attained national attention due to several highly publicized disasters. Despite these threats to worker safety and health, the U.S. relies on the mining of coal to meet its need for electrical power, with 42% of electricity in the U.S. generated through the burning of coal (U.S. Energy Information Administration, 2012b; United Mine Workers of America, n.d.). Furthermore, the production of coal continues to increase and reach record levels every year (National Mining Association, 2012; U.S. Energy Information Administration, 2012a). For this reason, the coal mining industry must continue to find ways to protect its workers while maintaining productivity. One potential approach to protecting workers while maintaining productivity is through improving the safety culture at coal mines. In order to achieve this culture, operators, employees, the inspectorate, etc. must share a fundamental commitment to safety as a value. This type of culture is known in other industries as a ?safety culture,? and can be defined as the characteristics of the work environment (such as the norms, rules, and common understandings) that influence facility personnel?s perceptions of the importance that the organization places on safety. Fundamental to improving safety culture within an organization is understanding the existing safety culture; improvements cannot be made without first elucidating areas that require improvement. This manuscript details the process undertaken by researchers at the National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) to assess the safety culture at five underground coal mines across the United States. The purpose of this manuscript is to present the aggregated results from those five safety culture assessments conducted at underground coal mines. Additionally, some general recommendations for areas where coal mines might focus their attention as part of their attempts to improve safety culture are offered.

Feb 23, 2014

By Charles T. Steuart

The Arkansas Novaculite of Devonian and Mississippian age is the most distinctive formation in the central Ouachita Mountains of Arkansas from the standpoint of both topography and lithology. The formation typically forms precipitous, narrow ridges (hogbacks) which reflect the steepness of dip and the resistance and thickness of the rock units. The Arkansas Novaculite varies from less than 200 feet thick in the north to locally over 800 feet thick in the south and outcrops over an east-west distance of 360 km (200 miles) in the Ouachita Mountains of Arkansas and Oklahoma. Most of the rocks of the formation are highly siliceous with novaculite predominating, and lesser quantities of chert, siliceous shale, conglomerate and rarely sandstone. Novaculite is commonly defined as a homogeneous mostly white rock, translucent on thin edges with a dull to waxy luster and composed almost entirely of microcrystalline quartz. The word novaculite comes from the Latin word novacula, meaning razor hone. This term was first used by Richard Kirwan in his mineralogy text of 1784. The origin of novaculite remains controversial but we believe it was a primary silica derived mostly from the alteration of submarine volcanic-rich materials, with numerous fine biogenic components and some minor clastics (derived mostly from foreland facies via turbidity currents) and deposited as an amorphous siliceous ooze in the deep Ouachita trough. It was subsequently converted to microcrystalline quartz during diagenesis by the compaction of the overlying rocks and the intense Late Paleozoic Ouachita Mountain tectonism. In the central and southern portions of the region three divisions of the formation have been defined: a Lower Division predominantly of light-colored novaculite; a Middle Division of interbedded dark chert and shale; and an Upper Division of massive often calcareous novaculite. In the northern exposures the formation is thinner and contains more black chert and shale, chert-shale conglom¬erate, sandstone and less novaculite. The massive novaculite of the Upper and Lower Divisions is a source of high purity silica (99+%). Indians were the first to use novaculite. They made their various tools and hunting implements from the weathered broken rock until they learned the quarrying techniques. The first white men in the area recognized the use of novaculite for sharpening their tools and knives: previously whetstones were obtained in small quantities from Europe. To this day whetstone is quarried mostly in areas which the Indians and possibly the Spanish previously worked. Some of the current mining practices have changed very little from those of the early quarryman. In areas where the novaculite of the Upper Division is poorly cemented, this friable tripolitic material has found applications in such uses as an abrasive, as a filler or extender in paints, plastics and other purposes. Some of the dense novaculite is suitable as a filler in fire bricks and also in plastics. Because some of it has the tendency to decrepitate when heated not all novaculite can be used for these applications. Several quarry operators are crushing novaculite for road, concrete, and other aggregate. This use was formerly rather limited due to the abrasiveness of the novaculite on crushing and screening equipment. Further potential uses of novaculite are speculative but include application of high purity silica in the production of silicon metal for solar cells, seed or "growing", and fusing quartz for electronics.

Jan 1, 1985

By S. K. Kawatra

It is common in coal-cleaning operations to produce a fine waste stream which contains a considerable amount of coal, but which is not economical to recover both because it is mixed with large amounts of difficult-to-remove clay slimes, and because the fines are often heavily oxidized. Conventional froth flotation machines cannot produce an acceptable product from such material in a single stage of flotation, and even flotation columns often have difficulty cleaning this type of feed. A new type of flotation column was designed specifically to deal with these problems, and was installed and tested in a coal-cleaning plant in Ohio. The feed coal contained 39.8% ash as fine clay, and 2.83% total sulfur, and was 80% passing 176 micrometers. The coal was a thickener product which had oxidized for some time, and was very difficult to float. However, using the new column it was possible to recover up to 85% of the calorific value in a product containing less than 11% ash, and up to 60% of the calorific value in a product of less that 8% ash. The bulk of the pyritic sulfur was rejected from the coal as well. Multistage flotation tests showed that the flotation column was able, in a single stage, to produce the best froth flotation product that it was possible to recover from this coal.

Jan 1, 1994

By G. Nash

Despite further declines in production for some producers, 1986 proved to be a landmark year for the asbestos industry. The key event was the adoption of The Asbestos Convention by the Inter- national Labour Organization (ILO) and its 150 member countries. The document, entitled "Safety in the Use of Asbestos", reaffirms the international consensus on the "controlled-use" approach to chrysotile asbestos regulation. The decision of the ILO has come at a critical point in time. It represents a major turning point and provides an important building block for the long term future of the asbestos industry.

Jan 1, 1987

By Ping Li, Baokun Zhou, Lei Yang, Changfeng Li, Erhui Zhang

A uniaxial compression experiment was conducted on standard sandstone specimens to explore the sandstone’s mutation characteristics and early warning interval during deformation and failure. Meanwhile, acoustic emission (AE) and digital image correlation (DIC) techniques were introduced to realize multi-field analysis and cross-validation from the stress field, deformation field, and elastic wave field. The mutation characteristics of rock failure were investigated based on the cusp catastrophe theory. The results showed four mutation points in the destabilization process of sandstone: compressional density, yielding, destruction, and residual retention. As an internal activity characteristic of the sandstone failure process, AE directly reflected the dynamic failure process of sandstone. The stress variation was closely related to the evolution of AE characteristics. Sandstone loading failure was a process of the mutations of releasable elastic strain energy, dissipative energy, and releasable elastic strain energy. The mutation of dissipative energy was used as the starting mark of the sandstone warning state, and the second mutation of releasable elastic strain energy was used as the end mark of the sandstone warning state. Besides, the warning range corresponded to the loading time of 178 to 208 s. Finally, the sandstone instability warning interval was re-determined from deformation field evolution characteristics in the sandstone damage process, with a loading time of 180–204 s. This was consistent with the warning interval specified using the cusp catastrophe theory. The combination of AE, DIC, and cusp catastrophe theory revealed the mutation characteristics and early warning interval of sandstone failure. Hence, the results provide significant importance to predicting rock failure.

Aug 23, 2023

By J. H. Howard

The purposes of this report are to summarize the findings of the Committee on the Challenges of Modern Society Non-electrical Project (a working committee of the North Atlantic Treaty Organization) and also, thereby, to provide an introduction and review of the current situation regarding non-electrical applications to those who are interested in the subject.

Jan 1, 1975

By J. B. Yianatos

This paper addresses the impact on performance of column height (H), and column height to diameter (H/D) ratio by modelling the effect of HID on mixing and consequently on recovery and grade. Mineral recovery increases with increasing H/D ratio for a constant column volume and feed flowrate, while the concentrate grade decreases to a minor extent. Columns 10-15m in height with H/D-10 are well suited for feed rates 150-600 L/min. Maximum H/D is determined by the gas carrying capacity, an important consideration for pilot units where H/D?200.

Jan 1, 1987

By Peter Zhang, I. BERK TULU, Morgan M. Sears, Mark Van Dyke, Heather Dougherty, Ted Klemetti, Gabriel S. Esterhuizen

Ground falls in longwall gateroad entries remain a concern in modern longwall operations. The gateroads are subject to changing horizontal and vertical ground stress induced by longwall extraction. These stress changes can result in failure of the strata around an entry leading to large deformations of the entry roof, floor, and ribs. The gateroad support systems are required to control the failed strata while maintaining safe access to the longwall face and unimpeded ventilation. This paper presents research that was conducted to better understand the stability issues in gateroad excavations and to develop procedures for evaluating support and layout alternatives for longwall gateroads. Using the results of a field-monitoring program and numerical model analysis of case histories, a conceptual model of gateroad support needs was developed. The conceptual model formed the basis for developing a set of equations that can be used to estimate likely roof sag and support loading for given roof geology and longwall-induced loading conditions. The developed equations were used to compare predicted gateroad stability to field study results, showing satisfactory agreement. The calculation procedures are used to demonstrate their application in assessing support alternatives at a case study mine. It is concluded that the developed analysis procedures provide realistic assessments of likely ground stability and can be used to evaluate alternative gateroad support systems at operating longwall mines.

May 13, 2021

By D. Kumar, R. J. Sweigard, J. Silva

The Forestry Reclamation Approach (FRA) recommends that the upper 1.22 m (4 ft) of spoil material on reclaimed surfaces should be left as uncompacted as possible to facilitate efficient tree root growth. However, the main concerns about applying the FRA to steep slopes is that the upper 1.22 m (4 ft) of loose spoil material could cause instability. Successful application of the FRA on the flat and rolling surfaces precipitated this investigation. Details of a field investigation conducted at a steep-slope mine site are available in an earlier publication (Kumar and Sweigard, 2011). A total of 70 survey monuments were driven into the slope in a regular pattern to monitor any type of slope movement. Quarterly surveying of the monuments were done to quantify slope movement, either horizontally or vertically. The methodology developed in this research for field slope movement monitoring was validated using computer model results. Analytical models based on the limit equilibrium method (LEM) and numerical models based on the finite element method (FEM) were developed for slope stability analysis. The LEM analysis was done using the Geo-Slope/W program following the simplified Bishop method. However, numerical models were developed using the PLAXIS computer program following the Mohr’s Coulomb failure criterion and strength reduction technique. The slope stability analysis was performed for two different scenarios: first with the top 1.22 m (4 ft) of loose graded spoil material and second without top loose graded spoil material. Finally, the field investigation results were compared with stability analysis results. Both of these approaches showed that application of the FRA on steep slopes is not causing any significant instability problems, due to 1.22 m (4 ft) loose graded spoil that would not exist otherwise for overly steepened slopes.

Jan 1, 2013

By Sadegh Elyasi

TBMand roadheader are two dominating excavation machines in underground tunnelling projects. The performance of these two tunnelling machines has been reviewed and analysed individually by many researchers from multiple points of view. However, there are almost no studies that have made an extensive comparison between these two machines, mostly from financial points of view. The current study is intended to characterize both financial and technical status of these two mechanical tunnelling machines in one of the biggest coal mines in Iran. The main objective of this study is to define the best method and equipment that meets a predefined economic goal, which is mainly to maximize the net present value. To this end, a technical and financial model based on the geomechanical and financial parameters involved in the project has been prepared and the financial part of the project has been carried out by applying COMFAR III financial analysis software. Subsequently, a sensitivity analysis of the model was conducted in order to evaluate the effect of involved parameters on the project. According to the results, a roadheader has better economic justification than a TBM, while the TBM has a better advance rate than the roadheader.

Feb 12, 2021

By V. O. Tenorio, K. P. Hague

Mines are constantly trying to improve production processes by optimizing work cycles, reducing operational delays, minimizing costs, controlling equipment utilization, and preventing occupational hazards. Currently, advances in digital mining technologies within the concepts of 5G and Industrial Touch Internet are allowing better control and monitoring of underground mining equipment, with centralized control systems that unify data analysis for proper decision making. A wireless 5G-based platform for controlling and monitoring systems for underground mine operations can be designed over a comprehensive layout in where bandwidth selection, sensor location, Wi-Fi repeaters and power distribution are put together to build a successful supervisory system. In order to confirm the validation of these concepts, a case study is proposed for a medium-sized underground mine with a multi-level network which includes tablets managed by production supervisors, along with other data collection devices installed in semi-autonomous mining equipment, collecting, and distributing data in near-real time, with interconnection to support and services areas on the surface.

Mar 2, 2022

By R. C. Gilmore

Computational fluid dynamics (CFD) has been used to model gas compositions in underground longwall coal mine gobs to study oxygen ingress and the development of potentially explosive methane-air mixtures that may form in the gob. The scenarios studied involve various headgate and tailgate ventilation and inertization schemes and controls. In a project sponsored by the National Institute for Occupational Safety and Health (NIOSH), researchers at Colorado School of Mines have used an innovative meshing approach, allowing easy adaptation of the CFD model to adjust to a variety of bleeder and bleederless mining geometries, with gob porosity and permeability scalable over a wide range. This paper presents the methodology of the meshing and scaling approach along with recommendations for using CFD modeling in longwall gob ventilation applications. The new meshing technique was utilized to evaluate the function of a back return in a progressively sealed gob. The back return was successful in maintaining sufficient oxygen concentrations in the tailgate corner of the longwall face.

Feb 23, 2014