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By H. Mischo, R. Ellmies

Uranium has been mined in Namibia since the 1970s. The worldwide increasing need for energy in the early 2000s has led to the development and opening of a second uranium mine in 2007 and has triggered an increased interest in uranium exploration, often referred to as “the Namibian Uranium Rush.” In all, four mining licenses have been granted by the Namibian Government, which currently has two mines in operation, a third undertaking trial mining and the fourth in project finance negotiations. In addition, highly intensive prospecting activities at additional deposits are at an advanced stage. The finalization of the strategic environmental impact assessment (SEA) on uranium mining in 2010, the first of its kind and scale in the world, has enabled the Namibian government to assess this uranium rush and its tremendous legal, socioeconomic and environmental impacts and to prepare for the different future scenarios conceivable when this article was written in 2011, including both a skyrocketing and a complete breakdown of demand scenario. The Fukushima disaster and plans of the Namibian government to significantly increase royalties and company taxes in 2011 have threatened the market situation, forcing investors to reevaluate Namibian uranium mining projects. However, with the tax and royalty increase initiative since withdrawn, most projects are back on track at this point in time.

Jan 1, 2012

By Pei‑liang Xu, Jun Wang, Xi Zhang, Deng‑pan Qiao, Tian‑yu Yang

The surface backfill, serving as the operational platform for continuing mining in upward slicing and filling stopes, is required to possess sufficient strength and thickness. Currently, there are limited model methods for determining the strength and thickness of the surface fill body. By analyzing the mechanical actions on the surface backfill, it is determined that its stability is mainly influenced by the combined effects of normal and tangential uniform loads under full-load conditions of trackless equipment. Assuming a circular contact surface between the tire of the trackless equipment and the surface backfill, and utilizing solutions from elastic mechanics theories such as the Boussinesq and Cerruti solution, the stress and displacement distribution of the surface fill body were obtained. Based on the maximum vertical stress condition, where the surface backfill body undergoes maximum deformation while still in an elastic state, and considering the stress–strain relationship, a model for the strength and thickness of the surface backfill has been established. According to the research findings, the design for the strength and structural parameters of the surface backfill has been developed to meet the full-load operation of the Atlas ST7 scooptram, with a compressive strength of 1.32 MPa and a thickness of 0.5 m. Numerical simulation analysis results indicate that the stress and displacement of the surface backfill align with theoretical analysis results. Practical results from industrial application in the western section of the Dahongshan Copper Mine demonstrate that the designed strength and thickness of the surface backfill meet the operational requirements for trackless equipment, resulting in significant engineering application effects and economic benefits. The research findings hold significant importance for advancing the theory of backfill mining and have high applicability and promotional value for similar mines.

Mar 24, 2024

By J. S. Lee

Alkyl hydroxamates are well known collectors for oxide copper minerals as evidenced by the large amount of published literature. Our studies on a wide variety of copper ores from around the world have shown that alkyl hydroxamates will recover most of the "floatable" oxide copper minerals from an ore. They are available commercially, and they offer many advantages over alternative technologies for oxide copper recovery. In spite of this, the full potential of hydroxamates has not been exploited in the industry. The objective of this paper is to provide relevant practical aspects and guidelines to facilitate successful application of hydroxamates in operating plants. A critical analysis of the available information and data, based on several case studies, notation testing, and microscopic analysis indicates that alkyl hydroxamates can effectively recover well-defined oxide minerals of copper, but not copper occurrences such as Cu-bearing goethite (often misidentified as cuprite) which report as Acid Soluble copper in chemical assays. Prior to any notation testing with hydroxamates, it is necessary to assess the various modes of occurrence of Acid Soluble copper using microscopic and microprobe analysis.

Jan 1, 1998

By I. Raposo, I. Moreno-Ventas, A. Palma, M. J. Díaz, M. Vázquez

The oxidative degradation kinetics of chalcopyrite have been studied by thermogravimetric analysis (TGA). The obtained data are necessary for the kinetic description of the flash fusion process, which can contribute to the optimization of the smelting process in copper extractive metallurgy. Activation energy (Ea) evolutions of the involved processes have been determined by several isoconversional methods; in this sense, the chalcopyrite oxidation processes could be adequately described, among studied models (E1641–16, Ozawa–Flynn–Wall, Kissinger–Akahira–Sunose and Friedman), by the Kissinger–Akahira– Sunose kinetic model. Using this method, Ea and A values are found to be very dependent on the conversion. Under lower conversion levels, higher Ea and A values have been calculated with respect to that found for medium and higher conversion levels.

The ability to track miners and communicate with them while they work in underground coal mines is important during normal daily operations, and critical in emergency conditions. As was evident during recent incidents at underground coal mines worldwide, communication with miners and the knowledge of their location is of great importance for rescue efforts and the preservation of life. Numerous technologies have been developed, adapted, and deployed to meet tracking requirements of the Mine Improvement and New Emergency Response (MINER) Act. Evaluating the performance of these systems has proven to be difficult for mine operators, system manufacturers, and regulatory agencies. The MINER Act of 2006 requires operators to improve accident preparedness by developing an emergency response plan specific to each mine. With the recent implementation of the provisions of the MINER Act of 2006, all underground coal mines in the United States are subject to the mandates of legislation concerning communication and tracking system installation. As of June 2011, 203 new or revised tracking and/or communication systems had been approved by the Mine Safety and Health Administration (MSHA), with nearly 50 other systems or revisions in the approval process (MSHA, 2011). At that time, the available approved systems for underground coal mine use included these types: ? Leaky Feeder Communication Systems ? Fixed Node-Based Communications and/or Tracking Systems ? Wireless Node-Based Communications and/or Tracking Systems ? Medium Frequency (MF) Communication Systems ? Communication System Peripherals Other types of tracking systems have since been developed and some manufacturers are seeking approval for use in this application. Some of the new products include Through-the-Earth (TTE) systems and various radio frequency (RF) adaptations. New technologies that are currently being developed and deployed in other industrial applications should also be considered, including acoustical, optical, inertial, and hybrid technologies To date, no uniform method has been employed in the industry to effectively compare and evaluate the performance of installed systems. Neither industry operators nor regulatory agencies can accurately assess the capabilities of installed systems in the continuously changing mine environment. There is need for a uniform evaluation method that provides the ability to assess how different systems and technologies perform in various mining applications, and whether they can satisfy the regulatory requirements.

Feb 23, 2014

There are presently in use many grinding mill control schemes and concepts. This paper presents one operating method of controlling the particle size of the cyclone overflows for proper metallurgical results and controlling the level of the cyclone feed sump and new feed rate to obtain lowest unit cost of finished (ground) material which is usually at the maximum grinding mill throughput. This system stresses simplicity of field instrumentation and control strategy. Both of these factors lead to better operator understanding and acceptance. The low capital investment of this system also makes it more attractive at the Buick Concentrator when compared to other more complicated systems utilizing mass flow measurement and a computer to calculate circulating load and infer particle size. Furthermore, it has the advantage of utilizing an actual measurement for control, rather than a difficult-to-maintain inferred value. There are several reasons for maximizing mill throughput at Buick. The milling rate before automatic control was too low when compared to mill throughput increases planned for the future. Through this new operating system, it appears Buick will not have to make major changes of mill motors and speeds to meet the increased? production rate. Also, since power costs continue to escalate, it is desirable to maximize the throughput to the grinding circuit and reduce overgrinding to achieve a reduction in power cost per ton of ore milled. Presently, 45% of the concentrators' total power is consumed in this grinding circuit.

Jan 1, 1977

By Kai Koosmen, Mehdi Serati, Tengzhou Wang

Spalling and rockburst are unwanted brittle failures at the boundaries of underground excavations that are commonly observed in hard rock and high-stress environments at significant depths, although, spalling has also been observed in comparatively shallow soft rocks. The crack initiation (CI) stress threshold (representing the stress level at which new micro cracks begin to form in an intact rock) is widely used to establish the in-situ spalling strength, and is generally regarded as the lower limit of the long-term rock strength. This study analyses the evolution of CI and other mechanical properties for a high-porosity sandstone with an average UCS of 38 MPa under unconfined cyclic compressive loading. The results indicate that rock properties are variably affected by cyclic loading with; no significant effect on Youngs Modulus; a moderate increase in Poisson’s ratio and fracture angle; a moderate decrease in UCS; and a major reduction in the CI stress threshold. All of these changes were generally amplified by cyclic loading at higher stresses. From the results, it is concluded that rockburst and spalling limit in underground structures may reduce over time if the rock is subject to repetitive cyclic loading, and that the reductions will be greater for higher cyclic stresses. This may be a significant factor in the design and operation of some deep underground structures.

Apr 26, 2022

Controlled blasting experiments in small development drifts were conducted at CANMET's Experimental Mine, from August 1992 to November 1993. The objective of these experiments was to develop suitable controlled blasting techniques for small development headings drilled by jackleg with 32 mm diameter holes. The experimentation also aimed to provide insight into blast damage mechanisms. Particular attention was given to the physical-mechanical properties of the rock and the rockmass structural data in order to make the results applicable to other geological environments. The drift faces were approximately 2.4 m by 2.4 m with 36 to 43 holes drilled to a depth of 2.4 m. Cartridged water gels, emulsions and semigelatin dynamite were used in the cuts and as primers, ANFO as the main explosive and decoupled 19 mm diameter semigelatin dynamite charges were used in the perimeter holes. Smooth blasting techniques and pre-splitting were tested in the underground mine. All the blasts were monitored with a multi-channel blast vibration monitor to which was attached sets of high frequency geophones and accelerometers. This first set of experiments has illustrated the efficiency of con-trolled blasting techniques to reduce blast damage and demonstrated the need for further research to improve the safe and efficient use of explosives.

Jan 1, 1995

By Muhammad Azeem Raza, Muhammad Zaka Emad, Muhammad Usman Tahir, Saqib Ahmad Saki, Muhammad Usman Khan

Shotcrete is a key initial rock support component used in underground mining and civil projects. The strength of shotcrete plays a vital role in providing and deciding the support adequacy. The strength of shotcrete is evaluated by its uniaxial compressive strength (UCS) test that is usually conducted on extracted core samples. Shotcrete cores are commonly extracted from the test panels along the direction of its application; thus, its strength perpendicular to the direction of application is often neglected. The true bearing strength of shotcrete is thereby ignored despite the fact that higher stresses act normal to the direction of its application. Although the anisotropic behavior of shotcrete is well reported, no study has reported extensive testing of this scale and nature. This study reports extensive testing of shotcrete cores extracted from tunnels of a mega hydroelectric project in Pakistan. The study reports 7- and 28-days strength tests of shotcrete cores. The research also investigates the anisotropic behavior of steel fiber reinforced shotcrete and suggests that shotcrete exhibits higher strength perpendicular to the direction of its application.

Dec 26, 2022

By Timothy Batchler, Khaled Mohamed

Standing supports have been used in coal mines for decades to enhance roof support capability. Sometimes standing supports are used as a tool to resist the lateral movement of spalled ribs. Researchers from the National Institute for Occupational Safety and Health (NIOSH) are conducting a testing program for different types of standing supports (steel and timber) to investigate the effect of lateral loading on their vertical loading capacities and the factors affecting their lateral loading capacities. In this paper, the mine roof simulator (MRS), at the NIOSH Pittsburgh research facility, was used to determine the response of steel props to vertical and horizontal loadings. Finite element models (FEMs) were developed and verified using the tested steel props. To justify the testing program for testing standing supports with end-conditions of rock-like materials, the verified prop models were used to study the effect of a wide range of roof and floor materials (gray shale, shale, and claystone) on the critical buckling loads of the steel props. Also, several lateral loading scenarios were evaluated in which the steel props were laterally loaded at different heights. The critical buckling load for steel props setting up against a claystone roof and floor was found to be one-half of that shown by the MRS test where roof and floor platens are made of steel. Minimum prop performance was observed when the lateral load was applied at the mid-height of the steel prop, especially at small lateral displacement (less than 2 in).

Sep 10, 2022

By İbrahim Çınar, Hakan Özşen

Mine workers in heavy and dangerous work are under several physical risk factors, for example temperature, humidity, noise, vibration, lighting and air velocity. Thermal comfort includes parameters such as air temperature, air humidity, air flow rate, radiant heat, metabolic rate and garment insulation. In this study, thermal comfort conditions were evaluated using thermal comfort indices defined as predicted mean vote (PMV) and predicted percentage dissatisfied (PPD) which were determined by measurements taken from an underground coal mine for approximately 100 days. Although the metabolic rate (light work) was kept at 2 met, it was found that predicted mean vote ranged between − 2.58 and 1.68. The predicted percentage dissatisfied index was found to reach 95%. According to the results, it can be seen that thermal comfort may have negative effects on occupational health and safety. The change in thermal comfort index values in the Soma Underground Coal Mine was investigated in detail and the reasons for the changes were determined. Furthermore, determining the optimal working environment for the mine workers was also an aim of this study.

By J. M. Mercier

Approximately seven (7) years of recent intensive mining activity in the Wasatch Plateau Coal Field of Utah has revealed distinct geologic patterns which, at times, profoundly influence reserve estimates, coal quality, mine layout, and reserve accessibility. Mine planning, economic feasibility, and resource recovery activities by Getty Coal Company utilize a multi-faceted approach by necessity when evaluating Utah properties. Two specific operating mines offer examples of the affects of adverse geologic conditions on mine operation and project economics.

Jan 1, 1984

By C. Newman, R. C. Ray

Originated and developed in the civil tunneling industry, the Ground Reaction Curve (GRC) has provided a robust methodology for evaluating and designing ground support in both tunnels and underground mining scenarios. This paper presents a preliminary assessment in the utilization of the GRC concept for the evaluation and design of the pillar-support system with respect to overburden stress and displacement. This initial assessment will be based on and backed by past research on this topic. Underground mine instrumentation is planned for a longwall mine in the Appalachian coal field based on the research and findings in this paper to support the postulated hypothesis. INTRODUCTION Since the early 1970’s, the mining industry has evaluated the structural stability of a pillar by dividing an approximated pillar load by an approximated pillar strength. While this design methodology has served the industry well in the past, as modern mining operations continue to develop in more complex geological and geometric conditions coupled with market economics, industry professionals are in dire need of a modified stability assessment approach which considers both the stress condition and material displacements. Within the civil tunneling industry, the GRC approach has been successfully utilized in designing underground support measures that enhance the stability of an underground excavation. Through the incorporation of current industry knowledge and understanding of ground and support behaviors this paper looks to investigate into preliminary assessment for the development of a Modified Support Response Method (MSRM) to further improve the analysis of local and global underground stability. CURRENT PILLAR DESIGN METHODS AND THEIR LIMITATIONS Globally, multiple pillar design methods have been utilized in the design of underground excavations. Each of these methods approaches the calculation of pillar stability a little differently with respect to material properties, underground geometries and stress conditions. Analytical solutions can be used to determine the strength of homogeneous materials like concrete, but not in case of non-homogeneous and non-isotropic mineral deposits in a mine. These equations are often derived using empirical methods. Pillar strength is defined as the maximum resistance of a pillar to axial loading (Brady & Brown, 1985). The strength of mine pillars is typically estimated through indirect methods. In the past, researchers have correlated the strength of a given size and width of a rock specimen to the strength of a mine pillar. The first study on the effect of geometry on rock strength was done by (Bauschiger, 1876) on Swiss sandstone samples. Since then several empirical equations to determine pillar strength had been published by many researchers like (Bunting, 1911), (Griffith & Conner, 1912), (Greenwald, Howarth, & Hartmann, 1939), (Holland & Gaddy, 1957), (Evana, Pomeroy, & Berenbaum, 1961) and (Holland C. , 1964).

Jan 1, 2019

By Jacob L. Brinkman, Catherine E. Johnson

Unmanned aerial vehicles (UAVs) are being explored by researchers to measure concentrations of gas emissions in situations where such measurements are otherwise extremely difficult to obtain, such as NO and NO2 (NOx) emissions from surface mine blasting. Recently, countries have imposed or are planning to impose surface blasting gas pollution regulations, which creates a need for an improved understanding of UAV-based gas measuring systems. The experiments detailed in this paper were performed to determine if airflow generated by the rotors, also known as downwash, unnaturally alters concentration measurements. Downwash turbulence could create locations of varying pressure, which could affect concentration. A UAV fitted with gas sensors was attached to a stand in a controlled environment containing a mixture of NOx. The gas sensor measuring points were placed at various distances on and from the UAV body to evaluate downwash effects on gas concentration. Results show that the presence of downwash turbulence causes no statistically significant changes to concentration measurements at any distance or direction from the UAV. Based on these results, it is possible to use a UAV-mounted gas monitor to measure concentrations without concern for downwash interference, provided the UAV and measuring point are entirely contained within the gas cloud.

May 20, 2021

By M. Ishaq, J. Rosami, J. Brune, E. Sidrow, C. Tsai, S. Slouka

Respirable rock dust poses serious long-term health effects to workers in mining and tunneling underground hard rock environments. When inhaled, respirable silica particles commonly found in quartz and other minerals will scar sensitive lung tissue and cause irreversible lung diseases. Characteristics such as concentration, type of mineral, particle size, and particle shape inhaled can harm workers to various extents. Therefore, this study characterizes rock dust particles less than 100µm in aerodynamic diameter that are released from cutting hard rock in the underground mining environment. In this study, laboratory full scale cutting tests on samples of potash rock were performed with radial picks to generate dust. Three stages of pick wear were tested: new, moderately worn, and severely worn. Comparisons between different stages of pick wear to dust concentration, size distribution, and particle shape characteristics are drawn from this study to start determining the scenarios when the released airborne dusts become potentially most hazardous for workers. Although further testing needs to be conducted to make viable conclusions, the moderately worn pick, or the pick with the most blunt tip, in these experiments are potentially the most dangerous. The blunt pick tip released the highest concentration of dust and generated particle shapes with the highest aspect ratio compared to the other two picks. The preliminary results of this study allow for the further development of optimum bit management and maintenance systems to control the exposure of respirable dust to mine workers.

Mar 2, 2022

By Virgil L. Barr

National income originating compared to physical production for an enterprise or an industry reflects its ability to strengthen the national economy. For a single industrial sector or for an industry this comparison can be useful to reflect changes that may occur in this ability to contribute because of changing supply-demand-income-investment equilibria. A favorable relationship can be postulated by specified economic incentive, and the accompanying technologic input required can be shown. The new index proposes the use of the Federal Reserve Board indexes of production divided by the constant dollar income originating in the petroleum industry which reflects increases or decreases in performance. When compared with other mineral industries and with, total industry, an approximation of relative strength is evident. By constructing three different hypothetical conditions for future petroleum imports, assuming a constant excess capacity requirement for domestic production, and providing an estimate for future domestic demand for petroleum, the impact on the performance index can be shown. Thus, a strong position for the petroleum and natural gas industry can be stated. If this is done, it becomes evident that because of restrictions on cost-price relationships, a drilling program that would provide enough domestic oil to meet demand may not be practicable. By difference, the amount of improvement in methods of production and processing through technologic advancements can be stated explicitly.

Jan 1, 1960

By M. Gunter, M. Buzon

"Talc formed by hydrothermal alteration of preexisting carbonate rocks is known to be nearly monomineralic, and lacking in amphiboles. In southwest Montana, talc formed from hydrothermally altered dolomitic marbles, and is still actively mined. These talc deposits are typically in contact with quartzofeldspathic gneiss and marble. Accessory minerals vary between these rocks and the ore producing body; the identification and characterization of such minerals requires carefully selected analytical methods. Recent litigation and ensuing confusion over the petrology and asbestos content of these deposits challenges the talc mining industry in Montana, and elsewhere in the world. INTRODUCTION Commercial talc has been mined from the deposits in southwest Montana since the 1940s, and by 1956 the region had output 200,000 tons of talc ore (Chidester et al., 1964). Commercial talc refers to rocks containing more than 20% of the mineral talc (McCarthy et al., 2006); the ores from Montana typically contain upwards of 90% talc. This region remains the leading domestic source of talc in the U.S. partly due to the reserves in the area, and partly due to the diagnostic purity of the ore compared to that of other regions, some of which are no longer actively mined. The mineral talc, a sheet silicate, is expressed by the formula Mg3Si4O10(OH)2, and therefore can form in geologic environments that are rich in Mg, Si, O and water. The protolith for the talc deposits in southwest Montana is a dolomitic marble, but other common protoliths include ultramafic igneous, mafic igneous, and siliceous dolomites (McCarthy et al., 2006). Physical properties such as hardness of 1 on Mohs hardness scale, white streak and slippery feel are among some of the reasons why talc is so widely used as fillers in a number of industries. In decreasing order, ceramics, paper, paint, roofing, plastics, rubber, and cosmetics are the leading domestic industries that use talc despite the decreasing trend in U.S. talc use and production since 1994 (Virta, 2015). The purpose of this paper is to describe the mechanism of talc formation in southwest Montana by focusing on talc deposits and surrounding rocks in the Ruby, Greenhorn, and the Gravelly Ranges, and to relate the mechanism of formation to the composition of talc ores. The compositional data show mineral content of selected ores, and the major and trace element content of those minerals, specifically talc. Our electron microprobe (EPMA), powder x-ray diffraction (XRD) and x-ray fluorescence data for samples from five mines in these three ranges provide continued evidence of the purity of these ores despite claims made during recent litigation that these ores contain asbestos. The five mines that we discuss include the Beaverhead, Treasure, Regal, Willow Creek, and Yellowstone Mines (Figure 1.)"

Jan 1, 2016

By E. Fidler

A recent headline in the Wall Street Journal declared, "trendy management schemes very often fail." Many of the management techniques addressed in the accompanying article are associated with quality management including reengineering, benchmarking, total quality management, and employee empowerment. The article made the point that executives, employees, and customers who are involved in such programs rate the effectiveness of these programs very low, and the programs often fail. Yet, we all know of companies that have made significant advances in their operations using these same quality management practices. Why do a few succeed while many fail? History has shown that the companies that successfully carry out quality management programs have two things in common: 1) Strong leadership committed to the success of the program. 2) A comprehensive plan for carrying out and maintaining the program. Stated another way -the reason many companies fail is the lack of committed leaders and inadequate planning. It is ironic that the title of the Wall Street Journal article is "The Best Laid Plans."

Jan 1, 1994

By MAURICE SUNKPAL, Taghi Sherizadeh, Kutay E. Karadeniz, Dogukan Guner, Samuel Nowak

Despite numerous empirical, numerical, and hybrid studies conducted on the subject of coal rib failure, mine fatalities related to rib failures continue to occur at around 1.5 per year between 2009 and 2021. To date, a standard methodology for the design of coal rib supports that can accommodate the wide range of unique conditions found in coal mines in the USA has not been developed, forcing mine operators to rely on the trial-and-error process or industrial legacy practices for the design of coal rib support patterns. In this study, to better understand the support systems’ effectiveness, various rib bolting scenarios were investigated. A coal mass constitutive model is implemented to a distinct element method (DEM) code, and rib factor-of-safety (RibFOS) analyses were performed by applying strength-reduction for the coal matrix and explicitly modeled face cleats. Ribs with various overburden depths and mining heights composed of solid Banded-Bright coal (BBC) were considered in this study. Different scenarios such as rib bolt length and the number of bolts were studied to quantify the effect of primary rib support density on rib stability. As a result of the unsupported coal rib analyses, a decaying exponential relationship is proposed between the mining height-overburden depth and the RibFOS. The developed coal rib models clearly show the coal-rib bolt interaction and illustrate how the addition of rib bolts restricts the movement of the coal rib. The results reveal that the strength reduction method in DEM code with the coal-mass model can aid in the development of practical primary support charts, which can help in the rib support design process. In addition, an unsupported RibFOS cutoff is proposed, beyond which the addition of primary support cannot stabilize the failed rib structure.

Aug 5, 2023

By G. S. Austin

New Mexico produced 83% of domestic potash and 27% of domestic consumption in 1992. The potash industry of New Mexico produces sylvite (KCI), langbeinite (K2SO4-2Mg(SO4)2), and artificial K2SO4. Average sylvite grade in New Mexico today is about 14%. The average grade of langbeinite is 8-10% Kp. Commercial potash occurs in the middle or McNutt Member of the Salado Formation (Upper Permian Ochoan Series). The 120-m-thick McNutt Member dips about 1° east and contains 11 of 12 potential ore zones in the Salado. The mineralogy and proportion of clay minerals, up to 7% of the ore, influence optimum milling procedures and ore grade cutoff.

Jan 1, 1994