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By Y. Wang, E. Forssberg, R. J. Pugh

The coagulation of dispersed ultrafine weakly-magnetic oxide mineral particles (e.g., natural hematite and chromite) in an external magnetic field can be described by interparticle forces. Essentially, coagulation occurs when the short-range London-van der Waals interactions and the long-range magnetic forces outweigh the stabilizing electrical double-layer repulsion. Using the classical colloid chemistry theory, the various components of the potential energy for different-sized particles at a series of ionic strengths and magnetic field intensities were calculated. The results of this theoretical analysis were then related to the results obtained from experimental studies in which the magnetic field-induced coagulation of the ultrafines of natural hematite and chromite in aqueous suspensions were investigated using a laboratory-scale electromagnetic solenoid. The experimental results relate the coagulation process (as determined by magneto-sedimentation analysis) to the particle size, the slurry pH and the external magnetic field. In the magnetic fields, the maximum coagulation occurred near the pH of zero-point-of-charge (pHzpc) of the minerals (where the electrostatic double layer repulsion was reduced to a minimum) enabling the particles to enter the "primary minimum" energy sink. On the other hand, in cases where the electrostatic repulsion was not suppressed, the long-range magnetic forces enabled coagulation to occur in the "secondary minimum." This caused the formation of chains that appeared to be relatively stable during sedimentation.

Jan 1, 1995

By B. Seymour

The National Institute for Occupational Safety and Health (NIOSH) is conducting research to develop safe practices for the use of shotcrete as ground support in underground mines, particularly mines operating in weak host rock. As part of this research, tests were conducted with a commercial poly-fiber reinforced shotcrete mix to develop a practical means of measuring shotcrete adhesion strength. Full-scale tests were conducted in a test frame equipped with concrete panels having three distinct surface roughness profiles. Adhesion test fixtures either embedded or epoxied in the shotcrete were overcored into the underlying concrete, and direct tensile tests were conducted to determine the bond strength of the shotcrete cores to the substrate after a selected shotcrete curing interval (1, 3, 7, 14, 28, or 90 days). Measured adhesion strengths typically ranged from 0.5 to 2.0 MPa depending on the curing age of the shotcrete samples. This paper presents the results of these tests, describes the portable test system components, and addresses some of the design issues encountered in the development of a rugged and reliable method for determining shotcrete adhesion strength in underground mines.

Jan 1, 2010

By R. Woods, O. A. Kiehn, C. A. Born, F. N. Bender

Development of the flotation reagent scheme at Climax Molybdenum Company's mine at Climax Colorado is reviewed. Features of the mineralogy, milling practice and background of reagent changes are outlined. Special attention is given to the hitherto unpublished details of the application of depressants for copper and lead impurities. The present rougher flotation reagent scheme utilizes a neutral hydrocarbon oil, low in unsaturates and wax, as collector with a sulfated coconut oil emulsifier and pine oil frother. Lime and sodium silicate are used as rougher conditioning and slime dispersant agents. Chalcopyrite and galena impurities are de- pressed in both rougher and cleaner plants by stage addition of Nokes reagent and sodium cyanide to yield a metallurgical grade molybdenite concentrate containing greater than 90% molybdenite and less than 0.5%, 0.1% and 0.05% iron, copper and lead impurities, respectively.

Jan 1, 1976

By K. J. Stanaway

Concentrations of minerals between 3.5 and 5 specific gravity such as ilmenite, rutile and zircon in large accumulations of sand constitute "heavy mineral" placers. Two fundamentally different modes of formation characterize "trap" and "bed" placer variants. Smaller and generally higher grade trap placers form during sediment erosion or reworking. Because of their smaller size, they rarely yield economic heavy mineral deposits. They become economic, either if they contain more valuable "heavies" such as gold, or, if they occur within or near much larger but lower grade bed placers. Bed placers form during sediment accumulation episodes in any environment and lithofacies where mineral supply and fluid dynamics are favorable. Three heavy mineral deposits are discussed to illustrate bed placer geology and how trap placers occur with and relate to them.

Jan 1, 1991

By M. J. DeJong, R. J. Mair, S. Ritter, G. Giardina

"For urban tunneling projects it is essential to predict and prevent building damage. Although various case studies and experiments have shown that buildings considerably modify greenfield soil movements, widely accepted damage assessment methods neglect this soil-structure interaction and simplify structures as linear elastic beams. This paper summarizes an experimental investigation of the response of more realistic structures to tunneling-induced deformations. Small scale structural models with façade openings and brittle material properties were 3D printed and tested in a geotechnical centrifuge. Soil and structure displacement data were obtained by image-based measurement. Results demonstrate that structures notably mitigate differential greenfield ground displacements. It is also shown that maximum soil settlements, horizontal soil displacements beneath the structure and structural damage in the form of cracking significantly depend on the position of the structure in the settlement profile. The results provide a basis from which to predict building settlement response with greater certainty. INTRODUCTION With continuing population growth and increasing urbanization expected in the next decades, there is an urgent need for a next generation of infrastructure. It is likely that a large part of this infrastructure will be underground. Such creation of urban underground space frequently involves the excavation of shallow tunnels in close proximity to existing structures and utilities. For example, along the Crossrail project in London more than 1,200 structures are located within a possible influence area of the tunnel construction (Torp-Petersen and Black 2001). The assessment of building damage plays a vital role throughout the planning, design and construction stage of urban tunneling projects. However, while predictions of tunneling-induced deformations in the greenfield can generally be made with some confidence, much uncertainty exists about how structures interact with ground movements arising from tunnel construction."

Jan 1, 2016

By Geoff Beale

In terms of their hydrogeology, most open pit mines can be divided into three categories. There are mines that occur above the water table, mines that extend below the water table in high permeability rocks and mines that extend below the water table in low permeability, tight formations. Mines that occur above the water table do not experience major ground water seepage. It may some- times be necessary to construct in-pit trenches and sumps to remove water from precipitation. But dewatering or enhanced drainage measures are typically not required. Open pits that extend below the water table in high permeability rocks find it cost-effective to pump from dewatering wells. This is done to lower the water table below the working pit floors, creating dry or depressurized conditions in advance of mining. If the rocks in the mining area are homogenous, complete drainage of the entire mining area may be achievable by pumping from wells. In this case, it is not necessary to consider drain- age enhancement. However, there are many open pits and excava- [ ] tions that can lower the water table using conventional wells, but for which drainage enhancement is also an integral part of the dewatering system. The Sleeper Mine in Nevada is an example of this. Hydraulic layering at Sleeper has prevented downward drainage of water as the main water table is lowered. In addition, there are many mines that have areas of low permeability wall rocks that do not freely drain as the surrounding water table is lowered. Ground water seepage also creates difficulties in mines that occur below the water table but for which lowering of the water table using conventional wells is not feasible because of the overall low permeability of the rocks. The volumes of water involved may be small. However, it is necessary to deal with all of the water inside the pit as mining proceeds. It is not possible to dissipate pore pressures in the wall rocks in advance of excavation.

Jan 1, 1997

By Omid Frough, Hossein Changani

Application of Tunnel Boring Machines (TBMs) is one of the main solutions to achieve a safe and high-performance method of construction in hard rock and soft ground tunneling. In order to adequately assess the progress and potential impacts of the tunneling operations with the TBM, it is required to record a series of data during the tunneling and process of the data to evaluate the TBM performance. Applying the right machine parameters during the excavation not only delivers an optimum penetration rate, but also prevents extra downtime due to over excavation or wear of cutting tools. In this paper, the effect of machine and operational parameters on TBM downtimes has been studied and supported with the real examples of TBM operation data.

Dec 1, 2022

By E. McCullough, S. Gaillard

"Diesel particulate matter (DPM) remains a health concern in many underground metal/nonmetal mines, and has been regulated by the Mine Safety and Health Administration since 2002. While the NIOSH 5040 standard method for DPM monitoring is required to demonstrate regulatory compliance, the FLIR Airtec DPM Monitor can serve as complementary engineering tool. It is a handheld instrument that offers near real-time measurements. As part of an ongoing field study, the Airtec has been used to survey elemental carbon concentrations (a proxy for DPM) in an underground stone mine. Via “spot-checking” and more prolonged area monitoring, this effort was aimed at determining spatial and temporal DPM variation in several key locations. INTRODUCTION Diesel particulate matter (DPM) is the solid fraction of the exhaust emissions from a diesel engine. It is largely made up of elemental and organic carbon (EC and OC, respectively), which can be measured as proxies for estimating mass concentrations of DPM. The National Institute for Occupational Safety and Health (NIOSH) considers DPM to be a health hazard and potential carcinogen [1]. It is believed to cause and/or exacerbate respiratory illness upon inhalation, deposition, and retention in lung tissue [2]. Since DPM exists in both the micro- and nano-particulate ranges, it can surpass typical auto-immuno defense mechanisms that keep larger particles out of the respiratory system [2]. Relative to other occupations, the DPM exposure potential for underground miners is high because these individuals work in enclosed environments where diesel powered equipment is frequently used [3,4]. A variety of engineering and administrative controls have been devised to reduce DPM exposures in underground mines, and increased airflow is often a key component of control strategies. In large-opening mines, which are most common in the metal/nonmetal sector, DPM abatement via increased ventilation can be especially complex due to moving and controlling the large air quantities [5]. The Mine Safety and Health Administration (MSHA) has regulated DPM exposure in metal/nonmetal mines since 2002. The final rule limits personal exposure to total carbon (TC, which is the sum of EC and OC) to an eight-hour time weighted average (TWA) of 160 µg/m3. To demonstrate compliance, operators must use the NIOSH 5040 Method [6]. However, the Airtec DPM Monitor (FLIR Systems, Inc., Nashua, NH) was developed as an engineering tool to provide near real-time measurements of both EC and TC for tracking personal exposures [7]. The portable Airtec works by capturing DPM on a filter and successively measuring laser extinction on the filter as DPM accumulates; the EC fraction of the DPM is dark, and so as it accumulates the filter becomes darker and absorbs more laser light [8]. The laser extinction value is directly correlated to EC, but since EC and TC are generally observed in consistent proportions (i.e., TC = EC*1.3), the Airtec is also programmed to display TC as a TWA [9]. There have been multiple studies conducted to validate the Airtec and the instrument has been adopted by some mine operators as a tool for their health and safety programs [3,8]."

Jan 1, 2016

By M. Stefanakis, A. Kontopoulpus, K. Adam

The application of Bacterial Oxidation as a pretreatment step for the extraction of gold from the Olympias refractory pyrite concentrate is described. A wide review of Bio-oxidation is presented focusing on the current process developments and commercial applications relevant to the treatment of gold bearing sulphide ores and concentrates. Preliminary batch and semi- continuous tests on the Olympas concentrate indicated that with Bacterial Oxidation quantitative gold liberation may be achieved. fie effect of such parameters as pH, Eh, temperature, particle size, operating pulp density and retention time on the extent of sulphur oxidation and subsequent gold extraction by conventional cyanidation are also examined. Finally, a preliminary evaluation of Bacterial Oxidation as a potential process alternative for the treatment of the Olympias concentrate is presented.

Jan 1, 1989

By III Kimball

For many years, Arizona merely shadowed EPA's environ-mental regulation of mining operations and waste. During this period, Arizona generally assisted EPA in the implementation of federal programs and enacted environmental laws patterned closely after their federal counterparts. A growing public concern about protecting water quality, particularly groundwater quality, eventually caused the State to depart from this pattern.

Jan 1, 1989

By K. Soucek

Extraction of hard coal reserves, but also of mineral resources in general in the underground coal mines includes in itself many anthropogenic interventions in the earth crust. These interventions are closely associated with the solution of stability problems in the mine and with occupational safety. One of potential applications of such geo-technical interventions in rock mass is the chemical grouting technology. The chemical grouts are very suitable to affect the physical and chemical properties of rock mass. With the present development of chemical grouts, primarily based on polymers, there come into existence new composite materials during the grouting process (the so called geo-composites), which properties significantly differ from the original rock. An important factor, which affects a choice of chemical grouts and at the same time the effectiveness of grouting technology is the resulting properties of geo-composites. The properties of a coal geo-composite differ from the ones of the unmodified coal seam. On the basis of the laboratory geo-mechanical tests, the differences of properties of both material types were found. While the pure coal samples were destroyed very brittle and explosive, the geo-composite samples were making higher level of tenacity and load bearing ability after overstep of material strength. The presented paper discusses the different behaviour of these original and modified coal samples. The X-ray CT scans were used for observation and demonstration of failure evolution in these samples of pure coal and coal geo-composites after compressive loading.

Jan 1, 2006

By David P. Keller, George Podolsky

Iron oxides are unique in that they are the only significant colored mineral found in a natural state suitable for use as a pigment after being pulverized to pigmentary size. The world production of iron oxide pigments is estimated by the authors to be between 350 and 400 kt. The fact that highly colored natural deposits of iron ore are found throughout the world accounts for its use in prehistoric man's artistic cave paintings. These early artists did not realize that they had established man's first paint test which now has some 20,000 years of exposure. In addition to abundance, iron oxides (about 7% of the earth's crust) have the advantage of low cost, permanency, and are non- toxic. Through the centuries, succeeding civilizations have utilized iron oxides as a major source for decoration and protection when these properties were desired. In the last century the chemical industry has improved on nature by developing a complete range of synthetic iron oxide pigments which surpass the pigments produced from natural iron ores in uniformity, color quality, and chemical purity. In the United States, the combined production of natural and synthetic iron oxides produced sales of over $97 million in 1980 (Spimad, Jr., 1980), increasing to $138 million by 1990 (Templeton, 1990) NOMENCLATURE With the increasing importance of the synthetic iron oxides it is necessary to make a distinction between the natural or mineral pigments and the synthetic pigments. Natural pigments are those products that are derived from selected ores and should not be confused with iron ores mined for steel production. Iron ores that are mined for steel must be capable of being mined and reduced to iron on a competitive commercial basis. These ores are selected on the basis of iron content and processing economics. It is therefore unusual when iron ores for steel production are suitable for use as mineral pigments. Natural pigment ore sources are selected for their special physical-chemical properties and are able to command a premium price over iron ores used for steel manufacturing. Synthetic pigments, and in this instance iron oxides, are those pigments produced from basic chemicals. Through chemical synthesis pigmentary particles are produced as opposed to the use of comminution, the major procedure common to all natural iron oxide pigments.

Jan 1, 1994

By E. I. Jurgens, K. E. Hanney, D. C. Comrie, R. H. Fletcher

Introduction The reclamation of mine/mill tailings areas is undertaken for a variety of objectives including safety, appearance, economical use of lands and forests and long term storage of a future resource. The establishing of criteria for these objectives at any site is a shared task of the government and mining company. Our attention in this paper is directed to uranium mine/ mill tailings as they are handled in the Canadian industry and in the unique Canadian climate. We focus our attention on the state of the art. Uranium is a ubiquitous mineral forming an average of 4 g per tonne of the Earth's crust. Ores are mined at about 500 g per tonne so that the residual content of uranium in tailings is comparable to average background levels. However, as in most mine/mill operations, the ore contains other minerals that become readily mobile after milling operations. Thus the main objective of tailings impoundment is the stability both physically and chemically of the mobile materials. Since the requirements for the operation and construction of tailings areas in Canada have changed considerably over the past decade, there exists a great many mine/mill tailings areas which while considered adequate in their day, would not meet modern criteria. However, most of these installations pose no concern or hazard to the public. The proximity of mine/mill development to inhabited land areas has necessitated more stringent modes of tailings operations and provisions for tailings site reclamation. The more important of these have been: 1) the prevention of dyke failure, with large liquid-solid outflows onto adjoining lands, and 2) the prevention of seepage from the tails of pollutants such as chlorides, sulphides, heavy metals and radionuclides. Uranium mill tailings are discharged as a slurry from the concentrator after the removal of generally only about 1000 g, or less, per tonne of uranium from the as-mined ore. As a consequence, a great volume of low level activity waste is generated. The amount of tailings is expected to grow in quantity in the future even faster than the increase in yellowcake production, as the demand for energy

Jan 1, 1980

By Sundar S. Saluja

Efficient and re1iable methods of fragmentation through blasting have been sought ever since the introduction of black powder in mining operations, but the pace of investigation became faster with the discovery of nitroglycerine. The development of modern measuring instruments and the need to blast more rock with the least damage has made the study of blasting mechanics and its application more important, particularly since the oil embargo. Investigations into the practical approach evolved by Daws (1909) and the work done to make it more useful is discussed. The work of several investigators is touched upon with particular reference to the development of computer programs to simulate and optimize blasting operations.

Jan 1, 1986

By P. Riveros, A. Pratt, G. Deschênes

The effect of pyrite, pyrrhotite, chalcopyrite, realgar and arsenopyrite on gold dissolution in cyanide media was investigated. The cyanidation of synthetic gold ores in the presence of various concentrations of sulfides was studied under constant experimental conditions. A mineralogical analysis of the minerals was performed. The leaching kinetics were determined. The negative effect of sulfides on the gold dissolution rate varies with the sulfide mineral and decreases according to the following order: realgar > pyrrhotite > chalcopyrite > pyrite > arsenopyrite. The chemical characterization of gold and sulfide minerals surfaces using X-ray photoelectron spectroscopy (XPS) was undertaken to identify the mechanisms involved. XPS analysis showed that a passivation layer of sulfides, arsenic or iron compounds might form on the gold surface as a result of the dissolution of the sulfide minerals. Key words: Gold dissolution, Cyanidation, Effect of sulfides, Leaching kinetics

Jan 1, 2003

By Thomas H. Hibner, Daniel Tempelis, John E. Shamma

Environmental protection of nearby resources is an issue that can not be ignored in tunnel construction. The Inland Feeder Arrowhead Tunnels Project is no exception. With keen interest from various stakeholders, Metropolitan developed a Groundwater Monitoring and Mitigation Plan. This plan provides for monitoring and management of selected water resource features within the San Bernardino National Forest along the proposed tunnel alignment. The plan specifically provides for monitoring of streams, springs, seeps, and piezometers for water temperature, pH, specific conductance, and chemical analyses, as well as flow or groundwater elevation. Metropolitan uses the data to evaluate for and manage potential impacts from groundwater ingress during construction of the Arrowhead Tunnels.

Jan 1, 2003

In 1988, at the request of members of the Society for Mining, Metallurgy, and Exploration (SME) Inc., the president of SME formed Working Party No. 79, Ore Reserve Definition. Its mission was to develop guidelines for the public reporting of exploration information, resources and reserves. These guidelines were published in the April 1991 issue of Mining Engineering,(pp. 379-384), and as a document entitled "A Guide for Reporting Exploration Information, continued on an ad-hoc basis until 1996. Working Party No. 79 was then renamed the SME Committee on Re¬sources and Reserves and became a standing committee. Since 1994, the Council of Mining and Metallurgical

Jan 1, 1999

By Bernd Hagenah, Eric C. Wang

New tunnels of significant alignment lengths such as mountain tunnels, base tunnels, as well as beneath urban centers pose unique environmental challenges. This paper highlights key environmental considerations for planning, design, construction, and operations by sharing lessons-learned from the authors' extensive project experience on these types of tunnels. Discussion of unique constraints include limited right-of- way, ventilation and emergency egress during the construction phase and revenue service, safety and security, and protection of existing structures. Practical approaches and applied innovative state-of-the-art solutions addressing distinct sustainability challenges and unique requirements are shared from US and international project examples.

Jun 23, 2024

By Byron C. Hardinge, Michael Sokaski, Paul F. Sands, W. Loring III Mc Morris, David J. Akers

INTRODUCTION In the early days of coarse-coal cleaning by the dense-medium process in Europe, loess was one of the materials used for medium solids. Newly developed cyclones were used to reclaim and thicken the loess suspension. On occasion, when the cyclone thickener at the Maurits mine in the Netherlands plugged, the overflow was found to be filled with clean coal free of impurity. From this observation stemmed the concept of the cyclone as a cleaning device. Development took place during World War II in the laboratory of the Dutch State Mines under the direction of M. G. Driessen. A 15-tph (13.6 t/h) pilot plant was in operation in the laboratory by 1945, when, in September, Driessen made the first public disclosure of the process in a paper presented to the Institute of Fuel in London.51 In April 1945, operation of this pilot plant was observed by H. F. Yancey, who was so impressed with the potential of the cyclone process that, on his return to the United States, a research program on the cyclone was immediately started by the US Bureau of Mines (USBM). This work led to an AIME paper in 1946 in which the first details of cyclone operation on American coals were made available.52 Commercial adoption of the cyclone proceeded in Europe, initially in the Netherlands, Germany, and France. In the United States, where coal is less costly and most of the coals are easy to clean and respond well to simpler cleaning processes, the first cyclone plant was not built until 1961.53 THEORY Before discussing the theory of a dense-medium cyclone, a brief description may be helpful to some readers who are not familiar with its basic operation. In a typical dense-medium cyclone, illustrated in Fig.7-51 a mixture of medium and raw coal enters tangentially near the top of the cylindrical section, thus forming a strong vortical flow. The refuse moves along the wall of the cyclone and is discharged through the underflow orifice. The washed coal moves toward the longitudinal axis of the cyclone and passes through the overflow orifice, or vortex finder, to the overflow chamber. Washed coal is discharged from this chamber, usually through a tangential outlet.

Jan 1, 1991

By S. K. Kawatra, K. A. O, DeLa&apos

On-line sensors and process controls are important for efficient operation of coal preparation plants. The objective of this paper is to describe the current practice in on-line measurement of composition, density, moisture, level, flow and weight. This paper also discusses how on-line sensors can be implemented in process control, and how sensors which are currently being developed can be utilized.

Jan 1, 1988