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By David Beck

In Australia, Safe Work legislation requires mines to have a documented ‘Safety Case’ explaining how a mine will safely manage all major hazards. A similar requirement is legislated or inferred by regulation in all jurisdictions. For small scale, instabilities leading to day-to-day seismic hazards, a ‘Stability Safety Case’ built around observational methods and measurement triggered responses can be effective because adverse situations are easily identified and the costs of lower control measures are not onerous. Also, if the influence of a volume of yield on the mine load system is small, the response of the system will be more predictable. However, for episodes of large scale mine instability, the hazard derives from the widespread, multi component influence of the event on the mine load system. As the system response depends on interactions between many parts, the resolution of predictions will be lower and situations can arise without local precedent. Further, as episodes of large scale instability change the stiffness and nature of the connectedness between parts of the mine load system, the behavior of the system before the event will be a poor empirical basis for forecasts of event related hazards. Most importantly, Triggered Action Response Plans (TARPs) and ‘traffic light’ warning systems cannot make design choices or identify new hazard phenomena. They are ‘lower’ control measures targeting explicit human-made instability hypotheses. As such, the Safety Cases related to management of hazard from potential large scale seismic events and mine instability cannot rely solely on TARPs. Mines that successfully manage meaningful dynamic instability always acknowledge the ultimate reliance on expert human intuition, knowledge and imagination to appreciate the range of possible hazard scenarios, to make stability hypotheses and propose solutions. Complex analysis, TARPs and measurements are critical steps in the human decision cycle, but only support the making and testing of ‘Stability Hypotheses’ made by expert engineers. Relying on expert skill and judgement as essential components of a Safety Case, however essential, introduces human vulnerabilities. Another challenge is that the expert decision making process is hard to document. Beck et al 2019 first described an organizational and procedural framework for maintenance of an ongoing large-scale ‘Stability Safety Case' where a degree of expert judgement and imagination is needed to manage a seismically active mine. The structured data appreciation process outlined sufficient measurements, analysis and appreciation to confirm the stability state of the mine and was applicable to all underground mines. After several years of implementation in various forms in stoping, caving and room and pillar mines, this update addresses lessons learned and describes some considerations for numerical forecasting to establish a base case, and some challenges for empirical hazard identification.

Apr 26, 2022

By W. L. Chen

In the United States hydraulic cyclones have been used for thickening, classification and cleaning in coal preparation plants for many years. The cleaning cyclones presently in use are based on using a "heavy medium", such as a fine magnetite and water pulp. The latest addition to cleaning cyclones is the one which uses ?water only?, or simply called "Hydrocyclone". Just as was the heavy medium cyclone, the hydrocyclones were originated in the Netherlands (1, 2). Plants using hydrocyclones were built in Europe (3) and test plants were erected in Canada (4, 5, 6) and India (7). Roberts and Schaefer Company has built four plants using hydrocyclone circuits. One additional plant is in the process of construction.

Jan 1, 1965

By John A. Riddle

Some of the pitfalls and problems in selecting and applying corrosion-resistant materials in uranium plants are discussed, together with some suggested solutions. Includes some cost data.

Jan 1, 1979

By Steve Kral

The third edition of the Underground Construction Association of SME?s (UCA) Cut-ting Edge series of conferences focused on a challenge every underground construction and tunneling project faces: controlling ground water. The conference, held in New York City in November, is a partnership between the UCA and The North American Tunneling Journal. It featured more than 20 technical presentations by professionals from around the world. Each described specific challenges unique to their projects and the solutions employed. More than 175 professionals attended the two-day conference that included an exhibition featuring 17 companies. In addition to the technical program, the Cutting Edge conference featured a site visit to the $10.4 billion East Side Access Project. Sponsors of the meeting included Soil Freeze, Traylor Bros., Kiewit, Skanska, Moretrench, Aecom and The Robbins Co.

Refractory copper ores (CROs) in central Africa contain copper minerals that are locked up in a micacious solid matrix or associated with carbonate, sulfide and phosphate minerals. Several researchers have reported that the recovery of copper from CRO material by an acid-leaching process is not economically feasible, due to the presence of excess gangue-acid-consuming minerals such as calcites, dolomite, asbolane and iron oxides. Since the proportion of acid-insoluble copper (CuS) is about 28% of total copper and total free sulfur is extremely small, sulfide flotation was considered unfavorable. Consequently, hundreds of millions of tons of CRO material have been stockpiled specifically at the Nchanga Mine of Zambia. In terms of copper distribution in CRO material, a significant portion of total copper exists as carbonates (39%) and oxides (17%), while 28% of the copper is acidinsoluble (CuS). The rest of the copper is in the form of carbonates (16%) and (hydr) oxides (17%). This means that only about 72% of total copper is recoverable through the non-oxidative acid-leaching process. In this study, batch leach tests were performed on CRO solids (d95 = 95%) to establish the gangue acid consumption values at different feed pH values and to evaluate the leaching characteristics of copper, manganese and iron within the CRO material. Subsequently, continuous leach tests were performed on CRO solids (106 um, 80% passing) using optimum leach conditions derived from batch tests. This paper aims to show that sustainable copper recovery can be achieved by selecting leaching conditions whereby gangue acid consumption (GAC) values become significantly small and the final concentration of manganese and iron in the leach solution are appreciably low.

Nov 1, 2011

Refractory copper ores (CROs) in central Africa contain copper minerals that are locked up in a micacious solid matrix or associated with carbonate, sulfide and phosphate minerals. Several researchers have reported that the recovery of copper from CRO material by an acid-leaching process is not economically feasible, due to the presence of excess gangue-acid-consuming minerals such as calcites, dolomite, asbolane and iron oxides. Since the proportion of acid-insoluble copper (CuS) is about 28% of total copper and total free sulfur is extremely small, sulfide flotation was considered unfavorable. Consequently, hundreds of millions of tons of CRO material have been stockpiled specifically at the Nchanga Mine of Zambia. In terms of copper distribution in CRO material, a significant portion of total copper exists as carbonates (39%) and oxides (17%), while 28% of the copper is acid-insoluble (CuS). The rest of the copper is in the form of carbonates (16%) and (hydr) oxides (17%). This means that only about 72% of total copper is recoverable through the non-oxidative acid-leaching process. In this study, batch leach tests were performed on CRO solids (d95 = 95%) to establish the gangue acid consumption values at different feed pH values and to evaluate the leaching characteristics of copper, manganese and iron within the CRO material. Subsequently, continuous leach tests were performed on CRO solids (106 um, 80% passing) using optimum leach conditions derived from batch tests. This paper aims to show that sustainable copper recovery can be achieved by selecting leaching conditions whereby gangue acid consumption (GAC) values become significantly small and the final concentration of manganese and iron in the leach solution are appreciably low.

Jan 1, 2011

By Ziyuan Liu, Xun Zhang, Yan Wei, Hang Qiu, Shaomin Lei, Yubiao Li, Yu Meng, Min Lin, Bin Liu

High-purity quartz (SiO2) is an important material widely used in many industries, including semiconductor technology, telecommunication, and optics. The content and distribution of impurities in quartz significantly affect the processing methods. This paper provides an insightful review on the processing of high-purity quartz, covering the analytical techniques, separation methods, and the critical procedures used to assess the quality of quartz ore. More importantly, the critical review of the thermal phase transition separation method for fine-grained mineral inclusions, micron-grade fluid inclusions, and lattice-bound trace elements is notably opened for the first time. It is proposed that the research field as a monopolized industry would benefit by expounding the critical problems that occur during the preparation of high-purity quartz.

Jun 22, 2020

By K. J. Shoop

An analysis of an iron ore processing plant showed that its performance was affected by seasonal temperature variations, resulting in reduced grinding efficiency in the winter months. Laboratory and pilot plant studies were conducted to determine the cause of the observed loss of efficiency at lower temperatures. Experiments were divided into two groups: 1) Drop testing, which was performed to determine the effect of brittleness and frozen pore water on the breakage characteristics of the ore. 2) Wet grinding, which was further divided into laboratory tumble tests and pilot plant scale tests. Laboratory tumble tests were performed to determine the effect of temperature on the grinding of iron ore. This was done by varying the percentage of fines and percentage of metamorphic clay material added to the iron ore grinding charge. The pilot plant scale tests were conducted as a scale-up of the laboratory tumble tests and to determine the effect of temperature on slurry rheology, and how this changing rheology affected the grinding of iron ore. The combined results of drop testing and wet grinding were used to make some predictions of the performance of plant scale autogenous grinding. In drop tests the breakage characteristics of the iron ore had no noticeable change in size stabilities for dry and water saturated samples over the temperature range studied (-25°C to 25°C). The effect of frozen pore water was not observed due to the low apparent porosity of the iron ore. The addition of fines to the test charge caused a decrease in the amount of new fines produced for both the laboratory tumble tests and pilot plant scale tests. The production of fines further decreased when tests were performed at the colder temperature. The increased energy consumption at lower temperatures was dominated by rheology phenomena. The addition of metamorphic clay material to the iron ore test charge resulted in more fines being produced in the laboratory tumble tests. This was due to the metamorphic clay material grinding easier than the iron ore. This caused an increase in the amount of fines in the mill, which in turn, would prematurely slow down the grinding of iron ore because of an increase in the viscosity of the slurry.

Jan 1, 1995

By V. F. Swanson

A petrographic study was made of the type and sources of mineral contamination occurring on phosphate rock products from Florida. Emphasis was placed on contaminants in the screened rock (+1 mm) since this portion of the product undergoes no physical beneficiation except for scrubbing to remove slimes. Since iron and aluminum con- tent of the finished product affect the salability, special emphasis was placed on identifying types and sources of these contaminants and relating chemical composition to visual characteristics. Wavellite derived from the overburden was the major aluminum contaminant with some aluminum being included as secondary clayballs. Iron occurred as phosphates in the overburden, and as colloidal oxides included in the phosphate pebbles. Chert and limestone contamination were derived from the Hawthorne formation underlying the phosphate matrix.

Jan 1, 1969

By Norman F. Schulz

The technical excellence of separation achieved in a mineral concentration process, or any other process where two constituents of any kind are physically separated from each other, is expressed uniquely and quantitatively by the Separation Efficiency: ES = (R ? Rg) where R is the percentage of the valuable constituent and Rg the percentage of the waste appearing in the concentrate. The Separation Efficiency meets all the usual requirements of a true efficiency and is independent of the nature of the process used. It can be visualized as the percentage of the feed material that, in effect, actually undergoes complete separation while the rest of the feed is distributed randomly and unchanged into the two separation products.

Jan 1, 1969

By J. C. Johnson

The problem of estimating pillar capacity in coal mines has motivated development of a variety of empirical equations. Most of these equations have arisen from experience and a very limited set of measurements that have, necessarily, been focused on particular regions or coal fields. Their applicability is often limited to a specific range of pillar sizes. This is of particular concern in the design of large gateroad pillars and small barrier pillars between panels. The result has been a variety of equations and equation coefficients that can calculate load estimates to size pillars. Inclusion of these equations in more sophisticated loading models, such as boundary element methods (e.g. LaModel and MULSIM) has been hampered by absence of a function that describes specific variation of coal strength within the pillar. A singular exception, to our knowledge, is a function corresponding to the Bieniawski pillar strength equation. Because of this, it is the only coal strength criteria inherently available in most boundary element models. This paper presents a general method for deriving local coal strength, as a function of distance from the pillar rib, for an arbitrary pillar strength equation. Integration of this function provides the strength of pillar regions, or cells, needed for boundary element models. The method is demonstrated for the Bieniawski, Maleki and Holland-Gaddy equations. The Maleki and Holland-Gaddy equations contrast strongly with Bieniawski as strengths are extrapolated to large pillars and barriers. This development provides a tool for incorporating any of the proposed empirical equations into a boundary element model, thereby allowing the analyst to choose the most appropriate equation for a particular region, coal seam and/or pillar size.

Feb 23, 2014

By Howard J. Brown

The Lucerne Valley limestone mining district is in the San Bernardino Mountains, one of the major ranges in the Transverse Range Province of southern California. Several large limestone mining operations are present along the north range front in Lucerne Valley, and the area is one of the premier limestone mining districts in the country. Resources are contained in Paleozoic carbonate rocks that are part of a thick late Precambrian and Paleozoic sequence that uncomformably overlies crystalline basement. The district has been affected by multiple episodes of metamorphism and deformation, as well as by a complex sequence of late Cenozoic structural events. Detailed studies, however, have demonstrated that these rocks can be divided into formations correlatable with late Precambrian to Permian strata of the Cordilleran miogeocline. The district is the leading producer of white, high-purity calcium-carbonate products in western North America. Pluess-Staufer (California) Inc. mines and processes high-purity white limestone from extensive deposits, and is one of the largest producers of high-quality limestone fillers and extenders in the western United States. Major factors influencing the genesis of economic carbonate deposits in the district include depositional environment, post-depositional processes such as diagenesis, dolomitization and/or silicification, regional and/or contact metamorphism and associated intrusive activity, faulting, folding, uplift and erosion, and preservation from erosion. Regional geologic studies, detailed geologic mapping, intimate knowledge of stratigraphy, and recognition of complex structural relationships have proven to be invaluable tools in the discovery of high quality calcium carbonate deposits in the district.

Jan 1, 1987

By W. Clark Ashby

Productivity is a fascinating concept. Like motherhood or apple pie, we know it as a good thing. Just what it means is not so clear. To a coal miner we assume it means tons of coal hauled from the mine. To the company president it means profit after capital, labor, and other costs have also been reckoned. To the government economist it means output in a balance of payments. What does it mean to the biologist, and can reclamation really be productive? In this paper we discuss productivity from a biological viewpoint, give some yield data for various types of reclamation plantings, and discuss how our demand for or acceptance of differing kinds of productivity is tied up in bigger questions of land use, environmental stability, and resource allocation.

Jan 1, 1981

By Charles W. Bauer

Most of the aluminum produced in the United States today is derived from foreign bauxite deposits. Earth Sciences, Inc. initiated a program to evaluate domestic non-bauxite sources for alumina in the 1960's. In the initial evaluation of alunite, domestic resources were not sufficient to support development. An exploration program led to the discovery of large deposits of alunite in Utah and several other western states. Identification of alunite is difficult as both its physical and chemical characteristics are similar to the minerals with which it is associated. Most of the significant alunite deposits in the western United States are replacement type deposits. These deposits have formed as a result of hydrothermal alteration of volcanic, sub-volcanic, and igneous rocks. Typical alunite deposits contain between 30% and 50% alunite between 50% and 70% quartz with minor amounts of other minerals. Four mineralogical zones are common in these systems. They include a siliceous zone, a quartz-alunite zone, a kaolinite zone and a chlorite-montmorillonite zone. Total U.S. reserves of alunite were estimated at 20 million metric tons (at 30% alunite) by the U.S. Bureau of Mines in 1941. Here recent work by the U.S. Geological Survey estimates reserves of 252 million metric tons and potential resources at 1.4 billion metric tons. Reserves and resources estimated for 23 properties on which field work has been done by ESI are considerably higher. Most of these properties have reserves and potential resources of several hundred million metric tons. The combined demonstrated reserves at these properties are estimated to be about 650 million metric tons. Inferred reserves are estimated at 2.5 billion metric tons and potential resources at 8 billion metric tons. It appears that the U.S. has sufficient reserves and resources for alunite to be considered as a potential non-bauxite source of alumina.

Jan 1, 1980

By R. V. Ramani, K. V. Raj, S. Bandopadhyay

The air flow problems in openpit mines are complex. Computational fluid dynamics (CFD) models can provide detailed information regarding air flow pattern, velocity distribution, temperature, and pollutant concentration in an enclosed domain of an openpit mine. A range of turbulent models can be selected with varying complexity and accuracy. Pollutant transport models, however, differ in their assumptions and structure as well as in the algorithms they use. As a result, predictions vary from model to model. This paper presents a study of pollutant transport in an actual openpit mine under a stable boundary layer. The objective was to test two turbulence models using similar geometry and the same input conditions and model constants. Measured data were used to compare the results of the two CFD models, namely, the kappa-epsilon (к-є) model and the Large Eddy Simulation model. Despite the complex synoptic situations, different meteorological input data and fast-changing conditions, the simulation results from both the models were in good agreement regarding the dispersion of pollutants.

Jan 1, 2015

By R. W. Plume

Gold extraction along the Carlin trend requires large withdrawals of ground water, which can be perched, unconfined at shallow depth, and (or) confined at depth. Five hydrogeologic units-Quaternary basin-fill sediments, Tertiary basin-fill sediments and sedimentary rocks, Tertiary volcanic rocks, Devonian to Ordovician siltstones, and Devonian to Ordovician carbonate rocks--form the framework for two aquifer systems that discharge along some reaches of the Humboldt River and its tributaries and are recharged by streamflow along other reaches. Ground-water withdrawals eventually could affect these stream-aquifer interactions. Further work is needed to quantify regional hydrologic processes and evaluate potential effects of mining on water resources.

Jan 1, 1992

By W. J. Martin

At the termination of mining, the quality of ground water in the ore-zone aquifer must be returned to a condition predetermined by the permitting agency. To immobilize the redox-sensitive elements (e.g., uranium, arsenic, selenium, molybdenum), it has been suggested that a reducing agent be circulated through the leached ore zone. We have conducted laboratory experiments to test the ability of sodium sulfide as such a reducing agent. Sodium sulfide lowered the redox potential of the effluent such that insoluble minerals containing the redox-sensitive elements should be stable. The uranium concentration of the solution decreased by more than three orders of magnitude. In column experiments, by the time ten pore volumes of the sulfide solution had flowed through, sulfide minerals were forming. The experimental results indicate that the addition of sodium sulfide should cause the chemical reduction of the leached sediments, thereby producing long-term stability of the ground-water/sediment system.

Jan 1, 1986

By Paul T. Allsman, Paul F. Yopes

17.1--CURRENT AND FUTURE STATUS OF SURFACE MINING PAUL T. ALLSMAN AND PAUL F. YOPES 17.1.1--CURRENT The history of surface mining essentially is one of mining coal, copper, iron and aluminum ores, of placer mining gold and tin, and of pits and quarries producing clays, gypsum, phosphate rock, sand, gravel and stone. Table 17-1 is a summary of the estimated world and United States production of crude metallic and non¬metallic ores and coal in 1969. It includes estimates of the quantities produced by surface-mining methods. Two-thirds of the 10 billion tons are mined from the surface, ranging from a third of the coal. 57% of the metallic ores, and nearly all clays, stone, sand and gravel. Production by surface methods in the United States, parallels that of the world with one exception: about 90% of the copper and iron ore is mined from the surface, whereas elsewhere only about half the copper ore is surface mined. In Canada, surface mining of the Athabasca tar-sand deposits is a recent large-scale unique operation. In surface mining of coal and, to a lesser extent, metallic ores, much waste is stripped, but in nonmetallic pits and quarries the ratio between waste and ore usually is small. Assuming that the stripping ratio for surface mining in the

Jan 1, 1973

By J. A. Harrison

Most coal being used in the United States has been subjected to one or' more processes of coal preparation. The physical and chemical characteristics of a coal have a marked influence on the ultimate uses that coal may have. The selection of the proper preparation processes may similarly be important in producing the best practical coal product for any particular use. The physical composition and distribution of physical constituents in the coal will partially determine the efficiency of the preparation process chosen and conversely distribution and concentration of coal macerals will, to a degree, be controlled by the preparation process. A number of preparation processes have been evaluated to determine this interrelation. If a coal having' certain specifications is desired, these evaluations trill assist in providing information needed for the production of this coal.

Jan 1, 1962

By Donald E. Ranta

An ore zoning technique developed by Climax geologists during the past forty years has been used to contour drill-hole assay values on cross-sections for fourteen porphyry molybdenum deposits in western North America, including the Climax and Henderson orebodies. Detailed geological studies of these large, complex deposits are essential in determining ore controls, which are the factors most critical to the zoning of MoS2 assays and to conceptualizing geologic models. The technique provides a detailed representation of the size, shape, grade distribution, and geologic continuity of the individual deposits. It demands a disciplined approach and adheres to rigorous rules while maintaining flexibility for adaptation to widely varying geologic conditions. By defining the limits that guide and control manual, computer-assisted conventional, and geostatistical reserve estimates, it exerts a strong geologic influence on the estimation process. A combination of ore zoning and geostatistical analysis of molybdenum deposits produces a significantly more accurate, precise, and defendable geologic reserve estimate than other methods.

Jan 1, 1983