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By Gordon Kidd

Inflation and burgeoning costs are two among many factors which have generated a new surge of interest in "fringe benefits" (sometimes referred to as "supplementary remuneration" or "supplementary compensation"). Other specialized forms of compensation ("perks", in the vernacular) such as company cars, windowed offices, etc., which also are the subjects of current study, are outside the scope of this paper. For businesses, interest in fringe benefits is based on concern for employees? welfare, compliance with government requirements, and an increasingly burdensome impact on bottom lines. In 1980, according to Fred D. Lindsey in the October 1980 issue of Nation's Business, employee benefits will cost American employers an estimated $420 billion. To paraphrase Winston Churchill, "some fringes!" Indeed, few if any administrators consider employee benefits as fringes. Employee benefits impact other major areas of a company's operations as well. As listed by Beadle (1980), these areas include employee relations, collective bargaining, short-term costs, long-range funding, manpower planning, compliance with legislation, taxation for the company and for the employee, corporate image in the community, competitiveness for staff, communications, administration, claims cost containment, etc., etc.

Jan 1, 1980

By Roe-Hoan Yoon, Kaiwu Huang

Derjaguin and Dukhin (1961) were the first to develop a model for bubble-particle interaction in flotation from first principles by considering the surface forces in wetting (or flotation) films. The model predicted that the energy barriers to bubble-particle attachment arise from the ζ-potentials of fine particles, which corroborates well with an earlier work of Fuerstenau (1957) reported for the flotation of quartz using dodecyl ammonium acetate (DAA) as collector. In the present work, a series of surface force measurements have been conducted by accurately monitoring the changes in bubble curvature during bubble-silica surface interactions. The curvature changes are then used to determine the capillary force, which is the sum of the hydrodynamic and surface forces. By subtracting the former that can also be determined from the curvature changes, one obtains the surface forces (or disjoining pressure). The results obtained as functions of pH and collector concentrations show that control of the ζ-potentials of bubbles relative to those of the silica surfaces is critical for maximizing the negative disjoining pressure, which is conducive to promoting bubble-particle attachment in flotation.

By B. W. Lawrence

Shaft alignment requirements are consistently met using conventional shaft sinking methods. Little attention has been given to achieving similar alignment accuracies using rotary drilled shaft methods. Alignment of these shafts is difficult to control and guarantee. Bare shafts and shafts that use drum hoisting systems can accept some deviation. However, combining drilled shafts with Koepe hoist installations presents new accuracy requirements for drilled shafts. This paper describes the importance of verticality with practical examples, and discusses various methods of measuring verticality and their respective limitations.

Jan 1, 1989

By Levent Ozdemir, Charles Merguerian

Between 1996 and 1999, a high-performance Robbins TBM [235-282] excavated a 5 mile long, 23´2? wide, and ~700´ deep tunnel through the subsurface of southwestern Queens. Low penetration rates (~6´/hr [actual] vs. ~9´/hr [anticipated])resulted from changed rock mass conditions mostly attributable to high-grade metamorphism of the rocks. Over a three-year period, as-built circumferential geologic mapping (scale 1?=10´) and digital imagery of the tunnel, fracture and fault analysis, structural, lithologic, and petrographic studies have shown that the rocks of the Queens Tunnel consist of orthogneiss of mesocratic, leucocratic, and mafic composition. These metaigneous rocks developed coarse-grained fabrics during Grenvillian (~1.0 Ga) granulite facies metamorphism, and retained their nearly anhydrous, poorly foliated character during subsequent high-grade Ordoviciande formation. Lacking a penetrative foliation, the coarse granoblastic rock texture and extraordinary garnet content (up to 50% in some zones) together proved animpediment to efficient chip production and resulted in bimodal production of blocks and excessive fines. TBM excavation of the Queens Tunnel was also hindered by geological conditions that included unexpected lithology and rock fabric orientation, a zone of crosscutting hypabyssal rhyodacite dikes, and unanticipated extent of brittle faults. The dikes and brittle faults produced blocky ground conditions and a collapsing face condition that produced cutter damage and decreased utilization. Such fundamental textural, mineralogic, and lithologic control over hard-rock TBM penetration can be predicted by careful pre-bid geological analysis. To determine the causes of lower than anticipated TBM performance, a detailed investigation was carried out that included analysis of operational data from the TBM data logger and an extensive laboratory test program on cores retrieved from tunnel walls. Integrated laboratory testing included punch, point load, tensile strength, Cerchar abrasivity, and linear cutting tests, independent petrographic analysis and machine performance analysis. These allied investigations have provided quantification that the rock mass exhibited an unusually high degree of toughness and rock directional properties and established geological causes for decreased TBM penetration rates.

Jan 1, 2003

By Manuel Gomez

This, report presents correlative data on ash and sulfur forms for Pittsburgh seam coal from Greene County, Pa. Prediction equations were developed for sulfur form distributions and washability characteristics. The equations developed were evaluated with an independent set of exploration core samples. It was demonstrated-that both sulfur distributions and washability characteristic's can be predicted from exploration core data ahead of mining. This information can improve the efficiency of selective mining techniques for the production of a uniform metallurgical coal product.

Jan 1, 1967

By M. Fan

Coal has in general a wide range of density from minus 1.3 to plus 2.0 g/cm3 because of its variations in purity, rank, and porosity, etc. The coal density has great impact on froth flotation performance, but much less attention has been paid to particle density than particle size. Our previous research results demonstrated that cavitation-generated nanobubbles around 700 nm in diameter can significantly improve coal and phosphate flotation performance over a wide particle size range. In this study, the effect of nanobubble on the flotation performances of different density fractions (minus 1.3, 1.3-1.4, 1.4-1.5, 1.5-1.6, 1.6-1.8, 1.8-2.0, 2.2-2.2, and plus 2.2 g/cm3) of coal was investigated using a bank of 10-liter flotation cells, a specially designed 50-mm-inside-diameter column, and a 152-mm-inside-diameter column. It was found that nanobubble has the biggest impact on the flotation performance of 1.4-1.8 g/cm3 medium-density coal particles.

Feb 23, 2014

By B. K. Cantrell

The U.S. Bureau of Mines and others have conducted a number of occupational exposure surveys since the publication of the International Agency for Research on Cancer report of 1989, which labeled diesel exhaust as a probable human carcinogen. These surveys have assessed diesel exhaust exposure using measurement of diesel aerosol and/or specific polycyclic aromatic hydrocarbons as indicators of exposure. This paper reviews present diesel emission standards, available diesel exhaust aerosol measurement techniques, and the results of the occupational exposure surveys. In the surveys, diesel aerosol was emphasized because it is a major component of diesel exhaust, is suspected to contribute to the health hazard, and is readily measurable. Three primary aerosol measurement techniques were used: respirable combustible dust, size-selective sampling, and measurement of the elemental carbon fraction. Occupations surveyed included mine workers, railroad workers, forklift operators, fire fighters and truck drivers. The studies found mean diesel aerosol concentration levels in the range of 0.004 to 1.74 mg/m3? Highest aerosol exposures were in confined spaces such as mines where heavy diesel equipment is used. Polycyclic aromatic hydrocarbons typically are found at very low concentration levels and are not unique to diesel exhaust.

Jan 1, 1996

By David G. Kidd

The principles of Ore Sorting in general and photometric sorting in particular are discussed with detailed reference to the Model 16 machine. The operating principles and design of the Model 16 are discussed and a case study presented to demonstrate the use of sorters to process an industrial mineral. In addition, an economic study is presented, to highlight the benefits of ore sorting, by evaluating the increased revenue that can be achieved using an ore sorter to process a particular ore body.

Jan 1, 1983

By Josef Arnold, Norbert Fuegenschuh

The “Eggequerung” is an important part of the German Railway’s (Deutsche BahnAG) modernized Dortmund—Kassel line. The heart of this 13-km-long (8 miles)construction lot is the double-track Egge Tunnel with a total length of 2,880 m(9,450 ft.). The tunnel was driven using the New Austrian Tunnelling Method (NATM).The construction contract also called for a reinforced concrete secondary lining, guaranteed for a full water pressure of 30 m (100 ft.) water column. Preliminary geological study already showed that very problematic geological-hydrological conditions would have to be expected. This talk describes the chosen NATM driving concept that was adapted to the prevailing geological and hydrological conditions, the special driving method applied in geologically difficult zones as well as the water control concept used during driving. The flexibility and the limits of the NATM under exceptional hydrological conditions are illustrated. Also described are reinforced concrete lining works for the watertight secondary vault (reinforced concrete secondary lining without water-proofing membrane).

Jan 1, 2003

By Ananta L. Yennamani

Blast movement measurement (BMM) transmitters are a practical method to measure three-dimensional (3D) rock movement because of blasting. The BMM transmitters are activated, programmed and installed in specially designed drill holes prior to the blast and the BMM detector locates the transmitters after the blast. The BMM software then calculates and summarizes the 3D movement of each BMM transmitter ball. This information helps to redefine the ore and waste boundaries and enables improved ore and waste selection, resulting in a genuine step change in grade control. The BMM program was carried out at Newmont Mining Corp.?s Phoenix Mine, in northern Nevada near the town of Battle Mountain. The mine is in a historic mining district that contains gold, silver and copper. The geology of the pit consists of different formations made up of sandstone, siltstone, limestone, chert-pebble conglomerate, shale, skarn and quartzite, to name a few. Some of the rock is extremely hard and a powder factor of up to 0.5 kg/t (1 lb/st) is required to get adequate fragmentation to ensure sufficient throughput through the crusher and the mill. The result of using such a high powder factor translates into considerable blast movement and heave. This movement means that the ore/waste digging polygons estimated by the ore control engineer from sampling the initial blast holes will no longer be located in their original posi-tions. The purpose of this project was to test the measurement method and to see if locating the digging polygons in the broken muck pile and excavating to those polygons will improve grade control through the mill. Case studies (Zhang, 1994), (Taylor, 1995), (Gilbride, 1995), (Harris, 1997), (Taylor, 2003), Barrick Goldstrike (Gold-strike Mine, 2008), Ruby Hill Mine (Hilkewich, 2009), (Porcupine Mine, 2005) and (Aguirre, 2010) have shown that, by accounting for the blast movement, there is a potential to increase mineral recovery by as much as 25 percent for individual blasts for only a modest cost increase.

Jan 1, 2011

By James N. Orlich

Meridian Gold Company's Royal Mt. King mine (RMK), a subsidiary of FMC Gold Company, is located approximately 40 miles east of Stockton, California on the western edge of the historic mother lode belt. Gold ore at RMK is associated with a series of northwest trending fault zones hosted in either meta-volcanic or meta-sedimentary rock types commonly referred to as greenstone sulfide and carbonaceous phyllite. Mineralogy studies show gold in both ore types to occur primarily as electrum in the form of 1 -20 um inclusions in pyrite with varying amounts of free milling gold. In carbonaceous ores, gold was not found to be closely associated with carbon. At the start of the current mining operation, three major ore resources were identified. North Pit and Gold Knoll pits were the major greenstone reserves while Skyrocket Pit contained over 60% of the total reserves as carbonaceous ore. Since North Pit and Gold Knoll were to be the first areas mined, the mill began operation in February 1989 with a flowsheet designed for greenstone ores with a carbonaceous expansion anticipated after depletion of the greenstone reserves.

Jan 1, 1992

By Wilson Blake

The occurrence of rock bursts in some deep mines throughout the world constitutes a severe operational hazard. In addition to endangering the safety of the miners, the rock-burst problem is a major factor in mining economically in deep mines because of the loss of production and expense owing to cleanup and repairs following a burst. Developing means of controlling or eliminating rock bursts has been the subject of intensive research for over 50 years. While much has been learned about the effects of rock bursts, little is known about their basic causes; hence, control measures have been at best only partially effective--attested to by the number and severity of bursts that continue to occur throughout the world each year. In the Coeur d'Alene mining district of north Idaho, the rock-burst problem continues as the silver and lead veins persist at depth. These veins are presently being mined at greater than 7,000 feet below the surface and will be mined to some 10,000 feet in the future. The majority of rock bursts in this district occur in pillars. While pillar bursting has been essentially eliminated in some deep-mining districts by longwall techniques, modification or application of this technique to the thin, irregular, and near vertically dipping veins of the Coeur d'Alene district has not been found to be practical. The creation of pillars is a consequence of the horizontal cut and fill mining method used. Figure 1 shows a vertical longitudinal projection of the silver vein at the Galena mine, illustrating the mining method. Stoping progresses between raises and is carried upward between levels. A horizontal pillar is created as a stope approaches a mined-out level. Recent broad-band micro seismic monitoring of rock-burst-prone stopes by the Bureau of Mines has shown that potential burst zones could be delineated weeks in advance of a burst and that a definite sequence of events took place prior to the occurrence of a pillar burst (1). Hence, time was available for control measures to be effected when a stope pillar reached a critical burst geometry.

Jan 1, 1971

By N. Arbiter

Fracture under low velocity free-fall and double impact, and under slow compression have been-investigated. The pattern of breakage and the size distribution of resulting fragments for sand-cement and glass spheres have been determined. Photoelasticity methods were used to simulate the stress distributions in free-fall impact in order to explain the observed patterns of breakage. Oblique fracture planes, occurring only in free-fall impact, develop along lines which coincide with the trajectories of principal compression as determined by mathematical analysis Breakage efficiencies for different modes of fracture were compared for both types of spheres. For the same specimen and loading system, static loading and low velocity dynamic loading induce geometrically similar stress fields resulting in reasonably similar fracture patterns and shapes of fragments.

Jan 1, 1968

By Justin Reed, Sara Bewley, Dwight M. Kinnes, Maryam Sadeghi, Ed Hart

This study compares wet gravity and dry magnetic separation for preconcentrating an allanite-rich rare earth ore from the Halleck Creek deposit. Material in the –300/+86 μm size range was treated to define a flowsheet that maximizes total rare earth oxide (TREO) recovery. The ore is dominated by feldspar and quartz, with hastingsite, an iron-bearing aluminosilicate. Because hastingsite’s density and magnetic response closely match allanite, it is difficult to reject using conventional methods. Two separation approaches were evaluated: MG12 spirals for gravity concentration and an Induced Roll Magnetic Separator (IRMS) for dry magnetic upgrading. MG12 spirals performed well in the rougher stage but provided limited gains when used as cleaners. When IRMS was applied as the cleaner stage, TREO grade and recovery improved substantially, showing that a dry magnetic cleaner circuit can effectively replace the wet gravity cleaner step. MG12 spirals remain suitable for highcapacity rougher duty, but dry magnetic separation delivers higher selectivity, simpler operation, and eliminates water use—offering a more efficient and sustainable preconcentration route in water-constrained environments.

Feb 22, 2026

By Xuchen Fan, Chenyang Zhou, Yuemin Zhao, Liang Dong, Chenlong Duan

A gas–solid fluidized bed using magnetite particles is an effective methodology for coal beneficiation in the field of dry coal cleaning. Broadening the size range of magnetite used in the bed decreases medium preparation cost. In this study, a tapered fluidized bed was used to investigate a magnetite particle size range of −0.5 + 0.074 mm. The results showed that a tapered fluidized bed effectively strengthens mixing of magnetite with a wide size range (−0.5 + 0.074 mm). The results of beneficiation experiments indicated that with increasing tapered angle, separation efficiency increased and then decreased. The highest separation efficiency was obtained at a tapered angle of 10°. The optimal results showed that the ash content of the concentrate decreased from 31.82% to 12.33% with a probable error of 0.11, which indicated that a tapered fluidized bed was efficient to improve fine coal beneficiation performance.

By James C. Hower, B. K. Parekh

Introduction The purpose of coal preparation is to improve the quality of coal to make it suitable for a specific purpose by (1) cleaning to remove inorganic impurities; (2) sizing-crushing or screening, or both; and (3) special treatment, such as dedusting. The properties and quantities of impurities in coal are of major importance in the design and operation of steam generating equipment. Although boilers are often designed and equipped to use a wide range of coals, no boiler will perform equally well with all types of coals. All coals have certain properties that place limitations on their most advantageous use. These limitations are especially stringent for many of the older installations. Because of a general lowering of quality of raw coal in recent years, the need for coal cleaning has significantly increased. Among the factors contributing to the need for increased coal preparation are (1) increased demand for quality brought on by market and environmental requirements; (2) increased extraneous dilution caused by mine, health, and safety laws; and (3) depletion of the higher-quality coal seams. The major characteristics of coal and impurities from the standpoint of mechanical cleaning are particle size composition, generally called size consist; density differences; the relative friability of the coal and its associated impurities; hardness; and strength. Some of the other factors related to preparation are petrographic composition and rank. RANK CLASSIFICATION Coal is a general designation for a great number of solid organic minerals with different compositions and properties; all are rather rich in carbon and have a dark color, generally black. Next to mineral oil and kerogen, coal is the most important reservoir of carbon in the world. Carbon is an indispensable necessity of life as well as the main source of energy. Coals are found in stratified deposits, sometimes at great depths. All coals owe their origins to slow decomposition and chemical conversion of immense masses of organic material. As found in seams, coal is a heterogeneous mixture of organic and inorganic materials. Not only are there large differences in the properties of coal originating from different seams, but also in coal removed from different locations in a single seam. A genetic relationship exists between peats, brown coals, lignites, biturninous coals, and anthracites. As a whole, the process of coal formation, or coalification, proceeds as a continuous transformation of plant material, each phase characterized by a degree of coalification, or rank. As a measure of this rank, the carbon content or some related parameter can be used.

Jan 1, 1991

By Jim V. Rouse

Adverse water-quality impacts of uranium mining and milling activities on both surface- and ground-water resources in the Grants Mineral Belt have recently been documented.1 In some cases, the impacts resulted in violation of existing regulations and license conditions and have endangered public health. Unfortunately, industry-sponsored ground-water monitoring programs do not adequately record the actual impacts of mining and milling on ground-water quality.

Jan 1, 1976

By Vishwajeet Ahuja, Benoit Jones

"INTRODUCTION Shotcrete lining forms an integral part of conventional tunneling and is widely applied for underground excavations. Early strength gain of the shotcrete is a crucial aspect for ground support and safety of operatives. Strength requirements are dependent on various factors such as lining thickness, ground type, excavation size and tunnel depth. The early strength gain is typically monitored using destructive tests, such as needle penetration, stud driving or coring samples for uniaxial compressive strength testing in the laboratory. Being destructive, these tests cannot be directly performed onto the lining without causing damage that must be repaired, which is a particular problem for permanent linings. For this reason and to avoid the need for operatives to work near to exposed ground and/or fresh shotcrete, these destructive tests are often performed on panels, which are sprayed at the same time as the tunnel lining. All current testing methods are also very local, testing only a small part of the lining or a panel, which may not be representative because the temperature history could be significantly different. Therefore, these tests do not provide an accurate or complete picture of the lining strength gain. New testing methods that are non-destructive and can scan the whole lining remotely would be extremely desirable. This paper describes a new method, using thermal imaging techniques, that achieves these aims. It also discusses the real-time on-site application of the method, providing insight into the experience gained and conclusions derived. Shotcrete Shotcrete used for tunnel linings requires immediate strength development. The strength development is a direct result of the hydration reaction of cementitious materials present in it. A progressive sequence of the hydration reaction changes it from a solid suspension (typically referred to as fresh concrete) to a solid skeleton with a porous network and thereafter, into a solid with predominantly discontinuous pores (Byfors 1980). In the case of shotcrete, early strength is needed to support the self-weight and then continuing early age strength gain is required to begin to support ground loads. These strength requirements, along with other workability needs, are met by careful concrete mix design, the use of admixtures, such as accelerator and superplasticizer (BS EN 934-5 2007), and supplementary cementitious materials, such as silica fume."

Jan 1, 2016

By Innocent John Arinze, Chidubem Okwudiri Emedo

This contribution presents the first multi-scale geophysical investigation conducted in the Abakaliki and Obubra mining districts (AOMD), southeastern Nigeria, for the exploration of shallowly emplaced (< 50 m) massive sulfide and barite mineral deposits. Raw airborne magnetic data covering the AOMD was acquired and subjected to diverse enhancement routines to facilitate the identification of areas of subtle magnetic anomalies for subsequent ground truthing. The mineralization is mainly made up of galena, sphalerite, and barite. The contrasting physical properties between these minerals and their host rocks make resistivity, induced polarization (IP), spontaneous potential (SP), and magnetic methods ideal to study and delineate the mineralization and possibly locate the ore bodies. Wenner DC resistivity and IP data acquired along the same parallel traverses are inverted using Res2dinv to produce 2D tomography models of resistivity and chargeability. The resistivity and IP models were successful in delineating zones of sulfide and barite mineralization. The ground SP data collected along the same traverses as the resistivity and IP data were interpreted as line graphs. The 1D SP models show a number of central negative anomalies that could be related to sulfide mineralization. These anomalies show fair-to-good spatial continuity and are in close agreement with the result obtained in the resistivity and chargeability model. This study suggests the presence of exploitable mineral deposits in the AOMD and demonstrates the superior interpretative ability of combined geophysical methods over a single geophysical approach.

Oct 20, 2020

By D. K. DeForest

The olfactory system (sense of smell) is crucial to the ability of fish to avoid predators, recognize kin, and synchronize reproduction (Baldwin et al. 2003). Copper (Cu) has been shown to impair olfaction in juvenile freshwater life stages of salmonids (including Pacific salmon and trout) in some laboratory experiments; and in the United States, public concerns have been expressed that current regulatory criteria for Cu in fresh water are not adequately protective of olfactory function in salmonids (e.g., OSU 2007; Pearson 2007). These concerns have largely been raised because some Cu concentrations that have caused olfactory impairment in salmonids in the laboratory are less than Cu concentrations that have been shown to reduce salmonid survival, growth, or reproduction (the effects endpoints that are typically considered in deriving ambient water quality criteria). However, two important and interrelated points that must be considered: (1) freshwater Cu criteria are "driven" by the sensitivities of several invertebrate species that are more sensitive than the olfactory impairment threshold in salmonids when (2) the influence of water chemistry on Cu bioavailability is properly considered in deriving Cu criteria. Bioavailability refers to the ability of various chemical forms of Cu to interact with receptors on the surface(s) of organisms and thus directly cause toxicity or uptake by the organisms. The toxicity of Cu and other metals to aquatic organisms is a function of water chemistry. For example, acute Cu toxicity in fresh water generally decreases as pH, water hardness (Ca2+ and Mg2+), alkalinity, and dissolved organic carbon (DOC) concentrations increase (Meyer et al. 2007). The U.S. Environmental Protection Agency (USEPA) has recommended hardness-based freshwater aquatic life criteria for Cu and other metals since the 1980s (e.g., USEPA 1985); and hardness-based metals criteria decrease (i.e., become more restrictive) as water hardness decreases. More recently, the USEPA has recommended freshwater aquatic life criteria for Cu based on the biotic ligand model (BLM; USEPA 2007), which accounts for the influence of multiple water chemistry parameters, including DOC, pH, alkalinity, Ca2+, Mg2+, and several other cations and anions. The BLM-based Cu criteria generally decrease as DOC concentration, pH, alkalinity, and water hardness decrease. Because DOC has a stronger influence on Cu bioavailability than water hardness, hardness-based and BLM-based Cu criteria can differ considerably. For example, in water that has low DOC and high hardness, the hardness-based Cu criterion would be relatively high (because it is driven by the high hardness) but the BLM-based Cu criterion would be relatively low (because it is driven by the low DOC). Thus, any evaluation of the protectiveness of Cu criteria against a given effect, such as olfactory impairment, must properly account for the chemistry of the exposure water. Meyer et al. (2013) compiled data on Cu-induced olfactory impairment and olfactory-induced behavioral effects from tests in which BLM parameters were measured. They demonstrated that the USEPA&apos;s BLM-based freshwater life criteria for Cu are protective against olfactory impairment, because it adequately accounts for water chemistry (whereas the USEPA&apos;s hardness-based Cu criteria are not consistently protective). Olfactory impairment by Cu is now receiving increased attention in Canada and Europe (e.g., Wall 2013; Stang 2013). Accordingly, in this paper we have expanded the analysis of Meyer et al. (2013) to consider copper guidelines from various other countries and whether these guidelines are protective against olfactory impairment.

Feb 23, 2014