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By D. Triantis

This paper presents the results of laboratory experiments for the detection of electric signals from Fiber Reinforced Polymer (FRP) sheet samples which have undergone a temporally increasing loading of bending type up to fracture. Electric signals that were recorded while the sample was subjected to bending are referred from now on as Bending Stimulated Currents (BSC), in order to differentiate them from the relevant signals emitted by materials that suffer uniaxial compressional stress. The latter signals are referenced as Pressure Stimulated Currents (PSC). BSC emitted from FRP sheet samples presented here, were recorded after applying three successive load steps to samples. The increase rate of applied stress was about 0.15kN/s. Initially starting from low load values to higher load values until the FRP sheet reaches at a state just before its failure. The BSC records from FRP samples are compared to equivalent recordings from cement mortar beam and distinguishable differences are discussed.

Jan 1, 2006

By Frigyes Egerer, Pál Bárczy

Introduction Charles III, Holy Roman Emperor and King of the Austro-Hungarian Monarchy, established one of the first mining schools in Europe on June 22, 1735, in Selmecbanya (Schemnitz in German and Banska Stiavmica in Slovakian). The old city, built around the ancient gold mines, is shown in a contemporary engraving in Fig. 1. Charles' historical decree consisted of 13 chapters and included: the deed of foundation, the definition of grants, instruction for educational policy and curriculum, disciplinary rules, and the appointment of personnel. The first professor of the school, Samuel Mikoviny, gave his first lecture the same year, in December 1735. The 250th anniversary of the establishment of the School of Mines was celebrated Sept. 2-4, 1985, in Miskolc. It was attended by representatives of other Hungarian and of several foreign technical universities. A silver medallion (Fig. 2) was issued to commemorate the occasion and a series of lectures

Jan 6, 1986

By M. J. Liesveld, D. Liesveld

For a Colorado mountain quarry, the Water Jet Channeling Method is far superior to Burning, Sawing, Drilling, or Shooting with Primer Cord, Water, or Black Powder. Throughout the life of our quarry, which was founded in 1947, we have used all the methods and turned to the Water Jet Channeler, which we invented and patented as our ideal way to remove dimension granite from our quarry. We jet the block on 4 sides and remove the block with plugs and feathers on the backside. The Water Jet uses approx 7.5 l/m (2 gpm) running at310,000 kPa (45,000 psi) to erode the crystals @ 1sm/h (10sf/h).The 0.533mm (.021”) nozzle oscillates back and forth to achieve an approx 5cm (2”) channel. Using the Jet, we do not lose corners or cause cracks in our red fine grain light class 5 granite.

Jan 1, 2004

By D. A. Elgillani, N. A. Abdel-Khalek

The role of ZnS04 in activation of sphalerite (ZnS) and deactivation of lead-activated sphalerite has been investigated. Adsorption of metallic ions at the solid-solution interface, electro kinetic results for sphalerite under different chemical conditions, and thermodynamic calculations were used to elucidate the mechanisms involved. It is shown that flotation response of sphalerite in absence of activators is rather weak and that adsorption of ethyl xanthate on the mineral mainly electrostatic in nature. Zinc sulfate is found to activate the mineral but only in a narrow acidic pH range. This is attributed to the increase of zeta potential as well as the possible increase in amount of negatively charged bulk precipitated zinc xanthate. Lead ions activate sphalerite in a wide pH range and the lead activated mineral assumes a flotation behavior similar to that of galena (PbS). However, addition of ZnS04 depresses the lead-activated sphalerite by replacing lead ions at the mineral/solution interface.

Jan 1, 1999

By D. F. Martin

Sustainability is typically understood as having three interrelated dimensions-environmental, economic, and social. However, far less attention has been paid to social sustainability than to the other two forms. The paper argues that one of the difficulties in giving substance to the concept of social sustainability is that it is inherently value-dependent and has major conceptual, definitional and therefore measurement issues. This is particularly the case in complex crosscultural environments such as those found in Australian mine hinterlands with significant Aboriginal populations. Nonetheless, a concept of social sustainability can provide an important counter to the usual focus on environmental and economic sustainability, and can productively guide the minerals industry in its engagement with the Aboriginal people of mine hinterlands. The paper outlines a set of principles for socially sustainable communities, and proposes means by which these principles can be implemented. It further suggests that these principles may have broader applicability than just in the case of Aboriginal people.

Jan 1, 2005

By M. Prasad, G. M. Rao, A. K. Majumder, T. C. Rao

Froth flotation was employed to beneficiate a lean-grade siliceous rock-phosphate ore containing fluorapatite, the phosphate-bearing mineral. The main gangue minerals were quartz, iron oxides and aluminum oxides. After the rougher stage, four cleaning stages were required to upgrade the ore. The liberation size of the phosphate mineral was below 200 mesh, The reagent scheme consisted of commercial-grade sodium silicate and sodium oleate. The effect of reagent dosages, number of cleaning stages and pulp density on the efficiences of separation were studied systematically. A flowsheet was proposed for the processing of low-grade siliceous phosphate ore containing 12.1% P2O5, 55.36% SiO2 and 15.45% CaO. The flowsheet provided a useable phosphate concentrate containing 34.18% P2O5 and 14.20% SiO2 with a P2O5 recovery of 70.4% (the weight yield was 25.0%).

Jan 1, 1999

By P. V. R. Bhaskar Sarma, P. K. Sahoo, G. Roy Chaudhury

A process was developed to treat an ammoniacal leach liquor containing zinc using Di (2-ethyl hexyl) phosphoric acid (D2EHPA) as the extractant. The objective of this work was to develop a process package for the treatment of complex sulfide leach liquors. Zinc extraction could not be carried out directly from the ammoniacal solution in mixer-settler units because of crud formation and low extraction efficiency. After neutralizing the free ammonia with H2SO4, the extraction efficiency was only about 40%, due to the high concentration of (NH4)2SO4. To decrease the (NH4)2SO4 concentration, the free NH3 was steam stripped, and the resultant liquor was subjected to zinc solvent extraction. An extraction efficiency of 98% could be achieved by controlling the equilibrium pH. Stripping studies were also optimized after removing ammonia from the zinc-loaded organic. A continuous 100-hr operation that included extraction, scrubbing and stripping, was carried out successfully.

Jan 1, 1995

By B. C. Cornilsen, X. Shan, D. H. Carlson, J. H. Johnson

Airborne respirable Diesel Particulate (DP) presents an additional health hazard in that it has been shown to be mutagenic. This problem is of increasing concern as more coal mines introduce diesel vehicles. If the DP present in coal mine air is to be controlled it must first be measured. This paper describes development of the laser Raman spectroscopic measurement of the amount of DP in DP/coal mixtures collected on filters in the laboratory and in coal mines. The Raman technique provides a chemical measure of the carbonaceous material in each component, and is not dependent upon particle size. When this work was begun there were no known analytical methods for this measurement. Side-by-side in-mine comparisons of the results obtained from Raman, neutron activation analysis, and size selective analyses (MOUDI and personal samplers) are presented. The neutron activation and size selective analyses were obtained by the USBM Twin Cities Research Center and University of Minnesota. Good agreement has been found among these three methods.

Jan 1, 1991

By Gemei Yang, Yihui Zhao

In caved goaf, the friction loss of fluid head is: [h = (R'+ R/Q/ )] Q (for one-dimensional transition flow). The R' and R, which are the functions of two dimensional spaces, are calculated through an empirical formula. Then, the bulking factor and permeability are determined. It is supposed that the airflow in porous media are similar to those in tiny tubes crossing each other. Therefore, the network calculation technique can be used to tackle the field transition flow problem. A lot of case studies showed that the emission of methane in mines mainly depends on the air velocity and has little relation to air pressure. Summing up our experience and experiments, we provide an empirical formula to calculate the gas emission rate per unit area. By means of mass conservation and network calculation, the methane content distribution in steady-state is worked out. Then the dynamic change in airflows and gas content can be analyzed by the characteristic-difference method.

Jan 1, 1987

By Gary A. Almeraris, Thomas F. Peyton

This paper chronicles the mining of a main interceptor sewer through a residential neighborhood for the MWRA's Boston Harbor clean-up. The Wellesley Extension Sewer Tunnel consisted of 490 m (1600 ft) of rock tunnel, 107 m (35V ft) of mixed face and 336 m (1100 ft) of softground. The tunnel was located 4.6 m (15 ft) below water table and passed directly beneath six buildings with as little as 7 m (23 ft) of cover. In addition, the tunnel ran parallel to and within 4.6 m (15 ft) of an existing sewer tunnel with flows up to 187,5 million liters (50 million gal.) per day. The rock encountered by the tunnel was comprised of gramodiorite, amphibilite and diabase. The soils which passed through the tunnel face consisted of tills, sands and non-cohesive plastic silts. The techniques developed and the equipment utilized to successfully mine this complicated ground are described.

Jan 1, 1991

By P. R. Khangaonkar, G. Bhaskar Raju

Three types of flotation columns were developed with a column dia of 8.0 cm and a length of 160 cm. The first type consists of an ordinary column fitted with a porous plate at the bottom. The second type consists of two electrodes at the bottom to obtain very fine and uniform bubbles generated electrolytically and the third is a combination of first and second types, i.e. to get both electrolytic bubbles and air from the compressor through porous plate. Three different ores were tested-gold tailings for recovery of scheelite, copper tailings (chalcopyrite) and oxide copper ore. In the case of scheelite and copper oxides, good results were obtained with the first type of column itself, whereas the third type column was found fairly effective in the recovery of chalcopyrite. The variables like the effect of reagent concentration, column height above the feed point, feed flow rate, current density, air flow rate, particle size etc. were examined.

Jan 1, 1988

By W. Petruk

Mineral liberations that would be obtained by grinding an ore to a specific size can be predicted by analyzing unbroken ore pieces, and mineral liberations in ground ores and mill products can be determined directly by image analysis. Predictions of mineral liberations are made by measuring size distributions and textures of mineral grains by image analysis and using liberation models. Ground ores and mill products are analyzed to determine the proportion of mineral that is liberated, and the data are used to evaluate mineral behavior during mineral beneficiation. The liberation data for minerals in a suite of mill products from a circuit are processed by a materials balancing technique to calculate recoveries of minerals in different types of particles throughout the circuit. The liberation-materials balance data define mineral recoveries; define the behavior of an ore in a concentrator, pilot plant or bench test: and indicate whether recovery improvements are possible and/or feasible.

Jan 1, 1992

By S. Ersayin, I. Iwasaki

Laboratory- and pilot-scale tests were carried out to study the effects of a magnetically enhanced hydroseparator on a magnetic taconite sample. The test parameters included feed flow rate, percent solids and magnetic field strength. Laboratory tests showed that magnetic iron losses could be effectively prevented by applying a magnetic field strength of 0.003 T (30 gauss) to a hydroseparator. A relatively uniform magnetic field within a pilot-scale hydroseparator was obtained by installing a magnetic grid within the device. The test parameters for the pilot-scale study also included the effects of magnetizing/demagnetizing the feed and magnetizing current. Magnetic iron losses were substantially reduced, even when the hydroseparator was operated at very high upward velocities. Results also show that increasing the field strength decreased the losses, but magnetic enhancement was successful even at the lowest field strengths, and the results show that magnetic iron losses were lower when the feed was magnetized. Key words: Hydroseparator, Magnetic field, Magnetic grid, Taconite processing, Magnetizing, Demagnetizing.

Jan 1, 2003

By Eleanora I. Robbins, Motoaki Sato

Many problems associated with acid mine drainage (AMD) are caused by the complex way molecular oxygen (O2) oxidizes reduced matter at surface temperatures. In aqueous solution, O2 kinetically "prefers" to go through the formation of hydrogen peroxide (H2O2) as an intermediate. Being innately unstable, H2O2 is quickly decomposed back to water and oxygen in the presence of dissolved Fe and Mn, both catalysts for the decomposition. Direct addition of H2O2 to AMD produced similar results. Ozone (O3) is a much faster and stronger oxidizer than either O2 or H2O2. In the laboratory, O3 rapidly precipitated Mn, Fe, Ni, Co, Pb, and Ag even in acidic solutions. The experiments indicate that AMD can probably be processed with ozone and metal oxides/hydroxide recovered in flow systems using only septic-tank-size reactors and small sedimentation ponds.

Jan 1, 2000

By D. A. Newman

A longwall chain pillar is comprised of two distinct zones, a solid elastic core enclosed by an exterior of failed or yielded coal. For the purpose of pillar design, the ability to delineate the extent of pillar yielding and correlate the yielding with the applied pillar load is of fundamental importance. A study was initiated on a longwall section of a West Virginia mine to: (1) delineate the location of the elastic core-yield zone boundary, (2) examine the stress distribution within the pillar, and (3) quantify pillar stability as the longwall face retreated toward an instrumented pillar. A US Bureau of Mines sonic velocity probe was used in conjunction with vibrating wire stress meters to define the elastic core-yield zone boundary and the migration of vertical stress toward the pillar core. The extent of the yield zone as determined by field results is compared with the extent of the failed zone as predicted using a series of equations developed by Wilson.

Jan 1, 1988

By Eli Curiel, Ingar F. Walder, Patrizia P. Schuster, Walt Keyes

Mansfield Canyon, of the Wrightson Mining District, Santa Cruz County, Coronado National Forest, Arizona, was actively mined in the late 1800's and early 19001s, with minor activity until 1953. The main products were lead, silver, copper, zinc, and gold occurring in polymetallic quartz veins. The canyon contains numerous adits and waste dumps, some of which generate metal-loaded acid. Samples of seeps, waste dumps and bedrock have been collected for various analyses: metal concentrations, acid base accounting (ABA), and water quality to evaluate the extent of oxidation and metal release from the start of mining until present, the potential impact, and reclamation options. Although the waste-rock piles within the canyon are small (2,000-10,000 tons), they have a high sulfide content with little or no neutralizing capacity. It is planned, therefore, to move the waste piles either to a constructed repository site within the canyon or to a copper leach facility to be used as an acid generator.

Jan 1, 2000

By Robert Dimock

The successful management of large dispersed mineral operations is dependent upon accurate and timely decision making. The plant locations providing the data to support the decision making process are generally separated by distances which elongate the time required to accumulate the data at a central focus. The need exists to examine operational data in context with total mining operations, and in relation to target projections and historical trends. The use of microcomputers for local information tasks is an established capability. Grouping microcomputers into local-area networks is rapidly becoming established. Interconnecting multiple local-area networks to provide a free flowing stream of information between all operational locations of a mining enterprise is possible with use of some emerging technologies. The benefit of the potential interconnections and rapid transfer of information can readily be seen from a production reporting perspective. Numerous other advantages exist' by providing routing to enable a workgroup to be established between separated work functions.

Jan 1, 1989

By H. Tutu

The legacy of gold mining operations continues to affect water quality in the Witwatersrand Basin in South Africa. The acid mine drainage (AMD) emanating from the tailings dumps liberates heavy metals from the ore minerals. The objective of this study was to characterise the geochemical processes that are important in understanding chemical evolution of polluted water in the study area. Analytical results for water samples collected in the catchment of the study area generally showed elevated concentrations of heavy metals in the vicinity of tailings dumps and mining operations and a decrease in the distal. Dams and wetlands, despite their proximity to the tailings dumps, recorded low concentrations of heavy metals and other pollutants. The characterisation of AMD was summarised in a conceptual model in which plots of redox potential versus pH and electrical conductivity versus pH were identified as the most important sub-models that captured the gross physical-chemical characteristics of polluted water and its interaction with the environment.

Jan 1, 2006

The US Bureau of Mines' dictionary of mining terms defines productivity as "the efficiency with which economic resources (men, material, and machines) are employed to produce goods and services." Or, the relationship between the physical outputs and the physical inputs used to produce those outputs. As demand for mine materials dropped, mining companies and equipment manufacturers discovered that ratios between the inputs and the final products were disproportionate to the profits realized. Some companies are fighting for survival. The US, while still the most productive country in the world in absolute terms, is looking over its shoulder as other industrialized nations continue to exceed its yearly productive growth rate. According to John Belcher, Jr., of the American Productivity Center in Houston, TX, the US has seen a steady decrease in productivity growth since the mid-1960s. During the post World War II period, the US labor productivity growth rate was 3.2% annually. The slowdown began in 1965 and by the mid-1970s, the country's annual growth rate was 1%. By 1978, labor productivity growth ceased to gain at all and from 1978 to 1980 a 2% decline occurred. Solutions to the productivity decrease are increasing product prices or improving productivity. By increasing prices, though, the producer runs the risk of pricing himself out of the competitive market. To maintain an acceptable profit level, prices must increase proportionately higher than required to offset production cost increases, Belcher says. Many companies are turning to in-house productivity improvement programs as an answer to increased costs and declining profits. These programs are geared toward management commitment and employee awareness of what productivity means. Companies are finding ways of measuring productivity levels in financial reporting, budgeting, and planning. Organizational teams have been formed to coordinate activities and oversee product management, and improve productivity of materials and capital investments. This special issue of Mining Engineering examines productivity in the mining industry. First, there are articles about various, and different, factors that affect productivity in each of ME's five main readership areas - exploration, mining, processing, coal, and industrial minerals. There is also a look at mining industry productivity from the manufacturer's view. The next section of this special issue is devoted to some topics that affect all areas and sectors of mining: research, management practices, computers, maintenance, and energy management. Then follows case studies in exploration, coal, and iron and steel. These studies provide examples of practices and strategies used by companies and operations to boost productivity.

Jan 11, 1983

By K. Anderson

There is a credible, cogent, and responsible argument that mining can be part of a sustainable future in countries with freely elected governments, transparent and enforceable laws, a closure plan with an adequate bond, and a small handful of other measures. This perspective, built largely upon the understanding of mining as a temporary use of the land, is coupled with a growing understanding of economic diversification as a tool to level out the ‘bust’ side of the boom and bust cycle. There are verifiable signs of progress that the sector has, at least in some venues, begun to embrace this view of ‘sustainability’ both in philosophy and practice. While laudable, there remains a conundrum not yet fully explored. It is conceivable that companies can fulfill all legal requirements, practice corporate responsibility in its broadest and most liberal interpretation, and yet leave behind, after the gates are closed and the lights turned off, a situation which is not only unsustainable, but far worse off than before mining started. Having observed this outcome, repeatedly, some critics have concluded that all mining should be stopped. Others recommend that it be vastly curtailed until regulatory regimes are re-vamped, communities fully empowered, and companies brought to heel. Yet others, including many within the industry, are looking to hold back this dark prospect with peer pressure, branding and competition for good will. In this paper, I propose to focus on this discontinuity, that gap wherein the chain of logic breaks and reasonable policies, reason-able choices, reasonable actions, may fail to deliver expected results. I suggest that any meaningful definition of post-closure sustainability must include the concept of human welfare, and increasingly, human security, over and above meeting the requirements of law, beyond retaining shareholder value and reputation, beyond discussions of subsequent land use and diversified employment. I suggest that self-determination, that ability of a people to hold for themselves the vision of their own future, and to have a sense of their power to implement it, may be both the most difficult and the single most important determinant of long-term sustainability in a community. The particulars will vary; a Canadian junior or an Australian multinational, a highly regulated state in the American west or a ‘failing state’ in Africa’s west, gold or sand and gravel. But the recommendation is the same: this must be a collective endeavor, a shared responsibility involving some combination of government, companies, communities, local and international NGOs (non-governmental organizations), each contributing in the ways most able.

Jan 1, 2004