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By C. Hutton

"SynopsisThe last commodities supercycle (2003 to 2011) was characterized by a belief in volume at any cost, where absolute output was deliberately prioritized over productivity considerations. This practice fuelled overoptimistic forecasting and planning, which in turn contributed to the economic crisis that followed. The sudden collapse of commodity prices has resulted in mining companies scrambling to find the right balance between optimizing current operations and preserving sufficient flexibility to grasp future opportunities. The runaway costs of building and operating mines have almost squeezed out profit margins, while lower ore grades are inflating production costs. Mining companies therefore need to look at the business with fresh eyes, and develop strategies to attract equity capital as traditional approaches are simply not working anymore. This is especially so in the context of a dwindling investor base that continues to demand greater returns, despite a significantly lower appetite for risk. This paper revisits the micro-economic concepts and demonstrates how pressure from shareholders to prioritize output contributed to spiralling costs and value destruction. Practical techniques are described to model cost curves to optimize a Mineral Resource endowment and address the need to rightbalance a business and preserve agility.IntroductionHenry Lazenby (2014) for the Mining Weekly writes, ‘Bruised and battered, the global mining industry today is undergoing a sea change. Practices and policies that might have worked wonders in the past are not as relevant today, and new approaches to running profitable mining operations need to be found.’ One significant practice the mining industry had during the last commodities supercycle (2003 to 2011) was chasing volume at any cost; absolute output was deliberately prioritized over productivity considerations (Goldsmith, 2013). Lazenby contends that in the face of falling and volatile commodity prices, many mining majors ‘across all commodity groups are currently grappling with sagging profits and low company valuations. This is often regarded as the result of the were in pursuit of growing their output at all costs in a high commodity price environment.’ Lee Hodgkinson, KPMG’s Canadian mining industry leader and quoted by Lazenby, says that ‘mining companies are now trying to find the right balance between optimizing current operations and preserving their agility to grasp future opportunities. The runaway costs of building and operating mines have almost squeezed out profit margins [whilst] lower grades of ore are inflating production costs. Mining companies need to look at the business with fresh eyes, and develop strategies to attract equity capital as it seems clear that some of the traditional approaches to the mining business are simply not working anymore."

Jan 1, 2015

By Dave Bigby

Hatworth Colliery, operated by RJB Mining (UK) Ltd, is successfully mining the Deep Soft Seam at a depth of 1000m using single face retreat longwalling. The seam is characterised by a weak roof generally comprising 4 to 6m of well bedded carbonaceous mudstones overlain by weak siltstones. The paper describes the layout and support design strategies which have enabled the colliery to adopt sole support by rock reinforcement techniques for its longwall gateroads. To achieve this success the colliery layout has had to be radically modified to take account of the in-situ horizontal stress field. The layout is also closely controlled by environmental considerations, the seam being one of the gassiest in the UK Economic support by strata reinforcement has been achieved using a combination of rockbolting of the roof and sides installed at the face of the heading, and systematic double birdcage cable bolting installed on drivage and supplemented ahead of the retreating panel. The layout and support strategies have been developed through a combination of detailed underground measurement of support and stress parameters backed up by numerical modelling using FLAC. The FLAC modelling has paid particular attention to careful representation of bedding properties and validation through underground stress measurement.

Jan 1, 1996

By Frank Haehnig, Kjell-Åke Averstad, Johannes Glückert

"AbstractThe Söderströmstunneln is part of the Citybanan project that is currently under construction in the centre of Stockholm. Main part of the lot Söderströmstunneln is a 300m long immersed tunnel connecting the inner-city islands Södermalm and Riddarholmen. It consists of three tunnel elements that have been immersed in summer 2013. Since the solid bedrock is descending in that area to more then 40m depth, the tunnel elements have been placed and are permanently supported on four pile groups that have been constructed in advance. The common Swedish system of steel core piles has been used to built the pile groups. Drilling and installation of the steel cores piles in free water depth of up to 20m had to be done from a pontoon. The steel core piles are connected with underwater concrete pile caps.IntroductionCitybanan is a new 6km long double track railway tunnel running beneath central Stockholm including two new underground stations Odenplan and Stockholm City. When completed in 2017 commuter trains will have their own tracks through Stockholm, whereas the remaining railway traffic will continue to use the exisiting two tracks (see Fig. 1). This will double the capacity of the railway traffic through Stockholm. The Swedish transport administration Trafikverket is the client for this project. The design and built contract is carried out by the German contractor Züblin Spezialtiefbau GmbH together with their Swedish subsidiary Züblin Scandinavia AS.As the new Citybanan tunnel is in large parts situated below the bedrock level, it can be executed as rocktunnel in the common drill and blast method. Between the two inner-city islands Södermalm and Riddarholmen the tunnel is crossing the Söderström, an arm of the lake Mälaren. Here the bedrock is descending to a deep valley with more then 40m depth. To connect the rock tunnels between these islands a 300m long immersed concrete tunnel supported on pile foundations is currently under construction."

Jan 1, 2014

By James E. Hill

Tremendous improvements in mining technology have been witnessed during the past 100 years. For example, before 1860 all blastholes were drilled manually and blasting was done with low-energy black-powder. During the 1860's both the pneumatic rock drill and high-energy dynamite were introduced, ushering in an era of mining mechanization that has steadily progressed since that time. Today, with the rapid implementation of the latest advances in communication science, mining technology is moving into a new era that goes beyond mechanization as such. Transistors, transducers, scanners, telemetry, and the like, all terms largely derived from the new communication sciences, add up to what is popularly know as automation-the communication of machine with machine. Automation is now playing an important role in selected parts of the mining process, such as hoisting, hydraulic roof supports, and underground surface locomotive haulage and belt conveyor systems. But this year marked the first attempt to auto-mate the total mining process with the commencement of production at the British National Coal Boards Bevercotes mine. If this full-scale experiment proves successful, it could lead towards other fully automated mines in both Britain and other parts of the world. This decade, there-fore, could be considered the one that provided the foundation for the mines of the future.

Jan 1, 1966

By E. D. Palmes

This report was prepared by New York University Medical Center, Institute of Environmental Medicine, 550 First Avenue, New York, New York under USBM Grant Number G0133066, Personal Samplers for CO, NO and NO2 in Air. The grant was initiated under the Coal Mine Health and Safety Program. It was administered under the technical direction of the Pittsburgh Mining and Safety Research Center with Dr. George H. Schnakenberg acting as the Technical Project Officer. Mr. L. Young was the contract administrator for the Bureau of Mines. This report is a summary of the work recently completed as part of this grant during the period 3/1/73 to 11/30/76. This report was submitted by the authors in March, 1977.

Jan 1, 1977

By M. E. Poad, J. K. Whyatt, T. J. Williams

Researchers at the U.S. Bureau of Mimes monitored rock mass response to mining of an experimental underhand longwall stope in Hecla Mining Co.'s Lucky Friday Mine, Mullan, ID. This stope design, the Lucky Friday underhand longwall (LFUL), was proposed as a means of controlling rock bursting while also allowing increased mechanization of mining operations. Instruments were specifically manufactured to monitor three geomechanical factors (backfill performance, ramp stability, and rock mass response) that directly affect the success of stope design. Despite considerable difficulties with instrument installation and survival in the harsh mine environment, especially within the stope fill, sufficient information was collected to suggest that the LFUL method was successful in achieving project goals. This conclusion, in addition to favorable economic and operational evidence, led the mine to adopt the method throughout the mine. Indeed, this study and mining experience suggest that underhand longwall mining could be considered a feasible mining method for rock-burst-prone ground throughout the Coeur d'Alene District. Further Reports of Investigations (RI) in this series present in-depth analyses of the effects of backfill on rock bursting and calibration of a stope numerical model.

Jan 1, 1992

By Weber P, Sneyd S

The total world steel production in 1998 amounted to approximately 780 000 000 t. The share of electric steelmaking was in the range of 35 per cent and is expected to increase further to over 40 per cent of the world's production within the next ten years. As electric steelmaking is primarily based on the use of scrap and as it is progressing more and more into higher steel grades the need for low-residual metallics will become increasingly important. Consequently, the demand for scrap substitute material will increase, reflected in the world wide spate of interest for DRI (Direct Reduced Iron) and HBI (Hot Briquetted Iron). The increased significance of DRI/HBI as a substitute for steel scrap has obviously emanated also from its comparatively lower and more predictable costs per ton and definable chemistry. In 1998 already 37 million tons of DRI/HBI were globally produced.

Jan 1, 1999

By J. D. Appleton, J. Ridgway, K. B. Greally

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). The results suggest that meaningful geochemical maps can be produced from very low-density surveys, and that existing data sets could perhaps be incorporated into such a map series with the use of a system such as Uniras software. There are still many problems to be resolved, however, including the compatibility of data derived from different analytical methods, and the precise methods to be employed will necessarily require international agreement. Sampling densities should be chosen on the basis of the scale of the geochemical and geological features to be distinguished and will vary from region to region. Reanalysis of selected samples from archives to increase the range of elements determined or to unify analytical methods is only likely to be effective if the original survey was at quite a low density

Jul 1, 1991

By G. W. Jones

In a previous report,6 results were given that showed the amount of natural ventilation in a manhole having a capacity of 74.l cubic feet when the number of ventilation openings in the cover was varied. from no openings to a maximum of 48. The results showed that the ventilation (air changes per day) in the manhole was proportional to the area of the openings in the cover, and also that the number or area of the openings was the factor that chiefly affected the ventilation.

Jan 1, 1937

By A. M. R. Neiva

The WNW-ESE-trending hydrothermal veins cut alternating mica schists and quartzites of mainly Ordovician age and, to the west, a Hercynian muscovite-biotite granite. They have been prospected and developed to a depth of 300 m and reserves of 20 t Au estimated. The paragenetic sequence and chemical compositions of the ore minerals are generally similar to those at Jales to the south. Gold, electrum and aurian silver form inclusions in arsenopyrite, pyrite, galena, sphalerite, pyrrhotite and quartz and also occur in veinlets that cut these minerals. Silver has been found in gold, electrum, aurian silver, tetrahedrite, freibergite and the Ag-Pb-Sb sulphide owyheeite. Early arsenopyrite crystallised at an estimated 480 degrees C and the more common, later arsenopyrite in which Au and Ag are generally included at 430-300 degrees C. Sphalerite crystallised at 307-100 degrees C. Monoclinic pyrrhotite may have been formed by the inversion of hexagonal pyrrhotite at 248 degrees C

Jun 16, 1905

By Verne E. Hooker

Near-surface temperature measurements in two granite quarries show that diurnal temperature variations are significant to a depth of 1 or 2 feet, and annual temperature variations are significant to a depth of at least 25 feet. As a result, ground stress anomalies due to temperature exist near the surface, and their magnitude depends upon the time of day and the time of year. Rock stress and corresponding temperature measurements were made in one granite quarry over a rock temperature range of 33° to 81° F. Measured rock temperatures show good agreement with values predicted from one-dimensional heat flow theory. Calculated and measured stress-temperature coefficients for the two granites in this study are given. Thermally induced stress variations in near-surface rocks tested were as large as 1,690 psi from combined daily and seasonal temperature changes.

Jan 1, 1971

By Etienne Audibert

No satisfactory theory has yet been advanced to explain what takes place when an explosive is fired in a mixture of firedamp and air. The only means of measuring the danger is to fire the explosive into the gas mixture and note the effect, but the conditions of firing must be chosen carefully. This report is presented in the hope that it will assist in determining what method to use. The experiments have been designed to show the effect of the principal factors involved in the conditions of firing, and the results give information that seems to have some value.

Jan 1, 1940

By Najdat I. Aziz

There are different schools of thoughts about the influence of gas pressure on coal strength. Researchers have reached contradictory results with regard to the effect of confining gas pressure on tensile strength of coal. Accordingly, this paper re-examines the influence of gas pressure on the strength of coal. A specially designed precision drill capable of drilling in a pressurised chamber was used to drill coal samples under both atmospheric and increased gas pressure environment. The drill cuttings were examined for particle size distribution using a laser controlled Malvern Mastersizer S particle size analyser. Petrographic analysis of the sample examined the effect of gas pressures on the maceral structure and the composition of coal. The paper demonstrates that there is a definite variation in the range of particle size distribution with particles obtained from drilling coal samples not subjected to gas pressures, in comparison with those obtained from samples drilled under confined gas pressure. Also observed were the changes in the rate of drilling in soft coal obtained from geologically-disturbed zones compared with other coal samples. Some variation on the maceral compostion of coals were also observed in relation to increased gas pressures and gas type.

Jan 1, 1996

This paper forms the second of a series, in which it is proposed to communicate the results of an extensive research into the influence of alloying elements on the physical properties of lead, now being carried out in the Metallurgy School of the University of Melbourne.Some general comments on this research were made by the present writer as an introduction to the first contribution by R. S. Russell*: It was there pointed out that it was the intention to prepare lead as pure as possible, to determine its properties and then to make alloys with the various elements added singly, and in various combinations, in order to determine the effect of each. This line of action is still being pursued.It occurred to the writer, however, that this fundamental attack might, with advantage, be accompanied by a parallel investigation in which lead of commercial purity would form the basis material. In this way, using a standard *Professor of Metallurgy, University of Melbourne.

Jan 1, 1934

By J. G. Haymes

This report by the Bureau of Mines is the first of two proposed papers on evaluation of spectrophotometric, spectrographic, polarographic, and other analytical methods for quantitatively determining impurities in high-purity tungsten. Some of the methods described are standard methods that have been successfully applied to determine low-level impurities, several are modifications of known methods, and some procedures are entirely original. The Bureau of Mines is actively engaged in tungsten research because tungsten has an extremely high melting point, in fact the highest of any known metal. The metallurgist must know the content of impurities in tungsten because of the marked effects even micro amounts of impurity elements have on its physical properties. The Bureau procured a number of analyzed samples of above-average purity from research laboratories of companies engaged in production and fabrication of tungsten. These samples were investigated by the analytical procedures of those companies for several metallic impurities. Subsequent analytical laboratory determination of impurities in these samples agreed with the analyses as reported. With this assurance that analytical methods were basically accurate for metallic impurities, procedures for the determination of several of these elements were modified to lower the limits of detection and increase the sensitivity of methods. Carbon and the gases hydrogen, nitrogen, and oxygen were determined by standard instrumental methods, modified to provide greater sensitivity for reliable determinations when content of these elements was low. After the reliability of the modified procedures was affirmed, they were used as a product evaluation guide in the development of a vapor-plating technique for the production of high-purity tungsten. The following list of elements can be determined by one or more of these methods: AI, B, Be, Ca, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, S1, Sn, Ti, V, and Zn. In addition, a vacuum-fusion method for the determination of H, N, and 0, and a conductometric method for carbon are described. Lower limits of determination and detection for each element listed are given.

Jan 1, 1962

By D. K. Chibwe, P. Taskinen

"This investigation consists of a numerical and physical modelling exercise on flow patterns, mixing, solid-liquid mass transfer, and slag-matte phase distribution in a 0.2-scale cold model of an industrial Peirce-Smith converter (PSC). Water, kerosene, air, and sintered benzoic acid compacts were used to simulate matte, slag, injected gas, and solid additions into the PSC. The 2D and 3D numerical simulations were carried out using volume of fluid (VOF) and realizable k-e (RKE) turbulence models to account for the multiphase and turbulence nature of the flow respectively. These models were implemented using the commercial computational fluid dynamics numerical code FLUENT.Numerical and physical simulations were able to predict, in agreement, the mixing and dispersion characteristics of the system in relation to various blowing conditions. Measurement of mass transfer indicated that fluid flow in the PSC is stratified. Blowing configurations and slag volume both had significant effects on mixing propagation, wave formation, and splashing.As a potential process alternative to increase conversion efficiency, we propose a combined blowing configuration using top lance and lateral nozzles. The numerical simulations were conducted on combined as well as lateral blowing conditions, and the results of the combined concept are encouraging."

Jan 1, 2015

By A E. Annels, I P. Hodkinson an, S P. Barr

Narrow vein systems represent an important source of gold, which have generally been exploited by small to medium sized companies. Their evaluation poses particular problems because of their grade and geological complexities. The determination of grade is arguably the most important activity in resource estimation, as it is generally grade and not tonnage that makes an orebody. This is particularly true of narrow vein-gold deposits whose resources are generally relatively small, though medium to high-grade (6 - 40+ g/t). They often display extreme grade anisotropy in all directions. Two grade populations are generally observed; 1) low, often subeconomic, background grades and 2) high-grades associated with discrete ore shoots. It is possible for gold to be distributed within the wallrocks as well as within the vein. Extremely high-grade values typify this style of mineralisation and require special consideration during grade estimation to determine if top cutting is valid or not. Estimation of both width and accumulation in 2D on vertical longitudinal projections or inclined planes have historically been used to evaluate narrow veins. Resource estimates based on traditional 2D methods is still widespread, but has in some cases been replaced by computer-based 3D modelling. Grade estimation methods are well-known, ranging from classical to geostatistical. Historically, classical methods such as inverse distance weighting have been used, though geostatistical indicator kriging methods are sometimes applicable. Geostatistical studies are driven by the production of reliable variograms, which in narrow gold veins is often problematic. It is generally difficult to define resources from drillhole intersections beyond the inferred and indicated categories with any confidence. In the majority of cases underground development is required to define measured resources and ore reserves. Trial mining/bulk sampling is often used to test estimated grades and also provides important data on ground conditions and the parameters relating to the proposed mining method required for ore reserve definition. Regular reconciliation should be undertaken between the estimated stope grades, grades indicated from stope/truck sampling and grades realised in the mill in order to determine whether correct evaluation strategies are being applied. The important feature of narrow vein-gold deposits is their strong geological controls; in response to this, geologists must understand the geology as best as possible.

Jan 1, 1999

By Gordon T. Austin

The combined value of production of natural abrasives, which include tripoli, special silica stone, garnet, staurolite, and emery, increased about 4% in 1990. The increase in the value of tripoli production was the result of an increase in the unit value. Emery increased owing to an in? crease in the volume of the material produced and an increase in the unit value. Special silica stone experienced a decrease in unit value and an increase in the quantity produced. Garnet showed a 10% in? crease in quantity and a 73% increase in unit value. Staurolite decreased about 8% in the quantity produced, and the value of production decreased about 10%. The fused aluminum oxide industry showed a 5% decline in the quantity produced and in the value of production. The silicon carbide industry saw a 10% decrease in the quantity produced and a 9% decrease in the value of production. Production for both industries decreased 7% in quantity and value compared with those of 1989.

Jan 1, 1993

By James Gibbs

In order to provide an initial approach to the deposits of oil shale, nahcolite, and dawsonite in the central area or the Piceance Creek Basin in northwestern Colorado, the U.S.B.M. and associated contractor personnel drilled and cased a 96-inch ID shaft to a depth of 2,371 feet. The shaft was constructed using ?big hole? drilling techniques and succeeded in giving access to previously inaccessible deposits of the above minerals. This report documents the construction from its beginning in January 1977 to its completion in January 1978. Procedures used and problems encountered are discussed in detail.

Jan 1, 1978

By William G. Pariseau

The research reported here concerns ground control in multi-seam mining and relates mainly to the analysis of stress about multi-seam room and pillar mines. The two variables of most concern are distance between seams and alignment of pillars between seams. The first year results of the two year investigation apply to the development phase of mining when the extraction is typically less than 50 percent. The second year effort is concentrated on retreat mining and barrier pillar safety when the extraction is typically greater than 50%. The procedures in both cases are readily applicable to more than two seams. Although two seam mines are the most frequent type of multi-seam operations, because of the potential for three seam operations in the Western United States, a number of three seam development analyses are also presented. The results enable one to make a rapid assessment of stability of rooms and pillars during production and barrier pillar size during extraction of adjacent panels. In the event of low safety factors, more site-specific analyses can be undertaken.

Jan 1, 1983