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By Keith L. Harris

The performance of the world economy improved significantly in 1984. Real world output!/ grew 4.3% (compared with 2.6% in 19831, the highest since the 4.4% increase recorded in 1978 (table 1). The output of industrial nations rose 4.9%, while that of the developing nations rose 3.7%. The United States and Japan had the largest increases in output of the major industrial nations, with respective increases of 6.8% and 5.8% (table 2). The components of real output with the most significant growth in the industrial countries were gross fixed investment (9.2%), consumer expenditure (3.1%), and public consumption (2.5%) (table 1). Industrial output, as measured by industrial production indices, has returned to about the 1980 level for most of the major industrial nations (table 2). Exceptions to this were industrial production in Japan and the United States; Japan's industrial production rose steadily throughout the 5-yr period and is now more than 16% above the 1980 level, and the industrial production index for the United States reached 11 1.2 (1980=100.0). Real total domestic demand grew at 8.7% in the United States, more than double the rate of Japan, which, at 4.0%, had the second-largest growth. Average demand for all industrial countries was up 5.1%. During 1984 the U.S. dollar showed great strength on international markets, contributing to large current-dollar negative net exports of goods and services and even larger negative net exports of the merchandise sector. While growing U.S. imports helped spread the benefits of the recovery, they also led to a widening of current account imbalances and growing trade tensions throughout the world.3/, 4/

Jan 1, 1985

All previous attempts to cut rock in boring by means of revolving steel cutters have failed, chiefly in consequence of the mis-shapen teeth grinding the rock and themselves simultaneously, until, after a very few revolutions, the points of the cutters were so worn that it was impossible to force them into the strata. The diamond drilling plant being cumbrous, complicated, and costly, and seeing that fully 70 per cent of the boring generally needed is in what is known as the" milder strata," it will be readily understood that much of the work done will not pay a dividend on the outlay, so great is the cost of removal, the wear and tear of the machinery, and the loss of diamonds. The Calyx Drill, however, invented by Mr. F. Harley Davis, has been constructed so as to overcome these difficulties, and will penetrate quickly and .at a low cost this 70 per cent. of the milder strata. The Drill has taken ten years' hard work and thought to bring it to its present state of perfection, and it will now drill with steel cutters the 70 per cent of the work performed by the diamond drills at a greater speed and at about one third the cost of the latter.The utility of the diamond drill for certain work is undeniable, but it cannot by any means be described as a machine of general popular usefulness that is to say, it is quite beyond the reach of the great masses of mankind.

As the chief field of the gold dredging industry in Otago is the district traversed by the Molyneux River (called above Cromwell the Clutha) and its tributaries, a brief reference to the geology of that region and the origin of its alluvial gold will not be out of place. The prevailing rocks are metamorphic schists, chiefly mica and quartz schists, pr.obably of Silurian age. Though these rocks do not contain many payable quartz reefs, gold appears to be distributed in small quantities all through them,chiefly associated with the quartz lamime and lenses. The river drift, however, contains numerous pebbles of quartzite, quartzoze conglomerate, and fme-grained slate. Seeing that these rocks are hardly known to occur in situ within the watershedof the Molyneux River, though Devonian and carboniferous rocks of similar character occur to the north-east and south-west, it seems probable that the schists were at one time overlaid by carboniferous and Devonian rocks, and that these have been removed by denuding agencies. Be this as it may, it is certain that the schists themselves have been greatly eroded by the action both of water and of ice, and that the resulting drifts have themselves, in many cases, been sorted and re-assorted by the same agents.Consequently the drifts are very varied in character and often developed on a grand scale. In geological age they vary from Early Tertiary (though some may be older) to Recent.

Jan 1, 1903

By Richard E. Danell

"There are a variety of approaches for wall control blasting in open pit mining operations. Safety forworking in the pit is the principal benefit. There are also a number of economic and productivitybenefits when appropriate techniques are used. The purpose and requirements of wall control blasting can vary quite significantly for different operations. When considering blast design, geology, geotechnical factors, drilling, explosives, economics and blasting history are all part of the engineering design process. In many operations, there is a high reliance on blasting history and economics for determining wall control blasting measures. This presentation outlines approaches that broaden the design process and discusses their advantages."

Jan 1, 1997

By Kenneth Pidgeon

The Boston Marine Industrial Park (BMIP) Boat Section, which is part of contract C04A2 of the Central Artery/Tunnel (CA/T) project, is currently under construction in South Boston, Massachusetts (Fig. 1). The Boat Section is approximately 900 feet long and varies in width from about 135 to 185 feet (Fig. 2). The depth to the top of the Boat Section base slab varies from about 28 to 31 feet below final ground surface and about 23 to 26 feet below normal ground water levels. The Boat Section is supported on 578 anchors drilled into the underlying bedrock each designed for a working load of 630 kips. Design and Construction Team The owner of the project is the Massachusetts Highway Department (MHD). The owner's representative is the Management Consultant, Bechtel/Parsons Brinckerhoff. The section design consultant (SDC) consisted of HDR Engineering, Inc. with GEI Consultants, Inc. as the geotechnical subconsultant. The general contractor was the joint venture of Kiewit, Perini, Atkinson, and Cashman. The boat anchors were installed by the subcontractor Delta Geotechnical Services, Inc.

Jan 1, 1994

By Bijan Taheri, Behrouz Maghsodi, Monireh Heshami, Reza Kohan

A common problem recently encountered with the increase in the rate of input feed at Enrichment Plant 2 of the Sarcheshmeh Copper Complex is the loss of value to the tails, translating to lower recoveries. The feasibility of the direct transfer of part of the high-grade concentrate from rougher stages to an appropriate position along the circuit was studied, and two positions were proposed for direct transfer of the concentrate. One position was the feed flow into cleaner cells, and the other was the feed flow into the recleaner cell. The results indicated that transferring the concentrate from the first unit of the rougher stage to the feed flow into the cleaner cells was feasible, with no limitations, while the second position required the installation of a set of hydrocyclones. It was found that the transfer of concentrate to the proposed positions not only addressed the problem of limited cell capacity, resulting in debottlenecking of the circuit, but also improved metallurgical separation efficiency up to 1.4%.

As far as is known at the present time, important ore occurrences at Mount Isa are restricted to the Urquhart Shale. These occur at Mount Isa itself, and some 13 miles north along strike at the Northern Leases.The primary silver-lead-zinc and copper orebodies occur as adjacent but discretc entities in lithologieally distinct host rocks. The copper orebodies occur in an envelope of "Silica Dolomite", whereas the silver-lead zinc orebodies occur in shale typical of the Urquhart Shale in general.At both Mount Isa and the Northern Leases, secondary lead orebodies occur at thc surface representing primary stratiform silver-lead-zinc sulphide accumulations in the fresh rocks at depth.Secondary copper orebodies are known only at Mount Isa, where they have formed in favourable environments, but unlike the secondary lead orebodies, not in the positions of the former primary mineralization that gave rise to them. The secondary copper is localized in shale remote from the point where the copper was released into solution by weathering. It was derived from very low grade fracture fillings and disseminations of chalcopyrite in the outcropping or suboutcropping crest of the "Silica Dolomite".Primary silver-lead-zinc orebodies arc oxidized without significant transport or secondary enrichment, but secondary copper orebodies arc characterized by considerable transport and extreme secondary enrichment.The original water table stood at approximately 1,150 ft (mine datum) and for the majority of the mine area controlled the base of complete oxidation fairly closely.An oxidized zone approximately 175 ft deep is general in the Urquhart Shale.Structures affecting ground conditions have influenced oxidation and leaching of the silver-lcad-zinc orebodies, and have had effects vital to the formation of secondary copper orebodies.

Jan 1, 1966

By P. Kolodziejczyk

Mining seismicity can be harmful both under and on the surface. ? Tremors are not totally damaging, but destructive to buildings and infrastructure, especially in highly urbanized regions, such as Upper Silesia in Poland ? Destroy the social appreciation, trust and support for mining industry ? To prevent or reduce these effects, engineers and scientists develop methods allowing prediction of ground shaking intensity near buildings and various losses that can result from it Evaluation and prediction of mining tremor?s damaging influence on buildings is usually solved with two steps: ? Estimation of local ground shaking intensity (based on known attenuation relation) and classification into one of several predefined intensity intervals ? Apply supposed relation between the shaking intensity interval and qualitatively defined damaging effects to express predicted effects This makes a mixed quantitative/qualitative procedure, difficult to analyze or optimize

Aug 1, 2013

By S. H. Lorain

This paper briefly describes the principal commercial and near-commercial deposits of gold-bearing gravel and the important placer-mining operations in Lemhi County, Idaho. It is on of a series on western mining districts being published by the Bureau of Mines. This paper is based on a field survey of the placer-mining districts of Lemhi County in the summer of 1938. Available information concerning gold-bearing gravels was obtained from prospectors and claim owners; operators supplied the data on mining operations. No attempt was made actually to test the gravels. The principal object of the examination was to indicate placer areas worthy of further investigation by prospective operators.

Jan 1, 1939

In order to maintain a production rate of 6,000 tonnes per day from underground at the Williams Operating Corporation, two independent mining areas were required which created a long narrow sill pillar between them. During initial mining of the sill pillar there were a number of significant ground falls [LeBlanc and Murdoch, 2000] and in March 1999, with no active mining ongoing in the sill pillar area, a rockburst of magnitude 3.0 Nuttli occurred. Extensive ground support was designed and installed to withstand events of similar magnitude [Bawden and Jones, 2002]. A mine wide microseismic system was installed to monitor mine induced seismic behaviour over the entire mine. The area most directly affected by the 1999 rockburst was rehabilitated using a highly ductile support design. Along with microseismic instrumentation, the areas were instrumented using conventional SMART Cables and SMART MPBX?s. Subsequent to this, the area was impacted by a large number of high magnitude seismic events [magnitudes between 1.7 and 3.5 Nuttli]. The ground support performed very well during these events, providing confidence in the mine?s ability to control the ground under severe rockburst conditions. Analyses of microseismic and conventional instrumentation, combined with numerical analyses of sequence alternatives, were used to develop an optimal mining strategy for the sill pillar area. The selected strategy involved utilization of instrumentation data and calibrated model results to analyze yield zones in the sill. The analyzed ?yielded? zones were assessed to be low seismic risk. Initial mining in the sill was then concentrated in these low risk areas, with the objective of further concentrating stress into the remaining seismically active area, in order to induce ultimate failure of the sill. Continuing large magnitude seismicity and resulting damage in the remaining ?high seismic risk? area, led to abandoning a second portion of the footwall access and the strategic decision to extract a stope near the centre of this zone in order to force final failure of the sill pillar. During execution of this plan two large magnitude seismic events occurred resulting in destressing and final failure of the remaining sill pillar. The paper provides a detailed description of this ?strategic mine sequence driven self-destressing process? and the implications to final extraction planning in this area of the mine.

Apr 1, 2005

By Fred W. Brackebusch

"The use of paste technology for surface tailings disposal may offer economic, technical, safety, and environmental advantages for both underground and surface mining operations. Paste is a non-Newtonian fluid having some shear strength during transport and placement. The strength is augmented after placement by consolidation, water loss, and by addition of chemicals. Economical dewatering systems are necessary to the success of surface paste tailings disposal. In an underground mine, the paste backfill plant can produce paste for surface disposal about 50% of the time because only about 1/2 of the tailings are needed for backfill. The distribution of paste to the surface stack involves expensive pumping equipment and thus a nearby location of the stack is desirable. The viscosity of paste can often be manipulated by modifying pH. Placement of the paste in a designed stack configuration depends on topographic and climatic factors as well as paste properties.INTRODUCTIONThe use of paste technology for mine backfill is becoming accepted for underground mines mainly because of ground control and economic reasons. Paste technology is just starting to be applied for tailings disposal with only a few hardrock metal mines worldwide using the technology; however, it has been used extensively for red mud disposal in the aluminum industry. The disposal of dry tailings is very attractive from environmental and safety points of view because of limited water which might potentially escape and pollute river systems. Dry stacking systems, however, are expensive because of filtration and truck transportation costs. Paste can be produced from most tailings streams by special types of thickeners. Furthermore, it can be transported in pipelines, therefore paste technology may be more economic than dry stacking but still have some of the major advantages. Understanding of paste technology has improved through experience with operating underground backfill systems in recent years and because of testwork and research programs by mining companies, consultants and equipment vendors. Thus we may be on the verge of taking a new look at tailings management using paste technology."

Jan 1, 2002

By R. H. Mullennex

Application of depositional analysis concepts is becoming an ever-increasingly more important and more useable tool in exploration and development of coals in the Appalachian basin. Over the past decade, a rather large number of studies, papers, and publications have addressed various aspects of depositional environments of coals and, to some extent, applications to development. As would be expected as regards a subject so complex as Pennsylvanian sedimentation in the Appalachian basin, certain academic studies have produced conclusions at variance in some aspects to those of other studies. Overall, however, there has been a building- block progression and general refinement with time of understanding of the depositional settings and other factors controlling Appalachian coal distribution, quality, and other minability parameters. Most attempts to explain coal seam characteristics have revolved around a basic deltaic model. Some have attributed certain seam attributes to upper delta plain deposition, other attributes to transitional-lower delta plain settings, and yet others to lower delta plain environments, and so on. While these approaches have provided valuable insight into some general coal characteristics, they are somewhat incomplete and are, in a sense, too broad for specific mine-scale applications. Further, it is apparent that in order for widespread peat accumulation to occur, there must be a drastic decrease in the energy of the depositional system and amount of sediment being brought in, compared to the active deltaic and coastal processes responsible for deposition of the large volume of clastic sediments that dominate the Pennsylvanian system of the Appalachians. Consideration of this fact implies that peats (coals) may not necessarily reflect depositional settings that are directly coincident with those associated with adjacent rocks. Cecil and Englund (1985) address this point, and quite correctly state that "the primary controls on major stages of peat formation are allocyclic processes involving paleoclimate, eustatic changes in sea level, and tectonics." While this statement is inarguable, it does not negate the importance and usefulness of depositional analysis in predicting reserve characteristics that may impact mining and marketability.

Jan 1, 1986

Jan 1, 1996

By Heloíza Döering Gasparin

Os efeitos de elevadas temperaturas e do tempo de exposição sobre as propriedades mecânicas de um ferro fundido cinzento hipoeutético foram avaliados em amostras de dois ferros fundidos da classe FC300, de mesma base, com diferentes percentuais de molibdênio. Ensaios de tração até ruptura a quente foram realizados em corpos de prova com diâmetro de 10 mm, usinados de um pino bruto de 30 mm de diâmetro. Os ensaios foram realizados a frio (temperatura ambiente) e a quente (200°C, 300°C, 350°C, 400°C, 450°C, 500°C e 550°C). Os tempos de exposição a elevadas temperaturas, após homogeneização térmica do material, foram de 0, 60, 90 e 120 minutos. As amostras com maior percentual de molibdênio (0,27% em peso) apresentaram melhores propriedades mecânicas para todas as condições ensaiadas. De acordo com a literatura a redução na resistência mecânica com a elevação da temperatura é atribuída à ocorrência de decomposição da perlita, como resultado da difusão do carbono vindo da cementita às lamelas de grafita, que é o responsável pelo aumento da quantidade de grafita no material. As análises metalográficas evidenciam a ocorrência deste fenômeno. Aumentos no tempo de exposição a temperaturas elevadas também contribuíram para a degeneração da perlita.

Aug 7, 2018

"Horizontal grinding mills have been used in the mining industry for more than a century, and due to their operational and maintenance simplicity they remain a widely used technology for various stages of comminution. The relative ‘efficiency’ of horizontal grinding mills compared to other comminution equipment is often debated, and efforts to improve the energy efficiency of these mills is an on-going area of attention for process engineers.The discharge arrangement design affects the material transport characteristics within a horizontal grinding mill. Material transport plays a significant role on efficiency of horizontal grinding mills. The magnitude of benefits that can be achieved with efficient material transport in AG/SAG mills has been demonstrated in a Greenfield milling operation at Mirabela Mineração’s SantaRita Nickel operation in Brazil. This grinding circuit was commissioned in October 2009, which was designed as a typical SABC circuit to grind 4.6 mtpa (575tph) to produce a P80 of 125um with 10-12% ball charge in SAG mill. The nameplate design capacity has been achieved in few days in ABC circuit without grinding media in SAG mill, and has been operating in ABC mode. The through has gradually increased to an average of 800 tph and recently 7% ball charge has been introduced to increase the throughput to +900tph.This paper investigates improved material transport using Outotec’s TPL™ (Turbo Pulp Lifter) technology and the opportunities this technology presents when designing horizontal grinding mills. Operational data, with particular reference to energy and throughput optimization, is presented."

Jan 1, 2013

By Parker A. J, Grimsey E. J

Studies have been carried out on the dead roasting of a copper-iron and a copper-nickel-iron sulfide concentrate, followed by segregation roasting with coal and leaching with either curpric sulfate in aqueous acetonitrile or cupric chloride in brine solution to preferentially solubilize copper. The effect of dead roasting and segregation roasting conditions on the overall leaching of copper and the separation of copper from iron and iron and nickel is reported. An excellent separation of copper from iron and a good separation of copper from iron and nickel can be obtained provided sulfur is removed to 0.5 per cent or less during the dead roast and provided the coal addition and temperature of the segregation roast are near the minima required for the segregation of copper.

Jan 1, 1983

By T. Deng

Flotation of rare earths is complicated by the number of mineral classes that carry rare earth elements, including carbonates, phosphates, and silicates that often co-occur within the same deposit. Gangue constituents often belong to the same mineral classes as the rare earth minerals themselves. Chemical regimes developed for specific separations employ customized combinations of collectors, modifiers, and depressants that are not directly translatable to other operations. In this rougher flotation case study, a reagent suite including phosphate ester and sulfosuccinamate, originally developed for the recovery of bastnasite and monazite from silicate hosted ore, could not be applied to a synchysite ore hosted in carbonate gangue because the suite was aimed at silicate gangue rejection only. The separation of a fluorocarbonate mineral from carbonate gangue required a different chemical regime involving the use of hydroxamate and sodium silicate. Maximizing rare earth recovery was complicated by the presence of slimes. The effect of desliming and the increase in grind size was explored.

Jan 1, 2014

By H W. Wu, D Humphreys

The structure of a comprehensive research project into mine fires study applying the Ventgraph mine fire simulation software, preplanning of escape scenarios and general interaction with rescue responses is outlined. The project has Australian Coal Association Research Program (ACARP) funding and also relies on substantial mining company site support. This practical input from mine operators is essential and allows the approach to be introduced in the most creditable way. The effort is built around the introduction of fire simulation computer software to the Australian mining industry and the consequent modelling of fire scenarios in selected different mine layouts. Application of the simulation software package to the changing mine layouts requires experience to achieve realistic outcomes. Most Australian mines of size currently use a ventilation network simulation program. Under the project a small subroutine has been written to transfer the input data from the existing mine ventilation network simulation program to æVentgraphÆ. This has been tested successfully. To understand fire simulation behaviour on the mine ventilation system, it is necessary to understood the possible effects of mine fires on various mine ventilation systems correctly first. Case studies demonstrating the possible effects of fires on some typical Australian coal mine ventilation circuits have been examined. The situation in which there is some gas make at the face and effects with fire have also been developed to emphasise how unstable and dangerous situations may arise. The primary objective of the part of the study described in this paper is to use mine fire simulation software to gain better understanding of how spontaneous combustion initiated fires can interact with the complex ventilation behaviour underground during a substantial fire. It focuses on the simulation of spontaneous combustion sourced heatings that develop into open fires. Further, it examines ventilation behaviour effects of spontaneous combustion initiated pillar fires and examines the difficulties these can be present if a ventilation reversal occurs. It also briefly examines simulation of use of the inertisation to assist in mine recovery. Mine fires are recognised across the world as a major hazard issue. New approaches allowing improvement in understanding their consequences have been developed as an aid in handling this complex area.

Jan 1, 2005

By AIME AIME

WITH the recent increase in the price of gold, its economic recovery at depths formerly considered impractical has become a present possibility. Two important difficulties must be met: pressure bursts of the rock, and the reduced efficiency of human labor subjected to the higher temperatures and the increased humidity at the greater depths. In the following abstract of a paper by J. H. Dobson, presented before the South African Institution of Engineers on

Jan 1, 1935

By L. R. Stoiser

The mineral resource potential of the Los Bronces deposit was successfully evaluated by an intense, coordinated program over a 37-month period (April 1978-May 1981) as part of an economic feasibility study. The program included more than 120 km of core drilling, 63 km of access road construction under adverse topographic and climatic conditions, detailed geological mapping, plus other related activities. This Tertiary-age copper-molybdenum deposit is composed of an earlier mineralized porphyry-type body intruded in part by a large complex of mineralized hydrothermal breccia pipes. Both intrusive and extrusive igneous rocks are present. Erosion, oxidation, leaching, and supergene enrichment of copper have resulted in a deposit now exposed at the surface that contains more than 368 Mt grading about 1% copper equivalent as sulfides.

Jan 1, 1982