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By Richard P. Schoemaker

INTRODUCTION IN underground mining operations the effects of economic and mechanical factors on costs and profits can readily be appreciated and can perhaps be expressed in exact figures and percentages. Less apparent, but frequently more important, is the influence of physical stress. Stress causes failure of supports, collapse of openings, rockbursts, and other damage which directly affects the costs of maintenance, and also to a certain extent the accident rate. Stress can, however, if properly directed, be an aid to mining operations. The caving methods in metal mining and the long-wall method in coal mining are well-known examples. In large-scale mining operations it is almost impossible to neglect stress-control. A better understanding of the mechanism of rock pressure and the application of its principles to practical mining will inevitably lead to a reduction in operating costs. Many theories have been advanced to give the mining engineer a practical outline for stress-control but, although today most experts agree upon the principles of stress distribution around underground openings, there is still no generally accepted theory that explains all phenomena. The main reasons for this incomplete understanding of the problem are the lack of accurate knowledge of the physical properties of rocks under field conditions, and the great complexity of these conditions due to inhomogeneity of the rock, stratification, tectonic disturbances, and many other unknown factors. The research on the rock pressure problems has, however, yielded some valuable facts which, expressed in practical terms, and adapted to local conditions, may become a valuable aid for mining operations. The purpose of this paper is to give a review of the most important accomplishments of this research with respect to the stress phenomena around small underground openings, such as tunnels and shafts, so as to arrive at an outline of the problem as it stands today. Special emphasis is placed on a new theory by the German mining engineer, Rudolf Fenner, which has never before been published or discussed in English. THE PRESSURE DOME THEORY The formation of a dome-shaped space around underground openings is well known from field observations. When openings are made in rock under stress, the rock in the top of the openings will often fail, and caving will continue until the openings have assumed a dome-shaped form, after which equilibrium apparently is re-established. The oldest theory which attempted to explain the phenomenon is the "beam" theory, which postulates that the hanging wall consists of stratified measures that behave as independent beams with fixed ends and a uniformly distributed load. When failure of the beam occurs, inward shearing at the ends will cause the formation of a dome-shaped space. The pressure dome theory, which more or less evolved from the beam theory, merely

Jan 1, 1947

By Harry L. Siebert

Pre-splitting was substituted for line drilling to achieve stable rock slopes and reduce excavation beyond the pay line on a Connecticut highway project in 1962-63. Changes have occurred in developing rock slopes that were not foreseen by Alan Bauer and Jim Scott who in the early days understood the relationship of explosive energy to stable slopes. Cushion blasting as currently used produces slopes designed to blend or complement the natural landscape with slope holes detonated after the main body of holes. Pre-splitting is the opposite. The best results have been achieved by detonating the pre-split line of the holes first to allow readjustment of the slope plane fracture and a separate blast for the main body of loaded holes.

Jan 1, 1998

The support of the roof in coal mines remains a critical safety issue with 3 fatalities from roof falls in 2007 and 430 injuries from roof falls in 2006. A snapshot survey by the authors of room design and support details as well as unplanned falls of ground in the industry revealed some useful data concerning support use, seam details, fall dimensions, bolt lengths and spacing and the stand-up time.

Jan 1, 2009

By W. Noel O?Brien

Introduction Since 1930 numerous improvements have been made in equipment designed for the mechanical removal of broken ore in underground mining operations. New applications of mechanical equipment, as? well as improvements and adaptations of well established systems, are being made continually. It is the purpose of this paper to discuss present-day equipment for the removal or transfer of broken ore by means of a powered hoist and scraper arrangement. The terms used throughout the paper are those commonly employed in the trade literature and by mining men. The terms slusher hoist, hoist, and scraper hoist are used inter-changeably to mean a machine, powered by compressed air or electricity, with drums for the winding of wire rope. The tail rope, also known as the pull-back rope or return rope, drags the empty scraper toward the tail-sheave, that is, back to the loading point. No attempt is made to cover the entire field of application of scraping methods. Rather it is the? writer's desire to emphasize the fundamental principles of scraping practice and design and to relate them to some modern applications. The available literature on scraping practice has been freely used. together with personal observation and information and advice of practising engineers and representatives of companies manufacturing slushing equipment.

Jan 1, 1951

By G. W. Holl, E. G. Fairon

A review of some aspects of shaft design by G. W. HOLL, Pr. Eng., Associate of the Mine Managers Association of South Africa (Fellow)- and E. G. FAIRON, Pr. Eng., F.S.A.I.E.E., M.I. Cert. M.E.E., M.I.Mech. E., (Visitor) The reasons for the choice of vertical shafts in preference to inclined shafts of comparable capacity are set out, and the conclusion that the former are superior in virtually all circumstances is substantiated. The shapes of vertical shafts sunk during the past sixty years are recorded, and the shapes of those sunk during the past decade are analysed. From this analysis it is clear that circular and elliptical (and quasi-elliptical) shafts are the shafts of the future and that the rectangular shape will conceivably become obsolete. The determination of the size of shaft is discussed and it is forecast that shafts of a diameter of 13 metres and over will probably be sunk without difficulty in the years to come. The depth of the shaft is determined intrinsically by the Mines and Works Regulations applicable to factors pf safety of winding ropes and the design of the winding system. The Blair winder is the most suitable winder for hoisting rock, men, and material from a depth of, say, 3000 metres on an economic basis. Tertiary shafts will, therefore, be unnecessary in future deep-level mining projects at the limit of depth now envisaged. A few other factors relating to shaft design are described.

By G. J. C. Young

In 1986 the city of Johannesburg celebrates its first century of existence. The fact that the city was founded to exploit the gold deposits which underlaid it, prompts this review of the gold process development in the mining industry of South Africa. Clearly a complete history of, the gold recovery process to date is not called for and it is proposed therefore to outline the most significant developments which have taken place since the middle 1930's, that is to say the last 50 years or so. Prior to this period the industry had seen the development of comminution processes employing cone crushing in closed circuit with vibrating screens followed by grinding in rotating mills and the gradual disappearance of stamp mills. The all sliming process was well established as a viable route and continuous dewatering in thickeners, continuous leaching and filtration were serious rivals for the earlier batch processes. Continuous processes for gravity concentration had also been developed and the recovery of gold from pregnant solutions employed cementation on zinc dust as opposed to shavings. Thus at the beginning of the half century under review the industry had adopted, or started to adopt, many of the processes still accepted as modern practice. However in some areas little change was evident this was especially so in the smelthouse where some thirty more years were to elapse before the hand stoked coal fired calcine and reverbatory furnaces were replaced by more environmentally acceptable electric furnaces. The most significant feature in recent history has been the mining of progressively lower grades of ore and the retreatment of tailings from earlier operations, much of the latter comprising tailings only a decade or even less in age. Notable among these operations are those on the East Rand near Springs in the Transvaal, in the Orange Free State at Welkom and more recently, massive reclamation of tailings close to the city centre itself. The carbon in pulp (CIP) process has been much publicised in recent years and all new plants erected during the 1980's have adopted this route for gold recovery. However the major proportion of tonnage milled in the industry is still subjected to the more traditional process of liquid solids separation by vacuum filtration. The discussion that follows will centre largely on the developments in the traditional process route, which for the sake of completeness is listed below: Comminution Dewatering Leaching Liquid solids separation Gold recovery Smelting

Jan 1, 1985

By Douglas C. Fraser

"Geophysical data are often presented on maps, sections or profiles with minimal data processing. A common example is magnetic data, in which the diurnal-free raw readings are merely contoured on a map. Other examples include profile presentation of VLF-EM data, IP pseudo-sections and airborne EM anomalies which may be shown on a map with only the measured amplitudes indicated.In recent years, efforts have been directed to the portraying of data in more useful forms. A number of algorithms (i.e., manipulative procedures and equations) have proven to contribute significantly to the usefulness of geophysical data. Some can be applied manually; others are sufficiently complicated to require a computer. Some merely alter the data to a more useful geometric form without altering the units. Others yield quantitative estimates of source body parameters such as conductivity and shape. Several examples follow:1. A simple algorithm is in common use which transforms noisy non-contourable VLF-EM data into less noisy contourable data. The input is the dip angle in degrees or per cent and the output is also in these same units.2. A simple algorithm has recently been developed which allows multi-level dipole-dipole IP data to be contoured on a map. Again, the units are not altered.3. A relatively complicated algorithm is in common use which transforms non-contourable height-sensitive helicopter EM data into contourable resistivity data,4. An algorithm has been recently developed which transforms non-contourable height-sensitive EM data into contourable weight per cent magnetite.The purpose of all the above techniques is to present the data in a simplified form. This, in turn, allows an easier assimilation by the user of much of the information content of the data."

Jan 1, 1981

Heatings, fires and explosions in New South Wales (NSW) and Queensland coal mines since 1972, are reviewed. Geological and mine settings are outlined. Where available, gas analysis and critical decisions are discussed. This paper updates work by NSW Department of Mineral Resources (1995) and the Queensland Department of Mines and Energy in a report on fires and explosion in Queensland coal mines (Richardson and Ham, 1996). Incident data has important applications in terms of evidence-based risk assessment and identifying key issues to be integrated into competency based training programs. Predictive indicators are reviewed in terms of coal parameters in seams where the incidents occurred.

Jan 1, 2005

By Dunne RC

The physical properties of an orebody require determination for virtually all mining projects, new and existing. The extent and regularity of such determinations being subject to the size and homogeneity of the orebody. Such properties have an impact at the design stage of new plants, with respect to equipment specification, and thus effects capital costs; and also impacts on the operating costs of new and existing plants, with respect to power consumption, production levels and part replacements. All of these can severely alter the bottom line and can be the determining factor in the economic viability of many projects.This paper examines some of the most common properties that are measured, the procedures utilised in determining these properties, and their variability under conditions of reproducibility, and to a lesser extent repeatability.

Jan 1, 1997

By Holla L, Tyminski A

Stowing has been successfully used in many countries as a means of controlling surface subsidence, minimi ing incidences of spontaneous combustion, maintaining gate road stability and maximising coal recovery.Australian experience in stowing is limited but in the future increased extraction of thicker and/or multiple seams by longwall operations and resolution of conflict of alternative land u'ses may necessitate the use of stowing in coal mining. At present there is little incentive for mining companies to introduce and operate a stowing system because costs have to be borne by the individual companies and benefits spill over to society and the State. Cost sharing by the industry and State incentives may overcome the problem of cost disincentive.

Jan 1, 1987

By D. K. Sarin

The sub-level caving mining method has been applied in base metal mines in Canada under a wide range of ore body and wall rock conditions. This method has been used for primary, as well as secondary mining of both small and large ore bodies of varying ore values. Early experiences of almost all operations were somewhat disappointing. This paper details the initial problems encountered, the design changes made and solutions evolved. Additional experience and the development of operating skills, have helped the method gain acceptance as a viable method for the mining conditions to which it has been adopted.

Jan 1, 1981

By R. M. Tyler

The importance of the heavy mineral sands to southern African economic well-being cannot be over emphasized. The value of the worldwide titanium dioxide industry is estimated at $7 billion. Six out of eight of the world?s proposed new project areas are in southern and eastern Africa, and a seventh at Tamil Nadu in India is partly owned by a South African company, Kumba Resources. The HMS industry can be highly lucrative; its return on capital is the best in the mining industry. There are, however, problems, particularly in the smelting technology. The often considerable affect of mining on environmentally sensitive coastal dunes is also becoming increasingly important. The medium-to long-term demand for Ti-dioxide pigment and ceramic grade zircon appears very healthy. If, as predicted, the costs of producing titanium metal can be reduced, then there is huge potential for the metal. In summary, the HMS industry is an attractive one to be in, with good returns and generally manageable risks. New business opportunities and their economic implications for Africa are discussed.

Jan 1, 2004

A review of the factors controlling stope wall behaviour such as excavation geometry, rockmass strength, induced stress, ground support, blast damage and drill drive layout is undertaken. In addition, the advantages and disadvantages of single lift stope geometries linked to vertical crater retreat are also analysed. Finally, key components of multiple lift stoping such as cut-off slots, production rings, stope undercuts and drawpoints are studied in detail.

Jan 1, 2000

By William A. Kapp

INTRODUCTION Coal is being mined from beneath residential areas, structures, bodies of water and other surface features in the coalfields to the north, south and west of Sydney. The particular problems faced by mine operators in these areas vary considerably due to differences in the overlying strata, the variation in the depths of cover and also depend on the number of seams being mined. Detailed subsidence work first commenced in the Southern Coalfield in 1965 and is now being carried out over areas of extraction at roost collieries. The analysis of the results of the early investigations and of the work which continues in other areas has shown that there is a consistent relationship between subsidence and mine geometry and has led to a reliable empirical method for the prediction of subsidence. In addition, particular aspects of each of the studies in the Southern Coalfield results in a clearer understanding of strata movements and of the resulting subsidence. The features of a subsidence trough apply generally to all areas but the magnitudes of specific features vary according to the stratigraphy of the particular coalfield. The aim of the subsidence work is to quantify the effects of subsidence for a range of mining geometries and mining conditions to enable the maximum safe recovery of coal from beneath surface features. The importance of local subsidence investigations is becoming more evident to mine operators and to authorities or organisations with surface interests. The subsidence work also provides important information on the stabilities of pillars of coal which remain unmined between panels of extracted coal. These pillars are not extracted either because of poor mining or geological conditions, or because pillar extraction is not part of the particular mining operation. Subsidence studies over these coal pillars clearly establish whether the pillars have remained stable or have failed to support the overlying strata. With subsidence studies continuing over several years, it is possible to assess the stabilities of these pillars on a long term basis. BACKGROUND TO THE STUDY OF SUBSIDENCE Geographical setting Most of the black coal production in Australia comes from the Sydney Basin. The coal seams extend for approximately 350 km along the coast of New South Wales and inland for distances up to 150 km. The City of Sydney is located near the centre of the coastal extent of the Basin where coal has been mined at a depth of 900 m. The Sydney Basin is part of the Main Coal Province of NSW and is divided into several coal- fields. The Southern Coalfield to the south of Sydney contained 15 operating mines and produced 12.7 million tonnes of raw coal during the 12 months to June 1981. The collieries discussed later are shown in Fig. 1. The prominent topographical feature of the area is the Illawarra Escarpment which rises to 400 m above sea level, or 300 m above the coastal strip along the South Pacific Ocean. The escarpment is mainly sand- stone and the weathering of the cliff line has resulted in a covering of talus material at its base. Several collieries are located near the seams which outcrop along the escarpment. The city of Wollongong is located in a scenically attractive area on the coastal plain. The suburbs of Wollongong extend north along the coastline, south to beyond Lake Illawarra and west to the lower slopes of the escarpment. The Illawarra Escarpment forms the eastern boundary of the Woronora Plateau. On a regional scale the surface dips gently to the west and thus forms a watershed for the rivers, most of which flow in a general north westerly direction, sometimes forming steep gorges in the sandstone. These rivers join the Nepean and Hawkesbury River system and flow into the Pacific Ocean north of Sydney. Seven dam have been constructed over the Southern Coalfield (Fig. 1) and with one large dam further to the west, their stored waters provide the needs of the Cities of Sydney and Wollongong and the surrounding districts. A large part of the area affected by mining is the undeveloped bushland of the associated catchment areas. In general no special precautions have been required with respect to subsidence with the exception of the dam structures and stored waters. With the increase in coal mining activities and the expanding residential development south of the City of Campbelltown in the outer Sydney Metropolitan area, subsidence is becoming an increasingly important area of research. Structures which have been affected or considered are townships and extensive residential areas, buildings of historical importance, major tollways, and a high pressure natural gas pipeline. The subsidence effects of mining beneath natural features within national parks is coming under study as mining approaches these areas. Geological setting The coal seams of the Southern Coalfield lie within the Illawarra Coal Measures. They contain high rank coking coal used in the local steel industry and for export. The Bulli Seam is mined extensively through- out the Southern Coalfield with the lower Wongawilli Seam being second in importance with regard to coal production. The top of the Bulli Seam is taken to be the marker horizon between the Permian Coal Measures

Jan 1, 1982

By H. J. Sutherland

This paper reviews the results of the subsidence research prop ram at Sandia National Laboratories. The manuscript highlights the following: the application of empirical methods (profile functions) to the subsidence above longwall panels in the U.S.; the use of the "rubble model" to describe the behavior of broken strata as it distends when it falls to the Mine floor (or top of the rubble pile) and then is subsequently compacted as it is loaded by overlying elements of strata; and, the application of physical modeling techniques (centrifuge simulations) and numerical techniques to study the failure mechanisms in highly structured stratigraphy. The capabilities of the latter two are illustrated ')y comparing their predictions to the results of a field case that has complicated stratigraphy.

Jan 1, 1982

By Alastair Grogon

Proper coupling of a geophone to a monitoring surface is probably the single most important step in accurately recording and measuring ground vibrations from a blast. Over the years, a number of monitoring methodologies have been published. Some of these were published as a "standard", by organizations such as the International Standards Organization, others as suggested methods by various authors in papers or text books, or in the users manuals supplied by seismograph manufacturers. These monitoring standards differ, and are sometimes apparently contradictory. The purpose of this paper is to summarize the coupling methodologies from a number of these "standards", point out similarities and differences, and discuss the technical basis behind some of the different methods.

Jan 1, 1998

By Richard R. Klimpel

This paper reviews the use of sulfide mineral collectors in industrial flotation practice. The approach of the paper is to characterize sulfide mineral collectors in a number of ways, including by chemical structure, by influences with different classes of mineralogy, by interactions with particle size, and by interactions with frother type.

Jan 1, 1999

By Michael Godard, Peter Cleyle

"Suncor Energy’s Project Millennium increased oilsands production capacity by an additional 95,000 barrels per day to its present level of 225,000 barrels per day. This massive venture included an expanded Mine, new Extraction and Upgrading facilities, as well as, steam and utilities infrastructuresIn the Primary Extraction process, removal of the bitumen from the oil sand begins with slurry preparation and is followed by primary , secondary and tertiary separation processes. The final cleaning step of the bitumen froth is the Secondary Extraction process, that removes residual water, mineral and solids to produce a clean diluted bitumen suitable for Upgrader feedstock.This paper will review the flowsheet of the Millennium Primary Extraction facility, from its recent commissioning through the ramp up to design production rates. In addition, new technologies in the Primary Extraction flowsheet will be reviewed.INTRODUCTIONAs conventional supplies of oil and gas are depleted in Canada, the Athabasca oil sands industry of Alberta becomes an increasingly important source of energy. Today, high quality crude from Alberta’s oil sands accounts for roughly 30% of Canada’s daily petroleum production. According to government projections, over the next 7 years, oil sands production is expected to more then double, and by 2010 more than half of Canada’s crude oil is expected to come from the oil sands.Oil sands deposits consist of a layer of sand saturated with bitumen covered by a muskeg overburden and underlain by silt and clay. The oil sand is mined where the overburden is economical to remove, typically less than thirty meters thick. The Athabasca oil sand deposits around Fort McMurrray is ideal for mining. Bitumen can be described as a diverse collection of hydrocarbons, organosulfur, and nitrogen compounds."

Jan 1, 2004

By Herbert P. Haschke

I. Changes made by the Economic Recovery Tax Act of 1981 (ERTA) which have an effect on investing in tax shelter investments A. Maximum ordinary income tax rate on individuals is now 50%. B. Maximum tax rate on long-term capital gains for individuals is now 20%. C. Maximum tax rate on alternative minimum taxable income for individuals is now 20%. D. Although not changed, the "add-on" 15% minimum tax on tax preference items and the possibility of paying the alternative minimum tax cause individual U.S. income tax planning to continue to be very complex. II. Real Estate A. The new Accelerated Cost Recovery System of depreciation (ACRS). 1. Mandatory for assets placed in service after 1980. ACRS will eliminate most if not all controversies with the IRS over depreciation. 2. Real property now depreciated over 15 years. Component depreciation is not available. 3. Accelerated depreciation is available - a 175% declining balance method with an automatic shift to straight line method at the optimum point in the asset's life. Alternatively, a taxpayer can elect to use the straight line method.

Jan 1, 1982

By E. R. Bauer

A primary goal of Ground Control Research, Bureau of Mines, U.S. Department of the Interior, is to develop information that can be used by the mining industry to reduce accidents and fatalities due to failure of mine roof. A specific research objective is to determine methods to detect hazardous coal mine roof. This paper reviews the existing and experimental techniques, and describes a recent Bureau of Mines contract research project that resulted in a simple technique and prototype instrument for evaluating mine roof competence.

Jan 1, 1986