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After some 50 years of worldwide research in relation to coal pillar mechanics and design as well as numerous workshops and technical papers related to these issues there is still some significant disagreement as to the approach one should adopt in the assessment and design of a coal pillar. Of course there are many different types of coal pillars that fulfil a wide range of roles at any particular mine and in this instance it is appropriate to have a 'tailored' approach for each pillar type in relation to the role it fulfils. However where it can become very difficult for the mine operators is when various researchers or consultants use or recommend significantly different approaches for the same type of pillar fulfilling the same role. By 1999 two pillar design techniques had been developed specifically for the Australian underground coal mining industry (ie The University of New South Wales Pillar Design Procedure, UNSW PDP and Analysis of Longwall Tailgate Serviceability, ALTS) and several other pillar design techniques were being practiced by individual consultants. The Australian industry hoped to resolve the issue of what technique to use for each pillar type and role, when it funded UNSW in 2000 to develop a 'Systems Approach to Pillar Design'. The findings of the abovementioned project were published in 2005 and while every attempt was made by UNSW to include the views of various local and overseas researchers and consultants it would be fair to say that a unified approach to pillar design in Australia was not adopted as a result of that project. This is the experience of one country where there has never been one central group solely undertaking such research in relation to pillar design (such as the Chamber of Mines in South Africa). This paper explores the Australian experience in terms of pillar research and what that experience may offer to researchers in Australia and other countries. At the First Australasian Ground Control in Mining Conference (2003) the first 'update' of the ALTS Design Methodology (ie ALTS II) was presented. In subsequent years the ALTS database was continually updated and significantly expanded such that it now includes detailed information in relation to both the tailgate (148 cases) and maingate belt road (58 cases). In addition to tailgate roof support and chain pillar design, the current version of ALTS (referred to as ALTS 2009) includes a maingate belt road roof support design module. This paper is also intended to update and summarise the development and application of the ALTS Design Methodology for longwall gateroad design over the last decade both directly and in the context of coal pillar research conducted in Australia over the last 15 years.

Nov 25, 2010

By G. W. Josephson

WHILE methods of utilizing blast-furnace slag have been developing, a great deal of literature on the subject has accumulated, but no comprehensive summary of information that would be helpful to engineers, contractors, architects, chemists, and others in under-standing and more successfully using this byproduct of the iron and steel industry has been published in the English language. The National Slag Association recognized the need for such a publication, and the Problems Committee of the Association under-took in 1943 to accumulate the necessary material. Over a period of several years this committee compiled pertinent information in manuscript form, and in 1948 the Bureau of Mines and the National Slag Association made an agreement whereby the Bureau was to prepare the data for publication as a cooperative bulletin of the Bureau of Mines and the National Slag Association.

Jan 1, 1949

By Zou Dingxiang

Rock blasting in the project of “Site Formation and Associated Infrastructure Works at Choi Wan Road and Jordan Valley” is the largest urban blasting project in the history of Hong Kong and also is rare in the world. More than 6.2 million of in-situ rock has to be excavated by blasting. The site is located in the center area of eastern Kowloon peninsula, surrounded by highways, registered cut slopes, high-rise residential buildings, MTR subways and the public utilities. The complex situations bring great difficulties and risks to the blasting works. A bird-view photo of the site is shown on Picture 1.

Jan 1, 2007

By Pablo Velasco

After becoming an oil exporter in 1972, Ecuador experienced a remarkable economic upswing until 1978. However, in 1979 and 1980, a combination of only slight improvements in agricultural output and stagnating petroleum output lowered rates of real gross domestic product (GDP) expansion to 5.3% and 4.3%, respectively. In current prices, the GDP in 1980 was estimated at $11.3 billion.2 The slowdown in growth is attributable in large part to the low level of petroleum exploration in the 1972-79 period. Ecuador's production of petroleum declined 4.5% in 1980 compared with that of 1979. The consortium of Corporación Eatetal Petrolera Ecuatoriana (CEPS), the State oil company, and Texaco, Inc., operating in Ecuador's eastern jungle region was responsible for nearly all of 1980 production, The volume of total crude petroleum exports from Ecuador dropped from 44.7 million barrels in 1979 to 40 million barrels in 1980, although crude petroleum export revenues rose from $1,032 million in 1979 to $1,294 million in 1980- The latter figure represented 54% of Ecuador's 1980 merchandise exports. Crude oil exports accounted far about 46% of the value of 1979 merchandise exports. The total nonfuel mineral exports in 1980 were valued at less than $1 million.

Jan 1, 1982

Advanced Jig Separation of Shredded Plastics The authors have reported that the RETAC jig is very useful in separating relatively low density particles such as plastics, and demonstrated that highly efficient jig separation of plastic components in discarded office machines is possible in pilot-scale tests. To further improve the separation efficiency, a hybrid jig (RETAC jig with air bubbler under the particle bed) which can separate plastics having similar specific gravities using differences in wettability produced by a pretreatment, and a reverse jig (modified RETAC jig for plastics lighter than water) were developed. This paper reviews the separation of shredded plastics using advanced jig separation technology (RETAC, hybrid and reverse jigs). Wettability control of the plastics for the advanced jig separation is also reported.

Sep 13, 2010

The process of hydraulic transport through pipelines, worldwide well known for the transport of fine-grain solids is also being used to a greater extent in mining for the handling of primarily coarse-grain solid û water mixtures for the removal of, for instance û coal and waste mixtures after coal winning using hydraulic monitors, tailings for backfilling underground and washer tailings and flotation waste to the dump. A large-scale test unit was taken into service at the Bergbauforschung GmbH (Mining Research Company) in Essen-Kray, GFR, to further improve this technology. The unit was planned and built by Krupp Industrie- und Stahlbau of Duisburg in cooperation with Bergbauforschung GmbH. The paper deals in detail with the demands made on this test unit and the technical results obtained on it and with the planned experimental research work.

Jan 1, 1980

By Edwin Higgins

SINCE the "Days of Forty-nine" California has been the premier gold producing state of the union. The greatest production was recorded in 1.852, during which year the state's placer and lode deposits yielded over 81 millions. This peak was followed by a steady decline to about 12 millions during the years 1888 to 189.3, a period marked by the cessation of gravel mining. After 1893, production increased to a new peak of over 22 million in 1915, thereafter decreasing steadily to something over 13 million in 1923. Today; California's gold production shows a decrease of 84 per cent. as compared with the output of 1852, and a decrease of 41 per cent, as compared with 1915. It is not a difficult matter to find the causes of this more recent decline. In 1916 there began an upward swing in the cost of labor, which represents approximately 60 per cent. of the cost of mining, and in the price of supplies, representing the remaining, 40 per cent. This rise continued until 1922 and since that year there has been no decided tendency either upward or downward. The increase in the cost of mining since 1916 is variously estimated at from 50 to 75 per cent.; the price of gold has remained fixed at $20.67 per oz. This condition resulted in wiping out the profits of the low-grade operations which, in recent years, have constituted California's main source of supply of gold ore. It is now predicted that there will be renewed activity in California- gold mining. What are chances for the materialization of this forecast? A boom or even a revival of gold mining must of necessity be brought about or accompanied by one or more of the following factors: 1. A decrease in the cost of mining. 2. An increase in the price of gold. 3. New capital for development. 4. The discovery of new deposits. 5. The revival of hydraulic mining.

Jan 1, 1925

By James M. Franklin

Research on modern hydrothermal systems provides quantitative measures of the processes of formation of hydrothermal fluids and of precipitation mechanisms from them. Studies of ancient deposits provide new information regarding volcanological processes that are related to the deposits, as well as data on their spatial and temporal compositional variations. Mew exploration guidelines result from both aspects of research. The most fundamental requirement for large metalliferous hydrothermal systems is an abundant heat supply for the upper two kilometers of the crust. This heat may come from a focused heal source (shallow-level subvolcanic intrusion), but ambient heat also may have provided enough energy for the reactions necessary to effect leaching of metals, especially where heat flow is particularly high (i.e. very large or high-temperature magmatic source, such as ultramafic environments). For most VMS systems, the majority of the metals were derived through leaching from footwall strata; in addition interstratal fluids may enter subvolcanic intrusions during episodes of magma a chamber "cracking," engendering some '?magmatic" component in the hydrothermal system. Direct contributions of metalliferous magmatic fluid also may be significant from arc-related or back-arc felsic or alkalis systems. These latter contributions may form exceptionally high - grade portions in some deposits. Subvolcanic intrusions, which are excellent indicators of high heat flow and may have been the direct driving mechanisms for some stems undergo two stages of alteration: On intrusion emplacernent. fluids may rapidly enter and react with their mesostatic portions, evident in the sills in the Middle Valley. High temperature interactions caused albitization and destruction of oxides and sulfides, releasing metals. During terminal hydrothermal stages, the metalliferous fluid collapsed into the intrusions, forming disseminated and vein sulfides.

Jan 1, 1998

Investigation on Multicomponent Semi-Autogenous Grinding

Sep 13, 2010

By Sven Reutzel

Investigations show that Co-based melts embedded by glass flux in a crucible can be under- cooled nearly as strong as samples processed containerlessly by electromagnetic levitation. This allows to measure magnetic susceptibility on undercooled melts while combining the use of a Faraday-balance and undercooling technique. The magnetic susceptibility of Co and Co-based alloys (such as Co-Pd and Co-Cu) is investigated as a function of temperature from superheated to undercooled state. This is done by measuring the change of magnetic force F, on a sample in a constant magnetic field Bo and an additional gradient field by means of a Faraday-balance. When liquid Co-based alloys are undercooled the magnetisation steeply rises if temperature approaches the Curie temperature. The magnetisation is measured for some Co-based alloys in liquid state as a function of alloy system and its concentration. The results show that the magnetic susceptibility of the liquid undercooled samples follows a Curie-Weiss behaviour, from which Curie temperature and magnetic moments for the liquid state are inferred.

Jan 1, 2002

By Chaoxun Zhao, Daniel Tao, Craig Blue, Narendra B. Dahotre, Rick Honaker, Bhupendra K. Parekh, Hongyang Han

Equipment wear and corrosion have significant adverse impacts on the operating cost and efficiency of mineral processing plants. In this project advanced surface enhancement technologies are being investigated to decrease the wear and corrosion rate of metal surface. Enhanced metal surfaces are achieved through surface conversion, enrichment, and coating by use of advanced High-Density Infrared (HDI) and other technologies. Studies have been done to determine the effects of process parameters on surface properties and identify optimum conditions. The microstructure of the enhanced metal surfaces was characterized by SEM, EDS, and microindentation. Laboratory wear testing was carried out to investigate the wear performance and the viable coating candidate was determined.

Jan 1, 2005

By P J. Dailey, S L. Burchell, R F. Chiappetta

In recent years, high-speed motion picture photography has become a powerful diagnostic tool and technique to study, analyze, evaluate, and aid in blast designs. Production blasting, typically lasting less than two seconds, requires an extended time base for observation and clarification of short-lived phenomena. Information obtained from high-speed photographic analysis is categorized into two main groups.

Jan 1, 1989

By AIME AIME

THE list of deaths reported during the year 1904 comprises the following names (the figures in parentheses indicate the year in which the persons named were elected to membership). Honorary Members.-Sir Lowthian Bell, Dr. Thomas M. Drown. Members and Associates.-Jacob Neff Barr (1884), John Walter Best (1899), A. Poyntz Blandy (1903), A. Cass Canfield (1876), William E. Carroll (1901), William E. C. Coxe (1874), Russell W. Davenport (1877), Isidor Davidov (1893), Louis M. Davis (1884), Edward Doerr (1897), Edward M. Ferguson (1878), C. Le Neve Foster (1893), Geo. Clinton Gardner (1878), Wm. J. Harris (1871), Richard P. Heckscher (1893), H. D. Hoskold (1.894), Wm. S. Hungerford (1882), Edwd. K. Landis, (1882), August Lengemann (1902), Wm. M. Lippitt (1900), Henry McCalley (1888), Robert J. McCartney (1897), Arthur McClellan (1871), Arthur S. Mahony (1888), Philip W. Moen (1888), Henry G. Morse (1881), Charles Parkin (1875), Clarence V. Page (1900), Rubens P. Patterson (1886), Henry Paul (1889), W. H. Pettee (1871), James B. Randol (1879), Irving H. Sevier (1904), Win. J. Sims (1902), John H. Slavens (1901), Chas. B. Squier (1886), Chas. W. Stickney (1891), Homer H. Swaney (1903), Walter B. Wilson (1892), Whittaker Wright, The following paragraphs, constituting the concluding portion of the Annual Report of the Council for 1904, have been withheld from publication until now, in order to make them as accurate and complete as possible. Jacob Neff Barr, a mechanical engineer of note, died on May 5, 1904. Being especially interested in railroad work, he invented the Barr contracting-chill process of casting car-wheels,

Jul 1, 1905

By Donald J. Olson

The North 27th St. ISS Extension tunnel will, under present plans, be the last constructed section of Milwaukee Metropolitan Sewerage District?s (MMSD?s) existing deep tunnel system. The 6.5 m (21 ft) finished diameter tunnel is approximately 3,260 m (10,590 ft) long and is located in NE Milwaukee County. When disputes over the pro-cesses to be used in owner-directed pre-excavation grouting in rock threatened the completion date stipulated between MMSD and the State of Wisconsin, the MMSD and J.F. Shea, the contractor, entered into a unique agreement. Shea accepted responsibility for all shaft and tunnel grouting and water control during the project in exchange for settlement of claims related to grout quantities and perceived delays. This significantly reduced risk for the MMSD and helped ensure the stipulated completion of the project.

Pilot-Scale Study of Deep Cone Thickener for Phosphatic Clay Dewatering

Sep 13, 2010

By Naj Aziz

The shear behaviour of reinforced rock joints is investigated for the bolt-grout-rock interaction and for failure mechanism. The effectiveness of the bolt application under lateral and axial loading conditions within surrounding materials is investigated in different medium strength. Double shearing testing of bolts were studied in concrete blocks of 20, 40, 50 and 100 MPa strengths, subjected to different pretension loads of 0, 5, 10, 20, 50 and 80 KN respectively. The experimental study was complemented with three-dimensional numerical analysis. Parameters examined include: shear resistance, shear displacement, induced strains and stresses during bolt bending process and its ultimate failure across the sheared joint planes. The conclusions drawn from the study were; the level of bolt resistance to shearing was influenced by the bolt profile configuration, the strength of the rock or medium influenced the level of load generated on the bolt, and the increase in bolt pretension has contributed to the increased shearing load of the bolted medium.

Jan 1, 2007

By Tjaar A. Louw, Albert P. Van Niekerk, Johannes J. Louw, Attie J. Goosen

Unlike molecular high explosives, commercial explosives based on ammonium nitrate do not detonate ideally according to the theoretical model for steady state, one-dimensional detonation. One of the reasons for this deviation from ideal detonation is the slower chemical reaction, due to less intimate contact between the oxidiser and fuel components. It is well known that the inclusion of gas pockets, such as microballoons, in the formulation of ammonium nitrate based emulsions and watergels enhances the performance of these explosives. Various different interpretations of the “hot spot” theory have been proposed to explain this phenomenon.

Jan 1, 1997

By Leonard J. Prosser, Dennis R. Dolinar, John L. Ellenberger, Gabriel S. Esterhuizen, Anthony T. Iannacchione

The room-and-pillar mining method is used extensively in underground limestone mines in the Eastern and Midwestern U.S. The rock mass is typically a near-horizontal, bedded deposit at relatively shallow depth. A survey of 34 mines was conducted in which data on roof spans, rock mass properties and support practices were collected as part of a National Institute for Occupational Safety and Health research project into ground control in limestone mines. The average room width is 13.5 m (44 ft), accommodating large mechanized equipment. The results show that the immediate roof beam can consist of many individual layers and can contain several near-vertical joints. In spite of the room widths, the roof is naturally stable in many mines. Observed roof instabilities can generally be related to excessive horizontal stresses or unfavorable geological structures that cause block fallout or beam failure of the bedded roof rocks. The survey showed that the rock mass quality of the limestone does not vary significantly throughout the Eastern and Midwestern U.S. Roof conditions and the need for support were found to be closely related to the thickness and competence of the first layer of limestone in the roof. The findings highlight the need to identify local geological structures and the roof beam characteristics so that support alternatives can be evaluated. Monitoring and observational technologies that are available for identifying potentially unstable roof are presented, which include: roof characterization using the Rock Fall Risk Index, automated logging of roofbolt hole drilling, microseismic monitoring and displacement monitoring.

By A. Johnson

When are SMART transmitters the smartest choice? To answer this question requires a closer look at SMART transmitter technology. It is necessary to understand this technology in order to recognize how it can best be utilized to give the greatest value for the application. And, once the decision to buy transmitters has been made, it becomes a question of whose SMART transmitter to buy. For, although the under-lying technology is similar, the differences that exist in how the technology has been implemented can make a dramatic difference in the end result. What prudent users of SMART technology do is to analyze their needs by application before making their buying decision.

Jan 1, 1988