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By Dennis R. Dolinar, Gabriel S. Esterhuizen

In this National Institute for Occupational Safety and Health (NIOSH) investigation, numerical modeling is used to evaluate the degree the pillar strength is increased with a rectangular pillar over a square pillar. Three-dimensional models are developed with pillar sizes and geometries typical of underground limestone mines in the United States. Physical properties for the models are based on geotechnical surveys of nearly 30 underground limestone mines. To examine the effects of pillar length on pillar strength with the modeling, a parametric study was conducted where the pillar width was held constant while the length and height were varied resulting in width-to-height ratios ranging from 0.5 to 1.5 and width to length ratios ranging from 1 to 6. There are two aspects to pillar strength and failure. At relatively low stresses, pillars can fail as a result of geologic structure. At greater depths and sufficient extraction ratios, the pillars can also fail as a result of the vertical stresses exceeding the pillar strength. The effects of increasing pillar length regarding both strength aspects are presented in this study. Equations were developed for the increase in pillar strength with both height and length based on the model results. The results from these equations were compared to those from previously developed empirical equations for rectangular pillars. For the more slender limestone pillars with a width-to-height ratio below one, there is little increase in pillar strength for length-to-width ratios above 2 and almost no increase with length for a width-to-height ratio of 0.5. Only with the more squat pillars is there a significant improvement in strength with length. The gain in pillar strength with length for the pillars is explained by the change in the ratio of the area of the pillar affected by the ends to the area of the pillar. For the squattest pillar, the change in strength is also affected by an increase in pillar confinement along the central length of the pillar as the pillar transitions from a square to a long rectangular pillar. With geologic structure, added pillar length can significantly improve the pillar strength, depending on the strike of that structure with respect to the long pillar axis.

By J. P. Smith

Permian salt measures carry extensive lenses of soluble potash salts in north central Germany. Potash deposits of Oligocene age are found in the Upper Rhine Graben of Alsace (France), and in the Catalonian Basin of Spain. These deposits are found in a wide range of structural settings. Reserves are large, and the production of potash salts is an important phase in the economy of each of these countries.

Jan 1, 1950

This modern plant consists of a battery of 72 Otto Wilputte Compound Under-jet Ovens with extensive plant for the recovery by-products. The ovens produce 9000 tons of furnace coke per week together with some 17,000,000 cub. ft. of coke oven gas, which is used for heating purposes throughout the works and for heating the ovens.Coal is supplied from the, company's colliel'ies and is stored under a Coal Handling Bridge of 264 ft. span and 365 ft. overall, capable of handling 250 tons per hour. The coal storage space of 1600 ft. can. be extended to a maximum of 2800 ft.Preparation of the coal for coking involves fine grinding which is carried out as follows:-Coal is dumped from rail waggons on to a conveyer belt which delivers it to a 12 ft. x 22 ft. Bradford Breaker, with a capacity of 400 tons per hour. The coal, then approximately 4 in. in size, passes, to the mixing bins; and after careful blending is reduced in the,hammer mills to a fineness suitable for the ovens.The fire coal is elevated to the main storage bin over the battery for subsequent charging by electric larry car. The average cokingtime is 15 hrs. 36 mins. At the end of ,this period the doors, are removed and the coke pushed from the oven by a mm. The coke, is, then quenched with fresh, water and sent to the Blast Furnace in 50-ton Copper Waggons.The gas is exhausted from the ovens by Brown Boveri turbine, exhausters of 23,000. cub, ft, per min. capacity. Exhaust steam from these is used for various. purposes in the By-Product plant. After removing the last traces of tar by Electrostatic Precipitators', the gas is bubbled through sulphuric acid, the ammonia forming ammonium sulphate, which is subsequently washed, dried and bagged for sa,le as a fertilizer. The gas then goes to the Benzol Scrubber Towers, where benzol and other derivatives are recovered and later redistilled and purified. The cleaned gas is then piped to the main works for heating purposes, being used with tar to fire the steel furnaces, and also the soaking pits and reheating furnaces.BLAST FURNACES.The company is at present operating two Blast Furnaces of 800, and 1000 tons nominal daily capacity respectively. The latter was...

Jan 1, 1938

The Skorpion process comprises three processing steps, atmospheric leaching in sulphuric acid, zinc solvent extraction and electrowinning to produce special high grade zinc. The major mode of impurity transfer was attributed to crud runs in the solvent extraction circuit. Crud may be described as a heterogeneous, partly inorganic, partly organic mass of material which accumulates predominantly at the interface between organic and aqueous solutions. The paper describes the route causes of the crud formation in the solvent extraction circuit and optimisation strategies which are being followed to prevent impurity excursions in electrowinning. Keywords: zinc oxide, solvent extraction, crud formation, colloidal silica

Jan 1, 2007

By Adrian J. Moore, Alan B. Richards

Airblast overpressure levels can commonly be increased by up to 20 decibels (dBL) by the effects of meteorology, due to inversions and wind shear. Existing atmospheric refraction models can provide a good evaluation of the effects of meteorology, but have been limited in the accuracy of their outputs by the accuracy of the meteorological data that is available for input. This paper uses case histories from open-pit coal mine blasting in the Hunter Valley area of Australia to provide examples of increases in airblast due to inversions, wind shear, and a combination of both. It gives details of our experience of the accuracy with which predictions and assessments can be made using meteorological data of various levels of accuracy, and on the design buffer that is required to prevent the exceedence of airblast limits. The accuracy of meteorological prediction and assessment will shortly be improved by the use of sounding equipment that gives continuous measurements of temperature and wind velocity at significant levels above the ground. The paper also gives details of an industry funded research project that aims to permit the effective use of this data at distances many kilometres (km) (miles) from the location of the sounding equipment, and to develop a short term predictive model that will permit the amount of meteorological reinforcement that will occur at firing time to be determined before a decision is made to tie up a shot.

Jan 1, 2005

By E. J. Babcock, W. W. Odell

The Bureau of Mines since its establishment has always taken an active interest in the utilization of lignite and in the development of the lignite dep'osits of the United States. Extensive lignite fields occur in the west central States, notably in North Dakota, Montana, Wyoming, Colorado, and Texas; there are smaller areas in several other States, some of which are widely separated. The total area of the deposits and the total amount of lignite in these several districts are so enormous that the economic value is seldom recognized. To the people of ·the west and west central regions, however, the larger utilization of lignite, in whatever form it may be, is of fundamental importance, and any new methods or uses that promise to open these great lignite fields for more general and more efficient use deserve careful study. Although these lignite deposits underlie areas of thousands of square miles, their development and general utilization has been rather slow. This is no doubt partly because many of the districts are not thickly settled or highly developed in manufacturing industries, but is largely because lignites, from their peculiar physical and chemical characteristics, are low-grade fuels. Most of the lignites in these areas are imperfectly developed coals; many have a more or less woody structure; some belong to the brown-coal type; and others are darker, denser, and more homogeneous, approaching subbituminous coal. The people living in the regions in which these vast deposits occur, especially in the west central part of the United States, are vitally interested in every effort toward bettering lignite as fuel and aiding its wider utilization.

Jan 1, 1923

By R. L. Amelunxen

"In January 1983, Gibraltar Mines Ltd. started an exploratory program on Column Flotation with hopes of improving performance of the Molybdenum Cleaning circuit. The encouraging results led to a column test trial in the Bulk Copper Cleaner circuit where the test unit has per¬formed well. A program was undertaken to understand the mechanics of column operation. A year and a half later, Gibraltar is considering the replacement of existing Bulk Copper and Moly Cleaning flotation cells with a fully computer con¬trolled Column Flotation circuit.BRIEF SUMMARY OF TESTWORKInitial testwork was done with a home made 20 inch diameter x 31 foot high column, equipped with a doppler flow-meter at the tail line and automatic level conrol. This loop maintained constant level in the column by throttling the tail valve. This column was placed in a variety of locations around the Moly circuit as shown on Figure 1 a, b. Test re¬sults indicated that the column could achieve much higher grades than the conventional cells, but recovery wise, the performance was low. Spillages from overloaded pump boxes were a common frustration during this time.Column control strategy was reviewed; and, in light of information received from McGill University, changed to conform with the methods that had been employed by D. Wheeler, of the Column Co. of Canada4 and Gaspe Copper Mines3.The column was tested replacing a portion of the bank, figure lc. The results obtained were more or less equal to the circuit. However, as we had Nitrogen gas connected to the column and not the regular cells, the column was kept in service. With the use of Nitrogen in the column, the usual copper depressant, Sodium Cyanide could be replaced with Sodium Hydrosulphide, hence lower operating cost.As time went on, a 10 inch diameter column was added in series to re-treat the concentrate of the 20 inch diameter column with hopes that the copper content would decrease from 0.6% down to 0.3% in order to save on subsequent leach¬ing costs. So far, results indicate there has been some im-provement, hut we are not achieving 0.3% copper. (See figure 1d)."

Jan 1, 1985

By D. Bienstock

The use of alkalized alumina in removing sulfur dioxide from a coal-combustion flue gas at 625° F was investigated on a pilot plant scale. The absorber was 26 feet long and 1.6 inches ED. Counter-current gas-solids flow at gas velocities of 8 to 15 ft/sec in the presence and absence of baffles, as well as solids entrainment at gas velocities of 20 to 23 ft/sec with solids recycle, were employed. The spent absorbent as regenerated as fixed bed with the reducing gases--reformed natural .7.7d hydrogen. Of absorption-regeneration were successful completed using the alkalized alumina rolled into spherical granules 10 to 16 mesh. There was no loss in activity of absorbent toward SO2 with a modest attrition equivalent to 0.l percent of the solids feed. Supporting studies were conducted on the effect of the sodium content in the absorbent, the composition of the reducing gas, thermal treatment to increase absorbent hardness, and removal of absorbed chlorine from the absorbent. A mathematical model was formulated to describe the removal of SO2 by alkalized aluminum from fixed and falling beds.

Jan 1, 1967

By D. Campos, J. M. Macedo, S. Chadwick

The incorporation of low cost technology transfer to increase the ability of locals to acquire and maintain long term employment are key ingredients for sustainable industrial development. Alcoa’s Alumar plant on the island of Sao Luis is the largest and most modern refinery/smelter complexes in northern Brazil. The plant has one of the most advanced Environmental, Health, and Safety management process in the aluminum industry. Technical assistance, training and financial support were made available to Alumar to address social sustainability issues. Through several programs led by employees on a voluntary basis and applying intensive and extensive training programs, Alumar has enabled local people to develop skills on agriculture and land management, wastes minimization, small business development and administration, all based on sustainable development and social responsibility concepts.

Jan 1, 2004

The 100th Annual General Meeting of The South African Institute of Mining and Metallurgy was held in the Gold Room, Transvaal Automobile Club, 60 5th Street, Lower Houghton, Johannesburg on Wednesday, 13th August, 1997. Obituaries The President announced the death, during the year, of the following members: Honorary Life Fellows and Past Presidents D.M. Jamieson, V.C. Robinson Fellows S. Goodwin, M.W. Johns Retired Fellows T.F. Muller, P.L. Nathan, N. Orsmond, R.J. Ortlepp, H.S. Sichel, K.E. Steele, W.B.L. Steuart, N.B. Vinson Member J.P. Hatfield Retired Members S.T. Baron, B.F. Pinder Retired Associate F.J.A. van Reenen In memory of the deceased and in sympathy with the bereaved, all rose and observed a moment of silence.

Jan 1, 1997

By M. J. GAVEN

COMING over from the plant on the Denver and Rio Grande yesterday afternoon I was an interested listener to a smoking-room conversation that had to do with the experimental plant near Rifle. The people who were talking didn't know me and I didn't know them, but I learned quite a little. I understood that the plant would never operate; that it was not intended to operate; that the "oil trust" would keep it from operating; that our tramway had eaten up all our money and still was not working and would not work; that the plant was run by a bunch of kids, and that the superintendent was probably the biggest kid of the bunch. I plead guilty to the latter. But the people who were talking were misinformed. The plant is producing oil. The first sample of oil that came from our unit at the Bureau of Mines experimental plant at Rifle, Colo., was produced on Sept. 18, the first that came out of the condenser, and it is still coming. This sample of oil may mean to the United States what the first oil produced from the first well meant.

Jan 1, 1926

By T. M. Barczak, S. C. Tadolini

Reduction in the recovery time required and improvements in safety during a longwall face move have compelled coal mine operators to examine and use pre-driven longwall recovery rooms. The recovery entry is developed at the longwall stop position and supported ahead of time so that the required combinations of standing and internal supports can be installed before the longwall face approaches. A calibrated three-dimensional finite element model, developed in conjunction with an underground test area, provided the critical components and design principals for a comprehensive parametric study. The study indicates that vertical, horizontal, and shear stresses concentrated on the outby abutment pillar corner of the recovery room resulting in deformations in the immediate roof above the primary roof support anchorage level. The results of the numerical model and field site observations indicated that the combination of the internal bolting system and the standing concrete supports are critical for the successful and safe extraction of the longwall equipment. Cable supports installed at and angle over the pillars can help stabilize the disturbed zone above the adjacent fender and outby pillars, however; standing supports are required in most sedimentary roof conditions to increase stability and assure a safe longwall extraction.

By T. L. Owen

Since 1993 Cyprus Amax has brought $2.5 billion dollars of greenfield and expansion projects into production, taking it from a mid-sized domestic minerals company into a major international minerals organization. The near simultaneous development of these multiple mineral projects in different locations around the world provided the opportunity for Cyprus Amax to develop a formal project management approach based, in large part, on an outsourcing philosophy. This formal project management system along with its outsourcing philosophy has served the growth agenda of Cyprus Amax extremely well. These preceding factors, coupled with the in-house retention of a core project group that fully understands the breadth of skills and abilities needed to undertake development of multiple large projects successfully, have been the cornerstone of Cyprus Amax’s project development success.

Jan 1, 2000

By Frank C. Stevens

Many changes have taken place in the "World Cement Market" since Joseph Aspdin discovered portland cement in the early 1800's. At the turn of the century, production of cement world wide was a few million tons; today, it is over one billion tons. By 1995, world production is estimated to reach 1.2 billion tons. Cement processing has changed from inefficient, small vertical kilns to large efficient, precalcining kilns, and large automated crushing, blending and grinding systems. Consequently the cost of production has declined in real terms, resulting in significant economic benefits to the general public. In addition, quality and uniformity of cement have increased, strengths have increased, and at least 25% fewer pounds of cement are needed for each cubic yard of concrete. Today, cement moves thousands of miles on the inland rivers and great lakes of the U. S., across Siberia and across the oceans of the world. The volume of cement moving more than a few hundred miles is almost 100 million tons, or 10% of world production. Today, on a per ton basis, it costs no more to move 40,000 tons of cement to the United States from the Western Pacific rim or from Europe than it does to truck cement 200 miles. For example, cement shipped by water from Spain costs $5.00 to $7.00 per ton compared to cement shipped by truck 200 miles at $16.00 per ton. This low cost water transportation has been a major factor for the increased movement of cement between countries. Table 1, Cement Production Summary-World, gives a global picture of production, export and import tonnages in recent years. Figure 1 is a graph showing CEMENT PRODUCTION SUMMARY WORLD WIDE.

Jan 1, 1987

By Wouter Hartman

Xuandong Coal Mine is mining coal in one of the most challenging underground environments in the world. This work has found that it is not only challenging but it also has the composition for some interesting rock mechanics and ground control conditions. The paper highlights the extreme mining and rock mass behavior conditions encountered when mining coal at 900 m below surface. It was found that the ground control environment associated with geological weakness, low coal material strength and stiffness, was reasonably well controlled; however, the chain pillar geometry and design did not take these geological weaknesses into consideration. Some of the chain pillars employed were quite large, which resulted in floor punching and secondary floor heave, which causes extreme difficulty for production. No barrier pillar has been employed except for the center 164-m-wide main headings pillar with a w/h ratio in excess of 40. After assessing the location and geometry of a 200-m-thick dolerite sill overlaying the coal measures, we found the probability of it breaking up into to smaller fragments and producing a larger goaf to be low. Therefore, the influence of the dolerite sill on chain pillar loading is considered small compared to the low coal, immediate floor and roof rockmass strength. It is further recognized that horizontal stresses could be locked up within the dolerite sill, which would likely result in regional bending that would be distributed through the chain pillars. This has, to some extent, already occurred, and the effects have been seen and felt through excessive floor heave, pillar punching, and coal bumps (seismicity). We?ve also found that there was a need to employ basic rock mechanics principals in assessing the stability of future multiple seam mining layouts.

Jan 1, 2012

By A Kamkar-Rouhani

The paper describes a mineral potential mapping of gold and other base metals in Mahneshan area, Iran, using geographical information system (GIS), in which, the method of weights of evidence is used to combine spatial data obtained from different sources to make prediction for mineral potential. This is a quantitative tool for mineral resource mapping that can be used to delineate and predict favorable areas for further exploration by using the characteristics of known and similar mineral deposits. In accord with the descriptive model for gold and other base metal deposits, the spatial distribution of 20 known mineral occurrences was used. In addition, digital evidential maps were used in this study. The maps include maps of lithological units, faults and first derivative of total aeromagnetic data, remotely-sensing data of alteration and also geochemical evidential maps produced on the basis of the results of chemical analyses of samples taken from the stream sediments in the area, and analysed for Cu, Pb, Zn, Sb, As, Ag, Au, Ba and Hg elements. The binary maps were produced and then combined with the model of weights of evidence using 20 known mineral occurrences to obtain a final map of the favourable areas for further exploration of gold and other base metals in the study area. The final map is a predictive GIS model of the mineral deposits in the area. An interesting matter about the final predictive GIS model is that the faults are mainly located in favorable areas which possesses the most probability of mineralisation. Therefore, the faults in these areas have priority for further exploration of gold and others base metals.

Jan 1, 2005

By Howard A. Perko

Soldier pile and lagging is a conventional means of temporary excavation shoring. Timber lagging design has traditionally been based upon the designer's experience or empirical rules. One such method is the Goldberg Zoino chart used by the Federal Highway Administration. Most of these methods restrict the designer to a consistent soil profile, certain pile spacing, construction grade timber lagging, and limited depth. The methods do not take into account surcharge loads or a variety of other factors that could arise. A designer working outside of ordinary circumstances with unusual loads, varying soil conditions, or alternate lagging materials has difficulty estimating lateral earth pressures. In rigid earth retention systems, lateral earth pressure is generally assumed to be constant along the length of the wall. In soldier pile and lagging systems, the lagging is often considerably less stiff than the steel soldier piles. As the lagging deflects, the soil tends to bridge between the stiffer elements resulting in a lower pressure on the lagging. Several previously published methods by others for determining this reduced pressure are summarized and discussed. These methods typically consist of using a portion of the active earth pressure in several different pressure distributions. A simple theoretical model is presented for determination of lateral earth pressures on wood lagging. The model is based on a three-dimensional "silo" shaped sliding wedge analysis. Results of the model are compared with other published methods. The model compares well with these methods which cover the normal spectrum of design situations. In addition, the model can be used to estimate lateral earth pressures outside typical situations.

Jan 1, 2008

By H. Richard Eisenbeis, Donna M. Watkins

Many technical professionals (tp)* desire to occupy upper level management positions. But career paths for most scientists and engineers do not extend beyond their specific disciplines. This is unfortunate. Our technical frontiers are expanding so rapdily that it is difficult, if not impossible, to make sound top management decisions without understanding the technical complexities involved. Technical professionals often are not considered for upper level management positions because they lack the managerial and interpersonal skills necessary to become successful administrators. You've heard this before, but a key component of these skills is the ability to communicate. Technical professionals are often unable to communicate as well as they should with nontechnical professionals and nonprofessionals within the organizations that employ them. Communication is important for managerial success Communication is the network of interactions whereby knowledge and understanding are conveyed from one social set to another (Flippo and Munsinger, 1982). In order to be successful, managers must not only be "good" communicators, they must be "effective" communicators as well. Good communication occurs when managers are able to formulate and transmit their messages in such a way that they are received and understood. Effective communication goes one step further: It occurs when recipients accept messages as legitimate and respond to these messages in the manner desired. Before promotion into upper level positions, managers must have developed organizational skills (planning, decision making, organizing, and controlling) and interpersonal skills (directing, influencing, and motivating). Applying these skills effectively is difficult without a highly refined ability to communicate. Effective communication, then, is basic to managerial success. Nowhere, perhaps, has the importance of being able to communicate effectively been emphasized more than in Mintzberg's landmark study of managerial roles (Mintzberg, 1973). Mintzberg's results indicate that executives typically averaged 36 written and 16 verbal contacts a day. These contacts were both important and trivial. They generally occurred in a random manner. Time spent on each varied. Scheduled meetings averaged over an hour. Desk work, telephone calls, and unscheduled meetings required an average of 15 minutes or less. Why technical professionals have difficulty communicating Three reasons why technical professionals do not communicate well are: • The work motivational patterns and personal attitudes of technical professionals are not conducive to effective communication. • Students in technical professions are not encouraged by educational institutions to develop their communication skills. • Organizations do not insist that all technical professionals be able to communicate in the language of business. The work motivational patterns of most technical professionals are indicative of internals and high achievers (Hunt, Salisbury, and Whittington, 1968). As internals, they believe they control their own destinies. As high achievers, they believe that task accomplishment is a primary indicator of success. To ensure a task is completed in the manner desired, tp's attempt to structure and define work situations so they alone are responsible for results. TPs consider the task accomplished when they, and perhaps other tp's, are satisfied with the results. From the tp's perspective, the task may have been completed. From a communication standpoint, two other factors may apply. First, solving the problem required very little interaction (and thus, communication) with others. Second, the tp's, considering the task accomplished, have little concern for how their "technical" answers will be translated to nontechnical persons needing

Jan 8, 1987

By Uusna S, Canning R. G, Goodheart B. A

The development of a process for removal of iron oxides from ilmenite is outlined whereby the Ti02 content of Western Australian ilmenites can be upgraded from 55 to approximately 90 per cent. In the first stage, the iron oxides are reduced with solid carbon (coal) to metallic iron. Experimental reductions were carried out in crucibles, a fluidized bed, and a small pilot plant rotary kiln. The reduced ilmenite was then agitated in aerated water, in the presenceof catalysts, so that the iron "rusted" away from the ilmenite grains and the precipitated iron oxide was easily separable by decantation.The influence of variables on the rates of reduction and oxidation are discussed. The oxidation rate was examined for both the physical oxygen transfer characteristics and electrochemically by reference to Pourbaix diagrams, in which redox potential is plotted against solution pH.The upgraded ilmenite is expected to be an attractive material for pigment manufacture, and the iron oxide has prospects of being a marketable by-product. The process may possibly be applied to other ores.INTRODUCTIONThere are extensive deposits of ilmenitic beach sands, Le. iron titanium oxides of the general formula FeTi03, 'occurring in the lower south-west portion of Western Australia, and although there has been considerable commercial development, local producers face keen competition on a freight-cost basis. Thus the removal of the unwanted iron oxide constituent would have the double advantage of reducing the freight differential and presenting a more attractivematerial to pigment manufacturers.

Jan 1, 1965

By P. W. Lotz

Traditionally, bottle roll tests have been used to optimize the extraction process for best gold extraction and recovery. Such tests typically involve exposing the ore to defined reagent concentrations (lime, cyanide and sufficient oxygen) and balance the gold input with recoveries and losses. With mounting pressures to accommodate sustainability issues during development work, it became apparent that much more information would be required on the interactions and kinetic behaviour of solid and solution species during the entire leach process. This information is vital to enable proactive management of critical issues such as cyanide, arsenic, water and tailings management. Inadequate management of these aspects has led to temporary closures and, in cases of non-compliance, to the dynamically changing regulations. MINTEK?s advanced leach facility (ALF) is being developed with the aim of bridging the knowledge gap between the gold leach process and the predictable environmental impacts upon discharge. The facility aims to monitor all parameters of relevance such as pH, Eh, dissolved oxygen, metals, cyanide species, and viscosity during the entire process to enable more informed decisions on practical interventions. The presented set of data reflects first experiences gained from processing a refractory gold ore concentrate. Attempts at optimizing the process were limited due to the developmental nature of the work. Data relating to leaches with differing preoxidation conditions and cyanide staging is presented.

Jan 1, 2009