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By Wilson Blake

A mathematical model based on the finite element method of stress analysis has been used to describe the behavior of the western wall of the Kimbley Pit as its slope was steepened from 45 degrees to 57 degrees. Theoretical stress changes because of slope modification are slight except at the toe of the modified slope. Magnitudes of stress created are small when compared with the strength of a competent rock. Resulting displacement patterns point out the need for determining the in situ state of stress at a site prior to excavation or modification. A comparison of model results with field measurements shows that, in general, the model has described the measured behavior of the west wall of the Kimbley Pit remarkably well.

Jan 1, 1968

By Hassan El-Shall, Rosana M. Macedo Borges, Ponisseril Somasundaran, Regis Stana, José Renato B. Lima, Patrick Zhang

The phosphate fertilizer industry is a large activity in Brazil because the soil has a phosphorous deficiency. The phosphoric acid that is produced is extensively used in the production of fertilizer. It is produced by reacting phosphate carbonaceous rock with sulfuric acid, generating phosphogypsum as a by-product. In 1991, there were about 29 million tons of phosphogypsum stored in Brazil. This has increased to an estimated 280 million tons in 2001. While the phosphogypsum is used in the cement industry and also in agriculture, the quantity used is much less than the production rate, and the stockpiles are still increasing. The radioactivity of this waste may not allow its continued use as a construction material and some other uses. However, Brazilian phosphogypsum contains a smaller quantity of radioactive materials than is reported for phosphate rocks from other countries. One important reason is the geological origin of the Brazilian apatite. All the large deposits being currently mined are igneous, not sedimentary, as is the majority of the phosphate rock produced around the world. An extensive study is being conducted to characterize the phosphogypsum generated in two production facilities in Sao Paulo state to develop safe uses for this waste and determine the environmental impact caused by the present method of phosphogypsum disposal.

Jan 1, 2002

By A. Pratt, G. Deschênes

This paper quantifies the detrimental effects of pyrite and stibnite on gold leaching kinetics. Means to reduce the effect of these minerals by addition of lead nitrate and oxygen are presented. A significant retarding effect was observed when the pyrite concentration was 20%. A pretreatment with lead nitrate reduced the extent of gold surface coating by Ag, Fe and S. Stibnite, at a concentration as low as 20 ppm, significantly affected the gold leaching kinetics through forming a passivating film of Sb(V) oxide possibly Sb2O5. The most practical way to alleviate the effect of stibnite is to leach the materials at a moderate pH with addition of lead nitrate. A low temperature reduced the efficiency of lead nitrate to counteract the effect of stibnite. The increase of dissolved oxygen is not favourable to alleviate the coating of stibnite on gold.

Jan 1, 2004

By Y. M. Jiang

Many underground instabilities, such as excessive shield loading and roof falls, occur at longwall faces causing safety problems and production losses. Such instability problems are directly related to roof conditions which can be categorized using geological information. . However, most geologic information describing anomalies and variations of immediate and main roofs are not available before mining resulting in unexpected problems in a longwall face. It is apparent that the evaluation of these geologic anomalies provides a great benefit for longwall stability. The purpose of this study is to evaluate roof categories associated with geological anomalies employing fuzzy set theory. The evaluation is based on real-time monitoring information, such as shield leg pressure, developing load on shields, intervals of periodic weighting, and the ratio of developing loads during periodic to normal times. This paper introduces the application of fuzzy set theory for characterizing roof conditions and evaluating of roof similarities.

Jan 1, 1995

By Bryson D. Trexler

Man's activity in developing, operating, and abandoning a mine often affects the quality of the ground water and surface water. Acid water drainage from mines is an example of an impact from mining that results in degradation of ground and surface water. New flow systems are created by the mining activity. The mining made possible complex chemical reactions that, with water movement, create a discharge of low pH, poor quality water. Remedies for these problems fall into two general solutions: 1) treatment of the end product and 2) reversal of some aspect of man's disturbance of the natural system. The relative reversibility of various aspects of man's impact from mining activities ranges from relatively easy to very difficult, from economically feasible to economically infeasible, and from technically possible to essentially impossible with present knowledge. The relative reversibility of a mine-related problem cannot be assessed without first understanding the detailed physical interactions that combine to form the problem. Acid water drainage is a combination of the availability of several chemical factors with the availability of water for a transport mechanism.

Jan 1, 1982

By William J. Shampine

The Floridan aquifer, which underlies all of Florida, yields water with a sulfate content of less than 50 parts per million in the north-western part and throughout most of the center of the State. In the southern part of Florida and along the most of the east coast, the sulfate concentration generally exceeds 100 parts per million and is as much as 1,700 parts per million. The sulfate concentration tends to be higher in the deeper zones of the aquifer. This map shows the sulfate concentration in the upper part of the aquifer. Sulfate is found in almost all natural water. Sulfate in rainwater is dissolved from impurities and gases in the atmosphere. Rankama and Sahama (1955, p. 314) report that the average sulfate content of rainwater is two parts per million; however, concentrations have been as high as 283 parts per million. Much of the sulfate in rainwater comes from hydrogen sulfide gas which is generated in shallow water on the continental shelves. The combustion of bituminous coal used for heating and industrial purposes seems to be an important local source of sulfate.

Jan 1, 1966

By David E. Thompson, Wesley E. Stimpson

The Massachusetts Bay Transportation Authority (MBTA) Red Line Extension Northwest is currently in the early stages of construction. The 3.1 mile extension of the Red Line from the existing Harvard Square Station in Cambridge, Massachusetts to Alewife Brook Parkway in Cambridge, Massachusetts will include a large, near surface hard rock, rapid transit station chamber at Porter Square in Cambridge (Figure 1). [ ]

Jan 1, 1979

By Mohammad Irshad, Larry H. Heflin

INTRODUCTION The planned 166 kilometer (103 mile) Metro rapid rail transit system in Washington, D.C. is being designed and constructed by the Washington Metropolitan Area Transit Authority. At the present time, 112.6 kilometers (70 miles) of this system is in operation and contains 21 route-kilometers (13 miles) of rock tunneling, and 14.5 route-kilometers (9 miles) of soft ground tunneling. An additional 2.4 kilometers (1.5 miles) of single track tunnels in rock are planned and 6 additional contracts will consist of some 8 kilometers (5 miles) of twin tunnel, resulting in 16 additional linear kilometers (10 miles) of single track tunnel in soft ground. The Authority plans, upon its evaluation and the recommendation of the General Engineering Consultant, to include an alternative design incorporating the convergence confinement method of construction known as the New Austrian Tunneling Method (NATM), for Sections E-5, E-6e and E-8a of the E-Route. The Metro system is constructed in a variety of geological conditions and crosses the boundary of two major geographic provinces. Rock tunneling is to the west of this "fall-line" boundary, soft ground tunneling to the east. The soft ground tunneling portions of Metro construction lie in the coastal plain which consist of a

Jan 1, 1987

By Slobodan Vujic, Goran Cirovic, Dragan Radojevic

Mine production systems (MPS) are characterized, more or less, by the following properties: uncertainty, subjectivity, impreciseness, polysemy, instability, indefiniteness and lack of data. From modern study aspect these MPS mathematically belong to the class of fuzzy systems. With this in mind, the usage of fuzzy sets is recommended as a methodology that treats impreciseness, indefiniteness and complexity of mine production systems in a satisfactory manner. Fuzzy modelling, discussed in this pa- per, is applied as a mathematical implement. The objective of the paper was to show production optimization in practice on the ex- ample of bauxite open pits where fuzzy linear programming (FLP) was used following the criterion per income. The variables in criterion function are linguistic variables while both variables and variable restrictions are presented by triangular fuzzy numbers (TFN). The term "satisfactory income" presented through triangle fuzzy numbers was introduced instead of "maximizing the income". sensitivity of the obtained solutions has been analysed

Jan 1, 1996

By R. Markovic

The objective of this research study was the investigation of heavy metal removal from wastewaters of the "SARAKA" stream by using low-cost materials. These wastewaters flow into Krivelj River and through the network of existing rivers into regional water reservoirs. Sawdust, cardboard and fly ash were used as reactive materials in laboratory studies. Sawdust was obtained from oak and fir-wood while fly ash from heating station Bor, bitter-oak and oak. Experiments were carried out using real Saraka stream wastewaters and the degree of removal for iron, copper, manganese and zinc was investigated. The content of these heavy metals in Saraka stream wastewaters was under the limit of III and IV class of water (Law on Water - Official Register of the Republic of Serbia). Parameters such as flow rate of water, pH and effluent volume, contact time between water and reactive material, etc, were monitored during the experiments. All used materials give satisfactory results for iron and other heavy metals removal; the highest degree of removal was obtained by using fly ash.

Jan 1, 2006

By H. E. M. N. Moursy, Hassan El-Shall, M. N. Ahmad, Ponisseril Somasundaran, C. R. Holland, D. Chandler, G. Walker, Regis Stana, Patrick Zhang

The reaction kinetics of the acidulation of Moroccan phosphate rock (32% P?05) using 45% nitric acid were investigated using the Shrinking Core Model (SCM) , a newly developed Diffusion Model (DM) and a newly developed Combined Reaction and Diffusion Model (CRDM). This was achieved buy conducting a number of experiments in a controlled batch reactor system at different temperatures. The conversion and the reaction rate were calculated at different time intervals. The SCM based on reaction time and the CRDM characterize the acidulation process of phosphate rock. Diffusion of nitric acid and the products of acidulation at the early stages of reaction through the phosphate rock were found to be the rate-controlling step, resulting in a dif- fusion coefficient, which controls the mass transfer process. The reaction kinetics were found to fit first-order kinetics especially during early stages of reaction time. The deviation of the kinetics from first-order at later stages was due to the fact that the overall reaction was mass transfer controlled with respect to nitric acid and products diffusion.

Jan 1, 2002

By Ralph P. Hackl

Biooxidation processes for treating arsenical and other types of refractory gold ores are touted by many as being simple, inexpensive and environmentally friendly. One of the advantages claimed by proponents of biooxidation is that arsenic is disposed of as insoluble ferric arsenate which is suitable for long term disposal in tailings ponds. However, there is considerable controversy as to the stability of ferric arsenate with respect to re-dissolution of arsenic. In particular, there is concern that the amorphous ferric arsenate produced at low temperature is not stable, especially at the alkaline pH's required for cyanidation. There is a general lack of published information on the stability of arsenical bioleach tailings. Past work on ferric arsenate stability has usually involved purely chemical systems and the use of synthetically prepared precipitates. Upon completing the Salmita bioleach pilot plant campaign (Hackl and Wright, 1989) the author had the opportunity to test the stability of the arsenical bioleach/cyanide tailings which were produced. This paper summarizes the results of that work.

Jan 1, 1990

By Robert F. Droullard

The U. S. Bureau of Mines (USBM) has investigated instrumentation and methods for measuring exposure to radon daughters in underground mine atmospheres. Both personal and area monitors have been studied through in-house and contract research. A field study in uranium mines identified some reliability problems that required additional work for the personal dosimeter systems. Improved versions of continuous working level detectors have been developed and tested for use as area monitors in underground mines. Test results for the personal and area monitors were satisfactory for underground mine applications.

Jan 1, 1981

By Gunnar Nord, Per-Anders Persson, Duri Prader

The paper gives a short resumé of the findings of the joint US - Swedish "Mechanical Boring (MB) or Drill and Blast Tunneling (DB) ? Workshop" in Stockholm December 1976. New developments and trends in both MB and DB techniques in Europe since 1976 are described, and information is given on some interesting new projects. Differences in contracting principles between the US and Europe lead to different practices for preinvestigations, design, excavation and arbitration and legal affairs. It is shown that this often leads to a higher cost in the US than in Europe for similar excavation jobs. A typical US tunnel job also has more men on the site than a similar job in Europe. This adds to the cost difference and is only partly balanced by a slightly higher rate of excavation in the US. A comparison is made between two quantitative methods of predicting MB penetration rates. These are in reasonable agreement. A probable future development in machine design is an increase in cutter load towards perhaps 25 tons per disc where the tunnel diameter is large enough to house the machine size dictated by the size of the very large electric motors required. Recent European developments in drill and blast technique include improved methods for cautious blasting, precision hydraulic drilling of small diameter holes, and non-electric interval blasting techniques. These developments still keep the drill and blast method ahead of mechanical boring costwise for tunnels in igneous rock whereas for most sedimentary materials mechanical boring has a lead, particularly for long tunnels.

Jan 1, 1979

By Alex Stewart

Most iron bearing ores treated by the R=N Direct Reduction Process yield products lower in phosphorus than the initial ores. The sulfur is also removed and generally is in the range of 0.02 to 0.05 percent in the final R=N product, independent of the sulfur content of both the ore and carbon fuel used. The mechanism and thermodynamic justification of the principal reactions leading to the removal of both phosphorus and sulfur and the control of sulfur in the iron concentrate produced are discussed and supported by the results of laboratory experiments. In substantially all iron ores (containing up to 4% sulfur as sulfate) and solid carbon fuels (containing sulfur from 1 to 8%) tested, the rejection of sulfur has been in the order of 90-95%, with not more than 0.02 0.05% sulfur in the final metallic iron product. With respect to phosphorus-bearing iron ores ranging up to 0.70% P205, the rejection to tailings has been in the order of 70-95%, resulting in not more than 0.03 - 0.07% phosphorus in the final product.

Jan 1, 1958

By W. -C. Huang

In this paper, a methodology for the reliability assessment of geogrid-reinforced unpaved roadways is presented, by taking into account the variability of the subgrade?s undrained shear strength. Analyses are performed using the Point Estimate Method and the Monte Carlo simulations technique. The undrained shear strength is represented by its correlation with the California Bearing Ratio and it is modeled as a random variable following a long-normal distribution. Analyses are performed for different types of reinforcement. The study provides a quantitative assessment of the variation of the system?s probability of failure with this parameter. Overall, the approach suggested in this study may be considered as a complementary approach on the traditional concepts of global or partial safety factors.

Jan 1, 2008

Little faith can be placed in a coal resource estimate without a clear understanding of the estimate's accuracy. Different types of coal resource estimates require different levels of accuracy. Prospecting surveys typically are done with widely spaced boreholes, while a much higher level of accuracy is required for mine design. Either way, a measure of the accuracy clearly indicates the level of confidence that can be placed in the results of the estimate. Geographic information systems (GIs) are becoming a commonly used tool for resource estimation because they not only provide a database management platform but also the graphical capabilities to visualize resource characteristics. interpolation methods used commonly in these resource studies do not typically provide a quantitative answer to the question: "How accurate is the estimate?" By comparing localized measurements at multiple locations to the interpolated thickness distribution used in a resource estimate, a quantitative analysis of accuracy can be obtained. The technique is demonstrated with a case study from Central Appalachia.

Jan 1, 2000

By N. Edmonson

During the last 30 years, a dramatic increase in the supply of byproduct sulfur substantially reduced the share of the market held by Frasch-mined (non-by-product) sulfur in North America. Even though Canadian sulfur production is not discretionary, the geographic remoteness from the large US markets and the high transportation costs associated with delivering sulfur to those markets has meant that Canadian producers act like discretionary producers in many important ways. They have effectively replaced the US Frasch producers as the cost-marginal sulfur source to large US markets. Implications of this change in market structure include more volatile sulfur prices and longer sulfur price recessions.

Jan 1, 1998

By Betty L. Gibbs

Before the first shovelful of dirt is removed from a developing mining property, a wide range of data must be collected, organized and analyzed. Among the key steps in this process are: • Visualization of the deposit from drill hole data and geologic interpretation, using all available information, including surface geology, geochemistry and geophysics. • Drawing of vertical and horizontal sections. • Construction of a 3D solid model of the deposit. • Contouring of deposit outlines and geological structure until the model represents best estimate of reality. • Estimation of grade and quality distribution. • Calculation of reserves. • Examination of possible mining methods. • Determination of economic feasibility. Many techniques are available to aid in this process of mine project feasibility analysis, from quick pencil calculations to sophisticated computer methods. However, time races faster in the complex modem business world than it did 50 years ago. Tried and true pencil methods take too much time. Opportunity may pass a mine developer by while a property is still in the first stages of analysis. In the days of hand techniques, initial analysis of the economic feasibility of a mining project usually stopped with reserve calculations and broad mine planning. Further planning was not done or was done only for the short term. Manual techniques require too much time and manpower to evaluate a longterm mining program. Mining-industry recognition of computer utility has increased. Most companies now use computers in technical applications and could not conceive of working without them. Building initial computer models of a deposit may take nearly as long as hand techniques. But the payback comes when changes are needed and a variety of mine plans are quickly tested.

Jan 1, 1990

By Richard B. Jacob

The High Gradient Magnetic Separator (HGMS), also known as the High Gradient Magnetic Filter (HGMF), is an effective device utilized in magnetic separation. This method of separation is gaining popularity in the separation of sub-micron material containing feebly magnetics. The most common use of this type of separator is in the removal of iron stained particles to improve the brightness of kaolin clay. Potential areas for use of this magnet include: (1) desulfurization of coal (2) the clean-up of mill effluent (3) removal of fine particulate matter from municipal and industrial waste (4) desulfurization of oil

Jan 1, 1983