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By Rodney L. Stone

As part of an overall laboratory and plant test program to determine mixing and other techniques relating to the more economic use of bentonite as an iron ore pellet binder, a settling test was developed for measuring the bentonite content within a pellet or within a batch of pellets. Between pellet batches, each containing a different level of bentonite, the dry fracture load is directly proportional to the bentonite content between pellets of the same batch, however, the fracture load is inversely proportional to the bentonite level; this is explained by a negative correlation between a pellet's size and its bentonite content and the fact that larger pellets can withstand a higher fracture load than the smaller.

Jan 1, 1968

By Anna Gustafson, Sohail Manzoor, Håkan Schunnesson

Sublevel caving operation relies on the estimation of ore grade at drawpoints, as the mine management uses grade to decide whether the material at a certain ring should be loaded or abandoned. Grade is estimated in various ways, including visual estimation, density-based calculation, and sampling and assay methods. The grade estimation at the world’s two largest underground iron ore mines owned by LKAB in northern Sweden is based on the density difference between ore and waste. The calculations assume a constant swell factor, a theoretical fill of 100%, and a linear relationship between bucket weight and material grade. This study evaluated these assumptions in detail based on the loading data for 12,237 buckets and concluded that the method has some shortcomings which render the assumptions invalid. Further research is required to deal with these shortcomings to improve estimation of the material grade.

Oct 17, 2022

By H. Akgun

Design of plugs for abandonment of boreholes and shafts may be governed by the bond strength between the plug and host rock. This paper presents the results of push-out tests on cement grout plugs in salt. Two expandable cement grouts have been tested. The average interface shear strengths ranged from 2 to 12 MPa. Peak shear stresses at failure, assuming an elastic stress distribution along the interface, were up to eight times higher. Standard deviations commonly reached 20%. Dissolution along the interface was observed, and may have been enhanced by clay inclusions in the salt. This dissolution appears to have reduced bond strengths. Application of the results to the design of plugs for larger openings (e.g. shafts, drifts, or boreholes) is discussed.

Jan 1, 1991

By Jerry G. Rose

This paper addresses a process by which both the disposal and utilization of preparation plant coal refuse can be simultaneously accomplished with an attendant benefit of significantly increasing the percentage of extractable coal. A laboratory study is described in which coal refuse was successfully utilized as an aggregate in low cost concrete (coal-crete) mixes under simulated mine environments. Coal-crete specimens with compressive strengths of 14,000 kPa (2,000 psi) were consistently produced. A construction sequence and mining plans are offered for placing the low-cost coal-crete pillars in accessible areas in room-and-pillar mines so that a Substantial portion of the remaining coal pillars could be extracted. The method could be applicable in areas where mining procedures do not permit pillar extraction because of possible surface subsidence, roof problems, or other conditions. Possible structural difficulties with the coal-crete pillar support system are discussed. Using a discounted cash flow analysis, the economic feasibility of mining with the coal-crete pillar system is investigated. The cost of the coal-crete pillar system is compared to the cost of a mining system which would have less coal recovery. The analysis indicates that although at higher coal selling prices the coal-crete mining system may yield an acceptable rate of return, the alternative of leaving the coal pillars is more attractive at the present time.

Jan 1, 1977

The recent mine disasters in Australian coal mines have initiated an introduction of Self-Contained Self-Rescuer (SCSR) as component in the development of new escape strategies for miners. These self-contained self-rescuers are closed circuit, demand sensitive breathing apparatus that make oxygen available to the wearer for a nominal period of time. Their operation is completely independent of the surrounding atmosphere. Once properly donned, the SCSR can assist a miner to escape from an area containing smoke, toxic gases or an oxygen deficient atmosphere. The duration of a typical SCSR is usually taken at the point of complete collapse of the breathing bag which is accompanied by an increase in breathing resistance and inhaled levels of carbon dioxide. Because the oxygen consumption (V02) and the heart rate are correlated, a prediction of V02 and consequently the duration of an SCSR can be made by monitoring the heart rate. Thirty-seven volunteers participated in field simulated escape trials at four underground coal mines. The results from the field trials suggested that oxygen consumption depends on the heart rate, the body weight and exercise rating of the miner. All the volunteers were asked to fill out the questionnaires to evaluate the performance of the units. The miners indicated that they could tolerate the inhaled temperature without any difficulty to breathing resistance. A complete statistical analysis of the field results is also presented.

Jan 1, 1997

By H. EI-shall

In this paper, the results of bench scale testing of five different flotation processes to separate dolomite from phosphate are discussed. The effectiveness of each process interms of phosphate recovery and MgO content in the concentrate is used together with the reagent consumption as the basis of comparison. The water quality is found to play a major role in the performance of these processes. Effect of water hardness as well as other parameters are discussed.

Jan 1, 1995

By Daniel B. Brimhall

The research presented here was initiated to investigate the role of atmospheric oxygen in the leaching of copper waste dumps. The problem of increasing the recovery rate of copper from these dumps is or great importance considering there are by conservative estimate in excess of fifteen billion pounds of copper located in dumps in the western United States. At this time, there is an increased interest in recovering copper from these dumps on a large scale. Large tonnages of low-grade material are being placed on the waste dumps of most copper mining operations in the western United States each day. The size of these dumps ranges from 5.5 million tons at Mineral Park, Arizona, to 4 billion tons at Kennecott's Utah operation (1). Leach solutions are recycled and contain ferrous and ferric sulfates. Large quantities of dissolved aluminum, magnesium and calcium salts may also be present. To this solution make up water is added to maintain the solution inventory and sulfuric acid is added for pH adjustment. Iron is introduced into the leach solution by the dissolution of the iron-containing sulfide and oxidized minerals present in the ore deposit. In addition to the iron from dump leaching, iron is also introduced during the precipitation process when the pregnant solution is passed over metallic scrap iron if cementation is used to reduce the copper in solution.

Jan 1, 1972

By Hans von Michaelis

The renaissance in extractive metallurgical practices for gold and silver recovery is far from over. This is one conclusion of a three year investigation into innovations in Cold & Silver Recovery by Randol International Ltd. (1981, 1983). The six volume reference report reviews a host of new processes and innovative applications of older metallurgical practices. Some of these were summarized by von Michaelis (1982, 1982a). There are several reasons to expect this renaissance to continue. One reason is the nature of gold and silver deposits. The list of known occurrences of These metals is very extensive. There are literally tens of thousands of prospects but over 99% of these are too low grade, too small or too refractory for a viable operation employing conventional processing.

Jan 1, 1983

By T. Braun

A greenfield open pit gold mine in Latin America suspended operations less than three years into an eight-year mine plan after a waste rock dump and heap leach facility sustained substantial damage from a deep-seated landslide. No injuries to employees were recorded because of the slow-moving failure. Due to early detection by the operations team, the owner had sufficient notice of the potential failure and successfully rinsed the heap leach facility prior to the failure event. Engineers estimated approximately 35 million cubic meters of mass movement below the waste rock and heap leach facilities. The original eight-year mine plan produced approximately 60,000 ounces of gold per year. After the failure, the owner terminated gold production, re-configured the mine site to a safe, standby condition and launched a detailed investigation into the root-cause of the failure. Approximately two years after the shutdown, legal interests filed a statement of claim and named three engineering design firms and individuals involved in the project. Several years of litigation, including discovery and deposition proceedings, followed as the legal process considered evidence spanning a 20-year timeline. Changes in project ownership and consulting firms during the development and operations phase complicated the process. In 2017, the plaintiff and last defendant settled. The author was involved as the corporate representative for one of the engineering design firms.

Mar 2, 2022

By P. O. Ripley

Into this tumultuous twentieth century, every second, two new babies are born. This is 5,412 per hour, and 130,000 per day. Relentlessly, consistently, alarmingly, they add to the more than three billion human beings who already inhabit the earth. Every tick of tier clock brings with it a problem child, the problem of another mouth to feed, another body to clothe, another human being for whom to provide. On the other hand, medical science has achieved a postponement of death, considerably past the period of a few years ago. Thus, life expectancy has been increased and world population has increased accordingly. Darwin (4) writing in 1962, suggests "It is curious how long the world is taking to perceive that we are living in what is a fantastically abnormal period of history, and one which must inevitably end soon, The first warning note of a possible population explosion was given by Malthus in 1799". He suggested that population increases geometrical while production increases only arithmetically and that soon we would not be able to feed the rapidly increasing population.

Jan 1, 1966

By Keith A. Heasley

Historically, the surface subsidence over underground coal mines has been predicted using empirical profile or influence functions which have little or no connection to the actual mechanics of the subsidence. Without a mechanistic basis, establishing the exact site-specific parameters to use in these empirical methods has been problematic. A practical subsidence predictive method based on mechanics has the appealing capability of allowing the determination of site-specific parameters from fundamental properties of the overburden with minimal field calibration work. This paper presents several case studies where a mechanics-based, boundary-element program is used to back-calculate the surface subsidence associated with various panels at several Northern Appalachian coal mines. The program used in this case study is called LAMODEL, and it incorporates a frictionless, laminated overburden into a general purpose displacement-discontinuity code primarily designed for calculating the stresses and displacements in coal mines or other thin scam or vein type deposits. In this paper, the program is used to calculate both the underground convergence and the resulting surface subsidence at five longwall panels and a room-and-pillar section. The fitted subsidence from the model is compared with the field measurements and analyzed. The results from the case studies in this paper demonstrate that the laminated model with calibrated properties can easily provide moderately accurate subsidence predictions and is fairly flexible for fitting measured subsidence. However, additional subsidence predictive case studies arc recommended in order to ultimately evaluate the potential of the laminated overburden model for practical subsidence prediction

Jan 1, 1999

By O. J. Tassicker

The Electric Power Research Institute (EPRI) initiated a program in 1976 to develop and demonstrate an instrument system for on-line continuous measurement of coal properties. The program has focused on the use of Prompt Neutron Activation Analysis (PNAA) for elemental determinations and microwave absorption for moisture determination. One of the major results of the EPRI program is the development of the CONAC (Continuous On-Line Analysis of Coal) instrument, with Science Applications, Inc. (SAI) as the prime contractor and Kennedy Van Saun Corporation as a subcontractor.

Jan 1, 1983

By J. G. Groppo

In 1992, 48 million tons of fly ash (not including bottom ash, boiler slag and FGD material) was produced in the United States, according to the American Coal Ash Association. Of this amount, 27.2% was utilized; although the percentage of fly ash utilized increased from 20% in 1980, there is significant potential to increase utilization. One of the primary driving forces behind increased utilization is increased disposal costs due to more stringent environmental controls and regulation. Fly ash is classified as a natural pozzolan and finds significant use as a cement additive. It has been found to increase the plasticity of the cement mixture while lowering the amount of mix water needed. In addition to improving leveling and finishing properties, fly ash improves pumpability as well as decreases the heat of hydration of the concrete mix which is particularly important in massive concrete structures such as dams where the concrete needs to cool as quickly as possible. The Loss on Ignition (LOI) of fly ash is an important quality when considering utilization. The LOI is primarily due to the presence of unburned carbon and the standard specifications for the use of fly ash as a mineral admixture in Portland cement concrete are given in ASTM C618-89a. which sets an LOI limit of 6%. However, many states have set a more stringent limit of 3%. The primary reason for the lower LOI specification is that carbon adsorbs air entraining agents which limits freeze-thaw resistance. This is particularly important in climates such as the midwestern US where multiple cycles of freezing and thawing are typical in winter.

Jan 1, 1995

By G. K. Hoffman

Humate, defined as weathered coal or mud-stone rich in humic acid (HA) and fulvic acid (FA) have been mined, primarily as soil amendments or drilling mud additives, in New Mexico for 15-20 years. The New Mexico humate resource is estimated to be 11 Gt, including weathered coal and organic mudstone. The HA and FA content determines the end-use, therefore a simple and consistent method of measuring organic-acid content was developed. The New Mexico Bureau of Mines and Mineral Resources method is based on repeated alkali leaching and acid precipitation. Precipitates of humate are ashed, with mass balance of solids maintained, to correct for material added during alkali-acid treatment. Analyses of upper coal member, Cleary Coal Member (Menefee Formation) and Fruitland Formation samples from the southeast San Juan Basin show ashing to be important in accurate analysis of FA content. Ash in the total FA fraction averages 70% compared to 2% in HA. The FA in weathered coal and organic mudstone are similar, although HA is significantly higher in the former. As weathering progresses, the FA content of weathered coal increases faster than in organic mudstone because of the greater total organic material in coal.

Jan 1, 1994

By Robert L. Russell

Production at Freeport Indonesia's Ertsberg open pit copper-gold mine started in 1972 at a rate of 7.5 kt/d (8270 stpd). Mill throughput remained at that rate for several years until the discovery of the Ertsberg East (GBT) ore body. This discovery prompted three succes¬sive expansion stages from 1981 to 1988 that boosted production to 20 kt/d (22,000 stpd). In 1988, the discovery of the huge Grasberg porphyry copper deposit launched an era of much larger expansions. The first of these was the installation of a fourth primary mill in 1989 that increased throughput to 32 kt/d (35,270 stpd). That was followed by an expansion of the crushing and screening plant and in 1991 the addition of a new south concentrator to bring production to 57 kt/d (62,830 stpd). The addition of a primary ball mill and the changeout of the original Denver flotation cells in 1993 brought production to its current level of 66 kt/d (72,750 stpd).

Jan 1, 1994

The effect of the chemical composition of pulverized bituminous coal particles on their physical transformation during the initial stages of combustion has been investigated. The results suggested that cenosphere formation does not require extensive thermal decomposition of the coal particles. The vitrinites in the bituminous coal softened earlier and developed larger cenospheres than the othe macerals. The coal particles swell to a higher extent during combustion than in pyrolysis; however, the cenospheres formed in the former process experienced a higher extent of fragmentation. The development of microporosity occurred predominantly after the resolidification of the swelled char particles. The type of macerals originally in the coal did not significantly affect the microporosity of the chars. Conversely, the morphology and anisotropy of the chars were strongly dependent on the maceral composition of the coal.

Jan 1, 1986

By David J. Kruse

Accurate field measurements are essential when validating a conveyor design. They are fundamental in determining a conveyor's behavior, its long-term maintenance requirements, and the life expectancy/ condition of the installed equipment. Field measurements are also invaluable in forensic engineering, particularly when vital equipment has failed This paper will discuss a wide variety of data acquisition equipment, field measurement techniques and accuracies achieved State-of-the-art, custom designed monitoring equipment, as well as, ''08-the-shely instruments and sensors, will be discussed.

Jan 1, 2004

By C. R. McKee

In-situ mining of hard rock deposits will only become successful as we understand the engineering parameters involved and the design limitations they impose. As recognized by Wadsworth1 the most critical area is the enhancement of permeability in a hard rock mass. Along with creating permeability, the appropriate flow and fragment size conditions must be generated to insure economic rates of mineral recovery. In this article our interest is confined to true in-situ processes in which boreholes are drilled from the ground surface or a mine drift to deeper strata. We assume that fractures and permeability enhancement will be due to explosives detonated in boreholes. Other techniques such as hydraulic fracturing do not produce the necessary size distribution to promote economic extract ion rates unless the medium is already highly fractured and interconnected. Notable exceptions where hydraulic fracturing is applicable are many oil, gas and salt deposits. For many in-situ processes, an array of explosive charges offers the opportunity of creating a distribution of many fractures not achievable by other techniques. Such a situation would be suitable, for example, to in-situ mine hard rock gold, uranium, copper or oil shale deposits and may enhance oil and gas recovery in certain situations. The purpose of our article is to review and extend the explosive permeability theory of McKee and Hanson 3,4,5 and to apply its results to derive design parameters suitable for in-situ mining.

Jan 1, 1981

By D. M. Abbott

The problem with best practices occurs when they do not work. This happens when the seldom-stated assumptions underlying the practice are not met. This paper provides some examples for the mining industry: (1) when core splitting is inappropriate, (2) when the use of fire assays for placer samples is inappropriate, and (3) when high-grading may be acceptable. Geologic conclusions are, in the final analysis, expressions of judgment predicated upon knowledge and experience. A geologic conclusion, however, purports to be more than an arbitrary determination—it is reached as a consequence of method. No specific method is required, but the method used must be an orthodox method, in accordance with orthodox definition of terms, and the one best adapted to the dealing with the questions asked about the property in question. Whether the so-called “best practice” is really applicable to the job at hand must be decided on the basis of professional scientific judgment. When one decides to deviate from a published “best practice” for sound scientific reasons, describe in detail in the report what the so-called “best practice” is, why it was inappropriate for the project, and why the method used was better. If one becomes aware that a “best practice” is being proposed, actively urge those proposing it to include in its description the underlying assumptions that must be met in order for the “best practice” to be valid.

Jan 1, 2014

By E. H. Cho

An acid mine drainage sludge sample containing 3.6% Mn, 0.18% Ni, 0.15% Co and 0.39% Zn was obtained from the central part of West Virginia and leached with sulfuric acid at pH 3 and at room temperature. Air was bubbled through the leach solution to precipitate the iron content from the solution at pH 4.5. The leach solution contained 258ppm Zn, 105ppm Ni, 90ppm Co and 2050ppm Mn. Three distinctive solvent extraction studies were performed to selectively extract these metal ions in a sequential operation with DEHPA, Cyanex 272, and then Lix 84. The AIO ratio was 1 and the extractants were diluted 10 times with kerosene. A study of solvent extraction with DEHPA showed that Zn could be extracted without Ni or Co up to pH 2.75. A pH of 2.75 is considered to be the optimum pH to maximize the selective separation of Zn from Mn. The separation factor of Co over manganese suggests that the two metal ions be extracted together by Cyanex 272. The separation factor of Co over Ni indicates that these two metal ions can be separated most effectively around pH 5.3. Also, Ni can be effectively extracted by Lix 84 above pH 5.5.

Jan 1, 1993