Search Documents

By Dan Plazak

Discussion by Dan Plazak The authors are to be congratulated for presenting a simple and practical tool for quick estimates of ground water flow rates. At the risk of detracting from the simplicity of the method, I would like to suggest a slight refinement to the equation as presented. As the authors noted, the Jacob-Lohman equation (1952) assumes confined-aquifer conditions. To use confined-aquifer equations in water-table aquifers, Jacob (1963) presented a correction to convert water-table aquifer drawdowns [Ahw] to equivalent confined aquifer drawdowns [Ah,: 2] [Ah Ah = Ah - w(1) Cw 2H where: Ah, = Drawdown in confined aquifer: Ahw = Drawdown in water-table aquifer and H = Original saturated thickness of aquifer] Substituting the above in equation ( I) of Hanna. Azrag and Atkinson [4nT Ah - 2H ) Qj2.25 T t(2) 1 nr2 S W] Since the above expression predicts lower pump rates, it causes the Jacob-Lohman equation to agree more closely with appropriate analytical and numerical models. Figure 1, adapted from Fig. 5 of Hanna. Azrag and Atkinson, illustrates the closer agreement of the modified equation to their numerical model, as reflected in Qm/QJL ratios closer to unity. The agreement improves particularly as drawdown [Ah] becomes large in relation to aquifer thickness H. An additional advantage of the modified equation is that Hanna, Azrag and Atkinson's correction factor C is much more stable as pit depth increases. Assuming, as did Hanna, Azrag and Atkinson, that their numerical model is an accurate predictor, it is clear that the modification incorporated in equation (2) improves the accuracy of preliminary estimates of ground water flow to a pit.[ ] References Jacob, C.E and Lohman. S. W.. 1952, "Nonsteady flow to a well of constant drawdown in an extensive aquifer." Transactions, American Geophysical Union. Vol, 33, No. 4. pp. 559-569. Jacob. C. E.. 1963, `Determining the permeability of water-table aquifers,' USGS Water-Supply Paper 1536-1, pp. 245-271

Jan 1, 1995

Current design guidelines for the surface catalysed oxidation of Fe(II) on Fe(OH)3 (Ochre) in passive mine water treatment systems are based largely on empirical data as the details of rates and mechanisms have not fully been revealed. Also the effects of elevated carbonate concentrations, typical of many UK minewaters, on the surface catalysed oxidation rate are unclear. In order to move away from empirical design and towards sound engineering that is based on geochemical and hydrological understanding it is necessary to quantify these reaction rates. In this study the effects of Fe(OH)3 and carbonate on the rate of Fe(II) oxidation by dissolved oxygen have been investigated with an aim to delineate the reaction mechanism. Experiments were conducted under well-controlled conditions. Preliminary results indicate that the surface catalysed reaction is an order of magnitude faster at pH ~6.4 with 200 mg/l Fe(OH)3 than the homogeneous rate and is dominated by an elevated rate of removal and oxidation of Fe(II) from the solution phase. It is also apparent that the oxidation rate of actual adsorbed Fe(II) is substantially retarded with respect to the homogeneous rate. Carbonates were not shown to affect the surface rate within the bounds of this preliminary study.

Jan 1, 2006

By Carl G. Schwenk

Rusk County is located in the northwestern portion of the state of Wisconsin, roughly 130 miles east of Minneapolis (Figure 1). The topography is generally flat with dairy farming the principal activity. Forest and swamp lands are common, as well as pasture and cultivated ground. Rusk County falls near the southern terminus of the Precambrian Shield and is covered by a thick layer of glacial drift. Outcrops are quite rare, but the few available exposures indicate that the subsurface is comprised of steeply dipping metamorphosed volcanics and sediments of Early Proterozoic age. A thin section of flatlying Cambrian sandstone is sometimes found directly under the glacial till. The depth to Precambrian basement has been recorded to be as great as 150 feet beneath the surface.

Jan 1, 1976

By K. A. Brunk

This paper describes Newmont's research, operations, history and experience with pre-treatment of preg robbing carbonaceous ores. The chemistry, physics and kinetics of chlorine treatment are described. Present operations, control strategy and projected changes are discussed. Included is a summary of the adsorption of chlorine into pulps and off-gas scrubbing.

Jan 1, 1987

By Immo H. Redeker

This is a final progress report on a cooperative project conducted by three private feldspar companies,** North Carolina State University, and the federal Bureau of Mines. The object of the project was to reduce the feldspar tailings disposal problems at the flotation plants in the Spruce Pine area of North Carolina. The initial phase of the project revealed that high tonnages of saleable feldspar and quartz were lost in the tailings and the three feldspar companies are now concentrating their efforts on feldspar recovery, either by reclamation from the tailings as suggested by the Asheville Minerals Research Laboratory or by improvements in metallurgy in the existing plants.

Jan 1, 1970

By W. W. Wen

The objective of this investigation was to study the electrokinetic behavior of oxidized coals to indicate the feasibility of separating oxidized coals from ash materials and pyrite by an mine flotation process. The effects of soluble inorganic electrolyte products from coal oxidation were also examined. The electrokinetic behavior of coals of different rank and degree of oxidation were studied by an electrophoreses technique. Generally, increasing the oxidation increases the negative value of the zeta-potential and decreases the isoelectric point (IEP). Flotation results indicate that the flotation recovery increases with decreasing pH values, and that with ferrous sulfate at pH 6.5 the flotation recovery is optimum while the pyrite was depressed. Comparing the flotation results with the electrokinetic results verified that in the presence of ferrous sulfate, the maximum hydrophobicity of oxidized coal with dodecylamine and frother is near its IEP which is around pH 6.5 to 7.0.

Jan 1, 1976

By Robert L. Runkel, Kenneth E. Bencala, Briant A. Kimball, Katherine Walton-Day

The solute-transport model OTIS and the reactive solute-transport model OTEQ were used to simulate geochemical conditions in Cement Creek, a tributary to the Anirnas River in Colorado. OTIS was used to depict instream zinc concentrations, and to simulate the effects of two remediation scenarios on zinc concentrations at the mouth of Cement Creek. These simulations do not account for effects of changing stream pH on metal concentrations. Preliminary simulations using OTEQ to account for instream pH changes were unsuccessful due to the spatial nature of mixing processes, and insufficient information about the thermodynamic properties of precipitates forming in mixing zones.

Jan 1, 2000

By J. Linhart

In vertical airways, falling material - solids-or water - may cause undesirable disturbances in the ventilation in the airway itself and also in neig¬bouring airways unless precautions are taken to stabilize the air flow. Such cases can occur, for example, - in shaft sinking by drilling from a pilot hole, - during the filling up of shafts, and - during the introduction of water into shafts in the case of mine fires. In an airway with upward ventilation the falling material will reduce the air flow and may even re¬verse its direction. In an airway with downward ventilation the air flow can only increase, but a reversal of the direction of ventilation may result in a parallel airway. These disturbances in the normal ventilation are undesirable as it must be the aim to have ventilation that is stable in quantity and direction throughout a mine. In order to be able to prepare suitable stabilization measures one must know the pressure generated by the falling material; this pressure will henceforth be called "aeromotive" pressure. The main factors determining the influence of falling material on the ventilation are - the amount of falling material and its height of fall, - the cross sectional area of the airway, - the pressure. difference prevailing in it, - the-position of the. airway in the ventilation. network, - the air velocity, and - other parameters, e. g. the density and grain size of the falling material. To determine the aeromotive pressure-measurements have been made underground during the sinking and filling of shafts and systematic studies have been carried out during the supply of water into a staple shaft. The present paper deals first with some fundamental theoretical considerations and then describes the measuring arrangements and the results of the series of experiments that have been carried out.

Jan 1, 1980

By Dean S. Rogers, R. A. Metz

The conventional role or exploration, development and grade control is examined in this paper within the context of the many and varied types of gold occurrences which are found at the Dome Mine. The account endeavours to trace the development of the total ore evaluation process, from diamond drilling through the exploration and drifting stage, to the stope development and planning phase of the operation, with an emphasis on sampling techniques and assaying procedure. The concept of ore reserve calculations is developed and the practice of grade control is described. In summary, the role of the geological, the engineering and the mining department is presented in relation to the contribution each has to make in the evaluation and exploitation of ore from one of the world's classic Archean gold deposits.

Jan 1, 1992

By Victor C. Storhok, Batric Pesic, Marlyn D. Ballain

No1ihwest Alloys produces magnesium from dolomite by reduction with ferrosilicon and aluminum. This process produces alkaline by-products in quantities that allow their consideration for use as commercial products. Two such products are dicalci­um silicate, termed as Di-Cal, and magnesium oxide, termed simply MgO. The alkaline properties of these materials offer acid neutralizing power, comparable to traditionally used lime. Thus, the materials warrant study for their use in various appli­cations where neutralization of acidic waters or process solutions are required. One such application is the treatment of acid mine waters with the objective of removing heavy metals. The chem­ical stabilities of the produced metal precipitates are critically important, from an environmental point of view, for their safe disposal in tailing ponds. The EPA regulates waste material dis­posal according to the results from TCLP testing. In this ongoing study, three mine waters were selected for treatment with Di-Cal and MgO. Lime was used as the control for these experiments. The waters were collected from the Bunker Hill mine, Berkeley Pit, and the Blackbird Mine. In addi­tion to testing the chemical stability of produced metal precipi­tates by the TCLP procedure, two other parameters were studied as well. They are: 1. the effect of water pH on stability, and 2. the effect of pH on the stability of resulting precipitates. In the first three months of study, it was found that neutral­ization with Di-Cal results in precipitates that range from equiv­alent to superior in performance as compared to those produced using lime for the waters from all three mines. An additional beneficial characteristic of precipitation with Di-Cal is the fast filtering characteristics of produced precipitates, when compared to the precipitates produced by lime. This property may be of significance when considering the improvement in drainage of tailing ponds and the volume of solids produced. This paper will discuss in detail the stability of metal precipitates with respect to various pe1iinent metals found in mine waters of Berkeley Pit (Cu, Zn, Mn, etc.), Bunker Hill (Zn, Mn, Ni and Co), and Blackbird Mine (Cu, Co).

Jan 1, 1998

By Mollie Hunt, William Riley, Russ Downer, Kate Willa Brown Requist, Víctor O. Tenorio, Geoffrey Gill

One of the first activities after returning to the Moon will be finding sources of water and materials for the construction of human settlements and other infrastructure. There is evidence of the existence of deposits in the bottom of craters at the South Polar region and in flat areas around. Based on geological data from the Moon, a block model representing a deposit or icy regolith has been defined in the vicinities of Shackleton Crater, with unique characteristics of shape, thickness, and water contents. A mine plan utilizing surface mine modeling software for ore extraction from an open pit- type of excavation to a delivery point near a water processing facility is proposed, with monthly, quarterly, and yearly schedules. Production results, dashboard charts and progress of the topographic changes are also presented.

Feb 1, 2024

By James H. Boettcher

Inflation and increasingly complex tax laws in the United States combined with rising national ism overseas have made the structuring of viable financing plans which meet the requirements of the various parties involved equally important in determining project success as the design of an efficient mining plan or selection of the optimal size equipment. Whereas the use of computerized analysis to design and evaluate the technical parameters of resource ventures is well accepted, computerized evaluation of the investment criteria (qualitative and quantitative) of the various parties to the project (mining firm, financial institution, product buyer, host government, etc.) is a more recent application which can make a material impact in strengthening project economics. By identifying the objectives of the parties and critically evaluating and testing them with the technical and economic/financial constraints on the project the sponsors can design a financial structure tailored to the attributes of the deposit. A myriad of new financial techniques have evolved for financing natural resource ventures, from "Commodity-backed bonds" to tax based limited partner- ships, but in every case the structure of the financing mechanism depends on carefully matching the parameters of the financial structure with the economic characteristics of the project and the objectives of its sponsors. This presentation outlines a methodlogy for computer based project evaluation in the design and structuring of stronger financial plans for natural resource ventures.

Jan 1, 1982

By J. B. Gwiazda

S.S. Peng The highlights of this paper are: The shield supports with lemniscate links will exert a tangential force on the roof strata, causing unnecessary and harmful roof movements, thus damaging the roof structure. The principal source of the tangential force is the horizontal movement of the point O, the pivotal joint between the canopy and the caving shield. When the support height is changed during setting, the point O will move along a curve upward and rearward toward the gob. As a result, it produces a vertical movement, causing the roof to move up a distance of t d, and a horizontal movement toward the gob, creating vertical fractures in the roof. The major purpose for employing the lemniscate- link system is to protect the hydraulic legs against the action of the bending moments induced by the tangential force that causes deformation or destruction of the legs. Based on these two points, the author suggested that, in order to eliminate the harmful effects of the lemniscate-link system and strengthen its advantageous features, a shield support with a new design of that mechanism has been developed. With the new design, the conventional rigid lemniscate links are replaced by hydraulic rams. When the pressure inside the rams reaches a certain level, the ram will yield.

Jan 1, 1987

By J. R. Sturgul

Thompson and Adler (1988) present a new simulator for use in designing conveyor belt systems for underground mines. Their model uses a large Fortran program to do a Monte Carlo simulation. Their approach is similar to that done by other researchers, such as Stanford (1965) and Newhart (1977). All Fortran based simulation models use an imaginary clock that is advanced a time increment. At each advance of time increment the program has to determine what is to take place in the system. Since many things can take place at different places in the system, this approach requires that a large amount of logic is needed at each step of the program. This, then, necessitates a great amount of jumping between different portions of the program. In fact, the Fortran program, CMBCS, takes up to 15 to 20 minutes to run on the mainframe and several hours for the PC. Such execution times are typical of Fortran based simulation studies. There have been other examples of Fortran based simulation studies in mining. Cross and Williamson (1969) presented a model of a working open-pit copper mine. Fosinato (1982) presented a model of the bucketwheel excavators for the large open-pit mines in Southern Victoria in Australia. These excavators discharge into a complex conveyor system, which can be thought of as being similar, but more complicated than the one modeled by CMBCS. All previous simulation studies using Fortran as the source code have several things in common: they all are very lengthy, often being of the order of 10,000 lines of code and take a great deal of CPU time to execute. The program of Fosinato takes more than 4.5 hours to run on a large mainframe. Also not mentioned by Thompson and Adler is the actual time it took to write the Fortran code. This, too, can be considerable, as Fosinato's program took several man years to write and de-bug. In order to change it, as the parameters change or as the mine increases, further large amount of time is needed. An alternate to such Fortran based programs is provided by using a special computer language known as General Purpose Simulation System (GPSS). This language is designed to solve a wide variety of discrete event simulation problems and appears to be particularly suited for mining situations as shown by Sturgul and Yi (1 987). Although GPSS was introduced as far back as 1961, it has not been used in mining to any great extent. However, the original form was quite crude and inefficient compared to modem versions. Perhaps with the increasing popularity and availability of these recent versions, this will change. Two such versions are GPSS/H for the mainframe and GPSS/PC for the personal computer. GPSS/H allows for interactive usage, such as allowing input data to be entered via a menu. GPSS/PC has excellent graphical capabilities and one can actually view the simulation in progress. In addition, one can halt the simulation and change values of various parameters. If a particular portion of the simulation is in progress via a concept known as "microwindows." These new versions have greatly increased the potential for using the language for mining situations. Mining applications of GPSS have been given by Sturgul and Yi (1987), Sturgul and Harrison (1987), Sturgul (1987), and Sturgul and Singhal (1988). Schriber (1987) presents a summary of the recent advances in GPSS.

Jan 1, 1987

By S. Budirsky

J.B. Gwiazda's article deals with an interesting problem that has not been studied thoroughly up to now. Gwiazda has proposed a technical solution that eliminates horizontal load imposed by the supports on the roof. That load is due to a discrepancy between the trajectories of the canopy and the overlying strata. It is true that the improved lemniscate guidance system proposed by Gwiazda could eliminate the horizontal load but, on the other hand, it would represent a higher cost of the supports, and it would complicate the already complicated mechanism of powered supports. That is why we must be convinced that the proposed improvement is actually needed. From that point of view, the following questions should be elucidated. As shown in Fig. 1, the point O travels along the curve a, which produces horizontal load on the roof in the direction of the coal face. As stated by Gwiazda, "such a high load is capable of destroying the roof above the support, causing rock debris to be scattered around the face." The results of our measurements carried out in coal mines of the Czechoslovak part of the Upper Silesian Coal Basin show that the convergence in the modern type of powered supports does not exceed several millimeters (not more than 10) per hour. Similar conclusions were drawn from field measurements performed in the Polish part of the Upper Silesian Coal Basin (see S. Romanowicz and H. Szopka in Proceedings, Scientific and Technical Symposium Simmex '85, Katowice, Poland, pp. 73 -83). The small vertical closure of the supports also induces a small horizontal displacement of the canopy. In addition to this, the transmission of forces between the roof and the canopy is influenced by the layer of debris on it, i.e., the canopy slides without imposing a greater horizontal load on the roof. This was deduced from field measurements of Voest-Alpine F 4/4600 powered supports equipped with rams instead of the common front lemniscate links (denoted as 1 in Fig. 5). In these supports, the pressurizing of the space of piston rod (la in Fig. 5) causes the rams to close, which induces horizontal load on the roof in a direction toward the coal face. After the setting of a support unit, the pressure in the piston rod space was found to drop, frequently to zero, because the small horizontal sliding between the canopy and the debris or inside the debris caused the horizontal reaction from the roof to fall to zero, although the debris were pressurized by vertical setting load. As a consequence, there was no horizontal load imposed by the canopy on the roof. A rise of the horizontal load was recorded only after the passage of the shearer and during lowering of the adjacent units. Thorough information on the results of the afore- mentioned field measurement is given in the paper, "Analysis of the performance of shield powered supports installed in a thick seam," published in Mechanizacja i automatyzacja gornictwa, 1982, No. 12, pp. 38-46. An English translation of the paper is available from the author. We have deduced from our observations that horizontal load imposed by the canopy on the roof in the direction toward the coal face is useful for roof control because it limits the displacement of the immediate roof toward the gob particularly during the rise working. We came to the conclusion that horizontal load on the roof toward the coal face should be induced on purpose. Could Mr. Gwiazda prove with the results of field measurements his contrary opinion? Has the small horizontal displacement of the canopy toward the face actually had an adverse effect on the roof? As shown in Fig. 2, during the setting of a support unit, the canopy imposes a horizontal load on the roof in the direction of the gob. In this case, I share Gwiazda's opinion that the horizontal load could have an adverse effect on the roof. Nevertheless, two important circumstances were neglected - the horizontal compliance of the supports and the interaction of adjacent units. The question of the compliance was analyzed precisely by I. Krumnacker in Gluckauf -Forschungshefle, 1984, NO. 5, pp. 219-223. He found that due to the clearance between the hinge pins and the eyes of the sheild and due to the elasticity of the steel structure,

Jan 1, 1988

By Susanne Pignolet

Ore microscopy has been applied to the complex lead-zinc-copper-cobalt-nickel ores from the Madison Mire in the Fredericktown subdistrict of the Southeast Missouri Lead District to predict potential beneficiation problems. It has been found that in some portions of the ore deposits, textures are present which may result in metal losses. In ores from the Bonneterre Transition Zone the intimate association of siegenite with chalcopyrite may result in cobalt and nickel losses to the copper concentrate. In ores from higher stratigraphic horizons, this association is relatively uncommon, and siegenite is commonly associated with bravoite. This latter association will increase the recovery of the cobalt and nickel in bravoite, even though some of the fine-grained bravoite will not be recoverable. Other textures which may result in potential beneficiation problems include coatings of covellite on chalcopyrite and inclusions of sphalerite in galena.

Jan 1, 1983

By N. Standish

Leonard and Newman (1989) describe concepts and plans of their forthcoming project designed to increase the bulk density of broken coal at various stages of its production and handling. This is an excellent idea and something that will certainly be useful to the coal mining industry worldwide. The authors seek to achieve bulk density increase by "reducing oreliminating, through chemical additives and engineering design, particle voidage and enhance particle consolidation trickling between the point of breakage (at the face) and loading (in the shuttle car) to increase coal bulk density and productivity." In the paper, they present some supporting results of bulk density versus moisture, with or without oil addition, from the steel industry research. Unfortunately, the paper contains many misconceptions and half-truths that detract from an otherwise excellent objective of the project of increasing bulk density by reducing particle voidage -"the bottom line evaluator." Correct.

Jan 1, 1990

By J. W. Leonard, D. A. Newman

Discussion by N. Standish and P.N. Standish Leonard and Newman (1989) describe concepts and plans of their forthcoming project designed to increase the bulk density of broken coal at various stages of its production and handling. This is an excellent idea and something that will certainly be useful to the coal mining industry worldwide. The authors seek to achieve bulk density increase by "reducing oreliminating, through chemical additives and engineering design, particle voidage and enhance particle consolidation trickling between the point of breakage (at the face) and loading (in the shuttle car) to increase coal bulk density and productivity." In the paper, they present some supporting results of bulk density versus moisture, with or without oil addition, from the steel industry research. Unfortunately, the paper contains many misconceptions and half-truths that detract from an otherwise excellent objective of the project of increasing bulk density by reducing particle voidage-"the bottom line evaluator." Correct. Theory Definitions Coal bulk density is the ratio of the mass of a collection of discrete particles to the volume that it occupies (ASA, 1980). There can be no possible argument about this definition. Mass and volume are readily measured both in laboratory and large scale installations. So, to obtain the bulk density, one simply divides the measured mass by the measured volume. It is here that we come unstuck as everybody who has ever had to reconcile book values with the measured stock tonnages knows. Where does the problem originate? Almost invariably in a too casual a reading of the above definition and the words "a collection of discrete particles." The word collection means "a number of objects collected or gathered together, viewed as a whole" (The Oxford English Dictionary, 1989). If one knows the bulk density of a pile of coal viewed as a whole,

Jan 1, 1991

By Y. T. M. Ocsa, V. O. Tenorio

This research is the result of a geotechnical study carried out in a natural slope in an Open Pit mine in Southern Peru, highlighting earthquakes as an important cause of instability within the case study presented. This leads to analyze the stability of a slope, according to the safety factor and thus consider a future construction in its environment according to the identified requirements. There are known disasters at national and international level that involve human lives because of the lack of analysis of slope stability conditions, which based on the results will allow to control and to take adequate corrective measures. These mass movements are classified whether they are soils or rocks, considering the mechanism and type of rupture, as well as the presence of water, the speed and magnitude of the movement. The movement problems are due to factors of inherent nature and constitute a reason to perform a calculation study to analyze and estimate the safety factor of each of the evaluated cases

Mar 2, 2022

By Mike Wardell-Johnson, Chris Campbell-Hicks, Craig Bitmead

Faster, simpler, cheaper and more accurate cyanide ex­tractable gold procedures are now available for grade control assay. Cyanide 'bulk leach extractable gold' or BLEG assays have previously been seen as desirable, due to the large sample size that can be treated, but not in common use due to the 24hr total assay time required. Sample sizes from 50g to several kilos can now be accurately assayed in less than 4 hours total time with the larger sample size increasing accuracy, without loss of precision, while greatly reducing the 'nugget effect' or coarse gold bias. Typical assay size is 200g, equivalent to 4 x 50g Fire Assays or 10 x 20g Aqua Regia Assays. Ongoing modifications and refinement of the procedures and reagents used also indicate applicability to the treatment of coarse gravity gold where substantial savings in both capital and operating costs for these circuits are possible. The successful use of this cyanide assay at the Bannockburn and Windine Well operations are cited to-gether with a compre­hensive comparative testwork program by Newcrest. Testwork at Gidgee and Lynas Gold operations is currently being initiated. Other operations using the method include Red Dome and Kidston; with Placer(Granny Smith) and PMA's Palm Springs operations to commence shortly.

Jan 1, 1995