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By T. Diering

Gemcom PCBCTM is a software package which has been developed over the last 22 years for the planning and scheduling of block cave mines. This paper presents an update of the various research and development activities done to PCBC recently. It also provides an overview of the current capabilities of the software including tools for both feasibility type studies as well as tools for operating mines. PCBC is used extensively by prospective and operating block cave mines and some of the recent applications are described.

Jan 1, 2010

By S. Park

In a flotation froth (and foam), air bubbles become larger due to coalescence, causing less hydrophobic particles to drop off. A bubble-coarsening model has been developed by calculating the changes in Plateau border area as a function of the initial bubble size at the base of a foam, liquid fraction, and foam height and then relating the predicted Plateau border area to the critical rupture thickness of lamellae film. The model predicts that bubble coarsens with increasing froth height, decreasing frother dosage, and decreasing aeration rate. The model predictions are in good agreement with actual bubble size measurements.

Feb 23, 2014

By A. W. Khair

This paper presents an analysis of surface subsidence characteristics in room and pillar mining using physical models and laser holographic interferometry (holometry). The analysis included the effect of various geometric parameters and different overburden materials (sand and gelatin) and resulted in the formulation of a more realistic model material for laboratory simulation of typical geologic overburden. Previous work using this technique involved the use of sand to model over- burden and detailed results are presented elsewhere (1). The main emphasis of this work was to develop a gelatin based mixture which would provide a better model. Initial work during the development of this model included testing various ingredients and monitoring the time dependent characteristics of the model, such as the surface penetration resistance. This value indicated changing deformability/ridgidity of the model with time. Once several models had been developed, holometry techniques were applied. Initial tests showed that the stiffness of gelatin created a bridging effect over the mine models, thus restricting deformation. At this point, a 0.5 inch (1.27 cm.) layer of sand was placed directly over the mine model with the gelatin mixture on top. The approach was to model different zones of overburden movement that exist as an extraction occurs (2). The sand would represent the caved and fractured zones which occur above the excavated area. The gelatin models the continuously deformed zone which occurs between the fractured zone and the surface. Holometry techniques applied to this model yielded successful results.

Jan 1, 1986

By J. W. Wilson, S. Nakajima, B. D. Singh

According to the Project Independence blueprint, a 270 percent increase in coal production is expected from western coal fields compared to an increase of 100 percent for the nation as a whole. Furthermore, 30 percent of the total United States coal reserves lie in the western states, which are classified as beyond the strippable limits and can be recovered only by underground methods. In view of the fact that the majority of the seams in the West are thicker than those presently mined in other parts of the country, it is important to consider the parameters that relate to mining thick seams and the factors that affect such mining systems. Apart from thick seams, a common feature of many western coal fields is the occurrence of multiple seams that lie in close proximity to one another. These multiple seam deposits present difficult mining problems that have not been encountered to any degree in other U.S. coal fields; for example, ground pressure changes in one mine level caused by mining in the other, sudden water or gas influx from the adjacent levels, the danger of spontaneous combustion in gobs and large and complex subsidence displacements on the surface. Perhaps equally important is the fact that the country can ill afford the present systems of underground mining that attain only 50 to 60 percent coal recovery. With the probability of increased thick seam mining, conservation shall be a focal point in future mine design systems. It is possible that in the future it will be forbidden to adopt the present day wasteful mining methods to ensure that coal can be conserved for future generations.

Jan 1, 1977

By I. S. Parrish

As noted by McKinstry (1948), "How to deal with erratic high samples is one of the knottiest problems in ore estimation." He described a variety of approaches and methods to alleviate the problem through the averaging and weighing of assay data and by "cutting" or "clipping" of the erratic assays. Bird (1991) elaborated on ways of dealing with the nugget effect (erratics). He listed several procedures for cutting. Bird's list has been reproduced and/or added to by several authors including Vallee (1992) and Stone and Dunn (1993). Missing from each of these otherwise excellent reviews is a definition, description or guideline to recognition of an "erratic," or just where or when cutting is warranted or justified.

Jan 1, 1997

By Kevin Erwina, Rajiv Chandramohana, Connor Meinkea

This paper explores prevalent operational challenges encountered globally in SAG mills, including suboptimal throughput, liner wear, excessive energy consumption, and SAG mill load stability. The paper delves into the root causes behind these issues, such as ore variability, poor operating strategy, or inadequate process control. Drawing on industry experience and case studies, the paper highlights the significance of addressing these challenges to enhance overall mill performance and efficiency. It underscores the necessity of tailored strategies, encompassing improved monitoring, optimized liner designs, and refined control techniques to mitigate these challenges and promote sustainable SAG mill operation.

Feb 1, 2024

By S. M. Hossaini, M. Ataei, H. Moosavi

The abstract highlights the importance of pillar stability in underground coal mines and the influence of rock mass strength and joint orientation on pillar behavior. The study employs numerical modeling using the distinct element code (UDEC) to investigate the impact of these factors on pillar stability. The research considers different joint orientations and varying rock mass strengths, analyzing parameters like stress distribution, displacement, and failure patterns. The findings reveal that both joint orientation and rock mass strength significantly affect pillar stability, with specific combinations leading to reduced safety factors and increased deformation. The study concludes by emphasizing the importance of considering these factors in pillar design for safe and efficient mining operations.

Apr 4, 2022

By B. S. Crocker

Introduction Pebble mill grinding can be defined as wet or dry grinding in a tumbling mill with pebbles used as grinding media instead of metal balls. To clarify the terminology, which may differ in the various mineral industries, it is essential to point out the differences between grinding with partially sized and carefully sized grinding media. When grinding with partially sized media (limited top size only), sizing is usually the setting of the primary crusher and there is no bottom sizing-all fines, chips, sand, and small sizes are included. This is often called run-of-mine or primary autogenous grinding. In this case the entire crusher discharge is fed into the mill and part of it becomes "charge" and the rest is "sand feed." When grinding with carefully sized media (i.e., media that is sized both at the top and bottom of the size range), no fines or chips should be present in the charge to the mill. This is pebble milling and the grinding media consists of ore, rock, Danish pebbles, gravel pebbles, or ceramic pebbles-media that is appreciably lighter than steel balls. The grind¬ing charge is fed to the mill to maintain a load and it does the grinding usually on a classified sand product of suitable size. If the grinding media is the same as the raw material being ground, this type of grinding is also called secondary autogenous grinding. Pebble milling was in common use in the gold mines of South Africa in the early 1900s. It is by far the oldest form of autogenous grinding. It may be used to grind crushed ores from a maximum size of about -% in. to all -10 µm. Pebble milling differs from "run of mine" grinding in many ways, but two big differences are: I) The ore itself is crushed to approximately t/4 in., or it may be further reduced to 8 or 10 mesh in a rod mill or fine crusher. 2) Then carefully screened ore of the correct size is placed in one or more stages of pebble mills to grind the ore to its desired final size. The media size is carefully selected to be the most efficient for the particular size reduction required in each stage. This is a precise practice, and pebble mills can be designed as easily and accu¬rately as can rod mills or ball mills by those skilled in the art. A pebble mill is a rotating cylinder in which the grinding media has been carefully sized for the job in hand. If the mill is doing coarse grinding, the media will be correspondingly large and the mill might be called a primary (or intermediate) pebble mill or a lump mill. If it is to do fine grinding, the media selected is proportionately smaller and the mill would be called a secondary or tertiary pebble mill. The media itself is normally rounded pebbles made from screened ore from the primary-crusher discharge. The charge could be rounded pebbles of the correct size removed from a primary autogenous mill, or the pebbles could be carefully sized gravel, sized beach pebbles, or sized flint pebbles. Usually the specific gravity of a pebble is from 35 to 55% of that of steel balls. It commonly varies from 2.66 to 4.2, depending on the specific gravity of the ore. Primary pebble mills, or lump mills, would be charged with pieces of rock up to 10 in. maximum and 5 in. minimum and would grind crusher discharge with a maximum size of 1/4 in. on hard ores and 3/8 in. on softer ores. Secondary pebble mills could be charged with pieces of rock screened on 4 x 4-in. square mesh and retained on 1 1/2 x 1 1/2 in. These mills would grind material with a top size of 8 to 10 mesh. Tertiary pebble mills could be charged with screened rock that would pass 3 x 3 in. and be retained on 1 x 1 in. and grind 35 to 48 mesh sands. Principles of Operation Media Size To operate a pebble mill efficiently it is imperative that great care be taken in screening the rock feed that is fed into the mill to round up into a range of pebble sizes that are suitable for grinding of the sands that are also being fed into the mill, having regard to the top size and the average size of such sands. Since most mill operators know from experience the correct size of steel balls to be used in a mill to handle different sizes of sand feed, it is convenient to relate the pebble size to a ball size. If the correct ball size is not known, it is relatively simple to conduct batch laboratory tests in 12- to 18-in. laboratory mills to determine the optimum size of steel ball. Also, Bond and others have published formulas for calculating the optimum ball size. When the correct size of the individual steel ball is known, then a pebble of the same weight will perform the same grinding if used in the proper size of mill and under the proper conditions, which will be defined later. This media size, as defined by the average weight of the individual pieces, is most important. The following tests will serve to clarify this point. Laboratory Tests Using Steel Balls or Pebbles. Several labora¬tory grinds were made to compare a given size and weight of steel ball with a pebble of the same weight but larger size, and of the same size but lighter weight. The following loads were used in the 12-in. laboratory mill: All 1 1/4-in. steel balls weighing 122 ± 10 g. All 1 3/4-in. pebbles weighing 123 ± 5 g. All 1 1/4-in. pebbles weighing 45 ± 3 g. To equalize capacity, the test with the steel balls was run only 34% as long as the tests with pebbles. In each case, 2,500 g of primary sands were ground at the optimum gravity for the media being tested at a speed 78 1/2 % of critical speed, and for 170, 340, and 680 revolu¬tions for the steel balls, and 500, 1,000, and 2,000 revolutions for the pebbles. The first test is summarized in Table 74 by showing the 80% passing size in microns for the feed and for each of the grinds. Two other tests are summarized in Table 75 showing the screen analyses

Jan 1, 1985

The Midvale Slag Site covers 300 acres in Midvale, Salt Lake County, Utah. Midvale (population 10,000) is part of the Salt Lake City metropolitan area (population 936,000). Between 1902 and 1971, United States Smelting, Refining and Mining Co. smelted ores on the site to produce copper, gold, lead, and silver. Figure 1 shows a picture of the historical Midvale smelter operations. [ ] When operations ceased, the site was estimated to contain 2 million tons of slag from these operations. The smelter no longer exists. In 1971, Valley Materials, Inc., acquired the site to process the slag into materials for railroad beds and asphalt highways. During the 1980s, the U.S. Environmental Protection Agency (USEPA) raised concerns regarding environmental impacts associated with the historical site operations. The Midvale Slag Superfund Site was listed on the NPL in 1991. The Site consists of two Operable Units (OUs): OU1 covering the properties north and adjacent to former ore smelting operations; and OU2 covering the smelter site itself. OU1 had historically been affected by wind blown slag dust and stack emissions occurring on OU2 and the Sharon Steel site further to the south. These emissions resulted in elevated levels of arsenic and lead in the native soils. The EPA issued the final Record of Decision (ROD) for the OU1 Site in 1995. The OU1 ROD required the implementation of institutional controls for the undeveloped portions of OU1 in order to restrict future land use to commercial/industrial purposes unless additional remediation was performed. Hence, the land comprising OU1 was originally considered in the ROD to be suitable for commercial or industrial purposes without the need for remedial action. However, development of OU1 for other land uses, including residential or recreational, would require additional assessment and probable remediation. The OU2 parcel was remediated by EPA to allow future land development, and the Sharon Steel site was remediated by EPA and deleted from the NPL. PROPERTY TRANSACTION AND REDEVELOPMENT In February 2006, a private development company, Mercer Bingham Junction, LLC. (MBJ) purchased 130 acres of the OU1 property for the purpose of performing environmental remediation, and developing mixed residential and commercial real estate. Development of the property was conducted in cooperation with USEPA Region 8 (EPA), the Utah Department of Environmental Quality (UDEQ) and Midvale City. The guidelines under which residential development could occur were defined by EPA. The 130 acres was to be developed for open space, residential and commercial use as part the Midvale City Bingham Junction development. Figure 2 shows the general layout of the proposed land uses. [ ] In May 2005, MBJ began pre-acquisition due diligence activities to purchase the 130 acres of OU1 north of 7200 South Street, which now comprises the Bingham Junction Development. This included the completion of Phase I and limited Phase II investigations. The Phase II investigations were performed to evaluate arsenic and lead concentrations in the planned residential areas of the site, and to explore the contents of the historic landfill on the property. The historic landfill area was on the far west side of OU1, adjacent to the Jordan River. Soil samples collected during the Phase II investigation showed that the planned residential parcels did not currently meet the criteria established in the Tech Memo and that additional placement of fill or soil excavation would be required for residential development in this area. An evaluation performed by the previous owner of the property, Littleson, Inc., showed similar results.

Jan 1, 2009

By Erik Sundström, Magnus Nygren

Having seen significant improvements to accident rates in the last 40 years, companies in the Swedish mining industry now show a greater focus on the development of safety cultures throughout their organisations and workplaces. However, there is a lack of research examining the different safety initiatives and strategies practiced in the industry today. This study explores the potential influence and consequences such initiatives may have on the development of safety cultures in the Swedish mining industry. Twelve interviews with experts on safety initiatives from four different Swedish mining organisations were conducted and analysed in a process based on qualitative thematic analysis to identify notable connections to safety culture development. The results of these interviews highlight proclivities in the implementation and use of safety initiatives such as subjects of focus, methods and desired effects. This enables the interpretation of the conceptualisation and methods for the development of safety culture in these organisations based on their approaches to safety development. We believe the results of this study can serve as support for discussions on safety culture development in the Swedish mining industry, and be of interest for international mining industries, in addition to approaches to research in this field. However, we also believe it is important to emphasise the opportunities to approach safety culture in mining from different perspectives than those common today.

Jul 19, 2023

By F. S. Kendorski

Several startup or longtime underground stone mines have experienced unanticipated roof control difficulties due to the variable geologic character of the roof strata. Careful mapping of roof conditions, and identification of controlling geologic and mine geometric factors, lead to an understanding of the mechanisms causing roof problems. Factors such as unexpected rolls of the roof strata resulting in a gradual change from strong to weak roof; encountering open water-filled master joints; roof strata delamination due to internal water pressures; local karst features with mud, sand, and water hazards; and sudden loss of limestone roof due to paleo-channel erosion are some recent problems described. Strategies for overcoming these problems are discussed and detailed.

Jan 1, 2002

By J. A. Botín

NPV is a static measure of project value which does not discriminate between levels of internal and external risk in project valuation. Due to current investment project?s characteristics, a much more complex model is needed: one that includes the value of flexibility and the different risk levels associated with variables subject to uncertainty (price, costs, exchange rates, grade and tonnage of the deposits, cut off grade, among many others). Few of these variables present any correlation or can be treated uniformly. In this context, Real Option Valuation (ROV) arose more than a decade ago, as a mainly theoretical model with the potential for simultaneous calculation of the risk associated with such variables. This paper reviews the literature regarding the application of Real Options Valuation in mining, noting the prior focus on external risks, and presents a case study where ROV is applied to quantify risk associated to mine planning.

Jan 1, 2012

By Charles E. Dandois

New is a relative term, and, when used with reference to a concept as old as shaft kilns can be applied to a number of designs. In this case the design that is the subject of this paper, is known as the ring or annular shaft kiln as developed by Mr. Karl Beckenbach of West Germany. The first&apos; operating unit was rated 185 tons per day and was installed in 1962. Today, there are approximately 84 units in operation in Western Europe and Japan. Twenty-one additional units are in the process of erection or on order. Developed sizes range from approximately 100 to 330 tons per day. Units of over 500 tons are in the design stage, however, the largest units presently operating are rated 330 tons per day, <the first: of this size having been installed in 1966. "Figure" 1 is an elevation view of the unit. It is a single vertical cylinder to which are attached the required service platforms, combustion chambers, injectors and distribution piping. Auxiliaries such as recuperator, exhaust fan and dust collector are mounted on the appropriate service platform. The charging pan, feed conveyor, etc. are mounted at the kiln top. At the bottom of the kiln is the silo with a vibrator type discharger, and mounted separately is the required blower for injector air and fan for internal cooling.

Jan 1, 1973

By J. C. Haptonstall

Stoping methods at the Homestake Gold Mine through 1978 had been traditional overhand cut-and-fill, shrinkage or square set. High costs, low-productivity and safety concerns prompted the mine to search for and adopt a "bulk mining" technique as a primary stoping method. Blasthole stoping had been successful but it is very development intensive, and was not suitable for the mine&apos;s accelerated mining program. Vertical Crater Retreat stoping was selected, and today accounts for over 50% of ore production. Case histories representing both the successes and failures of VCR stoping in the mine are discussed.

Jan 1, 1986

By Paul H. Johnson

A new system for leaching many types of ores has recently been developed on a commercial basis by J and J Research and Development, Inc. of Hanover, New Mexico. This revolutionary new leaching system consists principally of three new leaching reactors; viz, (1) a large, air-agitates, column-like reactor for leaching crushed ores that is constructed in an underground environment and has the inherent ability to do a very efficient job of leaching, (2) a vat-like, air-agitated vessel for leaching an rinsing finely ground ores and , (3) an air-agitated copper precipitation column that is built underground and utilizes an inexpensive dense or heavy scrap iron as a copper precipitant. Each of these new reactors have been used in a large leaching plant near Hanover, New Mexico.

Jan 1, 1973

By Adam H. Zimmerman

Introduction Noranda, like similar businesses, is suffering the pain of previously unheard of currency relationships, a cost structure built in better days, and conditions of gross oversupply possible in almost any commodity. Indeed, it does seem like the worst of all possible worlds is out there before us. To understand a Canadian natural resource company, you must know how the country is organized. So far as natural resources are concerned, Canada is not Canada. Canada is 10 provinces and each own the resources situated therein. Thus, the conditions of extraction, exploitation, and operation are all set by the province, while the conditions of trade and currency are set by the Federal government. This means that what may be the rule in Newfoundland may not be the rule in Manitoba or British Columbia. The second thing is that the Canadian currency has been a satellite of the US dollar for a long time. This means that we hold the unenviable and unjustified position of being the country with the second strongest currency in the world. What this has meant to us is what it has meant to an American operator. Since 1980, a pound of copper fetches 214% more for a Chilean than it does for us and a pound of zinc 115% more for a Belgian. From an American point of view, Canada is favored because its dollar is valued at 25% to 30% less than the U.S. However, because of industrial indiscretions in years past, Canada has a locked in labor cost disadvantage that is very hard to cope with. Canada has a unique situation with its labor unions. Many of the unions are, or have been, internationals and therefore gained undue strength in early days. Canada has a third political party of socialist persuasion. It is entirely funded by dues from laor union members. Thus, we have a politicized workforce. And finally, we have a public service that has the right to strike. This had made the public service unions by far the strongest now in Canada. What this means to the mining industry is that there is somebody out there blazing the trail. The unrelenting power of these public service unions probably creates a climate more conducive to excessive wage settlements in industry than would otherwise be the case. Study, Work, and Pray So what do we do when times get tough? In simple terms, we study a lot, we work harder, and we pray a great deal. We study a lot in terms of learning hitherto unknown strengths and weaknesses of our products, processes, and operations. We work hard in the sense that we do everything possible to improve our productivity. And we pray a lot because, so far, anything else we have done has not been enough. Some years ago, Noranda recognized that its principal base and precious metal operations were diminishing. To provide for the future, we should branch out into other resource type operations. These might be countercyclical and also perhaps a little more permanent. For this reason, Noranda entered the potash, aluminum, and forest products businesses. This, of course, was a &apos;brilliant&apos; strategy that was much applauded in its early days. We built an excellent potash mine, the smallest inte-

Jan 6, 1985

By C. M. Goodall

Solids and liquid phase residence time distribution data is reported for a laboratory column flotation cell. The effects of various physical flotation parameters on residence time distributions are reported and analyzed. A plug flow model with recycle is proposed for the froth phase and a tanks in series model for the pulp. By comparison of two and three phase residence time -distribution data it has been shown that the use of liquid residence time distribution data to predict the residence time distribution of the solids in a column is not valid.

Jan 1, 1990

By Rihab Guellala

In Tunisia, the Paleocene-Eocene series has an important socio-economic interest. It contains profitable oil and water accumulations. Moreover, it encompasses phosphate reserves. The present study uses seismic reflection prospection and borehole data for the reconstitution of the Paleocene-Eocene deposit structure in the Jerid area (southwestern Tunisia), a crucial step for the phosphate exploitation. Firstly, lithostratigraphic correlations incorporating water and petroleum wells were established according to different directions for a tentative approximation of the Paleocene- Eocene deposit geometry by following their lateral evolution. To give more details, seismic reflection profiles were interpreted in the second step. The Paleocene-Eocene formations were associated with their corresponding reflectors on the closest seismic profile using the relation of time and depth in petroleum wells. Analysis of lithostratigraphic correlations shows notable variations in the Paleocene-Eocene series thickness and depth. Seismic profile interpretation explains these variations by highlighting different buried tectonic features. The results confrontation reveals that the phosphatic deposit geometry in the Jerid area is mainly influenced by the (1) emergence of the Saharan platform and the Chott northern chain since the Late Cretaceous, (2) syn-sedimentary normal activity of E-W and NE-SW faults during the Paleocene-Eocene epoch, (3) reverse-reactivation of these faults, and (4) major Tortonian folding phase. This study can enormously enhance the Jerid area socio-economic development by presenting useful findings that may orientate the phosphate exploration.

Aug 15, 2021

By Xuehua Zhang, Shengxiong Yang, Huiqiang Yao, Gaowen He

"Seamount cobalt-rich ferromanganese crusts (hereafter crusts) are authigenic iron/manganese hydroxide/oxide deposits formed from direct precipitation of minerals from seawater onto a hard substrates surface. Crusts contain significant concentrations of cobalt, manganese, nickel, copper, platinum, rare earth elements and other valuable metallic elements, with potential economic value. Regulations on Prospecting and Exploration for Cobalt-rich Ferromanganese Crusts in the "Area" was approved by the Council and Assembly of the International Seabed Authority in July 2012, China and Japan became the first to obtain exploration contracts, which were signed respectively in April and January 2014.The crusts form pavements and are mainly attached tightly to the surface of the substrate, and less commonly crusts coat talus debris located on the surface of sediment and substrate rock. During prospecting, crust sampling methods mainly include dredge, TVgrab and sub-bottom coring system. During exploration, the sub-bottom coring will be the dominant method for crust sampling, and if necessary, ROV sampling will be used. Usually the samples collected by different methods provide a larger quantity than samples needed for chemical analysis, but sampling quantity is a question that should be considered for mineral resource evaluation that how to ensure that the sampling is representation for the sampling station. Using the samples collected by China from Pacific seamounts, according to the designed analysis flow and Qeqott formula (Q=Kd2), the minimum reliable assay sample quantity ("MRASQ") of crusts for Mn, Co, and Ni are obtained. In the case of the sample homogeneous fines at ~100 mesh size (~0.15 mm), MRASQ for Mn, Co, Ni is respectively 4.5 g, 9 g and 9 g. This result provides the basic data for crusts resources evaluation."

Sep 1, 2014

By Qiang Wang, Jiaqiang Yu, Chunhui Fan, Yong Wang, Changyu Jin, Jun Bai, Yu Lu

Accurate ore blending necessitates an in-depth understanding of movement trajectories of fragments and the spatial evolution of the displacement field in the bench during blasting, Accurate ore blending is currently one of the most complex challenges faced by mining engineers. In light of this problem, a systematic study was conducted in this paper using neural network and numerical simulation based on field monitoring data. A nonlinear mapping relationship was established between the mechanical parameters of rock mass and the displacements of the monitoring points. The measured displacements of monitoring points under blasting were input into the neural network, which used back-calculation to derive the mechanical properties of the rock mass. These parameters were then applied in a forward calculation to analyze the movement trajectory of the monitoring points. The results showed that the calculated displacements were in good agreement with the monitoring results during the. The average relative errors in the horizontal and vertical displacements were 4.12% and 15.2%, respectively. Furthermore, the muckpile profile was in an inverted recumbent “S” shape after bench blasting, which was consistent with the actual shape of the muckpile. This verified the rationality and accuracy of the method proposed in this study. Finally, the movement trajectories of particles in the bench and the spatial evolution law of the displacement field during bench blasting were determined based on the calculation results, offering theoretical support and fundamental information for accurate ore blending.

Dec 16, 2023