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By Nuno Cruz, Saúl Rodríguez

"When executing offshore bored piles there are several specific factors and problems to consider in order to guarantee excavation stability. One of the methods employed to carry out this type of work consists in setting up a floating work platform, typically a barge, and implementing a soil stabilization system that combines a partial steel guiding casing with third generation polymeric drilling fluids. The main aspects to take into consideration when performing offshore pile boring works are soil stabilization, project design, work methodology and operational aspects. An example of a work methodology problem arises before any pile boring work takes place as the steel guiding casing contains water, sometimes salt water. What to do with this water in order to replace it by an adequate polymer fluid will determine the stabilization capacity as soon as the shaft advances below the protection of the casing. Another example of operational problem may derive from barge movements while executing boring activities. This study is the result of extensive field data collection and concrete logging analysis from marine projects using polymers in different continents. The bored pile stability target was set ranging between 2% to 15% of concrete overbreak. Values above 15% or below 2% mean that there is a stability problem. Then the off-target pile’s data is collected, analyzed and classified under categories. Thus, a direct correlation is established between the problem category and the final results. Modifying steps in the pre-established construction methods or operational variables guarantees target results without the need to replace the approved construction methods. As a general conclusion, the worldwide experience in large diameter marine works, allows to provide truthful information and solutions for these problems. In knowing how to follow a logical sequence of work and applying adequate work methodology will be the key for success.GENERALBackgroundTo carry out the drilling process of offshore bored piles there are two main options to take into consideration: drilling the pile by using full guiding casing until final depth; or using a combined system of partial steel guiding casing and support drilling fluids.The knowledge and situations described in this paper come from the experience acquired in different projects where the second method was employed. This construction method consists in installing a steel guiding casing by vibration and thus covering the water table and further stabilizing the soil below it with polymeric fluids until reaching the pile’s final depth. The Fig. 1 schematic shows an example of this method where H corresponds to the length of the steel guiding casing whereas the remainder of the shaft’s length is stabilized by polymer fluid. The entire bored length is full of slurry up to top of casing.In most cases this kind of civil works results from the need to build a bridge or executing port structures in places where the creation of temporary artificial peninsulas with fill material is impracticable or not allowed. Hence the need to use floating work platforms, commonly referred to as barges."

Jan 1, 2017

Jan 1, 1996

By A. Thielen

In experiments for the production of steel the principal problem has always been the introduction into, or removal from, the iron of a definite quantity of carbon. Although the solution of this problem had engaged a more or less blindly and empirically directed effort for a long time, it was only with the development of analytical chemistry that the rôle which carbon plays in the constitution of steel was disclosed in its full significance, and that many of the problems confronting the steel-maker were thereby more clearly defined than before. For a long time, and to a certain extent even to this day, the percentage of carbon in steel has been the controlling means of deter mining its quality and hardness. In many cases the percentage of carbon alone has been relied on for judging large consignments, such as the large deliveries of wire-billets and blooms to America during the past twenty years; and though to-day the influences of the other constituents are recognized and many other considerations are taken into account, and though, moreover, some special steels, such as the Hadfield manganese steel, apparently dispense to a certain extent with the assistance of the carbon, yet fix our Bessemer, Thomas, Siemens and crucible steel the carbon still remains one of the most important constituents, and I venture to say it is indispensable. In order to produce in the Bessemer converter a steel of a certain required percentage of carbon, two methods, as is well known, present themselves. By the one the decarburization process is stopped when the desired carbon limit in the bath has been reached ; by the other the bath is completely decarburizecl, and then a calculated amount of carbon added in the form of spiegel, ferro manganese, etc. In Germany the latter method only was adopted, and it was retained when the Thomas-Gilchrist process for the production of low-Phosphorus steel from high-phosphorus iron eame into use, since from the nature of the new process complete decarburization is neces-

Jan 1, 1891

By Stephen C. Tadolini, Thomas M. Barczak, Peter (Yunqing) Zhang

A cooperative study was conducted with Emerald Coal Resources, L.P., an affiliate of Foundation Coal Corporation, and the National Institute for Occupational Safety and Health (NIOSH) to evaluate the effectiveness of (partially) pre-driven longwall recovery rooms supported with pumpable roof supports. This paper evaluates the load transfer mechanics associated with the advancement of the longwall face into the pre-driven recovery room and the widening of the room to recover the longwall shields. The results show that the yielding of the panel fender produced uncontrollable convergence that caused yielding of the shields and stiff pumpable roof supports when the face was approximately 10 ft from the recovery room. The shields continued to yield until the face advanced into the recovery room. Convergence in the pre-driven recovery room typically reached 6-8 in once the pumpable supports yielded and shed load through a declining residual load capacity prior to being cut out by the longwall shearer. Roof deformations occurred beyond the 32-ft horizon with total deformation ranging from 2 to 4 in, indicating that standing support was necessary to help control the span as the longwall face advanced into the pre-driven recovery room. Stability improved as the pumpable supports were cut out, thereby reducing the span between the shields and the outby pillars. In the end, the shields were successfully recovered under stable ground conditions. However, a disconcerting discovery was the load shedding of the outby pillars as the recovery room was mined into. It is postulated that this may be due to the progression of the rear “abutment” moving toward the recovery room as the panel fender and standing support in the recovery room yield and shed load. This behavior was not expected with a relatively narrow room that is fully supported with standing support. If this mechanism is indeed occurring, the width of the room and performance of the standing support becomes even more critical. Premature failure of the support can lead to excessive convergence on the shield line that cannot be controlled even with modern shields, resulting in roof instabilities that can lead to catastrophic results.

By C. C. Hamilton, G. R. Lane

Traditionally, mineral sands are evaluated by preparing several mineral products using a combination of heavy liquid-, magnetic-, and electrostatic methods. Whole-rock assays (WRA) are then conducted on ilmenite, rutile and zircon products in order to determine trace element contents, which may affect project feasibility. Combined methods can be time consuming, expensive and even outdated due to the use of banned and toxic chemicals such as clerici solution. Coupled with large field-sample quantities, these procedures can potentially introduce unacceptable sampling and related errors. Modern mineralogical analysis techniques can provide complete mineralogical inventories on a single THM product, reducing the amount of processing involved in satisfactory characterization of early exploration samples. A small exploration sample can be processed to produce a small THM concentrate using readily available gravity/density methods. In turn, the THM product is submitted for Whole Rock Analysis (WRA) and mineralogical inspection by X-ray diffraction (XRD), and microscopic evaluation. Modal mineralogy and textural data can be determined using optical methods, automated image analysis, and scanning electron microscope (SEM) based systems. Benefits of automation are reproducibility and the capability of rapidly analysing thousands of particles as opposed to manual optical methods. Automated systems include the use of Automated Digital Image Analysis (ADIS), and SEM-based systems such as the Mineral Liberation Analyser (MLA) and QemSCAN. For detailed mineral chemistry, microanalysis techniques ranging from electron microprobe (EMPA) to Secondary Ion Mass Spectrometry and Laser Ablation Mass-Induced Coupled Plasma-Mass Spectrometry (LAM-ICP-MS) are used. Examples of these automated and analytical methods are presented. ADIS at SGS-Lakefield Research uses optical characteristics to identify and measure mineral species in THM samples; rutile, pseudorutile, ilmenite and leucoxene can be distinguished. Analysis of a single THM product provides bulk modal mineralogy and grain size distribution of particles and the individual mineral grains. Textural information is also obtained detailing mineral associations as well as degree of alteration. Where textural and chemical resolution renders mineral identification ambiguous, SEM-based methods offer better resolution. Examples of this ambiguity are shown in this paper, which leads to QemSCAN as the preferred method where within-grain variability is concerned. Sampling and measurement strategies are followed to meet study objectives, providing a value-added framework for a sequential, cost-effective strategy, which will meet due diligence and bankable accreditation criteria. Studying a THM product by electron microprobe and LAMICP-MS may reveal potential fatal flaws related to mineral chemistry. Low detection limits in the range of 200 to 500ppm are possible using electron microprobe analysis for suitable matrixes (U, Th in zircon). For the detection of ultra low level elemental contaminants, LAM ICPMS is the most accurate method of evaluation. Elements including U, Th, La, Ce, Nb, and V in Ti-minerals can be determined down to 50 ppm.

Jan 1, 2005

By L. Mukka

The existing main mine ventilation system for the production areas to the Kiruna mine was constructed during the period 1994-1996 and extended with 4 more shafts, including fan stations, for the sea ore body from 1997-1998. Two papers have been presented from this project at the 7th US Mine Ventilation Symposium in 1995 and at The 6th International Mine Ventilation Congress in 1997. In 2005, pre-studies for a new main haulage level were started. Different haulage methods were presented including ventilation systems. The pre-studies showed that the existing ventilation system, including fan stations for the new main haulage system in the production area, could be extended. However, a new system for the central area, which was not in the initial investment program, would be needed. In the beginning of 2006, a decision was made to design a new ventilation system for the central area to make it possible to get air to the development work for the new main haulage system, independent of the haulage method. This system was operational by the beginning of 2007. The new main haulage system, which was decided to be located on level 1365 m, only requires that the existing shafts be extended - the capacity of the fans seems to be enough. However, the problem is that the existing level 1045 m and the new level 1365 m have to be in operation in parallel for approximately 7-8 years. The challenge for the moment is determining how to ventilate the production areas for both levels at the same time, while simultaneously constructing the extended system. This paper will describe the problems associated with the extension of the main ventilation system and some potential solutions for these problems. The new main haulage level 1365 m must be in operation by 2012.

Jan 1, 2009

In this study, a 3D model of the shovel motion based multi-body system dynamics in the Automatic Dynamic Analysis of Mechanical Systems (ADAMS) environment was developed. The kinematics model of the shovel was modeled as a multi-body system, which comprises the lower, upper, and the attachment mechanisms. The Euler-Lagrangian equations were employed as the computational framework to describe the dynamic behavior of the model. A virtual prototype of the shovel was built in the ADAMS software environment. This environment allows the visualization of a 3D motion of the general mechanical system and the prediction of interference of the moving components of the shovel. The numerical analysis and animation of digging, swinging and dumping motions for the shovel were performed. The superimposed display of the deployment for the shovel in three phases allows a detailed examination of the dynamic interference among assembly components. This research provides a solid foundation for further shovel dynamics performance studies. Keywords: Shovel, Spatial Kinematics, Virtual Prototype, Visualization

Jan 1, 2009

Traditional fine grinding mills in mineral processing relied on the use of steel medium for particle size reduction. The successful development of the Isa Mill(a horizontal stirred mill with 3000 litres of net chamber volume and 1120 kW rated motor power)adopted a novel product separator design that has led to a major revision of medium use in fine grinding. The Isa Mill separator has also successfully operated with a wide variety of medium types such as silica sands, river gravel, smelter slag, run-of-mine ore fractions and steel shots, with size ranges from 0.5 to 10 mm. A great flexibility of the Isa Mill operations has been achieved for processing a feed as coarse as 120 um to a product as fine as 5 µm. This paper discusses the performance of two inert grinding media used in the Isa Mills in Mount Isa Mines of Australia for processing galena and sphalerite bearing ores to below 10 microns. They are the copper reverberatory furnace slag (CRFS)and the heavy medium plant rejects (HMPR). A methodology was also demonstrated for comparing the medium performance and for scaling up the Isa Mills from a 1.5-litre laboratory batch mill to a full scale 3000-litre mill.

Jan 1, 2000

By P Wigley

New methods of analysing and modelling flotation circuits have been developed as part of the AMIRA P9 mineral processing research project. A study using these techniques was conducted on the Olympic Dam copper flotation circuit to provide the following outcomes: an estimate of the flotation cell hydrodynamic properties and froth performance characteristics, and identification of potential areas for improvement; an estimate of the feed floatability parameters for basic model development; and identification of potential flotation circuit improvement opportunities. A flotation circuit model of the Olympic Dam copper concentrator was developed using the data collected from mass balanced site surveys, along with hydrodynamic data, froth performance data and numerous laboratory batch flotation tests. The simulator that has been developed from the model has the ability to estimate the influence of selected changes (such as circuit changes) on flotation circuit performance. Several stream destination simulations were conducted to provide guidance for further testwork and possible circuit improvements. The results from these simulations are presented.

Jan 1, 2003

By H. J. Haselhuhn

Selective flocculation and dispersion processes for the concentration of hematite ore are strongly dependent on the ionic content of the process water. It has been noticed that magnesium ions are more detrimental to iron recoveries during desliming and flotation processes than calcium. This phenomenon was studied by measuring the zeta potential of hematite ore at various concentrations of magnesium, calcium, strontium and barium at a pH of 11. Results show that zeta potential inverts from negative to positive at very low concentrations of magnesium ions in the solution. It takes a significantly higher concentration of calcium, ions to achieve the same effect. This difference may be attributed to the ability of magnesium ions to adsorb to all surface hydroxyl groups, whereas calcium, due to their larger size, can only adsorb to every other hydroxyl group. This hypothesis was confirmed by results similar to those seen with calcium when this test was repeated with strontium and barium ions. The tendency for calcium ions to adsorb to every other surface hydroxyl group causes higher concentrations of calcium to be less detrimental to hematite concentration processes than magnesium.

Feb 27, 2013

By William C. Cassun

The important role of pit slope design in the overall economics of open-pit mining ventures has long been recognized and well documented.1 2 Any economic analysis of a pit slope design must reflect the trade-off between the benefits and the increased risk of slope failure inherent in steeper slope angles. The conventional practice in pit slope design is based on the factor of safety analysis.' The approach uses average values to arrive at a deterministic solution to slope stability. Past analyses based on this approach generally have had several drawbacks: 1. The risk from slope failure could not be quantified. 2. Only relatively simple pit wall geometries were considered. 3. The analyses were performed solely for the benefits of steeper slopes, seldom discussing the potential costs of slope failures. 4. Analyses were seldom considered in a year-by-year mine planning context. Recognizing that average values do not reflect the uncertainty in geomechanical parameters, a probabilistic philosophy to slope design has evolved. 4,5 However, this approach had not been fully developed to include complex slope geometries and mine planning consideration. In order to develop an integrated, pit slope design procedure, a research project was initiated at the University of Arizona during 1973 in conjunction with the Canada Center for Mineral and Energy Teleology. This research resulted in the development of a probabilistic design procedure. The remainder of this paper gives an overview of the probabilistic design procedure and a discussion of the requirements for the benefit-cost analysis of a pit slope design. Finally, the results of a case study undertaken at an operating mine are given.

Jan 1, 1977

By David Norval

The increased tendency to use hydrometallurgy as an extraction step towards final refining following a pyrometallurgical smelting process requires melts which have to be cast and or comminuted which can then be taken up into solution or leached. To generate surface area for optimal leaching, a common process is to granulate and in many cases mill, which is a general practice with friable material with properties associated with higher sulphur, carbon and silicon levels. However, in the case of metallic melts milling can be unfeasible due to the ductility of the granulated particles. Water solidification is capable of producing either fine particles by means of granulation or atomisation. Atomisation however, can produce particles as fine as 40 microns without a milling circuit.

Jan 1, 2005

By J. Wickens

Haile Gold Mine is located near Kershaw, South Carolina, approximately 50 miles south of Charlotte, North Carolina. Gold was first discovered at the site in 1827, and the property has been through several operating periods since. The relatively low grade and refractory nature of the deposit has been a challenge for efficient processing since the start of mining on the property. Early processing techniques included gravity separation and barrel chlorination. The last operation employed heap leaching in 1985 through 1992. After being closed and reclaimed for over 20 years, the property is poised to re-open and produce once again. In this chapter of the Mine?s legacy, flotation and ultra-fine grinding will be employed to achieve economic extraction of gold and silver from the pyrite. This paper briefly reviews some of the mine?s history, the metallurgical testing, the flowsheet and discusses design considerations. KEY WORDS: process plant, flash flotation, leaching, SMD, stirred media detritor

Feb 27, 2013

By Carlos Avalos Casillas, Saul Ortiz Landeros

The current work shows metallurgical results obtained at the Centro de Investigación y Desarrollo Tecnológico (Peñoles CIDT), as a continuation of the work first published in February 2012. With the aim of optimizing the economic values of the products, ores from San Julian (Fresnillo) were selectively floated to produce a lead concentrate and a zinc concentrate containing high silver values. In the laboratory, this included regrinding of the rougher and scavenger lead concentrate to increase the liberation of mineralogical species and thus lower zinc recovery. Cyanide leaching bottle tests were conducted to improve the value of the silver. It is proposed to leach the silver contained in the zinc concentrate and then recover the silver using the Merrill Crowe process. The results show a reduction of zinc recovery in the lead concentrate from 11.3% to 2.0% after regrinding to a P80 of 10 microns, improving the metallurgical quality and economic value of the lead and zinc concentrates. Also laboratory and pilot scale cyanidation tests showed that about 65 to 80% of silver will be leached from the zinc concentrate, after regrinding to a P80 of 10 microns. The proposed processing increases the economic recovery of silver from 72.7% to 78.8%.

Jan 1, 2014

By Steven Townend

Mining-related activities have been known to create a challenging operating environment for mining companies located in close proximity to communities. Issues such as noise, vibrations from mining operations, land use and emissions are often a concern for community residents. In order to develop good community relationships it is necessary to take a proactive approach. This paper documents this approach and also deals with the social implications for Vale associated with mining activities in the heart of the community of Copper Cliff, Ontario, Canada.

May 1, 2011

By Forrest T. Moyer

INJURY experience in the metal and nonmetal mineral industries during 1964 was better in rates of occurrence but worse in severity rates than in 1963. The frequency rate of injuries per million man-hours was improved at metal mills, nonmetal mines, and sand and gravel operations, and was virtually unchanged at metal mines; however" the rate of occurrence of work injuries at nonmetal mills, stone operations, nonferrous reduction and refining plants, and slag plants was higher than in 1963. The severity rate of injuries during 1964, data for which are presented for the first time in this chapter, was better at metal mills, nonmetal mines, stone operations, and slag plants. However, the severity rate was worse at metal mines, nonmetal mills, sand and gravel plants, and nonferrous smelters.

Jan 1, 1965

By J. Shawn Peterson, David S. Yantek, Adam K. Smith

Occupational noise-induced hearing loss continues to be one of the most pervasive health problems in the mining industry, despite over 25 years of regulation. One of the loudest pieces of equipment used in underground mining is the continuous mining machine. Noise sample data collected by the Mine Safety and Health Administration indicate that 42% of noise overexposures between 2000 and 2005 involved continuous mining machine operators. Previously conducted field and laboratory tests have determined that the continuous mining machine conveyor system is a dominant noise source. Loud impacts occur as the conveyor chain flight bars, used to move the mined aggregate, traverse their path from the top to the underside of the conveyor deck. Various noise control treatments have been applied to abate noise caused by the conveyor system. A durable polyurethane coating has been developed for the conveyor flight bars, resulting in a time-weighted average reduction of 3 dB(A) for an eight-hour work shift. In an attempt to further reduce continuous mining machine operator overexposures, a similar urethane coating has been applied to the tail roller component of the conveyor system. Laboratory results showed a 2 dB(A) reduction in sound power levels, but the component failed during underground durability testing. An outer steel sleeve has been added to the urethane coating of the tail roller to enhance wear resistance during mining. The urethane jacketed tail roller is the latest effort, combined with previous noise treatments, to bring the continuous mining machine into compliance with federal noise regulations.

By G J. Fleming

The Miwah prospect lies on the dilational 070¦ trending Miwah Lineament near its intersection with northerly oriented fractures within Pliocene volcanic rocks exposed between a NW trending segment of the dextral transcurrent Sumatra Fault, and the more northerly trending Samalanga-Sipopok Fault to the east. These faults reflect the continued interaction between stresses from the India-Australia plate located to the southwest, and spreading within theAndaman Sea to the north of Sumatra. A system of deep seated faults is believed to have facilitated emplacement of post-Miocene magmas and Quaternary volcanic centres at shallow crustal levels throughout northern Sumatra. Miwah mineralisation is associated with variably dipping structurally and lithologically controlled argillic and advanced argillic alteration. An oxidised supergene leached zone and a recent, thin, unaltered tuff blanket partly overlie the mineralisation. Mineralised zones are commonly brecciated and veined, and display quartz, quartz-alunite, quartz-alunite¦pyrophyllite¦kaolinite replacement assemblages, surrounded by more weakly mineralised, often vugghy quartzalunite¦pyrophyllite¦kaolinite advanced argillic, and argillic zones of quartz-kaolinite, quartz¦pyrophyllite¦kaolinite and smectite-illite-quartz. Propylitic assemblages are marginal to more intensely altered zones. Hypogene copper mineralisation is typified by enargite, luzonite, and covellite. The host mineral to gold is uncertain at present. Rare barite, native sulfur, and ?telluride also occur. Bornite and chalcopyrite have been observed in transported altered rocks in faults. Generally the mineralisation is anomalous in precious metals, locally enriched in Cu, erratic in Pb, and depleted in Zn, with a good correlation between Cu-As-Ag.

Jan 1, 1995

By George Watson, Gu Quanzhong, S. Gerard Sawyer

Bulkheads, also known as hydraulic seals, are used to seal abandoned workings and protect adjacent active mines from explosion and control unwanted inflows of water from poorly sealed shafts, water-bearing strata, and abandoned mine areas or gobs (1). At coal seam outcrops, bulkheads have typically been used to prevent access and to control acid mine drainage. Bulkheads have also been installed at outcrop openings located within the footprint of an embankment dam, or within the reservoir of an impoundment, to prevent stored water or slurry waste from flowing into active or inactive underground mine workings (2). Components of MICON Bulkhead Seal MICON bulkhead seals in mining applications refer to seals designed to impound liquids or slurry. The MICON bulkhead seal is comprised of two concrete block walls set in the front and back and a polyurethane/aggregate core (Figure 1). The two walls are usually dry-stacked, surface-bonded walls constructed with solid load-bearing concrete blocks (ASTM C90) or concrete building brick (ASTM C55). The surface bonding material used in the wall construction must be MSHA-approved. The type of stone, if any, used to fill the space between the walls is not essential. However, MICON generally uses No. 57 limestone in 50 lb. bags, specified to moisture control, shrink-wrapped and palletized. The polyurethane foam used in the construction of the bulkhead seal is engineering specified and formulated by density based on the optimization of cost, seal core thickness, required adhesive strength, the use of stone filler and other required physical properties.

Jan 1, 2005

By I. Jackman

"Gold is present in different forms and associations in different ores. Flotation is used to recover gold and minerals associated with gold, but the applicability and type of flotation vary. The purpose of flotation in a gold recovery plant is largely dependent on the mineralogical association of the gold, and environmental and economic considerations. In this paper, the role of flotation in the recovery of gold is reviewed. The paper will describe examples of gold recovery by flotation including flotation of native gold, gold associated with sulphides including specifically copper sulphides, gold associated with tellurides, gold ores containing carbonaceous material and gold contained in tailings.INTRODUCTIONFlotation is widely used in the recovery of gold. However, the objectives and the mode of application are quite variable dependent on the type of ore, the gold association(s), other metal values, marketing considerations and environmental requirements. In this paper, a range of different applications of flotation incorporated in the recovery of gold are discussed. The reasons for each particular application are outlined and metallurgical results are presented.The mineralogy of the ore and the gold associations are fundamental influences on gold recovery. The use of flotation to concentrate gold is dictated by the mineralogy of the ore and gold. The fundamental factors are mineral/gold size, liberation size, association of the gold and type of gangue minerals or other valuable minerals. Gold can exhibit a range of sizes in a host from relatively large size (+50 µ) to refractory size (1 µ and sub-micron size). Similarly, the gold can occur in a number of phases in the same host. For example, the gold was present as petzite (AgAu telluride), calaverite (AuTe2) and native gold in a gold telluride ore and each of these minerals was associated with the pyrite host.Understanding the gold mineralogy and association is important in establishing the correct process route. The gold mineralogy is established by good mineralogy, use of diagnostic tools such as diagnostic leaching and assay by size fraction analyses and basic metallurgical testwork."

Jan 1, 1995