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By G. Folmo

Allis Mineral Systems' GRATE-CAR agglomeration/induration/reduction process is currently being operated to process ilmenite at Tinfos Titan & Iron KS in Tyssedal, Norway. In this process, balled ilmenite concentrate is fed to a traveling grate where pellets are dried and preheated, using fully oxidized kiln exhaust gas. Hot preheated, semi-indurated pellets are fed directly to a ported kiln where reduction of the ilmenite's iron oxide fraction occurs in the presence of lump coal. The reduced pellet sand coal char are discharged from the kiln to an indirect rotary drum cooler. Cooled pellets and char are screened and magnetically separated prior to their further processing in a downstream smelting operation. The pellets are melted and the titanium dioxide and iron are separated. Operation commenced in late 1986.

Jan 1, 1992

By A. Suarez, M. Menendez, M. R. Gent, P. Riesgo

"Recent requirements to reduce thermal coal plant emissions, and ultrafine coal's tendency to produce these emissions due to its typically high ash and moisture contents have limited the use of ultrafine coal. Ultrafine coal in beneficiation plants are usually either disposed of in tailing ponds at a loss in combustible material or disposed of by blending with coarser higher-grade products, resulting in a reduction in marketed product quality. A study of the options for processing ultrafine coal, consisting of < 200 µm hydrocyclone overflow, with 38.8 percent ash content is presented here. Ultrafine coal was processed based on 200-µm sieve bend and 10-µm hydrocyclone classifications, enhanced gravity separation (EGS) and froth flotation concentration as well as combinations of these. Yield, combustible material recovery (CMR) and product humidity were evaluated as test results.Depending on the processing applied, product ash content could be reduced up to 49.7 percent, and up to 95.8 percent CMR of the actual run of mill feed could be attained. All of the processing options analyzed could reduce produced thermal electric plant emissions due to ash and moisture from 22 to 38 percent of the actual unprocessed ultrafine coal product.Froth flotation was found to be the optimal process, yielding a product with the lowest ash content attained of 19.5 percent and CMR of 92.3 percent. Being the most versatile of the processes evaluated, it is capable of producing coal with varied ash contents but is subject to potential variations in coal flotability. The most complicated of the processing options, a combined sieve bend recovery of the > 200 µm fraction and EGS processing of the 10 to 200 µm fraction was found to be the next best option, attaining a combined 90.1 percent CMR and 25.0 percent ash content. IntroductionMunicipal, regional and national objectives to reduce fossil fuel combustion emissions and their effects on air quality and global weather changes are affecting thermal electric plant operations. Plans and regulations such as President Obama's Clean Power Plan (U.S. Environmental Protection Agency, 2015), the European Directive 2010/75/EU (European Commission, 2010) and China’s proposed Enhanced Actions on Climate Change (Wei, 2015) are of major significance to thermal electric plant operations. Although thermal plant efficiencies depend in large part on the losses of heat by plant components, the ash and humidity contents of thermal coal invariably reduce plant efficiencies and increase emissions of carbon dioxide (CO2), nitrogen oxides (NOx) and dust.Any noncombustible material present in thermal coal will result in higher CO2 emissions per unit of energy produced. Since no particle emission control can be totally effective, it is to be anticipated that any reduction in coal ash content will also result in reduced particle emissions. Kurose, Ikeda and Makino (2001) reported that NOx emissions also increase with coal ash content. The effect of coal moisture content during combustion is complex. Kurose, Ikeda and Makino (2001) showed that an increase in coal moisture content significantly reduces thermal NOx to total NOx production, and Bosoaga et al. (2006) showed that it tends to reduce NOx emissions. Since the humidity, pyrite and ash content of thermal coals directly affect thermal electric plant efficiencies and emissions, minimizing these factors should facilitate, at least in part, compliance with thermal electric plant emission limits. This, in turn, would affect the specifications and prices of the coal preparation plant products."

Jan 1, 2016

By Jonathan K. Hrica, CASSANDRA L. HOEBBEL, Jennica L. Bellanca

Accidents involving powered haulage and mobile equipment like haul trucks are a major safety concern in the U.S. mining industry. They account for more than 50 percent of surface mine fatalities each year [1]. A recent National Institute for Occupational Safety and Health (NIOSH) analysis of 91 fatal incidents identified loss of vehicle control and situational awareness as key contributors [2]. However, the first-hand perspectives of operators are often missing, emphasizing the need for deeper insights into operators’ decisionmaking, lessons learned, sensory cues and mental strategies used during near-miss events. The findings in this analysis will help inform the development of training and safety solutions to prevent or reduce haul truck accidents.

May 1, 2025

By William F. Riggs

Inspiration Consolidated Copper Company, located in a semi-arid climate in Arizona, continually struggles with a water problem. This applies to quality as well as quantity. When the EPA considered installing a new centralized sewage plant to handle the combined waste from the municipalities of Globe and Miami, Arizona, they automatically assumed that He could use the sewage effluent for process water in flotation. The treatment plant was to be a tertiary system producing 1600 gpm of sewage effluent. Inspiration decided that this could possibly be a source of additional process water. It was decided to test sewage effluent from Miami Treatment Plant at the rate of 400 gpm since it was only a primary treatment plant. The 400 gpm was combined with the 5000 gpm of process water going to the Concentrator. After one week the results were disastrous. The recovery and final grade had each dropped approximately 5%. With the results from this brief run, it was concluded that sewage effluent from a primary treatment plant could not be used. Research was then brought into the problem to begin an evaluation of sewage effluent in flotation.

Jan 1, 1977

By J. M. Beck

Mineral property appraisers engaged in eminent domain actions on properties for which mining is the highest and best use must be fully competent in all phases of mineral resource estimation, mine project development, and mine operations (or retain the requisite competent assistance), as well as educated in eminent domain appraisal (USPAP Competency Rule). Failure to ensure such triggers the issue of appraisal competence and demonstrates a flagrant disregard of the myriad code(s) and guidelines to which the appraiser is subject. The cavalier assertion of some vague, undefined “latitude” in the valuation process does not exonerate the appraiser from a disregard of the USPAP Competency Rule. Lack of independence (i.e., “advocacy”) in mineral property appraisal is the usual result of a weak background in mining and/or appraisal theory. While it is readily apparent to those able to recognize it in reports and testimony, judges and juries cannot be expected to detect or recognize purposefully misleading (or even fraudulent) valuation concepts or testimony. Purposeful deception by the appraiser can lead to specious over-compensation of the property owner (thus victimizing the taxpayer); or, a failure to provide appropriate and just compensation to the property owner – yet, the purpose of an eminent domain proceeding is to leave the property owner no richer or poorer as a result of the taking. This paper highlights some of the deceptive practices encountered in litigation settings and raises issues of competency, professional ethics, and the effectiveness of the inherent enforcement capabilities within those institutions awarding professional certifications. INTRODUCTION The practice of eminent domain mineral property appraisal requires (particularly with respect to undeveloped mineral properties) that the appraiser possess the requisite level of competence in all phases of mineral resource estimation, mine project evaluation, mine development, and mine operation (through closure). To the extent the appraiser lacks such competence, it is incumbent on the appraiser not only to divulge this lack of expertise but also to seek competent assistance in the performance of the appraisal. This competence or expertise can only be obtained through a combination of appropriate and relevant technical education and direct mining industry experience. There exist a number of professional certification and/or credentialing authorities that speak to such competency. In a similar manner, eminent domain mineral property appraisal (as the term implies) also requires that the appraiser possess the requisite level of competence in the practice of eminent domain appraisal. This competence or expertise can only be obtained through appropriate and relevant education, direct knowledge of appraisal theory, particularly as it relates to the concept of eminent domain, and licensure.

Jan 1, 2019

By N. B. Aughenbaugh

The People&apos;s Republic of China has 582 Gt (641 billion tons) of proven coal reserves. At present, 576.5 Mt (635.5 million tons) of coal are mined a year which makes China the third largest producer of coal in the world. Underground mining accounts for 95% of the total production. This paper will discuss the coal districts, coal types, jurisdiction of coal mining, and methods of underground mining. The article also will outline China&apos;s objectives in future planning and development of its coal reserves.

Jan 1, 1982

By B. Simser, T. Butler, A. Hall

The longterm future of Glencores’ mining operations in the Sudbury basin area of Ontario, Canada likely depends on mining deposits at depths below two kilometres. To gain a better insight into the rockmass response to mining, a geological scouthole program has been implemented at Glencores’ Nickel Rim Deep and Onaping Depth Project to gain insight into rockmass conditions ahead of the devel-opment face. The scouthole program involves drilling long (up to 600 m) subhorizontal boreholes drilled ahead of the development end and collecting data about the rockmass conditions from various geophysi-cal and mechanical tools (in addition to conventional core logging). Once all data has been collected and the borehole is available, seismic sensors are installed up to 450 m down the hole as part of the micro-seismic monitoring program with the leading sensor always located ahead of the development end. The recorded seismic data is used to provide realtime insight into the rockmass response to mining. On May 20, 2017 a flurry of seismicity with a maximum moment magnitude (Mw) of 0.7 occurred causing damage to the ramp heading. Data from the microseismic monitoring system had indicated that conditions at the development end were changing prior to the rockburst. A back analysis of the scouthole data indicated a clear anomaly in the rockmass at the location of the rockburst. The scouthole data also provided sufficient information to suggest that once this anomalous zone was exited, mining conditions would improve. With the microseismic monitoring system providing realtime information from the rockmass, the area was re-habilitated and ramp development continued successfully. Details of the rehabilitation and adjustments to the ramp development are discussed. Some correlations between the scouthole data and recorded micro-seismicity are also presented.

Apr 26, 2022

By Adeyemi Adesina, Subhabrata Mishra, Syed Mohammed Mustakim, Malaya Kumar Jena, Shaswat Kumar Das

Utilization of low-grade manganese ore adopting the carbothermic reduction roasting process is a proven method to produce high-grade manganese ore. To minimize industrial waste and protect the environment, gas cleaning plant sludge (GCPS), which is a solid waste from steel industries, was employed as a reductant to perform the reduction roasting process. The optimum conditions to carry out reduction roasting of the low-grade manganese ore were found to be: a roasting temperature of 950 °C, a residence time of 2 h, 40% GCPS as reductant, and magnetic separation at 5000 G for a manganese ore size of –10 mm. A lowgrade manganese ore comprising Mn grade 31.27% and Fe grade 19.78% having a Mn/Fe ratio of 1.58 containing a high silica content of 26.48% was used for the carbothermic reduction roasting having mineral phases of pyrolusite (MnO2) and hematite (Fe2O3) as found from XRD. The gangue minerals were separated during the magnetic separation, and the upgraded product was obtained, which reached a maximum value of TMn 49.5% with RMn 76.55% and TFe 62.19% with RFe 42.51%. In the study, activated charcoal (AC) was also taken as a reductant for comparative analysis; the experimental results revealed that GPCS performed better than that of the AC, showing potential to be used as a reductant in metallurgical industries. However, the resultedMn/Fe ratio was very low for the reduced sample; therefore, it can be used for smelting along with high-grade manganese ores as a feed.

Mar 5, 2021

By Gary Brierley, Lok Home

"The majority of tunnels for civil engineering applications are now being constructed using some form of mechanical excavation. Beginning in the 1960s with rock tunnel boring machines (TBM), the tunneling industry has introduced both earth pressure balance (EPB) and slurry pressure balance (SPB) soil machines; mixed soil and rock machines and a variety of different mechanical devices for the construction of small diameter tunnels. Over time, these machines have become more powerful and more adaptable to a wider variety of ground conditions; so much so that tunnels are now being constructed in ground conditions and in the vicinity of third-party impacts that would have been considered beyond the state of the art just 10 years ago. Figure 1 is an example of a mixed ground crossover TBM used successfully at Mexico City’s Túnel Emisor Poniente II.All of the above is highly advantageous for the tunneling industry, but it has also placed a much higher level of risk on the performance characteristics of the tunneling machines, on the contractors operating those TBMs and on the manufacturers of those machines. Most of the risks for a tunneling project are associated with creating the space inside of which the finished facility will be constructed. In order to create that space, the tunnel contractor must make many decisions about the best way to excavate the ground, the best way to control the ground at the face of excavation and the preferred method for supporting the ground around the tunnel in a manner that is safe for the workers and stable with respect to all of the overlying and adjacent existing structures. If it is proposed to use some form of TBM in order to build the tunnel, then the TBM becomes central to all three of these activities and becomes an integral part of managing the risks associated with these activities."

Jan 9, 2018

By T. W. White

One of the objectives of today&apos;s mine superintendent is to increase his equipment availability. To this end we have seen improved scheduling procedures, preventive maintenance programs and extensive drive training and operating procedures. However, until recently, one area that has changed little in the past twenty years is the method of refueling and servicing mine equipment. In looking at mines across the country continually one encounters the hazardous oil soaked ground, the hand held fuel nozzle and the maze of hoses of the "traditional" fuel stop. By adapting technology developed in the construction and aircraft industry, current fueling and servicing practices can be easily improved. The result will be less nonproductive time, less downtime from engine failures and increased security from major refueling fires. The time saved almost amounts to having another truck in the fleet! One feature of the improved servicing practice is the implementation of high flow fueling. For trucks now on the market, a flow rate between 120 and 150 gam is feasible, about 90 gam greater than current practice. This flow rate could be increased even further as larger trucks come into use. A second idea borrowed from the aircraft industry is the use of positive lock type connection nozzles that automatically shut off when flow stops. These may be used for fuel, water, oil and hydraulic systems to eliminate spillage and assure that clean fuel, oils, and water are delivered to the vehicles. The reduction of fuel spillage lessens the threat of major fires resulting: in equipment damage and loss. Eliminating fire hazards will become even more important as the turbine engine with its lighter, more volatile fuels come into common use.

Jan 1, 1972

By William Ives

My presentation is from the viewpoint of the industrial mineral geologist, which is a relatively rare breed. Very few geologists become involved with industrial minerals for two reasons, I think: (1) Much of the industry utilizing non-metallic minerals has developed without the use of geologists in the begin¬ning and many of the management people, who generally derive from the processing plant supervision, tend to take raw materials for granted; and (2) non-metallic minerals are a very insignificant part of the curriculum of virtually all colleges granting a geology degree. One learns about the geology of industrial minerals by working with it. This "on-the-job-training" is probably best because it brings the geologist into close quarters with the production people and the production process. And the industrial minerals field has a distinctiveness when compared with the petroleum or metal mining field in that each deposit can yield a material differing in some aspect from that in any other or within the same deposit. The petroleum from a well in a given field will be similar to that from any other well, but a limestone on one side of a hill can differ signifi¬cantly in elemental composition, calcinability, soundness, specific gravity, or some other factor from the same ledge on the other side of the hill. This characteristic of almost certain variability creates problems sooner or later and provides for much of the employment of industrial mineral geologists. My job seen from the viewpoint of management is "Find us some rock we can extract and process at a profit." The industrial non-metallic geologist has much the same problems and approach as a detective. I do not mean the TV variety with the big mouths and the unfailing knack of spotting the wanted criminal immediately in a city of ten million people. Any real detective will tell you it takes leg-work, knowhow, and persistence to make a case. The same is true for the geologist who finds rock which can be quarried at a profit. I am responsible for finding raw materials for a company which manufactures portland cement and

Jan 1, 1977

Innovative mining technology came to Texas in the form of bucket wheel excavator/cross-pit spreader systems. Texas Utilities Mining Company put the first system to work at its Big Brown Mine in December 1985. The second such system was put into operation at the Monticello Mine in February 1991. The cross-pit spreader systems are mobile, electrically powered, excavation and conveyor systems, the principal components of which include bucket wheel excavators (BVE) and an across-the-pit conveyor (spreader). These crawler mounted machines operate as a unit; the BVE&apos;s excavate overburden, feed it via conveyors to the spreader which in turn conveys the material across the open pit and onto the developing spoil bank. The system at the Big Brown Mine is composed of 2 BVE&apos;s and an across-the-pit conveyor while the Monticello system is made up of 1 BVE and a spreader. The BVE&apos;s prestrip overburden preparing a dragline bench for the final removal of overburden. Numerous evaluations, including lignite production requirements, economics, overburden characteristics, rehandle reduction, spoil stability, and the compatibility with dragline operations, led to the selection of the cross-pit spreader system at the Big Brown Mine. The system has proven itself as a viable and economical means of prestripping. The system&apos;s success at the Big Brown Mine led to the development of a second such system at Monticello. The advent of the cross-pit spreader system is viewed by Texas Utilities Mining Company as a viable solution to recovering deeper lignite reserves in a safe and economical manner.

Jan 1, 1993

By W. M. Tuddenham

It would be most difficult to place a date on the beginning of the revolution in analytical techniques that we have witnessed in recent years; but there is no question that the period since the end of World War II has seen a major change in thinking with respect to control and accounting analyses. For reasons relating to competition, much of this change was brought about in the chemical industries and only more recently has begun to affect directly the mineral industries. In considering the subject outlined in the title of this paper, one might well be tempted to discuss solely the more exotic methods of control and automation which have come into being in the past short while. In this paper, however, an attempt will be made to take a broader view and consider not only the application of newer purely physical methods of control but also those phases of chemical plus physical analyses that have bearing on our industry.

Jan 1, 1962

By William J. Miles

The major health hazard from exposure to crystalline silica historically has been silicosis. Silicosis is the scarring of the lung from excessive exposure to crystalline silica. It has been recognized as an occupational disease for over two thousand years, since early Greek physicians noted the respiratory problems of miners, stonecutters, and quarrymen who were exposed to excessive quantities of mineral dust. During the industrial revolution, the incidence of the disease was greatly increased by the use of machinery which increased dust levels. Subsequently, the need for dust control was recognized and dust control measures were instituted. Silicosis is characterized by progressive breathlessness on exertion and develops over the course of years. X-ray images of the lungs show progressive scarring of the lungs. The symptoms are related to the amount of exposure to crystalline silica and the years of exposure.

Jan 1, 1990

By Trevor R. Ellis

Minerals appraisers/valuers often find great difficulty in attempting to employ the sales comparison approach to the market value appraisal of development and operating stage mineral properties. An important factor generally overlooked is a comparison of net operating income (NOI) margins on a per-unit-of-production basis between mineral properties, whether these be demonstrated or forecast margins. NOI margins can vary greatly between mines or quarries that are producing similar products. Ultimately, the expected NOI margin determines what a buyer is willing to pay for an income-producing property. Here, common criticisms of the sales comparison approach by mineral appraisers are introduced. These are counterbalanced by raising some issues in the way the inputs for the income approach are usually derived by minerals appraisers and by review of some conspicuous examples of the much-too-common misuse or abuse of the income approach in market value mineral appraisals. Example transaction analyses and sales comparison analyses are used to demonstrate the author?s methodology for adjusting units of resource in his transaction adjustment tables. The examples are used as the basis for a discussion of ways to employ adjustments for operating economics and many other factors, while warning against the potential for double counting. The conclusions include a recommendation that minerals appraisers attempt to apply at least two of the three valuation approaches when appraising the market or fair value of development and operating stage mineral properties, the two being the sales comparison and income approaches.

Jan 1, 2011

By John Barber

The Deep Ore Zone (DOZ) Mine is PT Freeport Indonesia&apos;s (PTFI) newest operation. Production at the mine began in September 2000. The DOZ Mine produces 25 kt/d (27,500 stpd) using mechanized block cave mining methods. The DOZ Mine has several major improvements when compared with previous block cave mines in the district. It has an independent and improved ventilation system, a flexible and efficient truck haulage system, and a more reliable crushing and conveying system. PTFI&apos;s copper and gold mining complex is located in the Ertsberg mining district in Irian Jaya, Indonesia (Fig. 1). The Ertsberg district is located in the Sudirman Mountains at elevations from 3,000 to 4,500 m (9,800 to 14,700 ft) above sea level. The topography is extremely rugged and rainfall in the mine area averages 3,000 mm/a (118 in./year). Freeport began production in the district in 1972 when the mill began processing ore from the Ertsberg openpit. Underground mining began in 1980 when the Gunung Bijih Timur-Ertsberg East (GBT) Mine was brought online using block caving methods. In 1991, the GBT Mine reached a maximum production rate of 28 kt/d (31,000 stpd). Ore from the mine was exhausted in 1994. The Intermediate Ore Zone (IOZ) was brought into production in 1994. It, too, used block caving methods and had a design rate of 10 kt/d (11,000 stpd). The IOZ is currently producing at a rate of 21 kt/ d (23,000 stpd). The DOZ was discovered in the mid-1980s by deep drilling from the GBT. The GBT, IOZ and DOZ deposits are all situated in the Ertsberg East Skarn System (EESS). In 1993, the first of several studies was completed that indicated that portions of the DOZ Mine could be economically mined using block caving methods. Limited development was started in 1995. Full-scale development and construction began in late 1997. The crusher and conveying system began operating during the first quarter 2000. The first of two main exhaust shafts has been com¬missioned, along with three of the four new main fans. The second exhaust shaft and fourth main fan will be in service by the end of 2001. Undercutting and production began in September 2000. The DOZ Mine will reach its design production rate of 25 kt/d (27,500 stpd) in 2003. A study is under way to determine if an ultimate production rate of 35 kt/d (38,500 stpd) is feasible.

Jan 1, 2001

By Matthew Geary, Stephen J. Marino, Jordan A. Schreiner

"INTRODUCTION Project Overview The Southeast Collector (SeC) is a new 15km long 3.0m internal diameter wastewater tunnel designed by Hatch Mott MacDonald (HMM) that twins the existing 2.6m diameter York-Durham Sewage System (YDSS) tunnel. Both sewage tunnels are located north of the City of Toronto in Ontario, Canada. The SeC provides much needed conveyance capacity for the rapidly growing York Region population, supporting development until 2036 and increasing sewage system security (Hatch Mott MacDonald and AECOM 2011). Construction of the SeC will also permit flows of the twinned section of the YDSS to be bypassed in order to clean, inspect and carry out any essential maintenance within the YDSS tunnel. Although owned and operated by York Region, the SeC spans two regional municipalities beginning upstream from the intersection of Ninth Line and Rouge Bank Drive in the City of Markham in York Region to the downstream Finch Avenue and Valley Farm Road intersection in the City of Pickering in Durham Region. See Figure 1 for the SeC and YDSS alignment. The project includes 19 shafts and chambers with depths ranging from 8 to 48m in addition to seven facilities supporting the operation and maintenance of the sewer. The construction contract was awarded to Strabag Inc. in July 2011 for $291M CAD. Construction Management services were provided by a joint venture team of Hatch Mott MacDonald and AECOM. Existing York-Durham Sewage System The YDSS tunnel was completed in 1979 and was constructed using an open shielded TBM with ribs and lagging temporary support, followed by installation of a 380mm thick unreinforced cast-in-place (CIP) concrete final lining. The YDSS sewer system has numerous connections that accumulate flows from various urban areas within York Region. The section of the YDSS twinned by the SeC flows under gravity conditions and had been putting a strain on the municipality’s potential for population and development growth having reached its maximum capacity of 420 ML/d. According to the York Region’s Water and Wastewater Master Plan, the existing YDSS would not have been able to handle wet weather flows past 2016 (Genivar and XCG Consultants 2009). The dependability of this section of the YDSS is also of concern because it is the main and critical connection between the sewer systems upstream and the downstream Duffin Creek Water Pollution Control Plant (WPCP)."

Jan 1, 2016

By Chee Theng

"Getting minerals out of ores is messy, but mineral processors learn to have fun with it. Celebrating the innate joys of the industry was the theme of this year’s Colorado MPD Conference. At the same time, attendees dug deeper for insights into problems that continue to dog the community, including tailings dam crises, water resource challenges, and a dwindling number of academics to teach and train the workforce (see box).Tailings dam crisesMatt Fuller of Tierra Group International Ltd. brought some of the audience to tears with his impassioned talk on “The Infamous Legacy of Upstream Tailings Dams,” which won the conference’s Lou Cope award for best paper. The talk was especially poignant coming on the heels of the January tailings dam failure in Vale S.A.’s Córrego do Feijão iron ore mine in Brazil, the latest in a series of catastrophic dam failures over the past decade that includes the Fundão dam failure in 2015.Noting that the two dams share a common characteristic — both are upstream tailing dams — Fuller explained the three basic dam construction methods and why certain upstream tailing dams are susceptible to failure (Fig. 1). The downstream, centerline and upstream methods denote the direction the centerline of the dam crest moves with each successive raise in elevation of the dam. With the downstream dam, the foundation for future raises is essentially the same as that of the starter dam, he explained. With the centerline dam, half of the dam is constructed on the same foundation as the starter dam, and with the upstream dam, each successive raise is built out over the top of the tailings.“Downstream dams are expensive to build because each successive raise is bigger, so the sustaining capex to build them keeps growing,” Fuller said. Many decades ago, mine owners realized they could construct a starter dam, put their tailings through a hydrocyclone, generate a coarse sand fraction and stack the sand over the top of the tailings to build the next raise. “Then, there is no sustaining capex, it all comes out of operations,” Fuller added. The footprint is smaller, and it is a favorable means of retaining the tailings."

Jul 1, 2019

By Steven W. Hunt, Glen R. Frank

Assessment of abrasivity and cutter life are necessary to properly manage risks when tunneling in mixed face ground which includes ground with cobbles and boulders. Maximizing cutter life requires: (1) abrasivity and strength parameters for soil matrix and rock clasts, (2) methods of combining both, (3) proper selection of cutters and (4) modified TBM operation including use of boulder detection methods from the TBM to help make operation decisions. This paper presents approaches for addressing these factors sufficiently to improve tunneling success in mixed-face and cobbly-bouldery ground. Current laboratory abrasivity testing will be assessed along with equivalent quartz content correlations to soil matrix and rock clast abrasivity. New approaches to combining abrasivity testing of both the soil matrix and rock clasts for various cobble and boulder volume ratios will be suggested to estimate cutter life and intervention intervals. Methods for detecting boulders and using detection data to modify TBM operations to minimize boulder impacts are provided.

Jun 13, 2021

By D. L. Monroe

Technical service is assuming an increasingly important role in the sale of asbestos fibre,, Manufacturers are examining raw materials more closely than ever before in order to, obtain the most efficient usage in their processes. Asbestos is one of the more difficult materials to evaluate and consequently has been are of the last to be subjected to evaluation. The main problem encountered in the evaluation of asbestos fibre is that minor differences in grade and texture are not shown up by chemical analysis, and are identified only by specialized physical analyses or actual production use. However, such minor differences become more critical as manufacturing processes are made more efficient, and many purchasing agents and plant chemists are applying a closer scrutiny to their supply of raw asbestos fibre. Many processes have been formulated around grades and qualities of asbestos fibre, which were standard some time ago, but which may now be subject to modification and improvement.

Jan 1, 1959