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By K. Awuah-Offei

The objective of asphalt mix design is to produce a mix with optimal performance using available aggregate stockpiles. Often, this process does not take into consideration aggregate plant stockpile inventories or the cost of aggregate in the mix. This is due to the lack of tools that enable the lab technician or the engineer to optimize the mix for good performance while reducing the cost of aggregate and managing the stockpile inventory levels. The Bailey method provides useful guidance on aggregate gradation selection for optimal performance. This work presents a linear programming model of the asphalt mix design problem. The algorithm is implemented in MATLAB as an Asphalt Mix Design Optimization (AMIDO) program. The program is successfully validated with real-life data. The results show that AMIDO can be used to successfully produce any mix design with known Bailey method ratios. Also, RAP can be included in a design easily by making use of the Bailey method ratios and AMIDO. This work improves the state-of-the-art in asphalt mix design for dense graded mixes and could potentially be modified for other mixes.

Jan 1, 2009

By W. J. Schlitt

The development of forced aeration as an approach to enhancing copper sulfide leaching is traced from its earliest development up to present day operations using this technology. Both large-scale field tests and commercial operations are covered. The historical portion is preceded by an introductory discussion of the role of air (oxygen) in sulfide leaching. Sufficient aeration may be achieved via naturally induced convective airflow. However, cases are identified where this is insufficient, leading to retardation of the sulfide leach rate. For these situations, forced aeration may be beneficial. The historical portion of the paper focuses on the major field tests that have been conducted in Montana, Nevada and Utah, along with commercial operations in the United States, Australia, Chile and Peru. The paper concludes with some general comments about the applicability of forced aeration, which are based on the information developed to-date.

Jan 1, 2006

The largest investment in mining equipment in Caterpillar?s history ? The F series mechanical and electrical drive trucks ? is rapidly advancing. Caterpillar showcased the 793F and 797F mechanical drive trucks and the 795F ac electric drive truck at MinExpo in 2008 and have continued testing since then. The 793F and the 797F have accumulated more than 75,000 hours of field testing and have proven their performance capabilities and their durability. The new Cat C175 engine that powers them has racked up 130,000 hours of field testing in mining trucks and more than 120,000 hours in power systems. Because of the success of these field-follow programs, the 793F is targeted to go into full production within a few months and the 797F late this year. Caterpillar engineers have been testing two 795F ac prototypes at the Tucson Proving Grounds in Arizona. The development program has provided input for the construction of a new 795F ac in Decatur, IL. The new truck recently shipped to a copper mine in North America where it will serve as the first field-follow 795F ac as it works at the mine. The 313-t- (345-st-) capacity 795F ac will enter a new size class for Caterpillar, and, as a result, the primary focus of the Caterpillar ac electric program has been on the 795F ac. The commercial launch date will be defined as the field-follow program progresses. ?It?s fitting that soon after producing the 50,000th Cat off-highway truck, we are now shipping our first ultra-class ac electric drive truck to a mine,? said Chris Curfman, president of Caterpillar Global Mining. ?Our new trucks further solidify our position as the one manufacturer to provide unparalleled options and unmatched customer support.?

Jan 1, 2009

By A. Ramage

Since late 2010, CH2M HILL has been working with a confidential client who holds a long-term commitment to sustainable development (SD). The commitment is aligned with all three elements of the triple bottom line: people and society, ecosystems and environment, and financial and economic systems. These commitments are carried forward by the firm?s executives, managers, and operational sites, and are evident in materials posted on the company?s public website. These materials include a formal sustainability report prepared in accordance with the Global Reporting Initiative (GRI) guidelines (GRI, 2006), a report that outlines key SD challenges and progress toward the GRI targets, and a delineation of risks and opportunities outlined in the firm?s Form 10-K and Annual Report. In keeping with its commitments to SD targets, our client wished to consider SD issues in its decision processes for facility expansion or new projects. The company engaged CH2M HILL to meet this goal, based on working relationships established through existing contracts and CH2M HILL?s leading capabilities in sustainable solutions.

Jan 1, 2012

By G. Caron, M. Boisclair

In 2005, CANMET-MMSL used its pool of expertise in ground control, open pit and underground mine engineering, mineral processing, information technology and applied mineralogy to launch a mine-to-mill research project. The objective of the project was to optimize the distribution of rock breakage energy among blasting, crushing and grinding activities, thereby maximizing the efficiency of energy utilization within comminution processes. Tests were designed to demonstrate that this approach could reduce the energy consumption, thus contributing to the reduction of Green House Gas (GHG) production in the Canadian mining industry. The project was accomplished in collaboration with DynoConsult and Dyno Nobel Canada Inc., a world leader in commercial explosives. Data analysis from 12 blasts (six with electronic and six with pyrotechnic detonators) in three different geological formations of a quarry (soft, medium and hard rock) shows that electronic blasting technology increases rock fragmentation by 15% (in hard rock) to 20% (in soft rock). A more uniform rock fragment size distribution is also obtained. The impact of the improved quality blast product on downstream processes of the quarry is a productivity increase of 5% in rock excavation and transportation, an energy reduction of 10% at the primary crusher and an increase of 15% of the primary crusher throughput. A soft-sensor prototype, based on primary crusher data (i.e. energy consumption, throughput, feed and product size distribution) and a simplified computerized process model, was developed for on-line measurement of the rock operating work index. Additionally, 385 rock samples and specimens were collected and prepared to determine the tensile and compressive strength of the rock material, to evaluate the aggregate crushing work index, and to examine the development of micro- and macro-fractures by means of binocular and SEM microscopy. Blast-induced rock damage was evaluated at the end of the laboratory testing program. Even though a reduction of rock hardness of around 30% was observed after blasting, the impact of the blasting method (i.e. use of electronic or pyrotechnic detonators) on the induced rock damage could not be observed. It is either absent or not perceptible with the accuracy of the measuring techniques and the number of samples analyzed.

Jan 1, 2007

By Frederic Souche, Andrew R. Klaetsch, Brian Hann, Nick Goodenow

This paper describes support of excavation (SOE) design and construction for three large diameter shafts excavated through glacial soil and controlled blasting in complex sedimentary rock formations. SOE in soil consists of unreinforced secant pile rings designed to resist lateral pressure in circumferential compression, eliminating costly steel core beam reinforcing. Controlled blasting at the shafts, adits, and tunnels in densely populated neighborhoods requires managing risks to the public, buildings, and utilities. Controlled blasting approaches limited adverse impacts to receptors nearby while achieving adequate production and fragmentation. A site-specific observational approach was used to adjust blasting parameters, limiting the impact on local stakeholders while maintaining daily progress and managing overbreak.

Jun 13, 2023

By M. A. Reyes, L. Yan

Heat and humidity buildup withn refuge alternatives (RAs) may expose occupants to physiological hazards such as heat stress. The Mine Safety and Health Administration (MSHA) regulations require RAs in underground coal mines to provide a lifesustaining environment for miners trapped underground when escape is impossible. RAs are required to sustain life for 96 h while maintaining an apparent temperature (AT) below 95 °F (35 °C). The National Institute for Occupational Safety and Health (NIOSH) tested a 10-person tent-type RA, a 23-person tent-type RA, and a 6-person metal-type RA in its underground coal mine facilities to investigate the thermal environment over a 96-h period. The test results showed that mine air and mine strata temperatures surrounding an RA occupied by simulated miners (SMs) increased over the 96-h test period. The test results suggest that RA manufacturers should consider this increase in temperatures when calculating and evaluating RA components during surface and laboratory tests. The findings can equip stakeholders with additional considerations for calculating the interior heat and humidity temperature profiles for occupied RAs not tested in situ.

By Jack Bedder, Nils Backeberg

"Native antimony metal is rare and antimony generally occurs together with gold, lead, copper and silver. There are more than 100 antimony minerals, although the sulfide mineral stibnite is the main economic mineral.Antimony enters the supply chain either as a result of mining (primary production) or recycling (secondary production). China has by far the largest antimony resources and is, as a result, the world’s center for antimony mine production. While China remains the leading primary producer, accounting for 69 percent (80.5 kt or 88,700 st) of the global 117.5 kt (129,000 st) in 2017, market consolidation and regulatory inspections across China leading to closures of facilities have caused a significant decrease in Chinese output from 115.8 kt (127,600 st) in 2015 (81 percent of global production).Tajikistan and Russia are the next largest producers of antimony after China, both ramping up production in recent years. Russia could significantly increase its supply of antimony if Polyus moves ahead with supplying 10-12 kt/a (11,000–13,200 stpy) of contained antimony from gold tailings. Australia and Bolivia are also significant mine producers outside China. The value of the different ores varies based on the metal content of the concentrates, with the most valuable gold-bearing ores sourced from Australia’s Costerfield Mine and the least valuable mercury-bearing ores sourced from the Anzob Mine in Tajikistan. On average, Bolivian and Russian ores trade at an intermediate value between those from Costerfield and Anzob. Nearly all of the rest-of-world production is exported to China, where the ores and concentrates are processed into antimony ingots and oxides.Antimony ingot production is not as widespread as is the case with antimony mine production, owing to the high levels of pollution that are associated with antimony smelting. It is for this reason that smelting has been largely confined to China and other Asian countries ,such as Vietnam and Myanmar, where environmental legislation has historically been less stringent. Tajikistan has become a growing producer of antimony ingot since 2014, coming from the commissioned metallurgical plant at the Anzob Mine.Antimony oxide production is undertaken on four continents with China being the biggest producer. There is also a considerable amount of oxide production in Europe (mainly Belgium and France), which relies on imported antimony metal feedstock, mostly from China.A new antimony project under construction by Strategic and Precious Metals Processing (SPMP) in Oman made progress in 2016 and 2017, and after producing first metal in April 2016 in test facilities, was set to be commissioned in the first quarter of 2018. Commissioning had been moved back to June 2018, with a potential ramp-up to 2-3 kt/a (2,200 to 3,300 stpy) of antimony metal by the end of 2018. SPMP is also reviewing producing antimony oxide as part of its flow sheet."

Jan 7, 2018

By Felix E. Mutschler

Alkaline rock-related precious metal deposits include: • orthomagmatic platinum group elements (PGE) ± gold (Au); • porphyry copper-silver-gold (Cu-Ag-Au, ±PGE); • epithermal Au-only, and Au-Ag-base metals; • submarine exhalative Kuroko-, Cyprus-, seamount- and Yellowjacket-type deposits; and • enigmatic deposits akin to Olympic Dam. Coeval epithermal deposits related to porphyry deposits suggest the two types represent separate immiscible fluids evolved in oxidized, CO2-rich alkaline magma chambers. Alkaline rock provinces develop above mantle hot-spots, but crustal structures control the final distribution of magmas and ore fluids. Prospecting guides for alkaline rock-related precious metal deposits include the presence of evolved alkaline rocks, pervasive K-metasomatic, redox and carbonatic alteration and low level Au (±Te, etc.) anomalies. Although alkaline igneous rocks crop out in less than 1 % of the area of the North American Cordillera and craton, alkaline rock-related ore deposits have produced nearly 13% of the total United States and Canadian lode gold production. Large (31-t or 1 million-oz) deposits are common (Fig. 1), and additional deposits and reserves are being discovered. New genetic models are evolving, making alkaline rock-related precious metal prospects attractive exploration targets.

Jan 1, 1991

By E. A. Sarver

The Fe(II) regeneration process is an important aspect of Alternate Anode Reaction Technology (AART) for copper electrowinning (EW). In AART, Fe(II) is oxidized to Fe(III) at the anode during EW, and it must be regenerated to maintain recyclable electrolytes. Regeneration is achieved via Fe(III) reduction by SO2(aq), and the reaction is catalyzed by activated carbon particles. To better understand this process, a kinetic model was developed and experimentally validated for the Fe(II) regeneration in the current work. The investigation focused on the primary reaction mechanism and the reaction rate dependence on four variables: carbon particle size, flow rate, initial Fe(III) concentration and initial SO2 concentration. The Fe(II) regeneration reaction is mass-transfer controlled in the presence of activated carbon. Carbon particle size and initial Fe(III) are the most influential factors under the conditions tested. Initial SO2 concentration is insignificant to the reaction rate.

Jan 1, 2007

By C. A. Young, J. D. Miller

The surface chemistry of the calcite/oleate flotation system was examined by in-situ FT-NIR/IRS. Spectra of combination and overtone bands of aliphatic stretching vibrations revealed gauche/trans conformational changes that occurred solely as a function of temperature. The conformational changes were attributed to the simple "melting" behavior associated with phase transitions. It was concluded that chemisorbed oleate at calcite surfaces is gel-like at temperatures below 22oC, resembles a coagel between 22oC and 31oC, and becomes micelle-like at temperatures above 31oC. By comparison, chemisorbed oleate at fluorite surfaces also undergoes these phase transitions but is additionally dependent on adsorption density. The conformational changes were observed at high chemisorption densities (> 2.0x10-10 mol/cm2) and attributed to molecular forces, primarily van der Waal's interactive forces, among neighboring chemisorbed oleate molecules. Similar analysis of in-situ FT-NIR/IRS spectra of surface-precipitated calcium dioleate at calcite surfaces did not exhibit this behavior thereby confirming that surface-precipitated calcium dioleate remains in an all-trans conformation. The results help explain why surface polymerization is not observed at calcite surfaces but is observed at fluorite surfaces.

Jan 1, 2002

Several common ratios used for determining spontaneous combustion activity rely on comparing the amount of various products of oxidation with the amount of oxygen consumed to produce these products. As coal gets hotter, oxidation reactions become more efficient meaning more products produced for less oxygen consumed. There are many problems associated with accurately determining the true amount of oxygen used. These problems relate to the monitoring technique (and its associated uncertainties) used to generate the results, deficiencies in the established equations utilized in calculations, dilution with other gases and other sources of oxygen depletion. Typically the oxygen deficiency is over estimated, resulting in the under estimation of the indicating ratio. For this reason the use of ?one off? calculations to determine the status of the underground environment is not recommended. Instead trends of these ratios should be used to identify increases which indicate an increase in oxidation intensity. This paper outlines problems associated with the monitoring techniques and equations used to determine the oxygen deficiency.

Jan 1, 2009

By H. Lawson

The Mine Safety and Health Administration (MSHA) issued Program Information Bulletin P09-03in April of 2008, providing formal guidance on using programs that model the redistribution of stress during underground mining of coal. A key part of this guidance is visual observation and mapping of ground conditions. If a correlation between ground conditions and model output can be established, the model is considered to be verified, and can be used to guide mine design in similar ground. A simple scale is recommended for ranking observed roof, rib, and floor conditions. This paper discusses optimization and implementation of a ground condition rating scheme in the gateroads of a deep underground longwall coal mine. Roughly 80% of each gateroad length deteriorated in a fairly uniform manner. However, this manner varied between gateroads, as did pillar size. The implementation of a ground condition mapping program, similar to that recommended in PIB 09-03, was successful in characterizing the ground response to mining in gateroads of a longwall coal mine.

Jan 1, 2012

By K. Oraee

The empirical rock failure criteria play an important role in predicting the mechanical behavior of rocks, since affecting parameters on the behavioral properties of rocks are complex and numerous. Usually the empirical failure criteria are obtained by statistical methods, namely by means of fitting the mathematical function onto the experimental data. For evaluation and verification of the results, however, the quality and accuracy of the fit must be considered. This paper studies the efficiency and accuracy of conventional empirical rock failure criteria using a new approach, which is based on the analysis of uncertainty amplitude on the constant parameters of each criterion. The approach adopted here, is based on the combination of some parameters such as Mean Squared Error (MSE), Root Mean Squared Error (RMSE), type of function, degree of freedom and the confidence level of constants. Correlation coefficient (R2) is then a comprehensive test and can be used effectively for comparison and accuracy of empirical rock failure criteria.

Jan 1, 2012

By Christy Z. Lueders

Introduction More and more women engineers are joining the traditionally male mining industry. Are they successful? Do they encounter special problems? How do men in mining respond? How can the mining industry effectively use its female resources? What contributes to the success of a woman in mining? What can male engineers do to ease the entry of female professionals into the workforce? An STM survey conducted last spring provided some answers to these questions. All BS graduates in mining, mineral engineering, and extractive metallurgy from 1960-1979 were surveyed. Nearly 60% of the female graduates, from 17 universities, completed questionnaires. The women were asked why they chose mining, how they relate to predominantly male co-workers, what job skills they have gained, and what areas of work they most enjoy. They were also asked how problems of a two-career family are solved. Data were gathered on salaries, titles, specialties, and products handled. Respondents, assured of confidentiality, are identified only by title. Many male mining executives were also questioned for their advice to women in mining. Profile of the Survey Participant The "typical" female mining engineer works with coal, is employed by an operating company, feels she works very hard to prove her abilities, does not want to be treated as an anomaly, and someday wants to be an independent consultant. Of the respondents, 44% listed coal as the most familiar product, 12% said copper, and the rest listed products from industrial chemicals to oil. Titles varied widely but women managers are rarely found. However, the majority of the survey population graduated after 1976 and thus lacks substantial experience. Of 102 female graduates, only 25 graduated before 1977. Since then, there has been a steady increase. The American Association of Engineering Societies reported that in 1980 more than 100 degrees were awarded to women in minerals engineering. Education Highly Valued Twenty-two percent of the women surveyed had graduate degrees, 38% planned further education, and 12% listed a PhD as their goal. The majority of graduate degrees are in technical fields. There were only two MBAs. Five women intended to pursue law degrees, and one woman, with a mining engineering degree and an MBA, is a part-time law student. Along with advanced education, the women agree that production experience is needed for career advancement. However, only 28% of the women have worked in production. Many women, especially younger grads, commented that these are the toughest jobs to get. This is a universal complaint, from males as well as females, though women seem to encounter more opposition. Several women mentioned they were small or slight of build and managers tended to shy away from hiring them for production jobs. Two-Career Marriages The most difficult problem for two-career couples is relocation. Whose career takes priority? Fifty percent of the women said transfers or offers would be examined on a case-by-case basis, weighing pros and cons for both parties. The husband's career took priority with 47% of the women; their own careers, with 3%. These statistics conflict with comments from two employee relations managers. Both said most female engineers they've encountered are married to men who follow their wives' careers. Seventy per cent of the married respondents said their husbands were also engineers. Four said their husbands were engineers at the same company. Some male and female engineers met on the job; others joined the company as a "package deal." Both partners being engineers can ease relocation problems, since an area or company offering one spouse a job can often provide a spot for the other. A company may benefit by getting two new hires for the relocation costs of one. Most companies contacted have policies that allow married couples to work at the same division, but discouraged them from working in the same department. With 40% of today's marriages ending in divorce, one risk is that one or both parties may quit. One personnel executive said there were several couples, each spouse in a different discipline, who were work¬ing out very well at his division. However, he recognized the potential for problems if, for instance, one gets promoted and the other doesn't, or salary increases are unequal. The personnel executive said he has actively recruited married couples, and would again, were each person competent.

Jan 10, 1981

In this study, the flotation performances of ethoxycarbonyl thionocarbamate (ECTC), dialkyl thionocarbamate (DATC) and xanthate copper sulfide collectors are compared by the structure-reactivity relationship using generalized perturbation theory and density functional calculation at the B3PW91/6-31G(D) level. The electron-donating power of xanthates is strong and, therefore, xanthates can strongly react with metal cation on the surfaces of copper and iron sulfide minerals through the formation of normal covalent bonds. This explains the poor selectivity of xanthates and also the high pH levels (above 13) required for the flotation separation of copper/iron sulfide minerals. DATCs are more selective for copper sulfide flotation, particularly against gangue iron sulfides. Although less powerful than xanthates, DATCs can perform copper/iron flotation separation at lower operating pH (commonly at pH levels below 11.5). ECTCs use an ethoxycarbonyl replacing an alkyl N-substituent in DATCs. The presence of the ethoxycarbonyl group effectively changes the functional group of collector from -C(=S)NH- to -C(=S)NHC(=O)-. The strong electron-withdrawing ethoxycarbonyl group adjacent to the C=S group decreases the electron density of the sulfur atom, which improves ECTC?s selectivity against iron sulfide minerals at slightly alkaline conditions. The lowest unoccupied molecular orbit (LUMO) of ECTC, which is constituted by the pz-orbit of every atoms in the conjugate -O-C(=O)-N-C(=S)-O- group and which is pleased with accepting richly d-orbital electrons (feedback electrons) from the (t2g)6(eg)3Cu(II) or t6e4Cu(I) configuration of copper cation on the surfaces of copper sulfide minerals, resulted in the formation of dative p-bond. The iron atom, which has a (t2g)6Fe(II) or (t2ga)3(ega)2 Fe(III) configuration on the surfaces of iron sulfide minerals (Fe(III) is the predominant composition at alkaline conditions), has difficulty in offering its d-orbital electrons (feedback electrons) to ECTC?s LUMO. ECTC collectors are powerful for copper sulfide minerals and very selective against iron sulfides, which has been further confirmed by UV spectra and bench-scale and industrial-scale flotation tests.

Jan 1, 2008

Effective gas management in coal mines, as well as proper ventilation design, is very important for maintaining the safety of underground coal miners. Advances in numerical modeling techniques have enabled evaluations of the coal mining environment using advanced grid designs and computed gas distributions through detailed mathematical models. These models help engineers to see the unseen areas of the mine through visualization of the data and ultimately help improve worker safety. This paper summarizes the modeling efforts conducted by NIOSH in the U.S. and CSIRO in Australia to address various gas management issues encountered in longwall mines. The modeling studies involved two of the most widely used grid-based techniques, namely computational fluid dynamics (CFD) and numerical reservoir modeling. This paper discusses the application of these techniques for gob inertization and gas control for spontaneous combustion, pre-mining degasification of coalbeds, gob gas venthole design and performance evaluation in longwalls, and gas management during development mining.

Jan 1, 2009

By M. L. Tucker, William H. Langer

Many countries, provinces, territories and states in the European Union, Australia, Canada, the United States and elsewhere have begun implementing sustainability programs. Most of those programs, however, stop short of sustainable management of aggregate resources. Sustainable practices do not always have to be conducted under the title of sustainability. This case study describes how Lafarge implemented the principles of sustainability even though there was an absence of existing local government policies or procedures addressing sustainable resource management. Jefferson County is one of three counties in the six-county Denver, CO, region that has potentially available sources of crushed stone. Crushed stone comprises 30percent of the aggregate produced in the area. And it plays a major role in regional aggregate resource needs. Jefferson County is home to four of the five crushed stone operations in the Denver region. Lafarge operates one of those four quarries.

Jan 1, 2004

By P. J. Bethell

Background Increasingly complex geological conditions, with the presence of high ash binders in the mining horizon were encountered at the A.C. I. Dugout Mine near Price, Utah. This led to the production of high ash coal from the Dugout Mine during 2003 and 2004. This material had poor marketability and posed operating issues for the utilities burning the coal. Ash levels increased from typical levels in the 9-12% range to between 15 and 25%. etween 15 and 25%. Reviews of the mine plan and expected geological conditions indicated that further periods of high ash production could be expected. Action Plan Detailed sampling of the mine high ash production was carried out. The majority of the coal from the Dugout Mine is trucked to the Savage Coal Terminal (SCT) at Wellington, Utah where it is stored in multiple piles by quality. Coal at the mine is segregated by a CoalScan 2600, on-line analyzer into high ash, low ash and rock chute (waste material). From these piles, the material is crushed prior to shipment to SCT. The samples obtained from the various high ash piles were subjected to detailed sizing and washability analysis. Once this information was obtained, alternative circuit configurations were evaluated to process this material into a salable product. Water supplies in the arid terrain where the plant is located are scarce. This factor played a part in the final circuit design.

Jan 1, 2008

By A. Mahmoudkhani

There has been a continuous interest in chemical aids for processing Canadian oil sands by hot water extraction process since the first commercial industry operation in 1967. Several inorganic and organic chemical systems have been introduced, of which sodium hydroxide is the most widely used extraction process aid by major producers. Use of NaOH, however, results in accumulation of sodium ions in recycled water, causing higher clays dispersion and producing tailings with poor geotechnical properties that turn into mature fine tailings. This is especially true for low grade and oxidized ores, which present the greatest challenges in bitumen recovery and produce the major portion of fine tailings. In this paper, we are presenting a novel method based on use of inorganic polymers as process aids for various low grade oil sands ores. Denver flotation cell and a laboratory scale hydrotransport loop were utilized to evaluate the effect of chemical dosage and operating parameters on the processability of oil sands samples from Athabasca region. Process tailings were examined for properties such as water chemistry, suspended solids, settling rate and the ease of tailing treatments. Our results demonstrate that the use of inorganic polymers during the froth process lead to a significant improvement in bitumen recovery from low grade oil sands and can improve further tailing treatments. This offers a viable solution that can be easily incorporated into current processing facilities and deliver several operational and economical benefits. Advantages in use of inorganic polymers versus sodium hydroxide are presented in details.

Jan 1, 2012