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By Sara J. Heinlein, George Malkos, James E. Lindell, Tony Pestonatto

The 79th Street Water Tunnel Extension Project was initially designed by the City of Chicago, Department of Public Works, to increase the capacity of the City’s south side water distribution system. MWH preformed a design review, prepared the final design and provided construction management for the City of Chicago Department of Water. Construction commenced in September 1995 and was completed in October 1999. The Project connected two existing water tunnels with a new 5.8 km (19,044 ft.) long, 4.9 m (16.08 ft.) finished diameter concrete lined rock tunnel utilizing TBM, drill-blast and mechanical hoe-ramming methods. In addition, approximately 61 meters(200 feet) of concrete lined variable cross section tunnel, a new gate shaft and a temporary construction shaft were constructed. This paper describes the construction of these features and the geological conditions encountered.

Jan 1, 2003

By P. R. Taylor

Three refractory gold concentrates have been tested to evaluate the effect of roasting with hydrated lime followed by cyanidation. The results indicate that it may be possible to roast in such a manner as to contain nearly all of the sulfur, arsenic and antimony in the roaster calcine. Cyanidation results indicate that the gold recoveries are greater than 80% for all three concentrates.

Jan 1, 1993

By I. Iwasaki, H. Dho

Two aromatic-type chelating agents, 1,10 phenanthroline (phen) and 8-quinolinol (quip), were tested as specific depressants for magnetite in the cationic silica flotation of magnetic taconite concentrates. Micro and batch flotation tests, along with zeta potential and adsorption measurements, were used. In the presence of a cationic collector, dodecylammonium chloride (DAC), the Fe/phen surface chelate electrostatically repelled DAC, and the magnetite was depressed. The negatively charged Fe(quin)2(OH)2- on the magnetite surface attracted the cationic collector and made magnetite floatable.

Jan 1, 1997

By D. Tao

More than 80 million metric tons of fly ash is produced annually in the U.S. as coal combustion by-product. Fly ash can be converted to value-added products if unburned carbon is reduced to less than 2.5%. However, most of fly ash is currently landfilled as waste due to lack of efficient purification technologies to separate unburned carbon from fly ash. A rotary triboelectrostatic separator has been developed and patented recently at the University of Kentucky with unique features. Several fly ash samples have been used to understand the effects of major process parameters on the separation performance. The results show that compared to existing triboelectrostatic separators, the rotary triboelectrostatic separator has significant advantages in particle charging efficiency, solids throughput, separation efficiency, applicable particle size range. Key words: Coal, Combustion Waste; Fly Ash; Particle charging; Separation.

Jan 1, 2008

By S. K. Kawatra, Harrison R. Cooper

In the last 30 years, on-¬stream slurry analyzers have proven to be of great use in the control of mineral processing circuits. This review discusses the two most popular methods, x-ray fluorescence and neutron activation analysis, and also considers techniques which are still under development.

Jan 1, 1986

By Q. Feng

Study has been carried out to apply fly ash as a high strength, water-resistant precast construction material through geopolymerization. Experiment results show that the working conditions such as water content, the concentration of NaOH, curing temperature and curing time, significantly affect the mechanical property of geopolymer matrix. Through optimization, an above 100 MPa compressive strength has been achieved with the geopolymerization products. Water soaking tests show that the geopolymerization product has a very high water resistance without losing noticeable compressive strength even after a one month soaking time. To elucidate the geopolymerization mechanism, microscopic techniques such as SEM/EDS and XRD are also applied to investigate the microstructure, the elemental and phase composition of geopolymerization products. The findings of the present work provide a novel method to apply fly ash as a high strength water-resistant precast construction material. INTRODUCTION Geopolymerization is a process of obtaining a polymeric structure from aluminosilicate by dissolving aluminosilicate sources in a strong alkali (NaOH) solution and condensation of free [SiO4] and [AlO4] tetrahedral units (Davidovits, 1985 and 1988; Duxson et al, 2005; Xu et al, 2000, 2002). After being cured at an elevated temperature for a specific time, the geopolymerization product shows a greatly increased compressive strength. Therefore, the product can be used as construction material such as bricks and road pavement. It provides a very promising method to apply aluminosilicate sources such as fly ash as a construction material for a sustainable development. Fly ash is a main industrial waste which needs to be carefully impounded because of its potential impact on environment. Many efforts have been tried to utilize fly ash as construction materials substituting Portland cement because of the following reasons. First, fly ash is a silica/alumina rich aluminosilicate source, which makes the specific material an ideal source for the geopolymerization process. Secondly, the particle size of fly ash is usually very small (< 50 microns) and it saves a lot of energy consumed during the production process of cement for grinding. Thirdly, fly ash is an ideal source for geopolymerization because it is reactive to alkali even at a mild temperature. In the past twenty years, many studies have been carried out on the geopolymerization of fly ash to a make construction material. However, there are some disadvantages associated with the conventional methods of treating fly ash (Palomo et al, 1999; Perera et al, 2007; Temuujin, et al, 2009; Hanjitsuwan et al, 2014). First, in most of the proposed geopolymerization methods, a salient amount of sodium silicate has to be added. It therefore makes it complex whether the achieved mechanical strength of geopolymerization products is due to a real geopolymerization process between fly ash and alkali or just largely the solidification of metal silicate in air at an elevated temperature. Secondly, the authors have noticed that when the geopolymerization product is soaked in water, the solution pH increases sharply and the products will lose its compressive strength gradually in water. Thirdly, the compressive strength of the geopolymerization product as reported is usually less than 50 MPa.

Jan 1, 2019

By D. W. Park

Underground openings resulting from coal mining activities have been a serious cause of subsidence problems in the Warrior coalfield of Alabama, which is the 11th largest coal-producing state in the United States (National Coal Association, 1986). The problem will be even more serious in the future because 17 Gt (19 billion st) of Alabama&apos;s 22 Gt (24 billion st) of coal reserves are classified as an under- ground resource (Tolson et al., 1982). Subsidence data in this area has been scarce com- pared with other coalfields (Conroy, 1980; Dunrud and Osterwald, 1980; Gentry and Able, 1978; Hunt, 1979; King and Gentry, 1979). This paper discusses the results of a study of subsidence overlying two longwall mines that contrast each other. One of them (Mine #1) is a shallow longwall mine where the coal strength is very high, and the other mine (Mine #2) is extremely deep with a low strength of coal.

Jan 1, 1987

By Keith Sarbutt, I. Jackman

The recovery of gold from a high grade telluride/sulphide flotation concentrate was investigated. Conventional cyanidation resulted in very slow rates of gold extraction. Historically, the refractory nature of tellurides has been overcome by fine grinding, the use of excess lime and long leach times. In some instances, pre­oxidation of the tellurides has also been necessary, to render the gold soluble in cyanide solutions. The former conditions did improve the rate of gold extraction from the present sample, but final recovery was still unacceptable. Chemical oxidation of the tellurides and leaching with oxygen improved gold recovery further. However, it was found that simple modifications to the cyanidation conditions overcame the detrimental effects of the complex chemistry involved in leaching a telluride concentrate. The incorporation of a solution change, or the application of a carbon-in-leach procedure increased the recovery of gold to over 97 percent in 96 hours. In every case, leaching was enhanced by the addition of lead salts.

Jan 1, 1990

By E. McCullough, S. Gaillard

"Diesel particulate matter (DPM) remains a health concern in many underground metal/nonmetal mines, and has been regulated by the Mine Safety and Health Administration since 2002. While the NIOSH 5040 standard method for DPM monitoring is required to demonstrate regulatory compliance, the FLIR Airtec DPM Monitor can serve as complementary engineering tool. It is a handheld instrument that offers near real-time measurements. As part of an ongoing field study, the Airtec has been used to survey elemental carbon concentrations (a proxy for DPM) in an underground stone mine. Via “spot-checking” and more prolonged area monitoring, this effort was aimed at determining spatial and temporal DPM variation in several key locations. INTRODUCTION Diesel particulate matter (DPM) is the solid fraction of the exhaust emissions from a diesel engine. It is largely made up of elemental and organic carbon (EC and OC, respectively), which can be measured as proxies for estimating mass concentrations of DPM. The National Institute for Occupational Safety and Health (NIOSH) considers DPM to be a health hazard and potential carcinogen [1]. It is believed to cause and/or exacerbate respiratory illness upon inhalation, deposition, and retention in lung tissue [2]. Since DPM exists in both the micro- and nano-particulate ranges, it can surpass typical auto-immuno defense mechanisms that keep larger particles out of the respiratory system [2]. Relative to other occupations, the DPM exposure potential for underground miners is high because these individuals work in enclosed environments where diesel powered equipment is frequently used [3,4]. A variety of engineering and administrative controls have been devised to reduce DPM exposures in underground mines, and increased airflow is often a key component of control strategies. In large-opening mines, which are most common in the metal/nonmetal sector, DPM abatement via increased ventilation can be especially complex due to moving and controlling the large air quantities [5]. The Mine Safety and Health Administration (MSHA) has regulated DPM exposure in metal/nonmetal mines since 2002. The final rule limits personal exposure to total carbon (TC, which is the sum of EC and OC) to an eight-hour time weighted average (TWA) of 160 µg/m3. To demonstrate compliance, operators must use the NIOSH 5040 Method [6]. However, the Airtec DPM Monitor (FLIR Systems, Inc., Nashua, NH) was developed as an engineering tool to provide near real-time measurements of both EC and TC for tracking personal exposures [7]. The portable Airtec works by capturing DPM on a filter and successively measuring laser extinction on the filter as DPM accumulates; the EC fraction of the DPM is dark, and so as it accumulates the filter becomes darker and absorbs more laser light [8]. The laser extinction value is directly correlated to EC, but since EC and TC are generally observed in consistent proportions (i.e., TC = EC*1.3), the Airtec is also programmed to display TC as a TWA [9]. There have been multiple studies conducted to validate the Airtec and the instrument has been adopted by some mine operators as a tool for their health and safety programs [3,8]."

Jan 1, 2016

By D. Dolinar, T. P. Mucho

Horizontal stresses are caused by global platetectonic forces. During 1995 alone they were largely responsible for the closing of two longwall mines in the United States. This paper presents six case histories from Pennsylvania, West Virginia, Kentucky and Alabama. In each case, a mine encountered roof falls or difficult ground conditions at the headgate caused by horizontal-stress concentrations. The problems are detailed, and the control measures adopted are described. In most cases, nearby longwall panels without stress concentrations were trouble free. The paper also discusses detailed measurements that were made at two adjacent Pennsylvania longwalls. One headgate was oriented to avoid a horizontal-stress concentration, and the other was not. Eliminating the stress concentration dramatically reduced roof support loads and roof deformation. The paper concludes that proper panel orientation and sequence is the key to maintaining headgate ground control. The optimum orientation is not parallel to the maximum horizontal stress, as previously thought, but rather it is 20o in the stress shadow of the gob. Other stress-control techniques, including artificial support, are briefly discussed

Jan 1, 1999

By Paul H. Johnson

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

Jan 1, 1973

By K. Whiting

In October 1993, the first two of a series of full scale passive biological treatment cells were constructed to treat mine drainage from the Burleigh Mine (located approximately 48 km west of Denver, Colorado in the Clear Creek/Central City Superfund Site). The two cells are each 19-21 m long, 10.7 m wide and 1.2 m deep. Each cell contains approximately 216 cubic meters of substrate (composted manure) and is designed to treat 60 L/min of mine flow. One cell is designed as an upflow reactor and the other cell is designed as a downflow reactor. The differences in flow hydraulics and treatment efficiencies will be tested in these two cell for approximately nine months before the remaining cells are built to treat all the discharge. The substrate material was selected based on a series of bench scale tests. During the tests, the amount of metals removed was determined. The design flow rate was based on a sulfide generation rate of 400 nanomoles of sulfide generated per cubic centimeter of substrate per day. Metal removal results for the first three months of operation of the two cells will be presented and compared to results of bench and pilot studies at other sites.

Jan 1, 1994

By R. Hogg, T. F. Dumm

Procedures for particle size analysis on respirable dust from coal mines have been evaluated. Using respirable dusts dispersed in a laboratory dust chamber, size distributions measured using cascade impactors have been com- pared with the results of a variety of laboratory sizing methods performed on samples collected on filters placed side-by-side with the impactors. The laboratory techniques included centrifugal sedimentation, laser diffraction/scattering and automatic particle counting. The general agreement among the various methods was very good, with systematic differences which can be attributed to the different definitions of size used. Simple conversion factors have been obtained which can be used to transform the laboratory data to equivalent aerodynamic sizes. Similar comparisons have been made on samples collected in underground coal mines. Again, the results are in quite good agreement although small discrepancies were observed in some cases. These have been attributed to some degree of agglomeration in the airborne dust, leading to slightly coarser apparent distributions in the impactor samples.

Jan 1, 1987

By Ava Walker

The first form of a surety bond was an honest handshake between two or more parties agreeing to a decision, and their personal guarantee of following through to completion. This has all changed. In 1895, the United States Treasury Department disclosed that $35 million worth of personal surety guarantees on file had become worthless. A law was then passed requiring all surety bonds, in favor of the United States, must be corporate surety bonds. Today, a surety bond is one of the nation&apos;s leading fi¬nancial instruments used to guarantee the completion of an obligation. One hundred-fifty years before cor¬porate surety bonds, outcrops near Richmond, VA, were being mined. These surface mines became under¬ground mines. Today, both are still being used to obtain a leading energy source, coal. Since that time, more than 5956 km2 (1.47 million acres) of coal mined lands have been reclaimed in the US (Coal News, August, 1987). More than 25,000 state and Federal mining permits cover¬ing 14,164 km2 (3.5 million acres) have been issued during the last 10 years. Coal production has exceeded 7.2 Gt (8 billion st). More than 5665 km2 (1.4 million acres) of mined land has been reclaimed by active coal mining opera¬tions and 267 km2 (66,000 acres) of abandoned mined lands have been re¬claimed by others. Reclamation bonds were freely writ¬ten in the 1970s. So why are they almost extinct today? Contract bond losses have been severe in the past several years, sureties reporting losses exceed¬ing 110%. But the same proof is not provided on coal reclamation bonds. A surety bond is generally required when one party has an agreement with another party, and that party wants a guarantee from a third party that a job will be completed according to the terms and conditions of a written contract. In the case of a reclamation bond, the surety company (surety) is the financial party. It extends the credit and a guarantee to the obligee (the State, Commonwealth, or Office of Surface Mining) that the principal (the coal operator/company) will complete the terms and conditions of the contract (the rules and regulations governing mining and reclamation). The Surety Association of America defines a surety bond as an agreement providing for monetary compensation should there be a failure to perform specified acts within a stated period. Webster&apos;s Dictionary defines surety in the following ways: "l: the state of being sure; 2a: a pledge or other formal engagement given for the fulfillment of an undertaking and; 3b: one who has become legally liable for the debt, de¬fault, or failure in duty of another." Banks never make accommodation loans. Either the loan is good or no loan is made. Surety companies feel the same way about surety bonds. In fact, the average person does not realize the dangers of becoming surety for another. How does a surety determine if a company is worthy of receiving surety credit? How is a coal account under¬written today for an obligation that may not be released for many years? When a surety company executes a reclama¬tion bond, it financially puts its name behind the coal company and its guaran¬tee that should the coal miner default on the obligation, the surety will fulfill the contract. How is the surety to determine if a coal company may still be in business five, 10, 20, or 40 years from today?

Jan 1, 1989

By John E. Crawford

A year ago, if I had the pleasure of addressing you, I would have discussed ocean mineral resources from a promotional standpoint. I would have described exciting indications of mammoth tonnages of sea-floor industrial minerals. I would have attempted to fire your imaginations as to the potential of a nation having the technologic know-how to exploit its submerged boundaries. As a first step toward this capability, I would have solicited your support for a Bureau of Mines? program aimed at determining the industrial worth of marine minerals and devising techniques and hard- ware for their recovery. We still need your support, but recently we have ventured out of the realm of planning and into your Government&apos;s first program in marine mineral engineering. Today, I wish to describe what we have done within the framework of existing research problems and our possible goals. I will be brief so as to allow ample time for questions, and I can do this with confidence because our program is so new that I need not be chagrined at not having all the answers.

Jan 1, 1965

By H. M. Breza

Recovery of phosphate concentrate at Texasgulf’s Aurora Mine has received increased attention as existing mine and plant production capacity limits are reached. Improved mining techniques and mineral processing of waste streams offer the potential to increase phosphate production without major expansion. Innovative processes are being identified to maximize pit mining recovery and to minimize waste stream losses. This results in more effective use of the phosphate. Texasgulf Inc., is a wholly owned subsidiary of Elf Aquitaine. The Aurora phosphate rock mine and refining facilities are located in North Carolina on the south shore of the Pamlico Sound. Phosphate ore is recovered by open- cast mining techniques. Draglines and other earthmoving equipment are used to uncover and mine the phosphate ore. The mined ore then is slurried and pumped about 8 km (5 miles) to the processing plant.

Jan 1, 1994

By P. C. O. Chukabarah

Atkinson&apos;s resistance square law is the cornerstone equation for traditional expression of energy losses in mine ventilation engineering. But the nomenclature for the various forms of energy losses are often confused for one another, misapplied or misinterpreted. These forms of energy were re-examined from thermodynamic and fluid-dynamic perspectives. Resultant expressions showed that both incompressible and compressible flow regimes in underground mines can easily be accommodated. Given the well-known three major energy forms, which are equivalent to one another but numerically unequal, corresponding equations to Atkinson&apos;s (pressure loss) for headloss and workloss were derived. The thermodynamic weight relational resistance ([w] s2/m5) associated with energy per unit weight (headloss) was dimensionalized for the first time. Also, normalized Atkinson-like equations for headlosses and worklosses were derived to ease direct computations in mine ventilation practice.

Jan 1, 1995

By John N. Murphy

The past five years have seen communications techniques and hardware developed by the Bureau of Mines and its contractors increasingly brought into use in U.S. mines. The Bureau of Mines philosophy has been to help develop and introduce new hardware that goes as far as possible toward meeting the mining industry&apos;s needs. The Bureau of Nines programs are also designed to provide continuous fallout of new communications capabilities which are introduced to the mine operators as they occur. As more progress is made in meeting mine comnications needs, it is hoped that the mining industry will readily adopt the equipment and techniques that it finds most useful in meeting its individual needs. This paper reports on recent advances achieved in the development of improved nine communications systems.

Jan 1, 1976

Gold cyanide equilibrium adsorption isotherms in the loading range typical of operating carbon-in-pulp/carbon-in-leach plants have been established and the effect of various cations and the presence of copper cyanide species quantified. It was found that the equilibrium loading of gold was enhanced by the presence of sodium or calcium, with calcium having an order of magnitude stronger effect. The presence of copper has an adverse effect on the equilibrium loading of gold. A unified model was developed to predict the effect of sodium and calcium concentrations in solution and the competitive carbon adsorption of copper on the equilibrium loading of gold on carbon. A satisfactory agreement between the measured gold equilibrium loadings and the model results was obtained over a wide range of solution conditions.

Jan 1, 2010

By Deepak Gupta, Brij M. Moudgil

Attempts were made to improve the recovery of coarse phosphate particles by adding selected frothers or precoated fine particles. A number of frothers for floating, specifically coarse coal and metallic minerals, were examined. Two of the frothers increased the flotation recovery of coarse phosphate by 3% on bench scale. Plant evaluation yielded improvements in overall phosphate recovery in the presence of these frothers. Addition of fine particles was also found to enhance coarse flotation under given conditions. Size, amount, and hydrophobicity of the fines added was determined to have a major influence on the coarse flotation efficiency. The grade of the product with and without frothers and particulate additives remained the same. Change in froth stability and viscosity are believed to be the primary reasons for enhanced recovery of coarse phosphate particles.

Jan 1, 1989