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By R. L. Virta

Common clay is a natural, fine-grained material composed of hydrous aluminum silicates. Shale is a laminated sedimentary rock that is formed by the consolidation of clay, mud or silt. Production About 150 companies produced common clay and shale in 41 states. In states not reporting production, common clay and shale probably was mined and sold for construction applications by companies not participating in the U.S. Geological Survey (USGS) canvass of producers. Domestic production in 2005 was estimated to be 24.8 Mt (27.3 million st) valued at $176 million. This was based on a preliminary survey of the common clay and shale industry. The leading producer states, in decreasing order by tonnage, were North Carolina, Texas, Alabama, Georgia and Ohio.

Jan 1, 2006

By Dean Brox

The use of Tunnel Boring Machines (TBMs) for tunnel construction of long tunnels in the Andes of South America has been of mixed success in the past due to a variety of reasons and key lessons can be recognized. A review of past TBM tunnel projects in the Andes has unveiled some interesting findings for different TBM tunnel approaches with both world records of progress as well as nearly in-completed projects with machines being abandoned. Key considerations for the use of TBMs for tunnel construction in the Andes include geological issues; (faults, rock type, rock strength, rock abrasivity, durability, groundwater inflows),depth of cover and the potential for overstressing/rockbursts, site access and terrain, portal locations, intermediate access possibilities, minimum tunnel size, support requirements, contractor and labour experience, and project schedule demands. TBMs offer highly recognized schedule benefits(high progress, no concrete lining) for a project if intermediate access adits are limited as well as hydraulic benefits for water conveyance projects. Minimum specifications for TBMs can be easily developed to suit the unique requirements of any project so as long as all factors are carefully considered. The overall conditions and factors associated with some projects may suggest that it is not appropriate to use TBMs due to a perceived high risk. Finally, access for geotechnical investigations by drilling in the commonly steep terrain of the Andes is typically difficult and often not impossible. Alternative approaches for geotechnical investigations for TBM tunnels including comprehensive mapping, high-resolution airborne electric-magnetics for delineation of possible fault zones, and rock block sampling is presented and discussed.

By Sam Ash

The Murray Mine was one of the first mechanized cut-and-fill underground gold operations in northern Nevada. At the end of 2002, mine production began to decline. So the mine entered a phase of remnant mining and began preparations to close down. The remaining mining took place along the ore waste boundary in previously condemned areas and in challenging ground conditions. To remain economically viable, new techniques were implemented in operations, geology, engineering and rock mechanics. These improvements pushed the edge of known and accepted mining practices and have allowed the Murray Mine to remain in operation.

Jan 1, 2006

By R. Tamblyn

Vertically stirred media mills are a highly effective low-footprint solution for the ultrafine grinding of industrial minerals. This work investigates the effect of media density on flow patterns within the mill. Direct irradiation of a media particle leads to decay through positron emission, consequently forming two anti-parallel gamma rays, which allow for the real time tracking of particle position. Grinding media of the same size, but with a range of specific gravities are followed using this method, and the effect on the flow within the mill is revealed. The technique is seen to be an effective method to highlight the velocity profiles within the mill, as well as the zones where grinding is less efficient ? areas of relatively low velocity and high residence time. The changing media is seen to effect the overall flow patterns within the mill, having consequential effects on the efficiency of the grind.

Jan 1, 2009

By F. Díaz-Fierros, D. Rubinos, M. T. Barral

The present work explores the reutilization of red mud, an industrial waste arising from the production of alumina, as a component of isolation technologies for hazardous substances. The work involved the study and optimisation of the geotechnical properties of red mud in conjunction with adsorption experiments of As(V) and Hg(II). The results from both types of experiments were integrated in a dispersion-diffusion model to calculate migration curves and minimum thickness of the red mud compacted layer. The geotechnical studies showed that compaction increased the stability and decreased the hydraulic conductivity of red mud barrier. Red mud sorbed high amounts of As (up to 44 mmmol kg-1) and Hg (up to 9.2 mmmol kg-1). The calculated minimum thickness of the red mud barrier was 1-10 cm for As and 2-19 cm for Hg, for an operation period of 35 years. The results obtained let to conclude that the reuse of red mud as a component of isolation systems of hazardous substances represents a viable alternative use of this residue.

Jan 1, 2011

By B. K. Belle

The use of diesel engine locomotives in South African mines can be traced to Van Dyk Consolidated Mines Ltd on the Witwatersrand gold mines in 1928 as a replacement for battery locomotives. The advantages and disadvantages were recognized in those days, and surprisingly, there are no significant additions to this list, but only refinements. In the absence of any Occupational Exposure Limit (OEL) for Diesel Particulate Matter (DPM) in SA, the Mine Safety and Health Administration (USA) rule is currently being used as a benchmark for the ventilation engineering designs. This paper discusses the ongoing SA journey of measurement and limitations of exposure data for ventilation planning and regulatory purposes. The currently accepted DPM limits are based upon the belief that they are economically and technically feasible for the mines to reach and are not necessarily health based. For SA underground platinum mines, a median TC/EC ratio of 1.8 with a range of 1.2 to 5.8 was observed. For SA coal mines, a median TC/EC ratio of 1.44 with a range of 1.25 to 2.13 was observed. While it is common practice in the USA to use the ratio of TC/EC for metal mines to be 1.3, the ratio found in local platinum mines is 2.2 and for coal mines, the ratio was 1.53 which is lower than Australian studies, i.e., 1.96. It has been shown that a need for critical analysis of TC/EC ratios exists, and possible reasons for variance must be understood before stringent adoption of overseas recommended limits for DPM. It is hoped that the findings from this paper would provide input to scientific approaches in developing appropriate conversion factors, limits for DPM and also in ensuring appropriate error factors (currently 1.14 for TC and 1.2 for EC) for compliance determination.

Jan 1, 2009

By D. Brandt

The Dos Pobres Mine is a copper oxide heap-leach mine located near Safford, Arizona. Mine production is 180,000 tons (163,293 tonnes) per day with a stripping ratio of 2:1. During the startup phase of the mine, the required fragmentation size was easy to achieve as the ore was highly weathered and fractured near the surface. As the mine depth increased, the proper fragmentation size became harder to achieve due to less weathering and different rock types. Because copper recovery increases as crusher product size decreases, achieving the appropriate product size at the crusher is the operating priority. The Engineering Department started a project to improve fragmentation through blasting and thus increase throughput in the crushing system. It soon became clear that input from other departments was going to be required to make this a safe and economical project. Therefore the Crush and Convey and Ore Control departments worked together to evaluate all available data on blast patterns and explosive loads and tracked performance and results. Using image analysis, Drill Energy Index and databases, we have been able to improve fragmentation size and verify the results while controlling costs.

Jan 1, 2011

The United States continued to depend on imported bauxite during 1995. Domestic bauxite mine production remained at about the same level as in 1994. It amounted to less than 1% of total world production. All of it was used for nonmetallurgical products, such as abrasives, chemicals, proppants and refractories. Metallurgical grade bauxite was imported from 12 countries. Principal suppliers for this 10 Mt (11.1 million st) of ore were Guinea (39%), Jamaica (35%), Brazil (17%) and Guyana (8%). The average value of imports, c.i.f. US ports, was $31/t ($28/st). Calcined refractory-grade bauxite imports totaled235 kt (259,000 st). It had an average value of $112/t($102/st) c.i.f. US ports. China supplied 61%, Guyana30%, Hong Kong 4% and France 3%. Imports of other grades of calcined bauxite, primarily for the abrasives market, totaled 259 kt (286,000 st).They were supplied by China (59%), Greece (20%), Brazil (14%) and Australia (6%). The average value was$74/t ($67/st) c.i.f. US ports.

Jan 1, 1996

By M. G. Irish, E. E. Vidal, M. J. Jahraus, P. R. Taylor

An experimental system has been designed to monitor on-line variations of leaching parameters in a closed circuit of cyanide leaching solutions and gold bearing ores. Experiments performed to deter-mine variations in some important leaching parameters of the solution: pH, dissolved oxygen, free cyanide, oxidation/reduction potential, gold content, temperature, pressure and solution chemistry. By comparing results obtained when the leaching solution is allowed to become acid or kept basic, it was possible to infer the chemical reactions that occurred between the solution and the ores.

Jan 1, 2004

By Stephen Davies

Mining at Hudson Bay Mining & Smelting's Snow Lake Division is now in the mature stage of the mines' lives. These base metal copper-zinc mines have been operating for more than 30 years. Stopes had small pillars called "crown pillars" left between them. These pillars range up to 100 m (330 ft) long by 40 m (130 ft) wide and 15 m (50 ft) thick. Hudson Bay have been successful in removing these pillars by using cable slings, electric scoops, longhole mining and diesel load-haul-dump equipment. The different shapes and sizes of these pillars has required that many innovative techniques be tried in order to find acceptable economic mining methods. An overview of the different methods will be outlined. Background Hudson Bay Mining & Smelting's Snow Lake Division is located in Manitoba some 800 km (500 miles) north of Winnipeg and 200 km (125 miles) by road from the Hudson Bay smelter complex located in Flin Flon, Manitoba (Fig. I). There are currently three producing underground mines and one open pit operating at the Snow Lake Division, producing copper and zinc concentrates. Pillar recovery is intensive and vital to continued production of these mature mines. The crown pillars are producing more than 50% of the current mine production. This figure will increase in the future. The two mines at which crown pillar recovery is taking place and that will be discussed are the 400 t/d (440 stpd) Rod Mine and the 1000 t/d (1100 stpd) Stall Lake Mine, both five-day-a-week producers. Crown pillar mining has been applied for some time at these mines. However, it was only recently that the crown pillars became vital to production. This has necessitated a number of innovative techniques to recover them.

Jan 1, 1992

Fully mechanized longwall mining with large mining heights (LMHs) in shallow-depth thick coal seams has been widely applied in Shenfu coalfield, China. Dynamic loading and rib spalling is serious when the LMH working face experiences periodic weighting in shallow coal seams. The advanced breaking position (fracturing ahead of the face) in the roof affects the strength of the mine pressure (weighting) when the roof is broken. Based on the theory of the “elastic foundation beam,” this paper presents a mechanical model for the advanced breaking of the roof, including a predictive formula. In an attempt to verify the formula, a field program consisting of multiple-point borehole extensometers installed in the roof in advance of the longwall face was performed in the No. 22201 working face of Zhangjiamao coal mine in the Shenfu mining area, China. The field measurement results show that the roof movement of the LMH working face is detected prior to roof pressure increase, and that the roof breaks approximately 5–8 m ahead of the face. This compares with a calculated value of 6.9 m, indicating that the formula developed in this research is reliable and should have application in predicting roof pressure associated with LMH working faces in shallow coal seams.

Jul 28, 2020

By S. Ersayin, I. Iwasaki

Application of a magnetic field was shown to be effective in controlling iron losses in pilot-scale cationic silica flotation in the processing of magnetic taconite concentrates. The design of a magnetic field distribution device and batch flotation test results using a 1.42m3 (50 cu. ft.) WEMCO cell are reported. Major losses of iron units in froth products were in the -25µm (500 mesh) fraction, and the application of a magnetic field decreased the flotation of fine magnetite, thereby improving the selectivity of separation. The “as received” sample was sufficiently magnetized and no further benefit was gained by magnetizing treatment. Selectivity was somewhat adversely affected by demagnetizing the sample, though its effect was minimal due to the magnetic field. The device is simple in construction, low cost and may be installed readily in existing equipment.

Jan 1, 2002

By Donald W. Stever

In 1995 I was asked to participate in a litigation matter between a corporation and its insurance carriers concerning insurance coverage for remedial costs at a large, environmentally contaminated closed-down former industrial facility. One of the buildings on this site became known to the lawyers representing the company as “the infamous Building 8”. This building housed millions of documents retrieved from various locations at the facility while it was being shut down. It became apparent that the facility management had no document destruction policy, and thus Building 8 contained internal memoranda, notes, copies of correspondence, permits, operating records, inventory records, and the like from fifty years of operation. Needless to say, some of these documents, all of which were subject to discovery by the insurance companies in the litigation, contained material that was less than helpful to the company’s case. Of course, there were also a few helpful documents, but the overall usefulness of these records was outweighed by the negative impact they had on the conduct of the litigation. A second example involves e-mail. Several years ago, acting on an anonymous complaint that we later discovered was made by a disgruntled former employee who had been fired, a small army of federal environmental investigators descended on a client’s operating facility and, armed with a search warrant, literally commandeered the facility’s EH&S department. The investigators impounded the computers of the EH&S personnel and extracted all of the data from the hard drives of those PCs, as well as all EH&S related files from the hard drives of several servers used by the facility. These computers contained many years’ worth of stored e-mails, draft letters and memoranda, and other documents that provided grist for a four and one-half year criminal grand jury investigation of the facility and its EH&S staff. Both of these companies would have benefited from following a rigorous, enforceable, corporate records policy. Here is a third problem. My client had, during the 1960s, made a brief, and unprofitable foray into the nuclear fuel processing business. It ultimately sold the subsidiary, and was forced to give the purchasing company a broad indemnity against future liability. As might be expected, years later the facility was found to have considerable soil and ground water contamination both by chlorinated solvents and low-level radioactive material. Several years into the remediation program, my client discovered a tractor-trailer load of files, apparently removed from the subject facility, sitting in a parked trailer in a company-owned lot 300 miles away from the facility, where they had been for nearly thirty years. These documents were not helpful to the client, but had to be reviewed, at considerable cost, by paralegals. Moreover, several of the boxes turned out to have been mildly radioactive, setting off a chain of health and safety issues that consumed tens of thousands of dollars of legal expenses before they were resolved. Today, formal, enforceable corporate records management programs have become an extremely important element of overall corporate management. What was for most of the last century little more than a low level warehousing function is now a critical, actively managed, operating function that affects every level of corporate management. The rapid assimilation into corporate culture of electronic document management and the prevalence of e-email as the primary means of internal communication have created records management complexities the likes of which were not even conceived of fifteen years ago. Record preservation and destruction are no longer matters that can be handled on an ad-hoc decision making basis. Because of regulatory requirements affecting various classes of documents and the litigation consequences of ad hoc retention and destruction of corporate business records, and the need to have the ability to quickly retrieve documents in either a litigation or business negotiation context, a set of records management norms have evolved over time that have become the core elements of virtually every corporate records program. However, notwithstanding the existence of a set of norms (which are the basic elements of a

Jan 1, 2005

By William R. Yernberg

The combined 79th Annual Minnesota Section of SME Meeting and 67th Annual University of Minnesota Mining Symposium was held April 11 and 12, 2006, in Duluth, MN. About 300 mining professionals attended, including engineers, executives, mining managers and suppliers, from throughout the United States and Canada. This year’s theme was “Success in the New World of Mining.” The SME Minnesota Section meeting included a keynote session, a special projects update, a general managers update and technical paper presentations. The University of Minnesota Mining Symposium program featured a panel discussion on Minnesota’s relationship with China. The combined meeting included a trade-show consisting of 64 booth spaces. Tradeshow demand exceeded expectations, and an additional 10 booth spaces were added in the registration lobby. Also included were an SME short course on pump basics and social events.

Jan 1, 2006

By P. Anyon

Exposure to the microscopic particles in diesel engine exhaust can lead to serious health problems, including the incidence of cancers, heart disease and increased susceptibility to respiratory ailments such as pneumonia, bronchitis, and asthma. In Australia, mining companies and state government authorities are actively responding to this major occupational health and safety issue. Their initiatives place considerable emphasis on routine monitoring of diesel particle matter (DPM) exhaust emissions, both for engine benchmarking and as a part of routine engine maintenance. Implementation strategies follow two complementary paths: determination of individual engines? emission signatures combined with periodic engine re-certification; and co-operatively agreed industry-government engine maintenance programs, which are subject to audit. Both strategies place heavy reliance on real-time measurement of DPM concentrations in engine exhaust, using ruggedized instrumentation, mainly based on laser light scattering photometry. Adding value to this cooperative approach, industry has also collectively funded a government agency to design and manage a database, into which the results of all-routine DPM testing can be uploaded directly by individual mines. This win-win outcome is a great example of how cooperative action between governments and industry can deliver the goods: in this case, a safer working environment, more efficient energy use and the capacity to benchmark performance with industry peers.

Jan 1, 2009

By John L. Kaplin

The underground construction for the Phase I Combined Sewer Overflow(CSO) Project is on an impressive scale by any measure, appearing more so in a midsize city like Providence, RI. The Narragansett Bay Commission recently completed $350 mil-lion in construction to improve the water quality in Narragansett Bay. This project included a number of serious challenges, delays, and disputes. Looking back on this complex project completed within budget, it is hard to consider the work as anything other than a success. Along the way, this outcome did not always appear certain.

?Classification System Efficiency (CSE)? is a simple, powerful concept which can be used to measure and improve ball mill circuit efficiency. This paper describes six plant case studies which demonstrate the use of CSE to diagnose and/or improve grinding circuit performance, with related improvements in circuit efficiency ranging from 3 to 30 percent. The increased effective mill grinding energy is recaptured from energy that was going into over grinding, which can greatly benefit downstream mineral separation. The achievable CSE for given circuit design/operating variables is described, providing every plant metallurgist with the means to determine the potential for increasing their particular grinding circuit?s efficiency through increased CSE.

Jan 1, 2012

By M. J. Sapko

The design requirements for mine ventilation seals have undergone a radical transformation in recent years, and these revisions have greatly increased the cost of the seal designs and their construction. For example, in the past two years, new federal regulations have increased the minimum design requirement to withstand explosion pressures from 138 kPa (20 psig) to 345 kPa (50 psig) or 827 kPa (120 psig), depending on whether the sealed mine volume is monitored continuously or not. Moreover, there is still a possibility that under certain conditions (such as detonations) even higher pressure requirements may be necessary. The ability of a monolithic, stand-alone mine seal to reliably withstand the full range of current and future pressures is becoming increasingly difficult and expensive. In an effort to develop a practical alternative, the West Virginia Office of Miners? Health Safety and Training (WVOMHST) and the National Institute for Occupational Safety and Health (NIOSH) have collaborated in a research effort to develop a practical, economic, and safe mine sealing technique that can enable mines seals to meet the full range of new explosion pressure design requirements. The basic idea is to use a barrier of common mine gob and rubble in combination with a conventional mine seal so that the pressure resulting from a gas explosion is reflected, absorbed, and attenuated, so the pressure on the ventilation seal is reduced. This paper discusses some concepts and preliminary test results for a ?Passive Mine Blast Attenuator? (PMBA) that can provide a useful alternative to increasingly larger and stronger stand-alone mine seals. Numerical models and full-scale experiments conducted at the NIOSH Lake Lynn Laboratory Experimental Mine (LLEM) show that the use of a PMBA can signficantly reduce the blast pressure and impulse on conventional ventilation seals. DISCLAIMER: This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not been formally disseminated by the National Institute for Occupational Safety and Health (NIOSH). It does not represent and should not be construed to represent any agency determination or policy.

Jan 1, 2009

By K. Sasaki

Diffusion phenomena in mine airways are important to trace gas and dust introduced into mine ventilation flows. Authors have carried out tracer gas measurements to check mine ventilation using concentration-time curves measured in mine airways, however dispersion mechanism to enhance effective diffusion have not been cleared. A numerical model using discrete tracer points dosed into tube flow has been presented to simulate their movements in consideration of turbulent velocity profile and fluctuation. Numerical simulations have been carried out to predict distributions of dosed points in tube flows with turbulent velocity profile, turbulent intensity profile and Reynolds stress. The numerical simulation results show that a combination of turbulent velocity profile and fluctuation creates extremely large dispersion of points in longitudinal direction and concentration curve with long tail was observed. This dispersion by velocity profile and fluctuation contributes large effective diffusion coefficient compared with original diffusion coefficient dominating in uniform velocity fields. Furthermore, the effect of Reynolds stress on the concentration-time curves is discussed.

Jan 1, 2009

By Don C. White

The Vulture mine near Wickenburg, Arizona was a major gold producer from 1863 to 1942, having yielded about 11t(12.1 st) Au and 8t (8.8st) Ag. Gold occurs as coarse native metal and electrum in quartz veins and also finely dis¬seminated within a quartz monzonite sill and its silicified wall rock. The sill is semi-conformable within a Proterozoic volcaniclastic-dominated sequence, all dipping north about 35°. Early mining focused on the vein-hosted gold, particularly in the immediate hanging wall and footwall of the sill. Later efforts included some open-pit mining of the outcropping sill and adjacent altered and mineralized rock. Two sets of post-mineral faults have complicated the orebody geometry. The sill is a 350 m (1148 ft) long apophysis from a quartz mozonite stock to the west of the mine area. The stock has been dated at 85 my and contains abundant lesser gold occurrences in its core and about its margins. The Proterozoic rocks are notably lean in precious metals except where altered in proximity to the Creataceous stock and sill. Circumstances dictate an interpretation of epigenetic mineralization related to the Laramide intrusion.

Jan 1, 1990