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By Carlo Grandori

Early experiences The first double shield hard rock tunnel boring machine, manufactured in 1973, belonged to the generation of machines that were equipped with 12" dia. cutters. The experiences made with the 4.3 m diameter prototype ROBBINS mod 144-151 have been reported at the 1976 R.E.T.C. of Las Vegas (1): it might be worth recalling here that, with a specific cutter load not exceeding 10 to 12 metric ton and a 4.8 r.p.m. cutterhead speed, the average advance rate was of 350 meters per month of 21 working days with a peak production of 1,050 m of advance in 40 working days, in widely weathered and fractured granitic rocks of generally precarious stability, where a precast segmental lining was routinely installed as tunnel support. Over the 8.2 km of the Sila Tunnels, several badly crushed or sheared rock zones were bored through without major problems, even with water inflows of up to 30 1/sec. The same machine, with an improved design of the telescopic-and-floating shield area and equipped with flameproof drive motors, was taken to Colombia where, from September, 1979 to March, 1982 it drove 7.5 km of the Rio Negro-Chivor Tunnel in competent siliceous shales of up to 130 MPa at an average rate of 20 m/day.

Jan 1, 1987

Underground mining has the potential to be one of the more dangerous industries in the United States and the world. Following recent disasters in Sago, WV; Darby, KY, and Crandall Canyon, UT, the mining industry was reminded of the need for a system to allow trapped miners awaiting rescue to survive following a disaster. To address this need, Battelle has developed a Mine Barrier Survival System (MBSS) that surpasses all current technologies and sets a new standard for keeping miners alive in the event of a fire, flood, explosion or collapse. The MBSS creates a temporary refuge for miners who cannot escape by using inflatable barriers and a post-fire atmosphere scrubbing system to define the ?safe haven? and remove CO2 and CO while replacing oxygen and providing heat. Current personal-protective systems in use are designed to provide breathing air for only a few hours when, realistically, it may take days for rescue teams to reach trapped miners. Battelle?s MBSS is designed to aid up to 15 miners for four days.

Jan 1, 2008

By James R. Brown

Mount Isa Mine should be regarded as a large mining complex rather than one mine. This arises from the geography, variety and extent of the orebodies, the mining methods, and the use of 14 shafts for ventilation distribution. A brief resume is presented here since comprehensive descriptions of lead-zinc mining methods {11}, copper mining methods {2 }{3}, geology 241, stope fill {5} and ventilation techniques {6}{7}, have all been published in the last five years. Mining extends over a north-south strike length of 2.5 miles (4 Ian) with a maximum width across dip approaching 3 200 ft (1 Ian). Current mining is to a depth of 3 150 ft (960 m) with the ore hoisting shafts extending 660 ft (200 m) deeper. The composite longitudinal section, Figure 1, shows a representational disposition of the copper and lead-zinc-silver orebodies in the central shaft complex where the main service and hoisting shafts are located. To the south the X41 man and materials shaft provides access to the copper area. The mine layout is typical of high tonnage track- less mines, utilising a large diesel fleet, raise- borers and some large diameter hole stope drilling. Mining methods include sublevel open stoping, slot and massfire, and a trial vertical crater retreat in the copper ore, and sublevel caving, sublevel open stopes with and without rib pillar recovery, and mechanised cut and fill in the numerous lead orebodies. All ore reports to one of the three crushing systems located below 19 level in the central shaft complex. Copper ore is hauled exclusively along the 19 level computer assisted Rockflo haulage system, and lead-zinc-silver ores report via central orepasses from Granby haulages on 13 level and 15 level. Tonnages hoisted during the 1977178 financial year were 5.0 million for copper at 3.2%. and 2.3 million for lead-zinc-silver at 7.8%. 6.3% and 7.06 oz/ton (216 g/tonne) respectively.

Jan 1, 1980

By Fernando Pendás, Jorge Loredo, Alumudena Ordóñez

Water derived from mine-tailings typically contains high concentrations of H+, SO4, Fe and other metals, and it frequently suffers a decline in pH and the development of acidic mine drainage (AMD). A paper describing the results of a series of laboratory experiments with real AMD and a subsequent field trial with a in situ pilot system to assess a potential method for remediating tailings-derived water is presented here. After testing different organic substrates, residence times and flow conditions during two years to determine the most appropriate treatment for a polluted Spanish AMD, a pilot scale system combining SAPS, ALD, oxidation/sedimentation ponds and an anaerobic wetland was designed. Preliminary analyses of effluent samples indicate acidity and metal removal is occurring within the system, although sulphate removal is not complete. The results of this small-scale field trial suggest a potential cheap, long-term alternative for remediation of acid mine drainage.

Jan 1, 2000

By William S. Brack

The mining industry is very capital intensive. Competition for shareholder investment has never been greater. Among our challenges is the need to meet shareholder expectations (return on investment), and one area of focus lies in our ability to deliver value on our capital investments. Our ability to meet project expectations affects not only the economics associated with the immediate project but also directly influences our ability to finance future projects. Moreover, our ability as individual companies to attract investor capital is influenced by how we have done overall as an industry, and our industry track record has not been that stellar. With safety, scope, cost, schedule, and quality as guiding principles, our project managers today must address high expectations on every project. This paper examines some items that should be on today's project management checklist. PROJECT ENGINEERING Herbert Hoover, himself a mining engineer, said Engineering is a great profession. There is the fascination of watching a figment of the imagination emerge through the aid of science to a plan on paper. Then it moves to realization in stone or metal or energy. Then it brings jobs and homes to men. Then it elevates the standards of living and adds to the comforts of life. That is the engineer's high privilege.

Jan 1, 2004

By Brian D. Smith, Batric Pesic

Typical sulfide gold bearing ores are refractory to standard cyanidation practice. This type of ore always needs some form of oxidative pretreatment to destroy the original host mineral matrix to make the cyanidation possible. The oxidative pretreatment can be achieved by roasting, autoclave leaching, bioleaching, or some other chemical method. Today, the most common practice of ore oxidation is either roasting or pressure leaching. The other methods are still considered developmental.

Jan 1, 1992

By Cynthia M. Walck, S. K. Grant, R. D. Hagni

The Post Gold deposit is located in the northern part of the Carlin trend. The mineralization at Post occurs in proximity to a Jurassic-Cretaceous composite stock. Most of the gold at Post is hosted by non-metamorphosed calcareous siltstone and highly altered diorite, adjacent to the low grade skarn. Endoskarn, exoskarn, hornfels and marble are developed outward from the intrusive. The skarn is composed dominantly of diopside, tightly intergrown with gannet, k -feldspar, and sphene. The highest grade gold values are adjacent to the skarn, which acted as a permeability barrier to fluid migration. Post is the first Carlin-type deposit at which a skarn has been recognized to play a significant role in the localization of gold.

Jan 1, 1990

By D. H. Desy

This research was undertaken to establish the lncendivity of aluminum alloys against rusty steel under frictional impact conditions at typical coal mine fan speeds, to determine any differences in incendivity among various aluminum alloys, and to Investigate less incendive materials as substitutes for aluminum alloys. With a specially designed apparatus, three aluminum casting alloys and three constructional steels were tested for incendivity in frictional impact against rusted steel in flammable methane-air mixtures. Although varying in degree, all aluminum alloys investigated exhibited a high ignition probability under the test conditions; none of the steel specimens tested caused any ignitions under the same conditions.

Jan 1, 1973

By Ottmar Burghardt

Sintering of iron ore has undergone a dramatic development world-wide. Today, the annual world production amounts to approximately 600 million tons. At present, the sintering process in competition with pelletizing, seems to offer certain advantages inasmuch as it allows the use of solid fuels. Also, its charging behaviour in the blast furnace is, in general, considered as being better than that of pellets. This is true, in particular, for the charging behaviour and the gas permeability in relation to the grain size. Moreover, instead of charging limestone into the blast furnace, for instance, the basic components which are necessary for the burden materials can generally be supplied in a simpler and more cost-effective way by using basic sinter instead of basic pellets. While in sintering, with basicity rising to the range of 1.6 to 1.8 CaO : SiO2, the capacity increases and the sinter quality shows improvements in most of its characteristics, the pro¬duction of basic pellets generally requires a higher fuel rate, when compared to acid pellets, while production capacity decreases and some of the quality characteristics deteriorate.

Jan 1, 1982

By Oren Tranbarger

The ability to sense or detect the coal/non-coal interface during mining can provide numerous advantages for improving net coal recovery and quality, for increasing productivity, and for mining coal which would otherwise be ignored. This is particularly true when considering multiple, pitching, and thin coal seams. This paper discusses the application of coal interface sensing and examines several potential coal interface sensing techniques with respect to state-of- the-art, design, performance, and cost criteria. Four interface boundaries are considered: the roof, the floor, the rib, and the forward region.

Jan 1, 1982

By B. K. Mishra

This paper focuses on the use of a numerical tool known as the discrete element method (DEM) to study the motion of ball charge in ball mills (14-18 ft). DEM is employed to simulate the motion of individual balls. While doing so, the effect of liner design on the grinding performance of the mill is studied. Two important factors such as the configuration of the liner and the geometry of the lifting surfaces are correlated with the overall mill performance. An attempt is made to show the effectiveness of the lifter bars in transmitting power from the mill shell to the interior of the mill with particular emphasis to large diameter mills.

Jan 1, 1992

By M. Yekich, W. R. Reed, G. Ross, M. Shahan

"Canopy air curtains (CAC) on roof bolting machines have been proven, through laboratory and field investigations, to protect miners from respirable dust, preventing dust overexposures. Another desired application is to develop a CAC that is mounted in the compartment of a shuttle car to protect the operator from dust. The challenges faced with this design include mine ventilation rates in tandem with the shuttle car tram speeds, causing cab airspeeds that may exceed 600 fpm, as found in this study of a central Appalachian underground coal mine. Prior research and laboratory testing indicate that successfully protecting a miner in high air velocities is difficult to achieve because the clean air from the CAC is unable to penetrate through the high velocity mine air and make it to the breathing zone of the operator. During this investigation by researchers from the National Institute for Occupational Safety and Health (NIOSH), dust concentrations of the shuttle car operator were measured. Also, air velocities experienced by the operator were measured using a recording vane anemometer. Results from the survey indicate that the highest exposure to respirable dust (2.22 mg/m3) occurred when the shuttle car was loading at the continuous miner, where there was an average airspeed of 157 fpm. While tramming, the operator was exposed to 0.77 mg/m3 of respirable dust with an average airspeed of 203 fpm. This study indicates that a CAC system can be designed to greatly reduce an operator’s exposure to respirable dust by providing clean air to the operator, since the majority of the operator’s dust exposure occurs in air velocities less than 200 fpm. INTRODUCTION NIOSH has issued a contract (#200-2015-63485) with Marshall University and J.H. Fletcher & Co. (Salem et al., 2016) to develop a canopy air curtain (CAC) for coal mine shuttle cars. The proposed design maintains a similar design to the roof bolter CAC by providing filtered air via a blower over the operator. The plenum, which will provide the uniform airflow over the operator, is anticipated to be built into the shuttle car canopy. One of the main interferences with a CAC is ventilation airflow perpendicular to the plenum airflow [Engel et al. 1987]. This ventilation airflow, if the velocity is significantly high, can shear the downward flow from the plenum. The shear caused by the ventilating airflow can reduce the effectiveness of the CAC by either disrupting the downward flow or allowing contaminated mine air into the CAC zone of protection."

Jan 1, 2018

By J. Herbst, I. Heber-Panu, Dan G. Cojocariu, E. Ene-Danalache, G. Poling

A general model which represents not only batch but also continuous flotation in multi-cell machines is presented. This model considers both the size distribution and the distribution of flotabilities in a size class for valuable mineral particles in the pulp. The general expression is shown to reduce to several previously reported models. In addition, a number of new models are found to arise for different specific assumptions concerning the flotability distribution and/or the size distribution of the particles undergoing flotation. Several of these new models are tested experimentally using laboratory-scale batch and pilot-scale continuous data. Model parameters are estimated from this data and a comparison of calculated recoveries and those experimentally determined are presented. Finally, the influence of the feed rate, aeration rate and valuable mineral content of the feed on the recovery is examined.

Jan 1, 1976

By Larry D. Patts

Section 317(e) of the Federal Coal Mine Health & Safety Act of 1969 directed the Secretary of the Interior to prepare standards under which all working places in a mine shall be illuminated by permissible' lighting while persons are working in such places. Section 317(e) further provides that such Working places shall be illuminated within 18 months after such standards are promulgated. In accordance with this section of the Act, there was published in the Federal Register for December 31,1970 a notice of proposed ru1emaking which prescribed the illumination to be provided in the working p1 aces of underground coal mines. In 1ight of written comments, suggestions, and objections to this proposed ru1emaking, the proposed standards were with-drawn and reproposed in the Federal Register for Wednesday, October 27, 1971. In light of further comments, suggestions, and objections, a public hearing was held on April 4, 1974 and standards were again reproposed and published in the Federal Register for April 1, 1976. Promulgation of the final lighting standards took place on October 1, 1976 which means that the underground coal mining industry must comply with face illumination requirements by April 1, 1978. As mentioned previously, the first proposed ru1emaking for illumination of underground coal mines was published in the Federal Register on October 27, 1971. In early 1972, Consolidation Coal Company (Consol) and the United States Bureau of Mines agreed to a cooperative study of underground face illumination; Conso1 felt that expertise in this field would become increasingly important. Conso1's initial efforts in illumination were aimed at investigati.ng practical lighting systems for underground face equipment. We were concerned with installing unobtrusive lights which provided sufficient face illumination for safety, but at the same time were readily maintainable, electrically reliable, and physically sheltered from damage.

Jan 1, 1977

By W. J. Roberds

A formal and explicit yet cost-effective approach is proposed to ensure that decisions made during mine development are optimum (with respect to their ultimate consequences) as well as defensible. This risk management approach is based on probabilistic risk assessment and established decision analysis techniques, and appropriately considers the relationships among various mine development decisions, tradeoffs among consequences, the uncertainty in predicting consequences, and the benefits of flexibility to respond to changed conditions.

Jan 1, 1992

By Hassan El-Shall

The results of laboratory and pilot plant testing of a newly developed process to dewater waste slurries from different industries are presented. Data indicate that an increase in solid contents from 6% to over 30% can be obtained in few minutes retention time in comparison to several years as required by currently used technologies. The economical as well as the environmental impacts of such process are discussed.

Jan 1, 1992

By Robert J. Whiteley, Colin Parker

Two major tunnel projects with a combined value of about $US700 million have been recently completed in Sydney using both soft ground and hard rock Tunnel Boring Machines. The first of these and the main entry in Australia for the Year 2000 Olympics was the New Southern Railway. This is 10 km of mainly soft ground tunnel linking the Sydney’s International Airport with the Central Business District. The second tunnel was designed to alleviate major stormwater pollution of Sydney Harbour and involved construction of the Northside Storage Tunnel. This is19 km of hard rock tunnel at depths exceeding 90 m that connects many of the northern Sydney suburbs of Sydney with the North Head Ocean Outfall. Case studies of these projects describe the use of innovative geophysical technologies comprising gravity and seismic tomographic imaging with geotechnical testing at the feasibility and design stages. This approach minimised construction and financial risk by effectively quantifying the significant geological and hydrogeological issues along these tunnel routes that exerted major controls on these projects.

Jan 1, 2001

By S. C. Tadolini, P. Mills

"INTRODUCTION This research produced a shotcrete formulation that extends beyond stabilization and can be used to restore the structural integrity of damaged infrastructure. The primary challenge was to develop a shotcrete or gunite with structural strength within a few minutes to prevent parasitic loading and allow ingress into damaged structures within a few minutes of the mix formulation being applied. This also applies to mining conditions where rapid support of progressive failures can minimize failure. An additional benefit was the discovery that the product had extremely high adhesion properties in addition to high flexural strengths. The approach to product design was the development of “single bag” dry mixes that are entirely self-contained, can be rapidly transported anywhere in the field or underground, and be deployed using simple equipment. Dry mix eliminates issues relevant to high shear water mixing, as water is added in the form of a mist at the point of delivery; thus low W/C can be achieved. However, as there is no onsite powder mixing, the product must have a high degree of inherent homogeneity. A commercial version of this material is currently offered as Minova’s Tekcrete Fast® product which has been successfully deployed in the mining industry and is currently being used in civil, construction and tunneling operations. The material can rapidly stabilize unstable ground in metal/nonmetal and coal mines. This paper described the technology development, product testing results and applications in mining and civil applications. BACKGROUND The original development of this product was to complete rapid stabilization of shock damaged structures, which falls outside the purview of normal construction and mining practices, due to the critical time issue and the nature of the damaged structure. The stabilization of damaged structures requires materials and equipment that can be rapidly deployed to place materials that have very rapid strength development. These materials need to be placeable at a distance to provide some degree of safety to the responders. In addition, the materials must be able to adhere to structural surfaces that have not been specially prepared and conditioned, and may also be highly fractured, dusty, wet, and quite possibly hot or extremely cold. The technology for the rapid delivery of large volumes of cementitious materials to vertical or even overhead surfaces currently exists. Pneumatic delivery (shotcreting) has been used in construction for over 100 years (American Shotcrete Association, 2014). Shotcreting has played a major role in structures like the Washington D.C. Metro subway system and been used in underground mining applications routinely to serve as part of the primary and secondary support system when used in conjunction with traditional roof bolts. Numerous rapid setting cements are commercially available. They are used for rapid repair of surfaces such as bridge decks, pavements, and commercial floors, as well as structural repairs of vertical and overhead surfaces. Few of these products are specifically marketed for use in shotcrete applications. The majority of rapid setting cements are based on, or at least contain, Portland cement as a principle component. Other components are added that help provide early strength, such as high alumina cement (HAC), organic polymers, chemical accelerators (which can also be added during concrete batching), and calcium sulfate hemihydrate (e.g. gypsum plaster) (Lea, 1971). Cementitious mortars prepared with some of these cements can achieve compressive strengths of 6.8 – 13.8 MPa (1,000-2,000 psi) within 1 hour. However, Portland cement mortar and concrete typically require many weeks of proper curing to reach significant levels of their ultimate strengths, even when used with set accelerators. Also, high early strengths require the use of large proportions of Portland cement in the concrete mix, which can lead to high heat evolutio"

Jan 1, 2017

By Noel Jarrett

Energy consumption and distribution in aluminum production, conservation accomplishments, and future goals are presented. Electrolysis and electrode manufacture show the greatest promise for major improvements. Means are proposed for reducing waste heat generation in smelting and for conserving energy in anode manufacture by furnace design and substitution of other materials for petroleum coke. Hall-Heroult Process modifications, alternative designs, and the Alcoa Smelting Process are discussed as energy savers. Scrap recycling, more use of aluminum in transportation, and the installation of offshore smelters in less developed countries are shown to be additional means of coping with possible energy dislocations.

Jan 1, 1981

By David K. Parrish, Duane A. Labreche

Analyses of jointed, cracked, and fractured rock masses are needed in a variety of applications, including estimates of reduced elastic modulus for damaged rock, estimates of permeability changes as a function of stress changes, and estimates of relaxed regions due to excavation. A numerical model of a jointed rock mass, the compliant joint model, was used to study the response of a jointed rock mass near a circular excavation. The joint constitutive model was linear elastic in shear and nonlinear elastic in the relationship between normal stress and joint closure. Initial stresses were geostatic and representative of stresses in a granitic jointed rock mass approximately 300 m deep. The joint properties were based on values that are representative of joints in granite. The results from numerical simulations were compared with analytical results for stress near a circular opening in an elastic medium having reduced Young's Moduli to simulate jointing effects on the rock mass. The differences in response between the two models resulted from the differences in the symmetry of elastic properties, the shear modulus of the continua, and the constitutive relations in the two models. For example, the non- linear anisotropic elastic continuum described by the compliant joint model resulted in vertical stress concentrations near the side of the circular opening that were 25 percent higher than the vertical stress concentrations in an isotropic linear elastic medium. The equivalent Young's Moduli in the vertical and horizontal directions of the compliant joint continuum deviated by as much as 50 percent from the values assigned to the modeled region prior to excavations. The perturbations of the elastic Young's Moduli extended to distances of two to three radii from the opening.

Jan 1, 1986