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By Nasri Munfah, Steffen Matthei, Vojtech Gall

"Conventional tunneling as defined by ITA WG19 is also known as the New Austrian Tunneling Method (NATM) or Sequential Excavation Method (SEM) was transformed in the US to deal with challenging tunneling conditions as an alternative to the more traditional tunneling methods. It is being used more often in urban areas, under difficult ground and ground water conditions, and with limited cover. Often the tunnel is of a large and non-uniform cross section in soft soils or weak rocks. The intent of using this tunneling method is to minimize impact on traffic and utilities and reduce disruption of everyday life of people and businesses. To meet these challenges, the industry developed technical approaches and implementation techniques and established sophisticated contractual relationships and collaboration in the field among various parties for successful implementation. This paper examines the development of conventional tunneling (NATM/SEM) in the US to deal with these challenges using recent examples such as Russia Wharf in Boston, Northern Boulevard Crossing, in New York, and Chinatown Station in San Francisco. INTRODUCTION / HISTORY Conventional tunneling or NATM/SEM is a concept that is based on the understanding of the behavior of the ground as it reacts to the creation of an underground opening. In its classic form the SEM/NATM attempts to mobilize the self-supporting capability of the ground to an optimum thus achieving economy in ground support. Initially formulated for application in rock tunneling in the early 1960’s, NATM has found application in soft ground in urban tunneling in the late 60’s and has since then enjoyed a broad, international utilization in both rural and urban settings. In the US the NATM/SEM tunneling method has been used successfully to address challenging tunneling conditions in urban areas. A large number of tunnels have been built around the world using a construction approach which was loosely termed NATM. During the years of discussions and the application of NATM a variety of terms have been used for the same construction approach. These terms were primarily aimed at describing the construction approach rather than the region of its reported origin."

Jan 1, 2016

By C. L. Schneider, R. P. King

The ability to predict the liberation spectra that will be produced by a closed-continuous grinding circuit is of fundamental importance for the design, optimization and control of most operations in an ore dressing plant. The only known approach through which such a calculation can be performed is the population-balance-model equation. The latest, and certainly most significant, advance made in this area is the solution proposed by King (1990), which requires one textural parameter measured directly from the ore being studied. The main advantage of King's solution is that, unlike the conventional solutions, it does not require the estimation of hundreds of arbitrary parameters that cannot be independently measured. However, King's solution relies heavily on a knowledge of the detailed internal structure of the Andrews-Mika diagram (Andrews and Mika, 1975), which has never been measured for any ore. The characterization of the internal structure if the Andrews-Mika diagram requires the measurement of the liberation spectra at several progeny sizes produced by the breakage of monosize-monograde particles at several different grades. In this paper, a procedure based on magnetic fluid fractionation for generating seven narrow-size, narrow-grade samples is presented. Each of these samples was then broken into six progeny size classes in an ultrasonic mill. The one- dimensional liberation spectra of each of the 42 progeny and seven parent particle samples were then measured by image analysis. The measured linear-grade distributions are presented in this paper. The calculation of the correspondent volumetric-grade distributions is discussed.

Jan 1, 1995

By Ravi Shah, Augusto Lucarelli, Daniele Peila

"In mechanized tunneling the annular gap between the segmental lining and the surrounding soil caused by tunnel driving, must be backfilled almost instantaneously with an adequate grouting mortar. The objective of this research is to perform a fully three dimensional modeled parametric study using FLAC 3D and evaluate the effects of backfill grouting on the tunneling performance. The research focuses on comparisons between different injection materials and state-of-the-art Bi-Component grout and their effects on the settlements on the surface. The research consists of testing a regular situation of tunnel excavation using a shielded machine with face under pressure. The tunnel dimensions and the soil properties are selected as close as possible to the reality and based on Turin Metro case. 1 INTRODUCTION Excavation of tunnels in urban areas can induce ground movements, which have negative effects on existing structures. In such scenarios, shield tunneling has become a well-accepted construction method in various ground conditions. It is characterized by relatively complex interactions between the soil, the tunnel boring machine (TBM) itself, the tunnel lining and the tail void grout. The problem to control the settlement depends on the face pressure, ground properties and back filling procedure and material of the tail void. The face pressure acts against the front to guarantee the face stability. In case of EPB TBMs the stability of the tunnel face is ensured through the excavated soil itself, which is conditioned and is maintained in compressed state within the excavation chamber. When excavating with TBMs a tail void is created between ground and the lining (Fig.1) after the TBM excavation and ring assembly that must be backfilled instantaneously by injecting the backfill material through the TBM’s tail shield. The process is of primary importance as it reduces the surface settlements and creates an immediate link between the ground and lining, sealing against ground water and leakage, reducing the differential movements between segments and providing long-term stability. The most used backfilling materials are: Inert mixtures that do not contain cement instead sometimes they are replaced by fly ash or other substitutes. A typical design of an inert mortar consists of sand, fly ash, bentonite and water. Pea gravel, which is constituted of granular materials with grain size ranging from 8 to 12 mm. This mixture is highly recommended for tunnels being constructed in rock mass with little deformation rates.Cement mortar is composed of cement, water, aggregates and sometimes bentonite. Cement controls the principle mechanical property of the mix, which can reach high values of 15-20 MPa in 28 days. The aggregates contribute towards the shear strength and reduce the pumpablity of the mix (Thewes and Budach, 2009). The reduced active systems have a cement content of 50-100 kg/m3, whereas the active system the binder component derives full hydration with cement content of over 200 kg/m3 ."

Jan 1, 2016

By W. C. Hellyer

The Granduc ore body is located beneath glacial terrain on the borders of British Columbia and Alaska, some 600 miles from Vancouver and 30 miles from Tidewater at Stewart, B. C. The concentrator and attendant facilities are located in wilderness country at an elevation of 2500 feet. The average annual snowfall is 65 feet. Surface facilities and ore body are linked by a 10 mile railroad haulage tunnel. This copper property has been developed by Granduc Operating Company on behalf of Newmont Mining Corporation and American Smelting and Refining Co. First production started in November, 1970. In August, 1966, Granduc Operating Company awarded an engineering and construction management contract to McKee-Swan Wooster, a joint venture of A. G. McKee of Canada and Swan Wooster Engineering Company Limited, to design a concentrator to treat approximately 7000 tons of ore per day. The isolated location of the Granduc ore body indicated comparatively high freight rates on consumable items of concentrator supplies such as reagents, grinding media, etc. A firm flowsheet for the flotation of the Granduc ores having been developed by the Danbury laboratory of Newmont Exploration Limited, attention was devoted to means of reducing operating costs. One obvious method was to reduce or eliminate the costs of steel grinding media by employing some form of autogenous grinding. two pilot plant operations were carried out at the facilities of Lakefield Research of Canada Limited, in which autogenous grinding of Granduc ores was investigated. The results of these investigations led to the selection

Jan 1, 1972

By T. Resende, J. Sismour

"Signs in underground mines are subject to variable airflow, which carries dust and moisture. Dust buildup reduces their visibility, hampering production efficiency and safety. Underground workers commonly must stop to clean signs in order to gauge their location, or find critical supplies or services. There are currently a variety of coating products, including dust and water repellants, available on the market that have the potential to reduce dust accumulation on sign surfaces. This paper describes a preliminary study to determine their effectiveness. The study involved a practical testing protocol using a trickle rock duster and samples cut from a clean, used road sign. Product effectiveness, under both dry and wet conditions, was evaluated based on photographic evidence by comparing changes in sign luminosity after a period of rock dust application. By analyzing the frequency of different pixel luminosities on the dust-covered samples, both uniformity of dust coverage and the total amount of accumulation was assessed. Results indicate that at least one product may reduce the amount of dust buildup on sign surfaces and increase visibility. INTRODUCTION In all underground mines, visibility of signage is critical. Signs inform miners of their location, direction toward escape routes, and location of supplies. Over time, sign surfaces can collect dust and can eventually become unreadable. The rate of dust accumulation on surfaces is often particularly high in coal mines, where both mining (e.g., cutting and drilling) and rock dusting activities can contribute significant amounts of dust to the airways. Several factors may contribute to dust buildup on sign surfaces. First, basic principles of fluid and particle flow are at play. When a fluid travels past a stationary surface, the velocity of the fluid at the surface boundary is zero. If a very small dust particle moving with air collides with a surface, it does not immediately fall off since the air velocity is zero at the sign surface. (This is the same reason that dust can collect on a rotating ceiling fan.) Further, once the collision occurs, other mechanisms may help keep the particle there – including friction that resists particle falling due to gravity, and adhesive forces due to humidity and/or static charges the particle and others already on the surface. Currently, the most common way to deal with reduced sign visibility due to dust buildup is for mine personnel (e.g., a compliance foreman, supply worker) to periodically clean sign surfaces – usually just by wiping them with a cloth. As a regular activity, this solution is inefficient; in cases of emergencies, it can also pose unnecessary risks. Application of an off-the-shelf coating to sign surfaces may represent a simple yet effective way to reduce the rate of dust accumulation. There are currently a variety of products on the market that may be suitable for this purpose, including dust and water repellants."

Jan 1, 2017

By Harry Verakis

Electronic detonator systems are an advance in technology beyond conventional electric detonators for initiating explosives and blasting agents. Their use is widening into the mining operations of the U.S.A. Each electronic detonator system differs in design, construction, operation, and testing features and each system is different than “conventional” electric detonators. There are benefits of electronic detonator systems which serve to improve blasting safety. With the introduction of electronic detonator systems for mine blasting, issues were raised about the application of MSHA regulations for shunting and circuit testing. The MSHA regulations for surface and underground mine blasting operations address the use of “electric” detonators. Although electronic detonators are initiated by an electric pulse or current, their design is unlike “electric” detonators. To resolve the issues of shunting and circuit testing with respect to MSHA regulations, a technical and field evaluation of electronic detonators was made and the results are presented.

Jan 1, 2005

By K. Chandrasekaran

Carbon-in-leach (CIL) is conventionally used in gold processing operations when preg robbing components are present in the ore. The CIL process is becoming attractive even in other situations when preg robbing is not a factor. This article discusses the situations in which the CIL circuit can be applied. The results of leach-carbon-in-pulp (CIP) and CIL circuits at Newmont Gold's Mill No. 2, No. 4 and No. 5 are presented for comparison: Mill No. 4 was initially designed for a throughput of 4.1 kt/d (4500 stpd). It is presently operating at an average throughput of 6.6 kt/d (7300 stpd) without significant changes to the original design. The design considerations of the Mill No. 4 CIL circuit are discussed. The design of any processing facility represents a series of decisions. The final design options should ultimately be resolved based on economic as well as technical considerations. Every design decision represents some sort of compromise. From the designer's view point, these decisions are made with the conviction that the final product represents the most prudent long-term expenditure. The design throughput rate is a decision reflecting a maximum return for the capital and operating costs that the plant will incur over the life of the mineral resource. The result is a plant that is not operator proof or maintenance free because it would be too costly to build. At some point, the incremental increase in the level of capital expenditure would not adequately compensate for the lower

Jan 1, 1991

By M. A. Trevits, G. W. Luxbacher, L. D. Patts

"It is almost a given that post-disaster mine conditions will have compromised the mine ventilation system, resulting in a hazardous atmosphere in portions of the mine, and often complicated travel through debris fields and roof falls. Robotic technologies provide the opportunity to gather valuable information to assist decision making or lessen exposure to dangerous conditions. MSHA's Mine Emergency Operations Division (MEO) has utilized a fully permissible mine robot, the V2, for a number of years, constantly updating the unit as new technologies became available. The National Institute for Occupational Safety and Health, as part of the MINER Act Extramural Contract Program, examined the need for additional robotic units and ultimately funded three different types of prototype technologies: two robots, the Snake Robot and the Gemini-Scout, and a mine rescue robotic assist vehicle known as the ""Mule"". The Snake Robot is designed to be lowered through a borehole and to conduct surveillance (gas monitoring, video and audio) in the immediate vicinity, while the Gemini-Scout, designed to be deployed in the mine opening, serves as a more mobile and agile exploratory tool as compared to the MSHA V2 robot. The Mule was developed in response to needs expressed by mine rescue teams for a versatile remotely operated support vehicle and it will move from prototype to MEO utilization in the near future. This paper describes the development of the robot prototypes and discusses their limitations in the prototype stage, possible enhancements and potential applications, as well as the utilization of the Mule. INTRODUCTION The conditions in a coal mine may be dramatically altered after a mine fire or explosion. For example, the ventilation system may not be functioning correctly as control devices may be compromised or damaged beyond repair. The visibility in the mine opening may be limited due to accumulated smoke and dust. Roof support systems may be damaged or no longer functional. Equipment and materials may be strewn about the mine opening. Debris fields, blocked openings, roof falls, flooded areas, gas accumulations and active burning make it very difficult or impossible for those managing the post-event emergency to permit mine rescue teams to enter the mine to conduct search and rescue operations. With the evolution of robots and robotic assist technology there has been a proliferation of purpose-built units for the military, police and law enforcement agencies, urban search and rescue and those contending with hazardous environmental conditions. In each case, the technology used is designed to limit human exposure to the unsafe conditions or to provide access to areas under difficult conditions. For example, a specially-designed marine robot has been deployed into the damaged core of the Japan’s Fukushima Daiichi Nuclear Power Plant to assess the conditions of the containment vessels, where melted fuel is believed to have accumulated. Human access to the area is prohibited due to dangerously elevated levels of radioactivity [1]. Multiple robots were deployed in Amatrice, Italy, to assist in the response after the 6.2-magnitude earthquake devastated the town. The robots were used to explore two medieval churches that were severely damaged and deemed too dangerous for human entry [2]. Tactical robots are regularly used by police and law enforcement agencies when the conditions of the emergency place intervening officers directly in harm's way [3]."

Jan 1, 2018

By John Callahan

A stream sediment (minus 80-mesh and minus 60-mesh panned concentrates) and lithogeochdcal survey for gold did not locate any Triassic-age placer deposits in the northern Wadesboro and southern Sanford basins in North Carolina. A stream sediment geochemical program for uranium funded by the North Carolina Energy Institute did identify one and anomalous site (8.5 ppm U; 5 ppm Th) near Covenington, North Carolina and eighteen possibly anomalous sites (1-1.6 ppm U) . Five of the eighteen samples with uranium levels in the 1-1.6 ppm range have high thorium levels (112-853 ppm) and may indicate a monazite source for the uranium. Gold values as high as .83 ppm in the stream sediments and 9.3 ppm in the panned concentrates were obtained during the survey. Small (<.5mm) flattened grains of gold (1-4 grains) were observed along with coarse kyanite and/or monazite in some of the panned concentrates. A distinctive pattern of high gold values in the sediments was observed in the vicinity of Mangum, N. C. where Minard (13) reported values as high as 2.1 ppm £ram a Triassic lithology. Follow-up gold analyses on over 400 rock samples from twenty-eight exposures near Mangum failed to obtain any high values (<55 ppb). The presence of coarse kyanite, monazite and gold in panned concentrates may be from a source younger than the Triassic lithologies that the streams currently drain or adjacent Paleozoic rocks.

Jan 1, 1979

By Weston Bourret

The need for wartime supplies of uranium for the Manhattan Project prompted a 1944 study of uranium in South Africa. Uraninite had been reported by R.A. Cooper in 1923 in a Witwatersrand heavy- mineral concentrate, and the search for uranium, therefore, included the district&apos;s 30 operating mills. The method of investigation was simple: take bulk concentrate samples from the Wifley tables and determine their mineralogy. Samples were taken on a daily basis, although weekly composites also were taken of some mills. In 1944, most mills had simple gravity circuits and produced (I) a gravity concentrate, and (2) an all-slime [-75 pm (-200 mesh)] product. The tonnage throughput was known, and from that, head assays could be calculated. Concentrate samples were sent to the United States for chemical analyses. A Geiger counter set up in a Johannesburg hotel room provided preliminary data. The early data showed uraninite to be widespread. Microscopic, mineragraphic, and siezing tests were all under- taken in Johannesburg. Ultimately, tests led to a high grade (+90%) uraninite concentrate. Platinum and other heavies were the impurities. In seven months, the investigations had reached the stage where it was possible to forecast an annual production of 5.4 to 7.3 kt (6,000 to 8,000 st) of U3O8. The estimate is still realistic. Additional details are found in Bourret (1981).

Jan 1, 1991

By Per-Martin Sandgren

LKAB&apos;s ores have specific mineralogical properties that make them especially suitable for the production of super-grade concentrates. Conditions are particularly good for this purpose at Malmberget, where a concentrate for high-purity sponge iron production has been produced for many years. Until 1978 the approximate assay was 71.2 % Fe and 0.45 % SiO2. Since then the assays have been improved by process modifications to approximately 71.5 % Fe and 0.20 % SiO2. Scope exists for still further improvement. In recent years the production of fractioned concentrates has been started. The material lies within the size range 74-125 µm and the approximate chemical analysis is 71.6 % Fe and 0.30 % SiO2. Other special products are under discussion. The Malmberget ores are also suitable for the production of high-purity direct reduction pellets with a SiO2 content below 1 %.

Jan 1, 1981

By C. Haycocks

Damage prediction during multi-seam mining is an essential precursor to optimizing mine design. Ground control problems associated with interaction are influenced by both fixed geological and site conditions as well as mining variables which may be controlled to varying degrees. To quantify interaction effects across an affected seam a hazard map approach was selected, which allows interaction data to be presented in a form that can facilitate future planning. Study mines were analyzed using boreholes as sources of geological and spatial data, together with information from mine maps which gives the extent of mining activity. To demonstrate the method the safety factor against interactively caused shear failure in the lower seam roof was computed. Input data included depth of cover, inner burden thickness, remnant pillar size, extraction ratio, immediate roof type, seam thickness, percent sand-stone, and rock strength values. These safety factors were then contoured to produce a hazard map. An assumption was made to assign a high safety factor at the outcrop line to permit realistic contouring of the safety factors. The software also allowed mine workings to be drawn onto the map to facilitate interpretation of the overall results. Hazard analysis permits delineation of unsuitable mining areas within a seam. The application of the method for refining mine design and improving reserve recovery is verified using case studies.

Jan 1, 1992

By M. J. Hrebar

A study was conducted to evaluate the applicability of large wheel loaders (Caterpillar 994 Class) for use as primary loading equipment in open-pit iron-ore operations. Field visits were made to taconite and gold mines that used large wheel loaders. Information was gathered on loader selection rationale; operation and maintenance experience; and production, availability and costs. Brief time studies were conducted to indicate machine performance and utilization. This paper summarizes the field data that was collected, including an economic comparison of wheel loaders and cable shovels in an iron-ore application.

Jan 1, 1998

By S. S. Klima, J. A. Organiscak

Researchers at the National Institute for Occupational Safety and Health (NIOSH) performed laboratory testing to examine and improve airborne dust capture and methane removal performance of flooded-bed scrubbers on continuous mining machines using a blowing face ventilation configuration to reduce respirable dust exposure to shuttle car operators. Several testing conditions were examined to minimize shuttle car operator dust exposure without adversely affecting continuous miner performance and production. Curtain-to-face setback distance of 9.1 m versus 15.2 m (30 ft versus 50 ft), face ventilation airflow of 226.5 m3/min versus 339.8 m3/min (8,000 ft3/min versus 12,000 ft3/min), and the use of side-body-mounted blocking sprays (on versus off) were the three primary parameters compared. Scrubber airflow was set and maintained at 198.2 m3/min (7,000 ft3/min) throughout testing. An examination of slab cuts versus box cuts and the location of the shuttle car (present behind the continuous miner versus not present in the entry) was also performed to demonstrate the effects of these constantly changing scenarios on scrubber performance. Results show that the best blowing face ventilation setup for minimizing shuttle car operator dust exposure for the tested parameters uses a 15.2-m (50-ft) curtain-to-face setback with 339.8 m3/min (12,000 ft3/min) face ventilation while operating the side-body-mounted blocking sprays. INTRODUCTION Coal mine worker overexposure to respirable coal dust continues to be a problem in U.S. underground coal mining operations, potentially leading to coal workers’ pneumoconiosis (black lung). The U.S. Mine Safety and Health Administration (MSHA) requires that respirable dust exposure to coal mine workers does not exceed a 1.5 mg/m3 average over the actual working shift (79 Fed. Reg. 24814 (2014)). Although using a blowing face ventilation configuration on continuous miner (CM) sections is beneficial for removing methane emissions from the mining face, it can be detrimental for dust control for shuttle car (or ram car) operators and any other workers on the return ventilation side of the CM when compared to exhausting ventilation. Even with machine-mounted scrubbers on CMs, shuttle car operators still have some of the higher dust exposures with blowing face ventilation systems (NIOSH 2011, Beck et al. 2015). Although scrubber discharge air is not completely clean, dust being blown around the scrubber inlet and therefore not being captured by the scrubber can further increase these dust exposures (Goodman 2000). Dust control problems are also caused by inadequate face ventilation quantities causing scrubber face airflow recirculation issues (Schultz et al. 2010). In order to minimize respirable dust exposures on blowing face ventilation sections, ventilation, water spray, and scrubber parameters were experimentally examined to improve operating ranges for both dust and gas control. Several blowing face ventilation factors were examined with respect to CM spray systems and scrubber operation. Curtain-to-face setback distance and side-body-mounted blocking sprays were previously examined in the laboratory for dust control on a full-scale CM model using a scrubber on a blowing face ventilation system (Goodman 2000). The blocking sprays produced larger dust reductions at the CM’s rear corners and return for a 6.1-m (20-ft) curtain setback distance as compared to a 12.2-m (40-ft) curtain setback distance with equal face and scrubber airflows of 169.9 m3/min (6,000 ft3/min). Because face ventilation airflow quantities, shuttle car operator locations, and tracer gas concentration gradients were not previously examined during these experiments, additional research was required to determine improved operating parameters for blowing face ventilation systems.

Jan 1, 2019

By David B. Costain

Three dimensional surface approximations are important means of evaluating physical and environmental factors that affect surface coal mining and reclamation. Computer approximated surfaces are projected as an array of square grid cells where individual cells define each parameter value respective to locations on the grid. Grid surfaces or grid cells within a surface can be compared or modified through application of standard mathematical functions. Surface approximations can be used to define the quantity and quality of marketable coal and to evaluate thickness and quality of overburden. Surface approximations also can be used to evaluate overburden swell factors wherein changes in post-mine topographic relief are related to expansion of unconsolidated materials in the backfill. Application of computer approximated surface to analysis of approximate original contour (AOC) standards allows an assessment of the quantity and geographical displacement of overburden and the distribution and numerical level of slope.

Jan 1, 1984

By M. L. Klohn

The Felder ore deposit is a 5,000,000-pound uranium deposit in the South Texas Coastal Plain. It occurs in the basal sand of an Oakville Formation (Miocene) alluvial system. The host sand is a carbonate-rich arkose which contains virtually no carbonaceous debris and has been reduced by the local introduction of hydrogen sulfide. The ore lies well within the reduced zone and occurs as coffinite and uraninite that fill interstices and coat and replace grains. The overall geometric configuration of the ore is that of a winged, crescentic ore roll. Weak mineralization extends the wings of the ore roll and gives greater expression to the roll character. Departures from the shape are controlled by discontinuities in bed- ding and by proximity of the ore to the surface. Associated with the uranium is a broad halo of anomalous molybdenum. Subsidiary mineralized trends suggest a pre-existing up-dip position for the main roll. Oxidation from the surface largely destroyed this previous roll by solubilization of uranium. Uranium subsequently migrated into favorably reduced sand and reprecipitated at the present roll position.

Jan 1, 1970

By W. A. Hoyer

Neutron activation analysis for mineral identification has attracted the attention of numerous investigators, judging from the publications on this subject in the past few years. 1-9 The appealing aspect of this method of mineral analysis is its proven sensitivity in the laboratory. In principle, activation analysis is one of the few petro-physical methods whereby a direct analysis for a mineral itself is possible in a borehole. The successful application of activation analysis requires the use of particular neutron reactions, measurement of selected gamma-ray energy intervals, and optimum bombardment and detection times. For copper analysis, Labanov et al., 10,11 using a low-energy PuBe source, reported an acceptable logging means. On the other hand, Pradzynski12, in analyzing ores and process tailings, used high-energy neutrons and photons for surface measurements of process samples. The work of Labanov et al. was based on measuring the rate of decay of the activated copper and hence was not as definitive as might be desired. Equipment is commercially available to carry out activation studies in the field 13,14 Gamma-ray spectra can be successfully transmitted over ordinary logging cables and, with borehole high-energy neutron accelerators and lower-energy chemical neutron sources, a variety of neutron activation methods can be studied. The purpose of the study discussed in this paper was to determine the feasibility and practicability of logging for copper using neutron activation techniques and commercially available equipment. The laboratory study showed that Cu could be detected in rock samples in the laboratory by high-energy neutron activation of 63 Cu. In the field, however, due in part to the large volume irradiated, the direct detection of copper using high-energy neutrons was not as promising. Detection of copper by measuring both the direct gamma-ray emission and the excessively strong low-energy gamma-ray absorption appears promising. Copper was not detected either in the laboratory or

Jan 1, 1972

By PEILIN LAN, LEONARD HILL, SIMON TIMBILLAH, BERNARD FOSU, CESAR SOSA-BLANCO

The use of sodium hydrosulfide (NaHS) in most of the operations in byproduct molybdenum flotation comes with safety concerns and, in some instances, a high reagent cost. Engineered solutions at the various operations where NaHS is used have immensely reduced the possibility of hydrogen sulfide (H2S) gas evolution. However, the threat of exposure remains, and this, coupled with the high dosages of NaHS consumed, supports the continued search for alternative depressants. This paper focuses on efforts to study the applicability of disodium carboxymethyl trithiocarbonate (DCMT), an organic depressant, as an alternative to NaHS. Bench-scale rougher flotation results for samples from the Sierrita copper–molybdenum (Cu–Mo) plant showed the best DCMT performance at 8 kg/t of DCMT, pH 10.5, 30 min of shear conditioning and 10 min of flotation conditioning. The Aminpro plant model simulation confirmed that 4 to 8 kg/t DCMT under certain shearing and conditioning times achieved superior or equivalent Mo–Cu separation efficiencies when compared\ to NaHS.

By P. Kawahata

Newmont?s Twin Creeks Mine, located in northern Nevada, is producing gold ore from surface mining operations. The ore is currently processed at three different on-site facilities depending on ore type and grade. Processing facilities operate under stringent geochemical blending constraints that must be met from mine ore deliveries and off-site sourced ore. To analyze various strategic options, the technical team utilizes the mathematical optimization approach. However, due to the size and complexity of the operation, there are unique challenges in optimizing life-of-mine production scheduling. This paper describes those challenges and methods developed to take advantage of different scheduling software to effectively compensate each other and result in reasonable guidance. This paper also describes how those scheduling results are reflected in detailed mine plan and cost estimate work.

Jun 1, 2013

By Henry B. Estabrooks

As was the case with many other mining companies, the management of Tennessee Copper Company&apos; viewed with some interest reports in various trade and technical journals of the successful use of ammonium nitrate-fuel oil mixtures as an explosive in coal stripping., construction, open pit mining and finally in underground salt mines. The apparently simple transition from the "interested" stage to a point where in excess of 80% of the ex¬plosives used is ammonium nitrate may be of interest. The Tennessee Copper Company operates five mines in the "Copper Basin" of Polk County which lies on the extreme southeast corner of Tennessee. The ore is a massive sulfide principally pyrrhotite and pyrite with some tough lime silicates as gangue while the walls are greywacke interbedded with schist. Average total production is 28,000 tons per 5-day week and an average of 422 feet of development per week. Development work consists of 8&apos;x 8?, 6?x 7?, 5&apos;x 7? and 4&apos;x 6? drifts driven with drifter drills using 1-5/8" carbide detachable bits and 5&apos;x 5&apos; raises driven with stopers using 1-5/8" bits.

Jan 1, 1962