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By Remo Grandori

"INTRODUCTIONDouble Shield TBMs were introduced in the market in the early seventies with three main targets:• Increase the TBM performances in term of advance per day thanks to the ability to erect a segmental lining simultaneously with the excavation phase.• Be able to advance through unstable and disturbed rocks under the protection of the shields• Provide a finished tunnel by installing a precast lining as the TBM advance.In 2003 SELI developed the design of the Double Shield Universal (DSU) TBM as an evolution of the original Double Shield TBM design.This new TBM design was targeted to improve: the TBM capability to advance through squeezing/converging rock formations under high cover, the telescopic joint design (allowing by such to operate the machine in double shield mode in very weak rock), the capability of the TBM to investigate and treat the ground around and ahead of the tunnel face.In the same lapse of time Single Shield TBMs, originally utilized for soft ground tunnelling, extended progressively their range of application to mix rocks and finally to hard rock tunnelling with increasing performances.This also thanks to the substantial reduction in the installation time of the segmental lining ring that contributed to minimize the TBM stand by time between two consecutive boring strokes.Today the choice between the two types of TBMs needs to be carefully evaluated project by project since one type of TBM may “prevail” in certain geologies and diameters and vice versa.THE VISHNUGAD PIPALKOTI TUNNELThe Vishnugad Pipalkoti Tunnel is part of the 444 MW Vishnugad Pipalkoti Hydro Electric Project (VPHEP) on Alaknanda river in Uttarakhand (India).The Owner is the Indian electric company “Tehry Hydro Development Corporation” (THDC) and the World Bank finances the project.The Headrace Tunnel total length is 13.4 Km and a section of about 12,3km will be excavated by TBM by SELI Overseas (Italy) in subcontract to HCC (India) the General Contractor for the project. The TBM will be delivered ex workshop in March 2016 and it is foreseen to start boring in the second half of 2016.Figure 1 below shows the location of the project and the following Table 1 summarizes the geometrical characteristics of the TBM tunnel."

Jan 1, 2016

By K. Rajamani

The word adapt means "to change so that one's behavior will conform to new or changed circumstances." Applying this definition to process controllers suggests that an adaptive controller can change its behavior in response to changes in the dynamics and disturbances of the process. In the minerals industry there are many control cases where adaptive control will provide superior control as compared with more traditional PID (proportional, integral, derivative) control. A typical plant uses as many as 100 to 200 control loops for lprocess regulation. Therefore, the task of initially tuning and then periodically retuning these controllers is a formidable problem, During the time the controllers are "un-tuned", product quality may deteriorate and unstable operations may result. Adaptive controllers are capable of tuning themselves, thus avoiding this problem. The computers commonly used in distributed control systems are easily capable of implementing adaptive controllers. In addition to the possibility of using the control computer to implement adaptive controllers, many distributed control systems will offer adaptive control as a standard feature in the near future.

Jan 1, 1984

By R. C. Milici

Historical production data and reserve decline rates can be used both to predict future coal production rates and to estimate when the reserve will be depleted. Reserve estimates inferred herein from historical production data and decline rates are commonly lower than estimates made from geologic data. The latter include significant amounts of lower quality (deeper, thinner, higher sulfur) coal which may be mined when the better deposits are depleted.

Jan 1, 1997

By Lennart Bergstedt

Boliden Aktiebolag, the prime base metal mining company of Sweden, annually treats some 11-12 million tons of sulphide ore in nine concentrators. Its first flotation plant was established in the early thirties for the complex Boliden ore. Since then, the number of mines and plants has gradually increased. Considerable effort has been devoted to the development of all phases of the technology of ore prospecting, mining, milling, smelting and refining. This has been necessary due to the complex and low-grade ores. The development of concentration has mainly been directed toward the arts of grinding and flotation. During the forties and fifties, open-stage fine crushing followed by two-stage grinding in rod and ball mills with cyclone classification was successfully introduced and used throughout the plants. The increasing cost of grinding media led to studies of an autogenous grinding technique as early as 1945. Basic test work commenced during the early fifties, with a. number of ores tested for pebble grinding. In 1956 a new pilot plant was built, with equipment installed for the continuous testing of pebble grinding and, later, for primary autogenous grinding of run-of-mine ore. The intensive test work showed that pebble grinding was feasible in almost all of the plants. At this early stage of testing, however, the merits of autogenous grinding could not be fully evaluated. As a. consequence the rod mill/ball mill grinding systems were converted to rod mill/pebble mill systems whereever possible. In parallel with the converting of grinding systems the development work concerning the merits of autogenous grinding went on. The major result

Jan 1, 1977

By H. K. Lin

The free-milling ore characteristics of the Fort Knox gold deposit are ideal for studying gold and silver behaviors in various processing circuits without serious interference of sulfide minerals and other refractory factors. A galvanic effect leads to faster silver dissolution than gold dissolution and, as a result, the Au/Ag solution concentration ratio increases through the leach circuit. In the CIP circuit, Au adsorption is more effective than Ag adsorption. The Au/Ag solution concentration ratio decreases from 10.0 to 1.0 as the slurry advances from CIP tank #1 to CIP tank #5, while Au/Ag ratio in the carbon increases from 3.2 to 15.3, as the carbon advances from CIP tank #5 to CIP tank #1. Silver is stripped more effectively than gold from the loaded carbon. The Au/Ag ratio in solution reaches 2.0 in the first 75,700 L of strip solution that pass through the loaded carbon; as the stripping process continues, the Au/Ag ratio in the strip solution increases. In the electrowinning circuit, the Au/Ag ratio in the spent electrowinning solution is significantly lower than that in the electrowinning feed, indicating that Au is more rapidly deposited onto the cathode than Ag.

Jan 1, 2010

By W. M. Lewis

Product losses to tailings ponds have long been a source of frustration for the mining and utilities industries. The utilization -of the Lewis Econosizer to recover lost products has proven to be very cost effective through reduced acreage requirements, cleaning costs and increased production. The unit is successfully operating in coal, aggregates, industrial minerals, clay, fly ash, heavy minerals and many other ores. Utilizing an upward flow of slurry in a free settling environment, particles stratify within the unit according to settling velocities and are removed as sized products. Ultra fines or clarified water is removed off the top of the unit. The Econosizer requires no power and only minimal maintenance.

Jan 1, 1998

By Abb Raymond

Finely processed industrial minerals in "powdered" form have long been utilized by the plastics, paint, rubber, paper, ceramics, and adhesives industries as fillers, extenders, coatings and special additives. These minerals, primarily calcium carbonate, talc, kaolin, titanium dioxide, and the like, have provided economic, uniform and consistent base materials which have, in turn, been used by the referenced industries to manufacture quality products. The focus of this paper will be the development of equipment and systems at ABB Raymond for the dry processing of such non-metallic minerals in order to meet what have become increasingly stringent requirements of the producers of these minerals. Changes in these requirements seem to have been accelerating rapidly during the last ten years, and it is expected this process will continue into the 1990's.

Jan 1, 1990

By Liming Yuan, A. C. Smith

Barometric pressure changes affect air density, leading to change in the mass of the gas in the gob. When the barometric pressure decreases, the volume of gas in the gob expands, while the volume of gas contracts when the barometric pressure increases, a process which causes the gob to “breathe” out and in. Although the concept of gob “breathing” is simple, its effect on spontaneous heating of coal in the gob area is not clear. In this study, computational fluid dynamic (CFD) simulations were conducted to model the spontaneous heating of coal in the longwall gob area under measured barometric pressure changes. A single longwall panel using a bleederless ventilation system was simulated. If there is no barometric pressure change, the intake airflow rate is equal to the return airflow rate. When the barometric pressure changes, these two airflow rates are no longer equal, and the difference between the two airflow rates represents the airflow rate the gob breathes in and out. The effect of inflow and outflow of gas on the potential spontaneous heating in the gob was investigated using the CFD model developed in our previous study. The effect of barometric pressure changes on the spontaneous heating was found to be dependent on the gob permeability and the coal oxidation rate. The effect of barometric pressure changes on oxygen concentrations in the gob was also examined.

Jan 1, 2010

By Gunnar Sparrman, Börje Ahlgren, Sten Rosenström

Starting in 1967 two major hydroelectric power projects have been implemented in East Africa viz. Kafue Gorge in Zambia and Great Ruaha in Tanzania. The two projects have similar characteristics and each consists of an underground power plant, a dam in connection with the power plant and a reservoir dam. The power plants are both designed and constructed according to principles applied in Scandinavia for a long time. Each consists of a headrace of a horizontal unlined rock tunnel with a length of about 10 km, vertical penstock shafts, machinery and transformer halls in large rock caverns and a tailrace of an unlined rock tunnel with a length of about 1 km. The head of the power plant of Kafue Gorge is 400 m, Great Ruaha 175 m, the capacity is 900 MW and 200 MW respectively. Both plants were executed in one stage, but building and erection works were made in two stages. However, the power plants show some interesting differences in design. The power plants are briefly described in the following, special regard being paid to the excavation works. GEOLOGY General The foundation of Eastern and Central Africa is made up of ancient crystalline rocks, consisting of sediments, lavas and intrusives, mostly intensively altered by repeated metamorphism. This repeated metamorphism - dynamic, ther-

Jan 1, 1979

By J. R. Parry

Over the past several years, computerized financial models have been an important part of Newmont's strategic planning process. Two applications will be discussed in this paper: a general purpose financial model of Newmont, and a detailed operational/financial model of Magma Copper Company. Newmont?s general purpose financial model was developed using Lotus 1-2-3. It was designed to aid management in assessing the financial consequences of investment and financing decisions associated with long-term strategic planning by simulating the consolidated effect from individual transactions. Not only is the model capable of assessing the sensitivity of specific decisions to changes in the external economic environment (i. e., commodity prices, interest rates, inflation and exchange rates), it can also evaluate the effect from operating and financial decisions, including changing production levels and cost structures at individual operating units as well as simulating several types of transactions, including equity and debt issues, acquisitions and divestitures. The analysis of Magma Copper Company required the development of a detailed operating and financial model of the Company. The model was developed using IFPS in the corporation?s UNISYS (then Burroughs) B7900 mainframe computer and included separate pro forma financial statements for each of San Manuel-Pinto Valley's mines and concentrators, as well as Magma's smelting and refining operations. The outcome of this analysis was the decision to merge Magma Copper and Pinto Valley Copper Corporation, and to recapitalize the new corporation in order to provide funds for a retrofit and expansion of its Arizona smelter and expansions of its refinery and SXEW facilities.

Jan 1, 1989

By Bruce H. Mason

The exploration for a commercially acceptable deposit of limestone is consid¬ered by many to be a relatively easy task; however, trying to locate a zone of high calcium limestone of economic thickness within a formation, which outcrops only in a narrow band varying in width from a quarter mile to ten miles, adds considerably to the normal problems experienced during an exploration program. The existence of varying glacial and karst features in the outcrop area intensified the problems encountered and complicated the interpretation of the economic value of the deposit. This paper highlights a recently completed five year exploration program during which approximately 3,900 acres of ground in seven civil townships were evaluated as potential sources of high-calcium limestone. Details are given with respect to the final site chosen and the methods used in determining the suitability of the site. This site exhibited many karat features and several methods were utilized to determine the effect of these features on the gross characteristics of the deposit. Aerial photography for both mapping and interpretation were utilized. Black and white panchromatic photography, black and white infrared and color infrared photography were flown. Resistivity, diamond core drilling and close-interval angering were used to supplement the information obtained from the aerial photography.

Jan 1, 1974

By Bo Hyun Kim, Mark K. Larson

Fault-slip bursts induced by mining activities can result in severe damage to nearby mine development. In general, engineers designing rock support in burst-prone mines not only need to consider stress redistribution resulting from excavation, but also dynamic loading that results from seismic waves generated by large mininginduced fault-slip events. In this study, we simulated dynamic waves in sedimentary rock from a blasting source and from a mining-induced-seismicity source using a Universal Distinct Element Code (UDEC) model with discrete fracture networks (DFNs). Our purpose was to investigate the stability of openings and the adequacy of existing support systems at an underground limestone mine in South Korea. A baseline model with only static loading was also simulated, which verified observed stability under such conditions. The results indicate that the current support system of shotcrete lining is likely to work well under dynamic loading caused by blasting. However, when the dynamic source was a far-field fault-slip event, the dynamic loading exceeded the support capacity of the shotcrete lining. Thus, if a mine is operating in ground with an elevated risk of mininginduced fault slip, mine engineers should consider seismic wave propagation and ground motion distribution from a remote, mining-induced fault-slip event to determine a suitable support design.

Jul 1, 2023

By B. H. Kim

The use of a 25.4 mm diameter water-only hydrocyclone for separating fine-size (-150 µm), high-density (>4.5 g/cc) particles from similar-size, lower-density (2.65 glee) particles was investigated. It was found that a single-stage separation recovered nearly 90% of the heavy minerals (7.0 g/cc), while achieving a volume reduction of about 70%. The use of dense medium in a single stage improved volume reductions to 90% at similar heavy mineral recoveries. In addition, computer simulations of a three-stage circuit were performed, which showed that recoveries approaching 97% with volume reductions of 95% were possible.

Jan 1, 1998

By B. C. Lewis

The mining industry has experienced a general trend toward an increasing number of longwall operations, an increasing percentage of underground coal being mined by longwalls, and increasing productivity from the longwalls. Longwall operators have not yet reached a state of mining euphoria. Competitiveness both within the industry and from alternate fuel sources is forcing continued pursuit of higher productivities and lower costs. The following graphics present trends in the industry. Longwall mines, as defined for this presentation, are those reportedly having longwall installations in each of the respective years. Production from both the continuous miner and longwall units is included in the longwall mines. Non-Longwall mines are all other underground mines. Productivity calculations are based on total employee-hours associated with the operation.

Jan 1, 1990

By P. McGrath

From the mid-1980s through 1997, Echo Bay Alaska evaluated reopening the historic Alaska-Juneau (AJ) gold mine. Their original proposed project underwent numerous modifications in order to minimize the potential for significant environmental impacts. One of the major modifications involved changing .the tailings disposal method from a conventional tailings impoundment to submarine tailings disposal (STD). In 1995, the U.S. EPA began work on a Supplemental Environmental Impact Statement (SEIS) to assess the impacts of the STD proposal. Key features of the STD impact assessment included fate and transport modeling to determine the extent of tailings deposition and the use of ecological risk assessment to predict marine impacts during deposition and ecosystem recovery following STD. A key feature of the SEIS regulatory process included a rulemaking proposed by EPA to exempt the AJ tailings from effluent regulations. Critical to success in moving the project forward was early development of an interactive working relationship with other regulatory agencies and the public.

Jan 1, 1998

By William J. Miles

For compliance with the Hazard Communication Standard and other federal and state regulations, numerous minerals, chemicals and products need to be evaluated for crystalline silica content at a threshold of 0.1 %. The polymorphs of crystalline silica that can occur in chemical and mineral products are quartz, cristobalite and tridymite. Other natural, industrial and synthetic amorphous silicas and hydrates must be distinguished from these polymorphs to prevent over-regulation in the workplace and environment. A number of industrial silica products are composed of glasses, expanded perlite, diatomite, slags, and precipitated and fumed silica products. Amorphous silica hydrates used for industrial products, include opal (hydrated silica of biogenic or inorganic origin), perlite, pumice and tuffs. In addition, crystalline and amorphous silicate minerals and chemicals, abundant in nature and industrial products, must be distinguished from the polymorphs of crystalline silica.

Jan 1, 1997

The properties of interfacial water at hydrophilic surfaces are of great importance in many technological areas including flotation, solid-liquid separation, dispersion and emulsions, flocculation, adsorption, corrosion, and soil contamination. This paper examines the use of FTIR/internal reflection spectroscopy (FTIR/IRS) to study the spectral characteristics of interfacial water at silica surfaces. FTIR spectra were characterized by consideration of the OH stretching region (3000-3800 cm-1) associated with the vibrational spectra of interfacial water. The broad peak in this region was deconvoluted in order to isolate overlapping spectral features that describe the nature of hydrogen bonding in interfacial water. Three distinct bands were found; -3600 cm-1 (free OH), -3400 cm-1 (incomplete tetrahedral coordination), and -3240 cm-1 (complete tetrahedral coordination) and the variation of their intensities with pH was found to be significant. This spectral information helps to explain orientation and bond ordering of interfacial water molecules at hydrophilic surfaces.

Jan 1, 1998

By Ralph C. Flow

In Cleveland County, North Carolina, one and one-half miles south of Kings Mountain, Foote Mineral Company operates an open pit for the production of spodumene, feldspar, mica, and commercial stone. Spodumene concentrate is sent to Footers Sunbright, Virginia plant and to other customers. Exton, Pennsylvania and New Johnsonville, Tennessee plants produce lithium compounds sold to the oil industry for multipurpose lithium-base greases, to the metal industry as welding flux, to the air conditioning market, and to the glass industry. Ceramic grade spodumene, feldspar, and mica concentrates go to other processing companies from the Kings Mountain plant. Waste amphibolite is delivered to a neighboring quarry operation.

Jan 1, 1962

By Egon Pohl, Peter Eckl, Friedrich Steinhäusler, Johanna Pohl-Rüling

RADON EXPOSURE AND CARCINOGENIC CELL TRANSFORMATION The highest radiation burden to miners is due to inhalation of radon and its short-lived decay products. The quantification of the risk associated with this radiation burden is complicated by modeldependent lung dosimetry, insufficient accuracy of past human exposure data as well as lacking knowledge about potential synergism of various carcinogens. Nevertheless, it is evident from epidemiological studies of miners that inhalation of elevated levels of radon daughters is correlated with increased lung cancer incidence (UNSCEAR, 1977). The situation is further complicated by the lack of reliable data on the biological variability of the latency period for the development of lung tumor under varying exposure conditions. At present information on variation with age is scarce, however, it is indicated that the excess lung cancer rate for workers exposed to high radon levels is considerably higher, if exposure occurs at ages over 40 years as compared to under 30 years of age (Sevc, Kunz, Placek, 1976). Furthermore, latency period is shorter by 6 - 7 years for smokers exposed to elevated radon levels than for non-smokers (Fry, 1976). Analysis of US- and CSR-uranium miner data revealed that the mean latency period is in the order of about 15 years (Jacobi, 1973). These uncertainties, together with medical diagnostic shortcomings, lead to the dissatisfying situation that at present the detection of radon induced injury of mining personal is primarily the assessment of the endpoint, i.e. radiation induced cancerous transformation of lung cells with typically less than 10% chance for recovery. Therefore it would be advantageous to develop practically applicable diagnostic aids to indicate already early precancerogenic changes of cell characteristics. This would permit the identification of specific population groups at increased risk for the development of lung cancer, thereby increasing the chances of more successful medical treatment. Despite continuous improvements in the reliability of test methods for the diagnosis of cancer cells there is still need for techniques, which enable the detection of transformed cells before the onset of invasion of the host organism. It is generally recognized that the transformation of a cell into a malignant state leads to a change of the cell surface, indicating a correlation between membrane-specific immunological properties and loss of growth control. Surface alterations on cells appear to be responsible in part for the malignant state and are not simply secondary effects of the transformation (Schnebli and Burger, 1973). Furthermore, membranes of cancer cells differ significantly from those of normal cells, particularly, in permeability properties (Rastogi, 1976). In dying cells, proteins, glycoproteins, peptides, aminoacids and their breakdown products are released, which block the permeation of the membrane itself. A mammalian cell can be considered as a 3-phase system (interior, boundary, environment) with the membrane forming a heterogeneous barrier between two subsystems. Under normal circumstances a difference of chemical potential is maintained on both sides of the membrane, causing an ion gradient across and fixed surface charges on the membrane. This results in a membrane resting potential (MRP) between cytoplasm and the bulk medium. It has been shown that MRP is a highly sensitive indicator for cellular reactions due to physical, chemical and biological agents, particularly whenever phenomena of transport and ion gradients as well as permeability are involved (Redmann, 1980). The primary interaction of the agent "ionizing radiation" with any form of living matter occurs at the cellular level. The component with the highest hit probability is the cell membrane. In the study presented MRP-changes of human cells were investigated with simultaneous measurements during irradiation and post-irradiation intervals up to six days. Furthermore, the suitability of MRP-measurements of human cells was tested as an indicator for early changes of cellular properties prior to the histological confirmation of carcinogenic transformation. EXPERIMENTAL METHODS Lung cells The biological specimen used were cultured human lung cells and human lung biopsy samples. Monolayers of lung fibroblasts (W138) were grown in petridishes using conventional culture techniques. In addition, transformed lung cells (W138SV13, subline 2RA) were used applying similar culture methods. All petridishes were incubated at 37°C and only cells in logarithmic growth phase were used. Freshly excised lung biopsy samples were obtained from randomly selected male and female patients (20 cases), where suspected or unclear malignancies were indicated by clinical or X-ray observations. At the time of sampling 80 % of the patients were or had been smokers in the past. The samples were taken by means of a stiff bronchoscope introduced into the trachea under local anasthesia with 1 % Novesinsolution (preparation with Atropin and Pantopen). This permitted the observation of both main bronchi down to the segmental bronchials. From each patient two tissue samples were excised from the mucusepithelial layer under visual control with fiber optics and transferred immediately into 1 % NaClsolution. One sample was taken from the suspected

Jan 1, 1981

By D. K. Grubbs

Red bauxites from Breadnut Valley, Clarendon Parish, Jamaica, are very homogeneous in texture. Bauxite minerals are uniformly distributed in a groundmass, the predominant grain size being smaller than l um (Figure 1 Although the deposits have a massive, non-stratified structure, they all seem to have been affected by postformational faulting which is evidenced by shear zones running subvertically through the deposits. These shear zones stand out very clearly because of a yellow staining along their faces. Often yellow zones, ranging from a few m to several cm in thickness, have developed. When the shear zones are cut at an angle, they appear as yellow veins. Near the surface of the deposits, yellow material forms shallow irregular lenses (Figure 2). In most cases, tree roots (hair roots), or their imprints, are associated with the shear zones or stained areas. In fact, the yellowish color is especially pronounced along these roots and often disappears where the roots end (Figure 3). The mineral composition and texture of red groundmass and yellow zones are markedly different. Secondary phosphate minerals and a higher goethite to hematite ratio characterize the mineral composition of the yellow zones. It should also be noted that Al-substitution in goethite from these areas is significantly higher than in goethite occurring in the groundmass (Figure 4).

Jan 1, 1980