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By R. C. Runvick

Gypsum resources are significant in the midwestern United States, with specific deposits varying in "place value" relative to the major markets served. Underground and surface mining operations produce gypsum from sedimentary rocks ranging in age from Silurian through. Jurassic. Although reserves tend to be limited at individual operating properties, potential resources are vast and future development will hinge principally on market growth and changing economic conditions. Most critical of the variables affecting the industry in both the short and long term will be the availability, type and cost of energy and both processing and distribution.

Jan 1, 1980

By Harry M. Conger

Thirty years ago, the U.S. gold mining industry was hanging on by its fingernails. Save for one great mine, the Homestake, most production was coming from copper smelters such as Kennecott and Magma. Even Homestake itself was under great pressure from rising costs and a fixed price for gold. The outlook was dim, to say the least. Today, as it has for most of the past decade, the American gold mining industry stands among the world leaders in production, and in the development of mining and mineral processing technology. What caused this dramatic change? Obviously, the freeing of the gold price was a major factor, as was the decline in South African production, but these events alone could not have created the U.S. strength we see today. It was technology, investment, and the determination of miners to build an entirely new industry that were the indispensable ingredients. The U.S. Bureau of Mines, with great foresight, had begun the research that led to heap leaching before the gold price began to rise, and Newmont had committed to build a small mill at Carlin, a move then considered quite risky. From that point, the U.S. gold mining industry was placed on lower-grade ores then being found in Nevada and elsewhere, but it was soon apparent that we would have to develop new technologies to deal with more refractory ores, carbonaceous as well as sulfide-bearing. This is now being done with considerable success. Despite its success, or perhaps because of it, the gold mining industry has come under pressure from various groups who characterize their activities as motivated by "public interest." The public interest they refer to properly include the health and safety workers and impacted communities, as well as protection of the environment, and with these concerns we miners have relatively little argument. In fact, we consider health, safety and the environment among our highest priorities, and not just because regulations may require us to do so. The argument, however, is not about the regulation of a viable mining industry, it is about a well-organized movement to attack and condemn mining in the media and to misrepresent its importance to the Nation and its willingness to accept responsible regulation. Once largely local or regional, the interest groups to which I refer are now quite large, national in scope, and even becoming international. This trend, taken together with finances raised from their dues and contributions, would make the interest groups formidable adversaries for mining, but their grip on the media enormously magnifies their influence. Unfortunately, it also makes possible the wide dissemination of incomplete, incorrect or slanted information. I am not here to "bash" the interest groups. On the whole, I believe that many of them have made positive contributions to society. As conservationists, however, I question their authority to make, or foster, decisions about which American industries and communities live and which die. To illustrate, I would like to present for your consideration the problem of cyanide, one of the issues over which the gold mining industry is most threatened. CYANIDE-POISON OR MIRACLE SOLVENT? Let me get this out of the way right up front: cyanide in most of its chemical forms is toxic. In some forms it is also listed as a carcinogen. These are adverse characteristics cyanide shares with a considerable number of industrial chemicals, including some that are widely used without the stringent regulations already in place for the mining uses of cyanide. In these uses, by the way, the risk to humans comes from direct ingestion of cyanide or cyanide-bearing solutions, or from the accidental acidification of solutions leading to release of hydrocyanic acid gas. That these risks are under control in mining can be seen from the fact that, in modern U.S. practice, there has never been a documented fatality attributed to cyanide! Because of its toxicity, cyanide cannot enter and be accumulated in the food chain. It can, however, be a threat to birds and animals that ingest cyanide-bearing solutions. Protection against this is, quite properly, a responsibility of individual mining operations, and considerable sums are spent each year to prevent or reduce bird and animal exposures. It should be evident, though, that many human activities, including highway traffic, windmills, use of pesticides and the like, result in bird and animal losses. Mining's use of cyanide, and the measures taken to protect birds and animals, should be considered in context. Cyanide must be kept out of surface streams and groundwater, and existing regulations mandate this. Any cyanide residues left in leach heaps, waste dumps and disused facilities must be eliminated, and we have proven technologies to do this now, just as we have means to detoxify tailings prior to disposal. The gold mining industry decries those rare instances when irresponsible operators fail to deal with contamination, and agrees that they should be held responsible. We do not agree, however, that the great majority of responsible companies should be punished, in advance, for accidents that have never happened. So much for the poison, what about the "miracle solvent?" Is that an overstatement? Well, consider the fact that gold has been called "noble" from earliest times, because it does not oxidize under atmospheric exposure, and that it appeared to the ancients to be utterly insoluble. Later generations of scientists did discover that it could be dissolved, but only by a combination of acids so potent that it became known as aqua Regia. Later still, it was found that chlorine would also dissolve gold, and attempts were made to base commercial processes on this, without a great deal of success. It remained

Jan 1, 1995

By Peter L. Dunn

With the advent of new high-strength magnetic materials, rare-earth magnetic separators have become more common place for processing heavy mineral sands. In many instances, rare-earth magnets have replaced conventional separators such as electromagnetic cross-belt and induced-roll type machines. This paper will present the results from a detailed test program developed to evaluate the performance of rare-earth drum and roll separators for processing heavy mineral sands. The effect of machine design parameters, such as magnetic element configuration and separator diameter, will be reviewed in light of these test results. The impact of basic operating parameters (i.e. feed rate and roll speed) on separation efficiency will also be presented.

Jan 1, 1999

By Brian T. Hamilton, Richard Piliounis, Cian Murphy

"The Eglinton-Crosstown Light Rail Transit line is a 19-kilometre corridor with a 10-kilometre underground portion currently being constructed by Metrolinx in Toronto through a densely populated urban environment. Tunneling works are being completed through two separate design-bid-build contracts that include consideration for a phased handover to a follow on contractor who will take ownership of the tunnels, including warranties, and will complete the stations and remainder of the system through a PPP delivery model including maintenance of the system for 30 years. Warranty provisions, settlement apportionment, tunnel leakage, potential delays and conflicts between contractors are just some of the risks the team managing tunnel contract integration had to consider when developing the PPP contract. This paper will present an overview of how these risks were assessed and allocated through the contracts and the strategies adopted to minimize risks to Metrolinx while ensuring successful procurement was maintained. INTRODUCTION The Big Move is a 25 year, $50 billion ($-CAD) plan for coordinated and integrated transportation in the Greater Toronto and Hamilton Area (GTHA) in Ontario, Canada. This plan has been initiated by Metrolinx, a division of the provincial government of Ontario, and its vision, goals and objectives are rooted in creating a high quality of life; a thriving, sustainable and protected environment; and a strong, prosperous and competitive economy for the GTHA. The Big Move will triple the length of rapid transit service in the GTHA to 1,725km, significantly increase the percentage of the GTHA population living within two kilometers of rapid transit, reduce commute times to an average of 77 minutes per person per day and decrease greenhouse gas emissions from passenger transportation per person by 29%. Work is currently underway on several projects and more than $16 billion ($-CAD) of the planned investment has already been committed. A key project that forms part of this commitment is the Eglinton Crosstown Light Rail Transit (LRT) Project which is being delivered in the City of Toronto under Metrolinx’s Rapid Transit (RT) Program. This complex and sizeable undertaking has been broken into a number of separate contracts comprising: LRT Vehicles contract; Eglinton West Tunnels Project; Eglinton East Tunnels Project; and a Public-Private-Partnership (PPP) contract to complete the underground stations, at-grade stops, all rail infrastructure and systems and to maintain the entire system for 30 years. The PPP contract, which includes an initial capital portion of approx. $5.1 billion ($-CAD), has recently been awarded to Crosslinx Transit Solutions, a Special Purpose Vehicle (SPV) consortium comprised of SNC Lavalin, Aecon, Dragados and EllisDon."

Jan 1, 2016

By Lok W. Home

INTRODUCTION Today, raise drilling (boring) has become the stan¬dard method of raising throughout the Western world. It is estimated that the majority of raise footage com¬pleted in 1977 was accomplished by the raise drilling method. Extensive replacement of the drill and shoot system by mechanized raise drilling has occurred be¬cause users have recognized one or more of the follow¬ing advantages. In a direct cost per meter comparison, mechanized raise drilling is economically more attractive than drilling and shooting. Mechanized raise drilling offers improved personnel safety over the drilling and shooting method. Mechanized raise drilling is a faster and more predictable method for excavation than is drilling and shooting. The raise cost per unit of length becomes less as the raise length increases, offering greater flexibility in the overall design of mines. Mechanized raise drilling provides a substantial reduction in labor requirements. 6) Mechanized raise drilling improves the working environment. 7) Mechanized raise drilling improves the rock in¬tegrity of round, unblasted raises. Increasing acceptance of the raise drilling technique is enhanced by continuing equipment development. Today, a wide range of machines and capabilities is available, machine drive systems have been improved, reliability has been increased, and cutter technology is being improved quite rapidly. Table 1 lists the four major manufacturers of raise drilling machines, cutters, and reamers, together with the approximate number of machines that each company had in operation at the end of 1977. Although Reed and Smith are major suppliers of reamers and cutters, they do not manufacture the drilling machines. Four or five other relatively minor suppliers have built machines, reamers, and cutters for raise drilling, but they did not have a substantial num¬ber of machines in the field at the end of 1977. MACHINES FOR MECHANIZED RAISE DRILLING There are three principal arrangements for making machine-bored raises. They include the use of standard raise drills, reversible raise drills, and blind-hole or box¬hole raise drills. Standard Raise Drills The standard raise drilling machine is set up on one mine level or on the surface, and a pilot hole is drilled from that level or surface to a level below. When the pilot hole has been drilled, the raise then is reamed back from the lower level to the upper level or the surface. This arrangement is illustrated in Fig. 1. Reversible Raise Drills The reversible raise drilling machine is set up on a lower level of the mine, and a pilot hole is drilled up¬ward to a higher level. The raise then is reamed back from the upper level to the lower level. This arrange¬ment is illustrated in Fig. 2. The machines used for this type of raise drilling normally are capable of being used as standard raise drills. Blind-Hole or Boxhole Raise Drills The blind-hole or boxhole raise drilling machine is set up on a lower level of the mine, and a full diameter raise is bored to a higher level without the use of a pilot hole. This type of machine is illustrated in Fig. 3. Drill Recommendations If access to upper and lower mine levels is equal, the standard raise drill should be used. The complexity of the equipment and associated handling procedures for boxhole drilling far outweigh any mechanical advantage or reduction in the number of operations, provided that access to an upper level is available. If there is good access to a lower level but only limited access to an upper level, the use of a reversible raise drill should be considered. If there is no access to an upper level, a blind-hole or boxhole raise drill is the only practical mechanized system. MACHINE SELECTION There are six major considerations in selecting a machine for raise drilling. These include operating range, cutter loading, machine structure and main¬tenance, drill string configuration, drive system, and automated controls. Operating Range As shown in Table 2 and Figs. 4 through 6, raise drilling machines are available for a wide range of hole sizes. Standard raise drill ratings range from raises of 0.9 m (3 ft) diam and 120 m (400 ft) length up to raises of 3.5 m (12 ft) diam and 900 m (3000 ft) length. Boxhole raise drilling machines are available for raises ranging from 0.9 m (3 ft) to 2 m (6 ft) diam with lengths up to 90 m (300 ft). Table 2 lists, among other criteria, the torque and thrust of typical machines; torque and thrust are the main criteria for analyzing the capacity of a machine. The raise sizes shown in Table 2 assume a condition of medium hard to hard rock formations and optimum cutter loading. The recommended raise size for a given machine can be exceeded when raising softer rock formations or when the operator is willing to accept a lower level of performance; the performance is related directly to the 1093

Jan 1, 1982

By Ramon S. Pizarro

The Masbate Province, Philippines, has been a gold producer for many years. Several gold properties were profitably operating until the outbreak of World War II in 1941. One of these properties was the Masbate Consolidated Mining Company that at the time showed an impressive production rate of more than 4,000 metric tons of ore per day and one of the lowest milling costs on record in the country at that time. Interesting enough, t was the milling equipment left abandoned at Masbate that gave birth to one of the giant copper producers in ASIA. In 1955, Atlas Consolidated Mining and Development Corporation started a new operation at its copper property in Cebu with the seven 2.4m 0 x 3m long (8'0 x 10' long) ball mills left abandoned at the old Masbate Gold Mine. Now, 25 years later, Atlas is processing over 100,000 metric tons of copper ore per day through its three copper concentrators, and, the seven old mills are still grinding, copper ores now.

Jan 1, 1981

By H. R. Green

The design of slurry launders has usually been based on strictly empirical concepts. An examination of the most common procedures reveals that they do not account for many of the variables that are recognized as Significant for slurry transport. These may include flow rate, volume concentration of solids, solids specific gravity, solids size distribution particle shape, launder geometry, and roughness of the wetted surface. It was decided to develop a design procedure, which would accomplish two things: First: Take into consideration most of the known significant variables and systematize the procedure to assure consistent results. Second: Provide a rational basis for examining and utilizing operating data to refine and improve the system. To accomplish this, it was necessary to develop a basic design concept. This concept has been developed through a complex development history, and yet still appears workable and technically sound. That concept may be outlined as follows: First: The solids transport velocity is the fundamental basis for slurry launder design. Second: The stream configuration, hence the launder size, is integrated with the solids transport velocity so that the actual stream velocity exceeds the solids transport velocity. Third: The launder slope is that which will achieve the required actual stream velocity. It was originally planned to utilize a series of charts and nomographs for the design procedure. A nomograph, based on data given in Taggart's Handbook of Mineral Dressing (1), was developed to determine the solids transport velocity. The velocity thus determined was used with Manning charts to determine the launder slope .and configuration as though the fluid were water. It was planned to utilize a "slope adjustment factor" to increase the slope to compensate for the apparent viscosity of the slurry. All attempts to develop a suitable correction factor failed. This failure was principally due to the complex relationship of viscosity to the required slope. It was then decided to revise the entire approach. Specifically, the present procedure is based on the Darcy-Weisbach flow equation, which is rationally preferable to the Manning equation. The Camp (2) equation is used for the solids transport velocity. The necessity of reference to the Moody curves for the Darcy friction factor is avoided by using the Colebrook and White (3) equation. The resulting mathematics require iterative solutions for several of the unknowns.

Jan 1, 1978

By R. V. Ramani, K. V. Raj

"The air flow problems in open pit mines are complex. Computational fluid dynamics (CFD) models provide a detailed knowledge of the airflow pattern and velocity distribution, temperature, and pollutant concentration within an enclosed domain of the open pit. A range of turbulent model can be selected for varying complexity and accuracy. Pollutant transport models, however, differ in their assumptions and structure as well as in the algorithm they use; as a result, prediction varies from model to model. This paper presents a study of pollutant transport in an actual open pit mine under stable boundary layer. The objective is mainly to test two turbulence models using the same input conditions, model constants, and similar geometry. Measured data are used to compare results of the two CFD models, namely, the kappa-epsilon (?-e) model and the Large Eddy Simulation (LES) model. Despite the complex synoptic situations, different meteorological input data and the fast changing conditions, the simulation results from both the models are in good agreement regarding the dispersion of pollutants.INTRODUCTION Modeling of contaminant transport under Arctic air inversion is an important step for an assessment of the amount of pollutants within the open pit. The Airflow in open pit mines is of larger scale and does not follow the principles of pipe flow. The air flow problems in actual open pit mines are thus far more complex. CFD models provide a detailed knowledge of the airflow pattern and air velocity distribution, temperature, and pollutant concentration within an enclosed domain of an open pit. There is no known application of CFD in three-dimensional modeling of air flow in large open pit mines. Two equation RANS kappa-epsilon (?-e) and Large Eddy Simulation (CFD) models, however, have been developed to solve the stable boundary layer (SBL) problems in Atmospheric Sciences (Baklanov 2000, Basu and Porté-Agel 2006, Dop and Axelsen 2007, Bandopadhyay et al. 2014). Because an exact flow situation in open pit mines is not known a-priori, it is therefore, necessary to investigate various turbulent models to identify the appropriate model that would simulate the flow phenomena with reasonable accuracy, and predict the contaminant distributions within the pit. Dispersion models differ in their assumptions and structures as well as in the algorithm they use and, as a result, predictions vary from model to model. Furthermore, it is also important to investigate the behavior of a CFD model in simulating a complex phenomenon such as the transport and distribution of contaminants in open pit mine under Arctic air inversion. The simulation of an enhanced period of turbulence in SBL is of particular interest because traditional air pollution dispersion models cannot explicitly treat such intermittent events, and yet the SBL is often the worst-case scenario in an open pit pollution transport"

Jan 1, 2015

By W. Irwin

Global warming hitherto viewed as a distant threat to the environment, is now the subject of fierce goo-political debate. The debate centres around the time frame required to achieve environmental compliance, and the cost implications of meeting that objective. Since coal is the fuel of choice for power generation, the priority objective of energy producers is the pursuit of environmental protection measures that allow coal to be burned without any attendant negative impact on the environment. From an environmental point of view, public attention is today firmly focused on the impact that all industrial activity has on the environment, and coal is singled out from other fossil fuels as being the product of an inefficient smokestack industry. Despite coal's poor public image it is unrealistic to suggest as some do, that use of this fossil fuel as a primary energy source should be drastically curtailed. Coal which already generates about 35% of the world's electricity is continuing to increase its share of this rapidly expanding market, and to argue against its use is flying in the face of reality. However, changes are required in the way coal is used in some of the new clean coal technologies, since many include advanced methods of combustion. Indeed changes in the way coal is used is a vital link to the future of coal as a primary source of energy, and increased coal utilization will be directly linked to changes in its use. Discussion of various issues that affect coal utilization are the focus of this paper.

Jan 1, 1998

By K. A. Natarajan, M. K. Yelloji Rao

The electrochemistry of sphalerite and chalcopyrite was investigated under both open-circuit and applied potential conditions. Emphasis was placed on the selective dissolution of sphalerite from a mixture of sphalerite-chalcopyrite flotation concentrates as a function of applied potential, acid concentration, pulp density, and time. Morphological studies using a scanning electron microscope (SEM) were also carried out with chemically leached, galvanically leached, and unleached surfaces of sphalerite and chalcopyrite. Selective dissoulution of sphalerite could be achieved if the mixed chalcopyrite-sphalerite concentrate slurry was maintained at a negative applied potential of -0.4V (SCE). Probable mechanisms involved in the selective dissolution of zinc are disscussed.

Jan 1, 1990

By Franz Wilhelmstoetter, Christian Karner

"The Confederation Line is phase one of Ottawa’s light rail transit, which consists of 13 stops and stations. The project’s center piece is a 2.5 kilometer (1.6 miles) long tunnel with three underground stations leading underneath downtown Ottawa and is constructed within feet of adjacent buildings. The downtown stations, Lyon and Parliament, are caverns approximately 16.5 m (54 ft) by 18 m (59 ft) in a horseshoe configuration constructed in rock, while the third station, Rideau, is approximately 22 m (72 ft) by 18 m (59 ft) in an oval configuration and constructed in mixed ground. The paper will discuss design decisions made early on in the project such as excavation method, unique construction sequencing, and equipment selection, and go on to include corresponding progress rates. The paper also documents design and construction challenges of large caverns in very close proximity to existing buildings and varying ground conditions. Finally, an overview of achieved construction milestones and a current construction progress will be presented. Station cavern excavation is expected to be completed in early 2016. INTRODUCTION The number of urban metro construction projects has certainly increased over the last decades. Cities are growing rapidly all over the planet and many are striving to keep up with the increased demand for public transportation. One of the most feasible types of inner-city transportation with the capacity for large quantities of passengers are metro (subway) systems. Still, large construction projects in dense urban areas often affect the city’s residents in mostly negative ways. During construction, residents face the obstacles of road closures, noise, dust, economic loss for businesses, and property value losses are common. In other words, individuals are directly affected by the way new infrastructures are planned, designed, built and operated. The tunneling industry offers unique opportunities of keeping these side effects to a minimum and possibly avoiding them all together. Although challenged by a variety of constraints (some of which will be discussed in this paper), urban tunneling applications offer a chance to keep cities environmentally, economically, socially, and culturally sound during construction."

Jan 1, 2016

By J. A. McKeown, B. M. Sanders, A. Dadgar, R. H. Sergent

This paper describes the leaching of gold with Geobrom® 3400 from a very rich (6.2 kg/tonne) black sand concentrate and its subsequent recovery by ion exchange resins and solvent extraction. The dissolution of gold from black sand ranged from 94 to 96%. Gold loadings and recoveries of nearly 100% were achieved by both ion exchange and solvent extraction methods. The kinetics and equilibrium of loading gold onto ion exchange resins and its elution from the resin were studied. The commercial ion exchange resins PAZ®- 4, DOVEX®- 21K, and Amberlite® XAD- 7, and Great Lakes Chemical experimental GLR-30 were evaluated in this work. Diethylene glycol dibutyl ether was used in all the solvent extraction work for gold recovery from Geobrom leach solution. The consumption of Geobrom was about 130 kg per tonne of the concentrate processed. Therefore, the cost of lixiviant to extract 3.11 x l0-2 kg of gold from the black sand was only about $1.00. Based on the electrochemical regeneration of bromine, the economics of bromine process vs. cyanidation were investigated.

Jan 1, 1990

By John A. Shuster, Joseph A. Sopko

Construction of two shafts, as well as associated deep concrete structures, for a major storm sewer project in Milwaukee, Wisconsin required ground water control and temporary ground support to depths ranging from 19.2m to 55.0m. Lowering of the site ground water table eras not possible because of potential consequences for existing nearby structures. Construction entailed completion of two shaft collars into bedrock. In addition to the shafts, several adjacent connected. structures were completed. Ground freezing was selected to provide temporary ground support and ground water control for all excavations. The first application of using reinforced frozen earth was successfully incorporated on the project. The procedure enabled the contractor to create openings in excess of 9.1m in height, without bracing, through highly stressed frozen earth walls. Design features and construction procedures for completion of ground freezing and related excavation are reported.

Jan 1, 1989

By James Veri, Andrew H. Stern, Gerald N. Torbert

When mining coal, the occurrence of high methane liberation rates can often overwhelm the existing ventilation capabilities of the working place and result in elevated levels of methane gas. These “gas-off/stand-by condition" events often limit the production of the section and increase the potential opportunity for the occurrence of an ignition. This paper investigates the potential effectiveness of using a continuous miner equipped with an integral dust scrubber which was modified to provide high flow rates to reduce these events during active coal mining. Work was undertaken to quantify various adaptations of the mining system, by simulating site parameters in the controlled environment of an instrumented "full-scale" test facility. Monitoring (in real-time) of velocities and gas concentrations at many fixed points was also undertaken in an attempt to learn the effective limits of the system at high release volumes of gas.

Jan 1, 1997

By Liuming Wu, Willis Forsling

The complexation of Alizarin Red S (ARS) at the surface of hydrous fluorapatite particles has been investigated at 25.0 C by means of potentiometric titrations, adsorption experiments in 0.1 M NaCI ionic medium, and Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT) studies. A chemical model describing the reaction at the aqueous mineral surface has been established under equilibrium conditions according to the reaction [== -CaOH2 + HA2 - « _ =PO CaA2 - z + H30&apos;; to (int.) = -5.61 ± 0.02 3 a =PO- logBs-1110(int.) ( ) within the range 8.40 <_ -log[H ] <_ 9.80.] Experimental data were evaluated using the computer program FITEQL on the basis of a constant capacitance model for the electric double layer. The surface complex structure, has been proposed to involve the quinoid and alpha phenolic oxygens of ARS coordinated to the calcium sites on the fluorapatite surface.

Jan 1, 1993

By Kenneth M. Reim

In 1971, United States Borax & Chemical Corporation (U.S.Borax) initiated a mineral exploration program on federal lands in Southeast Alaska, with the commitment that any possible development would be done with great care for the environment. This program resulted in the discovery of a molybdenum deposit and the location of mining claims in 1974, in an area 45 miles east of Ketchikan, now called the Quartz Hill Molybdenum Project (Figure 1). At the time of this mineral discovery, the area was part of the Tongass National Forest, managed by the Forest Service, United States Department of Agriculture, and open to mineral entry and multiple use. In late 1978, the area was designated Misty Fjords National Monument and closed to mineral entry, and in late 1980 the area surrounding Quartz Hill was classified as Wilderness. These new laws and regulations, as well as the special interest environmental groups which oppose resource development, have significantly delayed and increased the costs of developing Quartz Hill.

Jan 1, 1983

By Lj. Obradovic

The aim of this paper is to study the feasibility of copper and gold recovery from the old flotation tailing dam at Bor, Serbia. Laboratory leaching experiments were carried out using a composite sample taken by drilling from 16 - 40 m depth. Different oxidation agents as FeCl3, Fe2(SO4)3 and H2O2 were used. An H2SO4 solution with a pH less than 3 was used for leaching. The influence of a number of parameters on the recovery of both elements as temperature, pH, duration of leaching and concentration of oxidation agents was also studied.

Jan 1, 2006

By Brad Grothen, Lok Home

The choice of TBM type is never easy, but it becomes especially challenging when faced with a hard rock tunnel with expected high water flows and pressure. Slurry Shield tunneling has a long history of being used in these conditions to minimize the risk, though this method has brought with it other risks along with cost considerations. At recent projects around the world, another method has been proven to effectively manage these project risks without utilizing Slurry Shield tunneling: Shielded, NonContinuous Pressurized (NCP)-TBM tunneling in rock with a comprehensive grouting program. In this paper, the authors will analyze the use of Shielded NCP TBMs at projects around the world as compared with slurry shield tunneling in rock under water pressure. Recommendations will be given in order to establish a clear picture of the optimal tunneling method.

Jun 13, 2021

By Joseph F. Peters

The paper will begin with the physical parameters of design in a wire saw. These will include such things as the type of wire used, abrasives, horsepower of operation, and drive components. It will then go into the many uses of wire sawing in the quarrying and finishing of granite. This will include a step by step program of the removal of a block unit of granite from the quarry site through the finished slabbing and jointing in the plant. After this, there will be a small insertion of possibilities of wire sawing techniques in underground excavation work. This would be speculative only. I will use the example of powerhouse type of excavation work given to me by Dr. John Reed, and try to explain how I would attack this type of work using wire saws. Several slides of both design criteria and actual installations were shown.

Jan 1, 1997

By A. Venkatachalam

Spinel ferrites, like NiFe2-2x Znx Ti4 O4 Fe CO1.5 Ge0.5 Tix O4, Ga1-x Fex Ni CO O4, Nil-x Fex Mn2 O4 have been prepared using the respective metal oxides in Stoichiometric quantities, by the ceramic method. The oxides were homogenized in acetone medium, pelletifed by using poly vinyl acetate as the binder. They were fired at 1000°C for 100 hours for compound formation. Chalcogenide spinels such as Zn1-x Cux Cr2 Se4 where 0=x=l and Cu1-x Fex Cr2 Se4 where 0=x=0.3 have been prepared by using 99.99% pure elements and then fired at 1000°C in quartz ampoules under vacuum conditions. X-ray diffraction studies of these compounds indicated a single cubic spinel phase. DC resistivity studies of the compounds were taken between 300-700K using LCR bridge by two probe technique. Thermo-electric power measurements were taken between 300-500K for all the compounds. Initial susceptibility studies have been carried out using a low field (0.506) and from which the nature of magnetic dimains and Curie temperatures were determined. Magnetic hysteresis measurements were carried out at 300K and at 80K, using alternating current hysteresis loop tracer, at 2K02 field. Mossbauer spectral measurements were carried out using Co57 source embedded in a copper matrix and an absorber containing 0.3 mg/cm2 of the sample. The spectra has been fitted by Mossfit Program. The catalytic effect of the spinel ferrites NiFe2-2x Znx Tix O4 where 0=x=1 has been studied by using the model reaction of decomposition of H2O2 at temperatures from 40°C to 70°C. It was found that the spinel oxides were found to possess poor catalytic activity.

Jan 1, 1990