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By Giuseppe Gaspari, Xiangrong Wang

The pandemic emergency is forcing transit agencies to define strategies allowing social distancing, which are more challenging in underground interchange stations in crowded downtown cores. Toronto Transit Commission’s (TTC’s) Bloor-Yonge Station Capacity Improvement Project in Toronto was approved to meet increasing demand and represents an opportunity to fight COVID-19. This paper discusses cost-effective solutions in expanding the cut-and-cover station box over the existing Toronto Subway Line 2 and connecting it through ventilation openings in the cast-iron tunnel liner. Potential uplift risks and structural damage due to minimal vertical clearance were analyzed via three-dimensional finite element analyses with advanced constitutive laws to simulate the multi-stage construction process. Based on the simulation results, a series of countermeasures, including excavation support systems, king posts, ground-consolidations, and liner reinforcements were integrated into comprehensive design options to ensure the serviceability and structural integrity of the subway tunnels.

Jun 13, 2021

By J. A. G. Llerena, J. Sattarvand

Tailings dam failures have been occurring in recent years. They are considered more vulnerable than hydraulic dams due to the lack of regulations on specific design criteria, and stability requirements regarding monitoring during the construction and maintenance process. Thus, monitoring the dam is essential to know the dam's existing state and ensure its safety. One of the reasons tailings storage facilities fail is slope instability caused by moisture content. A relationship does exist between moisture content and surface strength, early detection of seepage would help to assess the physical condition of the dam. Moreover, to cover the tailings dam area in an efficient way Unmanned Aerial Vehicles (UAVs) are suitable because of their versatility and high-resolution data acquisition. Mounted with a high-resolution RGB camera, and thermal, or hyperspectral sensors UAVs can acquire good quality images that combined with image analysis and machine learning algorithms yield a good estimate of soil moisture.

Feb 1, 2023

By George Weinman

GEORGE WEINMAN: Our first group leader for the discussion, "Ups and Downs of Downsizing," wishes to remain anonymous. ANONYMOUS PRESENTER: When George and Jamie asked me to do this, I thought a while about what to say and went through several variations of what I’ll present today. I came up with the title "Ups and Downs of Downsizing." A lot of downsizing has occurred in all of our industries-mining in particular. While this downsizing has gone on there's no doubt that all of us produced more and more, probably with less and less people and less and less resources. But I contend that there's also a big downside associated with this. I disagree with a point made in the keynote presentation yesterday, the point being that vendors are bringing new technology to us. I can agree that the major changes associated with equipment and similar items are being brought to us by vendors. But I do contend that there's an awful lot that's getting away from us-especially if you factor in the integrated supply or the strategic alliance or the various and sundry related purchasing techniques. I contend that we are missing a lot of, let's call it, lesser technology; not major equipment changes, but different tools, different techniques for doing things, different left-handed widgets. The integrated suppliers, to some degree, are bringing this to us; but I am concerned about the small guy who comes up with a good idea but deals through integrated suppliers rather than having direct contact with plant people. They're probably going to go somewhere else and market their wares. That's what I'm hearing from a lot of smaller vendors. I also think that we are losing a lot of our knowledge base. Every time you shrink an organization somebody leaves. The bottom line: less people. When a person leaves-and I don't care who he or she is, be it the janitor who's cleaning the bathroom, the operator, the engineer-when that person leaves there's some knowledge that goes with that per- son. And sometimes that knowledge is quite valuable. I've worked more or less at the plant "low." I can't tell you how many excellent, viable projects have come from people who said, "Look here. There's a better way of doing this." And, you know, they were right. Now, maybe they didn't have the resources or the expertise to develop these ideas into full projects, but they had that basic idea. Someone may say, "Well, if we put a no. 6 skyhook here, so we can lift this particular pump without bringing a crane from 30 miles away ...." No. 6 skyhooks are a bit expensive, but what if we put together a little structural steel here or whatnot?

Jan 1, 1998

By R. H. King, D. R. Schricker, R. E. Cameron

Mine managers rely on their experience, section foreman's daily reports and occasional time studies to make important production, maintenance and forecasting decisions. This information is often subjective and imprecise, consumes expensive engineers time, is often biased and is restricted to short time periods. Managers need better information. Furthermore, if a recently purchased machine is being evaluated, a large increase (>10%) in productivity may be obvious, but small increases are usually masked by other variables. In today's highly competitive markets, cumulative small changes are important, especially since managers have already exhausted most available, obvious avenues of improvement. A technique to separate these charges from effects of other variables and to quantify the target effect is necessary. CSM researchers are addressing this need by developing an intelligent decision support system (IDSS). It provides key production and maintenance information to support management decisions by recognizing patterns in mining machine sensor data and representing knowledge about mine management, operations, layout and equipment. A continuous miner section at Western Fuels-Utah Inc.'s Deserado Mine in Rangely, CO is the test facility for the research. Power transducers located in the sections load center provide kilowatt versus time data from continuous section equipment. The IDSS pattern recognition algorithms classify the kilowatt versus time patterns into individual machine operating modes. It produces an output similar to a typical industrial engineering time study but continuously, automatically and without an engineer in the section. It is relatively easy for a time-study engineer to identify the stop and end points of a cycle element and classify it by looking at the machine and glancing at a stop watch. The problem is that monitoring system hardware and software do not have these unique capabilities. Consequently, IDSS algorithms must automatically define the begin and end points of machine tasks and identify the task by recognizing patterns in kilowatt versus time data. However, many mines have file drawers of time-study type data that are not very useful. So, IDSS contains the knowledge representation subsystem (IDSS/KRS) to produce short reports containing only key information. This is difficult because mine environments continually change and information requirements differ for each management level. Consequently, IDSS/KRS must learn and adapt to new conditions in a dynamic mining environment. Western Fuels-Utah owns and operates the Deserado Mine, located about 19 km (12 miles) northeast of Rangely, CO (Upadhyay, 1988; King and Eros, 1988). One longwall and two continuous miner sections produce about 900 kt (1 million st) of coal annually for the Deseret Generation and Transmission Cooperative's 4000 MW power plant located near Bonanza, UT. Three mine monitoring systems control the underground mine, the preparation plant and the unit train load out. Pattern recognition IDSS/PRS produces a listing of begin and end times for each machine operating event as shown is Table 1.

Jan 1, 1991

By Henry N. McCarl

From the earliest use of crushed and broken stone as landfill for eroded gullies in trails and roads, to the mixing of sand and gravel with cement to make concrete, men and women have found mineral aggregates to be useful materials in satisfying human wants. Crushed stone, sand and gravel, volcanic cinders, pumice, manufactured lightweight aggregates, slag, cinders, expanded perlite and vermiculite, and a great array of recycled materials such as grog (broken or crushed brick) and fly ash have served as mineral aggregates. These materials have provided bulk and strength in portland cement concrete, bituminous concrete, road base, fill, concrete block, and plaster and stucco finishes. Mineral aggregates provide many special characteristics such as compressive and tensile strength, surface textures, weight and density, thermal and acoustical insulation, abrasion resistance, and impermeability to various concrete products and mixes. While most materials used as mineral aggregates are consumed on the basis of their low unit values, the large volumes extracted in the United States each year make them one of the most valuable mineral resources in current production. In 1960, US production of construction aggregate was just over a billion tons per year (Meyer and Zelnick, 1991). Two decades of accelerated interstate highway, residential, and commercial construction brought the total annual production of mineral aggregates to roughly 1.4 Gtpy by 1970 and just over 1.6 Gtpy by the late 1970s. General economic and related construction slowdowns in the early 1980s saw annual US production of aggregates fall to below 1.1 Gt in 1982, and then rise to just over 1.7 Gtpy in 1990, a new peak in mineral aggregate production and use. Per capita annual consumption of mineral aggregates was approximately 5.68 t/capita in 1960, 6.89 t/capita in 1970, rose to a high of 7.25 t/capita in 1979, and has since settled to just under 7 tpy for every man, woman, and child counted in the United States Census of 1990. The value of these materials came to approximately $9 billion in 1990. During the period 1960-1990, roughly half of all mineral aggregates were used in the construction of residential, commercial, and industrial structures, and the remainder was consumed in highways, bridges, and other transportation facilities such as railway roadbeds, airports, and water-related projects (Meyer and Zelnick, 1991). During the period 1988-1992, public works (highways, waterway projects, road maintenance, etc.) represented closer to 60% of annual mineral aggregate demand with residential and non-residential construction approximately 40%. The growing market share of public works projects has been mostly due to the dramatic slowdown in residential, commercial, and industrial construction during the 1988-1992 period.

Jan 1, 1994

By Palmer C. Sweet

Kyanite. andalusite, and sillimanite are anhydrous aluminum silicate minerals, and they have the same chemical formula, Al2SiO3. Dumortierite and topaz are also classified as aluminum silicates although they contain boron and fluorine respectively. Mullite (a rare mineral named for its discovery site, the Scottish island of Mull) is produced when kyanite, andalusite, or sillimanite are heated. Synthetic mullite, also classified as an aluminum silicate, is formed by melting alumina and silica, bauxite, and kaolin or alumina, kaolin, and kyanite, depending on the type of synthetic mullite desired. These materials are either sintered in rotary, periodic, or tunnel kilns, or fused in an electric arc furnace. The world's largest producer of kyanite is the United States. Domestic kyanite is presently produced from one company at two sites in Virginia; Kyanite Mining Corporation mines kyanite from Willis Mountain and adjacent East Ridge in Buckingham County in the central Piedmont province of Virginia. Internationally, kymite is produced in Australia, Brazil, India, Kenya, Sweden, and Zimbabwe; the former USSR also produces kyanite (Fig. 1). Andalusite is produced by Piedmont Minerals Company, Inc. in the Piedmont province near Hillsborough, NC. Andalusite is also produced in France, India, the Republic of South Africa, and Spain (Fig. 1). Sillimanite is produced in Australia, Brazil, India, Spain, and the Republic of South Africa; the former USSR is also thought to be a major producer (Fig. 1). Some of the countries produce only for domestic use. Synthetic mullite, made by sintering and by electric arc fusion, is produced by Mulcoa (Mullite Company of America) in Andersonville, GA, and by Washington Mills Electro Minerals Corporation in Niagara Falls, NY. Annual world production of kyanite, andalusite, sillimanite, and synthetic mullite is approximately 672 727 tons (Potter, 1988). GEOLOGY Mineralogy Kyanite is a blue to light-green, triclinic mineral that occurs in long, thin-bladed crystals and crystalline aggregates in gneiss, schist, and pegmatites. The mineral has a hardness of 5 parallel to the long axis of the crystal and a hardness of 7 across the crystal. Andalusite is a yellow, brown, green, or red orthorhombic mineral that occurs in thick, almost square prisms in schist, gneiss, and hornfels. Gem quality andalusite exhibits a strong pleochroism; brownish-green in one direction and brownish-red perpendicular to it. Andalusite also occurs in placer concentrations where it has weathered out of rock. Sillimanite is a brown, pale-green, gray, or white orthorhombic mineral that occurs in long, slender, needlelike crystals in schist and gneiss. Chemical and Physical Properties Chemical and physical properties of kyanite, andalusite, and sillimanite are noted in Table 1. Kyanite is the only mineral that irreversibly expands when heated (calcined to produce mullite) and may offset the shrinkage of most ceramic or refractory ingredients when heated.

Jan 1, 1994

By A. Bhargava, V. Nasri

Traditionally, secant piles have been utilized to provide temporary support during excavation for shafts and cut-and-cover tunnels. As an alternative, the secant piles can be included into the permanent structure, where they serve as the envelope sustaining the lateral loads and gravity of the permanent structure in addition to supporting the excavation during construction. This has several benets, such as shorter building times and lower excavation costs. Recent construction of an approach structure and an underground station as part of Montréal, Canada’s Réseau Express Métropolitain (REM), one of the biggest transit systems in North America, was completed with remarkable success using this. In this paper, a case study based on a project that employed secant piles as the permanent liner is presented. Techniques to guarantee a watertight construction with over a century of service life are described, along with a variety of structural and waterproong methods applied to create an economical design.

Jun 23, 2024

By Larry A. Enloe

The 16-to-1 milling operation is Sunshine Mining Company's first new silver and gold producing facility. The 16-to-1 underground mine and mill are located approximately 64 km (40 miles) southwest of Tonopah, Nevada. Ore re- serves in the epithermal vein deposit are estimated at 0.91 Mt (one million st) of ore, at an average silver grade of 206 to 240 g/t (6 to 7 oz/st) and an average gold grade of 1.2 g/t (0.035 oz/st). The underground mine uses a large diameter blasthole stoping system of mining using highly mechanized rubber-tired equipment. The mill uses conventional cyanide leaching with countercurrent decantation and Merrill-Crowe precipitation. The mill start-up was in February 1982 resulting in the first pour of dore' in March 1982. The mill's present annual production is approximately 31.1 t (1.0 million oz) of silver and 264 kg (8500 oz) of gold.

Jan 1, 1984

By Anthony Harding

In a world of technology and electronic communication, it is easy to forget what engineers do best with a problem: sitting around a table, exchanging views and ideas with sketches and respecting everyone?s view. This was the approach adopted in the project to arrive at a solution for the cross passage opening sup-port for the Seattle University Link Extension. Schedule and space constraints usually impede concurrent cross passage excavation and tunnel boring machine (TBM) operation. And where the space is constrained, opening support solutions that maximize available cross sections are of great benefit. While there are a number of solutions that minimize space, some of these solutions can require expensive steelwork and extensive drilling and fixing. However, following a detailed round-the-table discussion of the options and constraints, it was identified that a shotcrete shell would not only limit obstruction of the space during installation, but also permit easy installation, particularly around services, and avoid costly steelwork and drilling and fixing.

By J. A. Herbst

A state of the art computer simulation package, named UTAH-MODSIM is being developed. This package can run on a mainframe (eg. UNIVAC) as well as on a microcomputer (eg. IBM/PC with at least 512 kBytes of core memory). Friendliness was the major concern in developing this software. The user simply generates a complete flowsheet by presenting the flowsheet on a graphics terminal. This flowsheet defines the circuit to be simulated. With the minimum required data, the user can obtain a complete mass and water balances within a few minutes. Moreover, this package will provide scale-up and capital cost information of specified equipment relevant to design. In order to illustrate the utility of this software, three design examples are given. They are: a) A typical multistage crushing plant. b) A reverse closed grinding circuit comparing one stage with two stage classification. c) A standard closed grinding circuit suitable to liberate a specified fraction of chalcopyrite from a copper ore.

Jan 1, 1986

By Justin R. Patts, Andrew B. Cecala, A. KYLE LOUK, Emily J. Haas

The National Institute for Occupational Safety and Health (NIOSH) and the former U.S. Bureau ofMines (USBM) have given a significant effort over the past four decades in researching and developing engineering controls and interventions to reduce mine workers’ dust exposures during the bagging and palletizing of industrial minerals. Workers performing manual bagging and palletizing of 50- to 100-pound bags typically have some of the highest dust exposures of all workers at mining and mineral processing operations. This paper will provide an overview of available dust control technologies for bagging operations and present the findings of a recent case study that was conducted at four different industrial sand operations to identify the current types of bagging and palletizing technologies being used and to evaluate their effectiveness in reducing workers’ exposures to respirable crystalline silica dust. An evaluation will also be performed to determine if further reductions in respirable dust levels can be achieved by incorporating additional modifications or improvements into the existing technology.

Apr 3, 2020

By Donald P. Tuchman, Emanuele G. Cauda, Steven E. Mischler, Elaine N. Rubinstein, Jay F. Colinet

The PDM3600 and PDM3700 are two closely related person-wearable dust monitors manufactured by Thermo Fisher Scientific. Both are based on tapered element oscillating microbalance technology and provide nearly real-time, mass-based readings of respirable dust concentrations. From a monitoring perspective, the primary difference between the models is the PDM3600 has an integrated cap lamp with attached inlet, while the PDM3700 has no cap lamp and a revised inlet attaches to the worker’s lapel. Using coals of varied origin and employing a wide range of concentrations, side-by-side measurements from these instruments were collected under controlled laboratory conditions and then compared. By use of ordinary least squares and weighted least squares regression methods, followed by mixed model analysis, results suggest there is no statistically significant or practical difference in instrument performance. The two monitors are equivalent for the field dust concentration measurements for which they were designed.

Feb 28, 2024

By Yang Ge, Yuzhu Pan, Mansheng Chu, Jue Tang, Cong Feng, Lihua Gao, Zhenggen Liu

The low-grade nickel laterite ore used in this study was successfully upgraded through selective reduction by industrialized rotary kilns followed by magnetic separation. The results indicated that both iron metallization extent and nickel metallization extent showed obvious linear correlation. In addition, rational roasting temperature and prolonged grinding time could enhance the overall fineness level of reduced laterite nickel ore. The moderate roasting temperature at a range of 1100–1150 °C should be suitable enough to a conversion of total nickel to metallic nickel and partly inhibited the conversion of total iron. Ultimately, the obtained ferronickel alloy with a nickel content of 7.32% and an iron content of 84.15% was prepared successfully from the lowgrade nickel laterite ore containing a nickel content of 1.92%. Nickel and iron recoveries were 96.72 and 89.08% respectively, which achieved the highly efficient recovery and utilization of iron and nickel from low-grade laterite nickel ore

By James L. Coburn

Leaching is defined as a form of extraction in which a valuable constituent is removed from a solid body by mass transfer to a solution which, for the purpose of this discussion, is considered to be an aqueous medium. Historically, leaching has been applied to the recovery and purification of many elements. This paper, however, is directed toward the recovery of copper, uranium, vanadium, and precious metals included in the following systems: 1. The leaching of copper minerals, sulfides and oxides, by acid or by ammoniacal leach solutions with or without an oxidant. 2. The leaching of gold and silver, either native metals or as minerals by an oxygen-containing alkaline cyanide solution. 3. The solubilization of certain uranium and vanadium minerals by oxygen or oxidant-bearing lixiviants. Many other systems of this general type exist, but from a production standpoint, these three systems account for most of the major values recovered by leaching.

Jan 1, 1975

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 Farzad Moradpouri, Kianoush Barani, M. R. Azadi

The aim of this paper is to assess the effect of microwave treatment on copper sulfide ore for ball milling and bed breakage. Liberation analysis of ground products in eight size fractions showed that microwave pretreatment liberated more chalcopyrite particles from the bed breakage product than the ball mill product. In bed breakage, microwave pretreatment caused a 2% increase in chalcopyrite liberation on average. Microwave pretreatment produces more elongated particles in ball milling and more rounded particles in bed breakage, respectively. Microwave pretreatment produces coarser chalcopyrite particles with a wide range of sizes. This effect is more significant in bed breakage compared with ball milling. Micro-flotation test results showed that in ball milling, treated and untreated materials have similar metallurgical performance and there is a little difference (1%) between the average Cu recovery values. However, in bed breakage, the average recovery for the treated materials is about 5% higher than the untreated materials.

Jul 8, 2021

By R. W. M. Lai

In flotation or hydrometallurgical leaching of minerals, the cumulative metals recovery for a given process condition generally approaches a maximum value or an asymptote as the process time increases. This paper discusses the experimental methods of identifying and obtaining the asymptote of metals recovery through kinetic studies. In flotation, the kinetic asymptote of metal recovery, or ultimate recovery, is a function of grinding and collector dosage, but within a realistic variable range, is not a function of pH or temperature. However, variations in grinding, collector dosage, pH and temperature, all exert noticeable effects on flotation kinetics. Frothers generally have a minor affect on the asymptote, but have a major affect on flotation kinetics. The asymptote from batch flotation is found to be identical to that of a continuous flotation. In hydrometallurgical Leaching, the asymptote of metal recovery for a given leaching system is a function of such variables as temperature, particle size, and acid concentration.

Jan 1, 1983

By X. Cai, L. Jiang, G. Fu

A process for recovering manganese from low-grade manganese oxide ore through a reduction acidolysis-selective leaching method is investigated. Two types of biomass, sawdust and straw, were used as reductants. Reduction acidolysis, using concentrated sulfuric acid, was used to disrupt the structure of the biomass, allowing the biomass to be hydrolyzed into monosaccharides. Analysis by X-ray diffraction revealed that Mn2O3 was reduced to MnSO4. Then, in the selective leaching process, iron was removed through the formation of goethite. The optimized experimental parameters are as follows: reductant to ore mass ratio of 0.4, sulfuric acid to ore mass ratio of 0.9, water to ore ratio of 0.5, aging time of 18 h, leaching temperature of 95 °C, leaching time of 90 min, and solution pH of 2.5 to 2.8. Under these conditions and using sawdust as the reductant, the manganese leaching efficiency and iron removal efficiency were 91.8 and 99.2 percent, respectively.

By A. H. Kaksonen

Numerous reactor designs for biological sulfate reduction have been reported. Fluidized-bed bioreactors (FBR) can efficiently retain biomass and allow high mass transfer and reaction rates. This work reviews the development of various sulfate-reducing FBR processes for treating acidic metal- and sulfate-containing waters and recovering metals from bioleaching liquors. The FBR process performance was evaluated with continuous flow experiments under various operational conditions: fluidization rates, influent pH values, metal, sulfate and salt concentrations, hydraulic retention times, electron and carbon sources, and temperatures. Substrate utilization and sulfide inhibition kinetics were determined with batch FBR-kinetic experiments. An artificial neural network (ANN) model was used to predict the performance of the FBR. Sulfate-reducing bacteria (SRB) were characterized in FBRs with molecular and culture-based approaches with the aim to gain a better understating of the bioprocesses. Based on the studies, FBRs are well suited for the combined removal of metals, acidity and sulfate from water.

Jan 1, 2010

By Robert W. Burns

Gentlemen, my subject today is glass reinforced plastics. By definition, this encompasses a wide variety of materials: at least a half dozen basic varieties of polyester, epoxy, and phenolic; virtually infinite compounding variations within the basic groups: literally limitless variations in the amount and the nature of the glass reinforcing. Complicating all of this is the fact that different modes of application of the same material fall appreciably alter' the product's general strength and suitability. These many, many differing materials are what we conveniently call "glass reinforced plastics" or, more simply, fiberglass". This common name is actually a large part of the problem when dealing with fiberglass materials. Far too often a specification is written calling for simply "fiberglass reinforced polyester', based on successful prior use of a polyester laminate. Such a specification is very nearly worthless since such tremendous variation is possible under it. Success of a laminate furnished under such a specification is entirely dependent on good fortune

Jan 1, 1962