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By G. Buchan

This paper discusses the design of long panels for longwall mining at Twentymile Coal Company (TCC) from conception to implementation. The case study of the long panels at Twentymile includes extensive mine plan reengineering in the early 1990's to world record production months in 1996 and 1997. The obstacles of subsidence engineering, environmental regulations, conveyance, ventilation, equipment design, and continuous miner (CM) development timing had to be overcome to successfully begin longwall production within a 4 year time frame. The background and some detail for each of these areas listed will be discussed to show how the coordination of many facets must be pulled together to implement a successful long panel mine plan.

Jan 1, 1998

By Fan Jiang, Haigang Wang, Shi Liu

"This paper describes several applications of Electrical Capacitance Tomography (ECT) in gassolid two phase flows. A new image reconstruction algorithm was evaluated by both simulation and experiments. It is then applied to the online measurement of solids distributions in square circulating fluidized beds (CFBs) and good results were obtained. From the measurement of solids distributions in the bottom zone of a CFB, a bubbly fluidization pattern is identified. A cross-correlation technique was combined with the solids concentration measurements to obtain the flow rate through the dip leg of the cyclone, i.e. the circulating rate of a test CFB. The same· technique was applied in a dense phase pneumatic transport pipe provides the solids concentration, and the flow rate of a wavy gas-solids flow.IntroductionElectrical capacitance tomography (ECT) has been developed for imaging multiphase distributions in the 90's of the ·last century. It is a non-intrusive method. The principle of ECT can be firefly described as follows:Firstly ECT uses a number of electrodes to surround the measuring zone, depicted by Fig. I. The capacitances between the electrodes are measured in turn and an array C is obtained that contains a total number of m independently measured capacitances. Meanwhile the measuring zone is virtually divided into a grid of n pixels, represented by an array G, named the image vector, the gray level of each pixel represents the local value of the concentration of the material. As the material distribution will be reflected by the capacitances between each pair of electrodes, such distributions can be reconstructed according to the measured capacitance, a process called image reconstruction. A common image reconstruction method is called linear-backprojection (LBP). It linearize the relationship between the dielectric distributions in the measuring zone and the capacitances between the electrodes as the following:"

Jan 1, 2004

Under the AMIRA P9 project the three-product cyclone-an off-shoot of the conventional hydro-cyclone-that produces three distinct products has been developed. The three-product cyclone shows great promise as a classifier in mineral processing. Industrial and pilot plant trials performed to assess its performance in the classification of the UG2 platinum ore, indicate that the presence of an extra overflow product stream that captures the mid-sized particles, provides improved classification efficiency. To assess the split on component density, samples from the feed and product streams were screened and assays by size for chromite (? = 4.8) and silica (? = 2.65) were obtained. Results from tests performed using this type of hydrocyclone in a number of applications indicates that it can be applied successfully in circuit configurations where the conventional hydrocyc-lone is not suitable. Utilising the three-product cyclone to classify the UG2 platinum ore resulted in an intermediate overflow product stream containing the mid-sized low density silicates and relatively fine high density chromite particles while the finer overflow contained mostly fine silicates and chromite particles. The coarse chromite and silicates reported to the underflow. Due to the increased number of products, the method of using efficiency curves was extended to cater for the increased number of products in the three-product cyclone. Although significant differences in the classification performance of the three-product cyclone were noticed with variations in machine variables a consistent method of assessing the performance was applied. The efficiency curve was adopted and applied and separate efficiency curve properties were obtained for each product stream. The methodology was applied to the component data, and efficiency curve proper-ties for each key component were obtained and compared. This paper discusses the application of the efficiency curve to cyclones producing more than two products and extending the methodology to the different components in the feed.

Jan 1, 2014

By Kirk Ellison, Eric S. Lindquist, Peter Faust, Stephen M. McLandrich

"The 181 Fremont Tower will be an 800-foot high-rise with a 60-foot deep basement located in a dense urban part of downtown San Francisco. The design and construction methods of the subsurface elements navigated a variety of site constraints such as loose fill and soft estuarine soils, shallow groundwater, contaminants, historic obstructions, small work area, proximity of adjacent buildings, and the on-going excavation and build-out of the adjacent Transbay Transit Center (TTC) train box. Design of the approximately 260-foot-deep drilled shafts (some of the deepest foundations ever constructed in San Francisco) was proven by a full-scale load test that provided unique data on the frictional capacity of the deep soil and Franciscan Complex bedrock in the region. Design and construction of the shoring system for the 5-story basement excavation was exceptionally challenging because of the on-going construction for the TTC. To allow for flexibility during construction, hydraulic rams were placed in a transfer waler along the shared TTC shoring wall that could adjust the forces transferred through to the TTC excavation if required. Open and steady communication between the shoring engineer, the geotechnical engineer, and the shoring/foundation contractor was crucial in order to satisfy the complex constraints of this site.INTRODUCTIONThe 181 Fremont Tower is a new build mixed-use tower, currently under construction in the dense urban core of the South of Market District of San Francisco, California. This high-rise will consist of 54 above ground floors with the roof level 700 feet high. Atop the roof will be some architectural features including a spire that will top out at just over 800 feet, which will make it the second tallest building in San Francisco upon completion.The tower is being developed by Jay Paul Company and the architectural design is by Heller Manus. The structural engineer and geotechnical engineer for the project is Arup North America Ltd (Arup). The shoring designer is Brierley Associates (Brierley). The general contractor is Level 10 Construction (Level 10) and the specialty foundation contractor and excavation contractor is Malcolm Drilling Co., Inc (Malcolm)."

Jan 1, 2017

By Y. J. Wang

In the mathematical analysis of electrical networks, the electrical devices are often modeled using idealized network elements such as current sources, voltage sources, and resistors. An analogous approach is outlined here for the modeling of mine ventilation networks, which can be considered nonlinear resistive networks. The modeling technique proposed uses five basic (non-reducible) elements: the H element, the Q element, the D element, the R element, and the N element. These elements are characterized by their (a) pressure gain or loss, (b) air quantity, and (c) pressure-versus-quantity relationship, each of which may be known or unknown. In addition to the definition of the basic elements, the necessary conditions for which there exists a unique solution are discussed. This is performed using theoretical developments derived from electrical circuit theory and illustrated in example networks. The proposed procedures are useful in the solution and characterization of mine ventilation networks.

Jan 1, 1996

By H. Nejati

Experimentally, the Semi-Circular Bending Moment (SCB) fracture toughness test results of Basalt Specimens Under Illumination (BSUI) have shown reduction in fracture toughness and failure force as a result of micro-cracking. The fractographic investigation of BSUI confirms initiation and extension of micro-cracks. Determination of a relation between strength reduction (herein fracture toughness reduction) and density, location and orientation of thermo-mechanical induced cracks due to microwave radiation is critically important. Numerical modeling can bridge strength reduction and the density of thermal microcracks generated due to microwave radiation. Discrete Element Modeling (DEM) is a power tool for simulation of micro-crack initiation, coalescence into macroscopic fractures and failure mechanisms in brittle rock specimens under different stress regimes (herein combination of pure tensile stress due to SCB testing, and thermal stress due to microwave radiation). For this purpose, a DEM modeling of SCB testing of basalt using EDEM (i.e., a DEM based software). DEM models are calibrated according to results of experimental SCB testing as reported in previous papers. This paper first reviews some background data on SCB fracture toughness, and experimental results of fracture toughness of microwave treated SCBs. Then it proposes a new methodology for simulation and validation of rock samples exposed to microwave illumination with regard to experimental results, and discusses the correlation between fracture toughness of BSUIs and density of micro-cracks, which is attributed to applied microwave power and duration of illumination.

Aug 1, 2013

By J. E. Allen

The trend in refractory technology for the copper and nickel industries has been to higher quality raw materials and improved processing technology. These changes have been dictated by the changes in pyrometallurgical processes in these industries. For example the introduction of flash smelting, reaction type smelting and auxiliary slag cleaning furnaces havedemanded better refractories materials. Extensive field applications and improved laboratory testing procedures have helped make this transition possible. Changes in refractory technology, primarily in basic refractories, are followed from the late fifties to the present and into the future.

Jan 1, 1994

By Richard L. Sanford

This paper summarizes the results of the development of a Directory of Computer Programs Applicable to U.S. Mining Practices and Problems. The Directory is funded by the U.S. Bureau of Mines and includes a sampling of computer usage in operating and manufacturing companies, consulting firms, computer companies, research organizations, universities, and various U.S. government agencies. General references to computer applications throughout the mining industry are discussed as well as the availability of programs to interested organizations or individuals.

Jan 1, 1978

By M. Sanchez

In the last decades, the Chilean copper mining and metallurgical industry have had to modify their technological processes to meet the environmental regulations implemented by the Chilean government, and also to support the pressure of the public opinion. Thus, air quality standards for sulfur dioxide and particulate matter (primary and secondary), plans for reducing emission of arsenic by the Chilean copper smelters, effluents discharge limits, among others regulations were applied by the environmental agency. Additionally, agreements on cleaner production were carried out by mining sector and government. Now, a draft law on mine closure, and another on environmental mining wastes (abandoned mines) are being discussed by the authorities and the mining sector. In the context, production and environmental impacts in different ways to produce copper in the Chilean mining industry are reviewed and regulatory tendencies as well as abatement technologies today used are exposed and discussed in this presentation. Pyro, hydro and electrometallurgical processes employed and their current effluent and contaminants are presented showing various alternatives of treatment in the copper industry. An update of regulations established in Chile vis a vis copper production, with an especial attention to mine closure are also presented.

Jan 1, 2007

By C. Y. Jia

Adsorption of Thiooxidans ferrooxidans and Mycobacterium Phlei on the surface of pyrite and galena was studied. From the experimental results, it was observed that Mycobacterium Phlei adsorbed preferentially on pyrite than on galena at neutral and alkaline pH values, while Thiooxidans ferrooxidans is not at all pH range, and the scanning electron microscopy photograph also indicated that. FTIR and XPS of two strains of bacteria indicated that there are much functional groups on surface of them, such as O?H, N?H, C-O, C?N, C?O etc, but S-O group occurred on Thioox-idans ferrooxidans cell surface and the P-O group appeared on Mycobacterium Phlei cell surface, and the content of C?O?H and C?O?C groups on Mycobacterium Phlei cell surface is higher than that on Thiooxidans ferrooxidans cell surface, this also been known from UVS investigation. The affinity of these groups to metal ions on sulfide minerals is able to explain the selective adsorption.

Jan 1, 2014

By Jean-Pierre Birat, Ana-Maria Iosif, Denis Ablitzer, Olivier Mirgaux

"Integrating environmental considerations into the product traditional process design is now the major challenge for steel industry. Life Cycle Assessment (LCA) is nowadays considered as an appropriate method for assessing environmental impact and selecting new technologies to reduce CO2 emissions for steel industry.In this paper we propose a new methodological concept which combines LCA thinking with process simulation software in order to carry out the life cycle inventory of classical steelmaking process.Using Aspen PlusTM software, a physicochemical model has been developed for the integrated steelmaking route. This model gives the possibility to carry out life cycle inventories for different operational practices in order to optimise the use of energy, to calculate CO2 and other emissions and to control the mass and the heat balances of processes.It is also shown that such approach can be used to design and assess new technologies for steelmaking without large industrial application.IntroductionDuring recent years, it was recognised that CO2 emissions are the major factor of the global warming effect. In order to meet Kyoto requirements, the steel industry is embracing the challenge of sustainable development by improving its competitiveness and economic success while reducing its environmental impacts. Integrating environmental considerations into the traditional product design process, for powerful eco-efficiency, is now one of the major priorities for steelmakers.The European Steel Industry has measured up to this challenge by creating ULCOS (Ultra Low CO2 Steelmaking) consortium that has taken up the mission to develop breakthrough steelmaking process with the potential to reduce CO2 emissions (Eurofer, 2005). In order to develop technologies to reduce emissions, it is necessary to assess the environmental impact of the classical steelmaking route (coke plant, sinter plant, blast furnace, basic oxygen furnace, continuous casting and hot rolling)."

Jan 1, 2009

By E. Larsen

Marine tailings disposal may in some cases be the best solution to one of mining’s major environmental problems. The public standing of this solution is poor, partly because of past bad practices. Among the tailings problems spreading of super-fines and toxic substances stand out. The two are often interrelated as heavy metals, insoluble to sea water, tend to adsorb on fines and spread piggyback on them. Only one paper seen, has addressed the mineralogy of fine particles in suspension. The topic was a secondary tailings deposit. Studies on the sedimentation of fines in large river estuaries show that different minerals sediment sequentially as the salinity of the river increase. Mineralogy in the particle size range where particle separation takes place, has so far, naturally been in focus for the mineral processors. Next to nothing is known about the fines which may cause environmental problems. Tailings disposal has, due to its complexity, to a large extent been taken over by specialists in other fields, biologists, engineering geologists, chemists. The basics of the subject ought also to be given more input by the mineral processing community. A drawn out battle about tailings discharge into some fjords has taken place in Norway. The detractors focus at fine particles (could be dangerous nanoparticles) spreading and emphasize the effects. Calculation is simple: 5 million tonnes tailings annually discharged, containing 1 wt. % < 1µm determined by laser diffraction, results in 50 000 tonnes of nanoparticles let loose in the environment. The industry`s difficulty to answer, is lack of basic research on this topic. Test work to develop a methodology to address the problem is described. One thing the mineral processors know is that final tailings may be comprised of tailings from separate separation processes, with different properties, some of which may require special treatment. One tailings stream from a Norwegian mine is investigated in such a context.

Jan 1, 2016

By J. C. Bayles

Jan 1, 1886

By William R. Barton

It is generally conceded as axiomatic that the aggregate producer and the average urban resident have mutually incompatible goals. The producer wants to be near his mass market and the average resident wants him as far away as possible. The traditional economic decision to mine local material to avoid transportation costs is increasingly challenged by zoning and planning bodies and by citizens&apos; groups. This conflict generated much written and spoken word and offered opportunity for great flights of rhetoric. The pressure on the producer also has forced re¬appraisal of the need for the classic confrontation with indications that much of the conflict is more apparent than substantive. In New England several factors combine to increase complexity of the siting problem. It is a region of high land values and population density. Due to the proximity of metropolitan areas, even rural communities have experienced a prolif¬eration of environmental groups with concomitant enthusiastic regional planning and critical watch over land use. In New England where there is little public understanding of the necessity for, and the realities of, mineral production a sophisticated approach to aggregate production site location is required.

Jan 1, 1975

By Adam Gerondale, David Hemstreet, Lisheng Shao, Kenji Yamasaki

"Foundation soils of a proposed single-span bridge over a busy railroad in Anchorage, Alaska included a layer of sensitive, non-plastic to low-plasticity silt. Slope stability analyses showed that, without ground improvement, the proposed abutments would not be stable immediately following the design earthquake due to the liquefaction of the sensitive silt. Wet soil mixing was selected to mitigate the liquefiable soils and assure abutment stability because: (i) it is a non-vibratory method and can be used for areas adjacent to the railroad tracks and underground utilities, as well as in areas not sensitive to vibration; and (ii) preand post-ground improvement testing, such as SPT or CPT, is not required. Eliminating the liquefaction hazard at the site also allowed for the abutments to be economically supported on shallow spread footings. A total of 511 soil-cement columns were constructed at the two abutments, each with a diameter of 8 feet (2.4 m) and an average length of 20 feet (6.1 m), extending from about 30 to 10 feet (9.1 to 3.0 m) below finished ground elevation. The columns were laid out in a shear wall pattern (in the longitudinal direction of the bridge) to increase stability under the loading by approach embankments.INTRODUCTIONAlaska Department of Transportation and Public Facilities (Alaska DOT&PF) is currently constructing West Dowling Road Overcrossing in Anchorage Alaska. It will be a single-span, steel box girder bridge approximately 200 feet (61 m) long and 100 feet (30 m) wide. It will have approach embankments, about 40 feet (12 m) high, on both sides. It will carry the new extension of West Dowling Road over double tracks of Alaska Railroad and Arctic Blvd. Foundation soils of the abutments consist of surficial fill and peat layer underlain by soft silt which is likely to liquefy and lose strength under shaking by a design earthquake. Both deep and shallow foundations were considered to support the bridge abutments. The design team pursued the option of improving the foundation soils and using shallow footings. Several ground improvement methods were evaluated, out of which wet soil mixing was selected as the best option.In situ wet soil mixing (hereinafter simply soil mixing) is mechanical mixing of soil in its location with cement slurry and produces soil-cement (soilcrete) columns that are stronger, less permeable, and less compressible than the original soil. Soil mixing is used for various applications including reinforcement of soft soils, excavation support, liquefaction mitigation, cutoff walls, etc. This paper presents a case history of soil mixing successfully used to improve foundation soils of bridge abutments to allow the use of spread footings."

Jan 1, 2015

By E. L. Litchfield

Spark ignition of combustible-gas mixtures is a relatively old subject of investigation and has been treated both experimentally and analytically by many people. Elements of static and current electricity are almost always present in mining and industrial operations, and the spark can be an extremely efficient source of ignition. Thus the practical interest of such problems as the "intrinsic safety" of electrical apparatus is obvious. Ignition and quenching phenomena are the primary laboratory representatives of combustion phenomena that are dynamically nonsteady, and such nonsteady phenomena playa considerable part both in industrial processes and in safety matters, although they are of less immediate practical interest. Considerable effort has been expended by the Federal Bureau of Mines in investigations of spark ignition.5 6 7 8/ Primarily, this work has established the significance of several of the parameters involved. Although the

Jan 1, 1959

By V. Kecojevic

The objective of this research was to establish the relationship between production, consumption and energy cost in the surface mining of bituminous coal. Specific energy sources such as diesel, gasoline, electricity, explosives and bituminous coal were considered in this study. Gain in net energy, proportion of the cost of energy consumption and total energy cost relative to total revenue of extracted coal were determined, and a new energy efficiency index and a new energy-cost ratio were established. A case study on an operating surface coal mine was carried out to demonstrate the application of the newly developed method. The results of this study can be used by the mine operators in establishing strategies for the optimization of energy production and consumption, and for reducing the cost of bituminous coal extraction.

Jan 1, 2014

By Robinson Leon-Diaz, Alberto Jaen-Toribio, Raymond Blanchard, Mike Deevy, Miguel Fuentes-Llanos

"Tunnels designed to NFPA 502 are required to withstand the RWS time-temperature curve, more specifically prevent progressive spalling and loss of strength of steel reinforcement. Fire boards or spray-on layers can be effective, however, these solutions have capital and whole-life cost implications. The use of “fire resistant” concrete based on a suitable aggregate with polypropylene fibers has also increased in recent years. This article presents a new methodology for thermal and structural analysis of segmentally lined tunnels, which permits the analysis of project specific fire curves and an assessment of different fire protection strategies. The effectiveness of fire boards is assessed along with whether “fire resistant” concrete alone is a viable means of achieving the required protection. Finally, since NFPA 502 recommends water-based fixed fire-fighting systems for Category C and D tunnels, we discuss the question of how a fixed fire-fighting system should be addressed within the structural design. INTRODUCTION Protecting road tunnels from structural damage and collapse is a key requirement for both life safety and business continuity. Where road tunnels are part of key highway corridors, protecting business continuity is a high priority for owners, operators and the Authority Having Jurisdiction. For existing tunnels, compliance with NFPA 502 may require upgrades with either passive fire protection and/or water-based fixed firefighting systems. For new tunnels, compliance with NFPA 502 requires a combination of good practice in design and fire testing. A water-based fixed firefighting system is a Conditionally Mandatory Requirement1 for Class C and D tunnels, i.e. all tunnels greater than 300m and 1000m long respectively. The basis for fire safety design of new tunnels and assessment of existing tunnels is the worst-case fire scenario. A number of factors, including but not limited to the following, influence this design fire scenario:"

Jan 1, 2016

By Valentine Chanturiya1

We have developed a classification of geochemical barriers according to their origin, i.e. natural and artificial, and according to methods and areas of application. There has been an examination of the interaction between different classes of geochemical barriers with sulfate solutions containing nickel, copper and iron. As natural barriers, carbonates (calcite and dolomites) were used. For artificial barriers, a mixture of serpentine and carbonatite, thermo-activated copper-nickel dressing tailings, and a magnesium-containing sorbent based on brucite was used. Keywords: geochemical barriers, physical-chemical geotechnologies, treatment of natural and waste water, recovery of nonferrous metals

Sep 1, 2012

By Mohamed Hamoud

Relative permeability curves represent an important element of special core analyses, but challenges remain in obtaining valid results and the extrapolation and use of existing permeability results is problematic. This situation is compounded in cases where core properties are altered from changes in effective stress. During the production of oil and gas reservoirs, the effective stress changes as a result of changes in pore pressure or temperature. Therefore, changes in rock properties such as porosity and permeability will occur and will consequently influence reservoir performance calculations. An experimental program was carried out to understand the behavior of dense, reconstituted sand samples at low effective stress states. Drained triaxial compression tests were set up to study the effect of stress alteration on relative permeability data through porous media. Initially, a saturation stage was performed followed by isotropic loading to bring the core sample to reservoir fluid and stress conditions. Then, while axial (deviatoric stress) loading was applied to the sample, a series of absolute and relative permeability tests was performed under steady state flow at different levels of strain during pre and post peak shearing stress. The stress-strain behavior results from the study revealed that the absolute permeability decreased during isotropic loading (compaction) and increased during shearing (dilation). However, the shape of relative permeability curve changed from contraction to dilation and showed higher initial kro and the lower initial kro respectively. The goal of this project was to understand the behavior of both absolute and relative permeability at different stresses. It is expected that geomechanical processes will be adopted for special core analyses to support the current integration of geomechanics into reservoir engineering. This will be required if, during SAGD, conventional and/or unconventional reservoir simulation, reservoir engineers implement a proper set of relative permeability data at each in situ state of stress, instead of constant curves throughout the field?s life.

Jun 1, 2012