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By M. Sagisaka

Coal is expected as one of the main energy sources for a long period because of vast deposits. However, two large barriers to utilize it are suggested, i.e. the carbon dioxide emissions and ash disposal. The authors chose principal methods and areas to utilize coal ash and analyzed the environmental impacts caused by the ash treatment considering the source of the ash. According to the analysis based on lifecycle thinking, an optimized ash treatment system can reduce the integrated environmental impact. It suggests that coal can carry out its role for several decades without disturbances from the point of ash treatment.

Jan 1, 2006

By Clifford J. Lewis

The role of calcareous minerals in that area of the environmental improvement program involving the control or elimination of sulfur oxide emissions is discussed, and a new concept in gas scrubbing, rendering possible the use of calcareous rocks more extensively for this purpose, is presented. Calcareous rocks are defined as the more common limestones, consisting essentially of calcium carbonate and magnesium carbonate. The effect of magnesium carbonate on the reaction rate of limestones and lime toward sulfur oxides in aqueous scrubbing systems is pointed out. The relative economics of lime- stone versus lime as aqueous scrubbing reagents for sulfur dioxide are indicated.

Jan 1, 1974

By Edmond O’Donovan

Selection of conveyor drives is an area of great confusion that frequently leads to poor system performance or overcapitalization. Many papers have dealt with the performance characteristics of different drive types, but users have often found that this only leads to further confusion. This paper presents the drive requirements from the "conveyor's" point of view. The drive requirements of different classes of conveyors are examined to illustrate why some drive types work well in certain situations but poorly in others. The appropriateness and shortcomings of different drives are examined in this context, along with the recurrent issue of load sharing.

Jan 1, 2000

By Hans Svensson

INTRODUCTION The Alimak method of raising (Fig. 1) was intro¬duced in 1957. Because of its flexibility, economy, and speed, it soon became the most used system of raising in the world. With the same unit, raises of various areas, inclinations, and lengths can be driven. Air-motor¬-driven raise climbers normally are used in mines with short raises (Fig. 2). For longer raises electric or diesel-¬hydraulic drives are used. The Alimak raise climber is designed entirely in ac¬cordance with the instructions of the Swedish Board of Industrial Safety (Arbetarskyddsstyrelsen). There are good margins of safety concerning the breaking strength of the material and the raise climber comprises safety devices and features that practically eliminate the risks of accidents. The drive gear of air-driven climbers is equipped with an air-operated brake which is automatically activated when air for the motors is shut off. There is a safety device which activates automatically at overspeed and a speed-regulated brake for descent by gravity, by which the raise climber can be taken down to the bottom of the raise in case of cutoff of the air supply. The raise climber climbs along a pin rack welded to a guide rail which also comprises pipes for air and water. The guide. rail can be extended by using 1- or 2-m (3.2¬or 6.4-ft) sections as the driving progresses. Each guide rail section is bolted to the rock wall by special expan¬sion bolts of Alimak design. Men ride up to the face in the cage, traveling com¬fortably and easily while material is transported on the platform. There is no dangerous climbing up ladders. The men are well protected during ascent and arrive in good condition at the face. The greatest advantages of raise climber systems are flexibility and versatility. The equipment provides a comfortable working position in vertical as well as in¬clined raises of any area and length. The direction may

Jan 1, 1982

By Larry B. Bramlett

Regional radiometric, magnetic and geologic data point to Copper Mountain as an area of general uranium favorability. Sub-regional radiometric and magnetic data direct interest to a specific section of an overthrust Precambrian granite. Detailed magnetic and resistivity surveys in this area show local targets of interest, one of which corresponds to Rocky Mountain Energy's North Canning deposit. On the basis of these data a second and previously untested target was drilled resulting in the intersection of uranium horizons similar to those at North Canning. This integrated geophysical approach can be used for uranium exploration in geologically similar areas.

Jan 1, 1979

By Neil D. Donnell, O&apos

Bituminous sands of the Lower Cretaceous McMurray Formation in northern Alberta constitute the ore for the surface mining operation at Syncrude Canada Ltd. These sediments represent a complex succession of fluvial, estuarine and marine depositional environments. Grade prediction is realized through a combination of geological interpretation, computer modeling, and reference to past mining experience. Accurate forecasts of feed grade permit reliable predictions of volumes for removal to meet budgeted synthetic crude oil production. This planning facilitates efficient allocation of mining equipment and resources. The feed grade to the Extraction Plant is monitored at various points along the delivery system.

Jan 1, 1984

By Paul D. Chamberlin

There are many unit operations applicable to the processing of gold/copper ores. Deciding which are most applicable to your ore can be done using a series of tree diagrams. The diagrams show generalizations, not definitive rules. And the listing of process alternatives on the diagrams is very limited although there are dozens to choose from. Three questions help point the way to proper process selec-tion: 1. How much gold is in the ore? 2. How much copper is in the ore? 3, What is the cyanide consumption when leaching the ore?Halogens can also effectively leach gold ores and gold/cop

Jan 1, 1996

By John F. Bryce, Fazley A. Azhar

With increasing economic pressures to produce more with less, the material handling industry is turning to engineered solutions to reduce the number of people required to operate its facilities, monitor maintenance trends, pin point problems, increase throughput, decrease downtime, identify weak links in the production system, and increase times between scheduled maintenance. One solution to these problems is to implement a Total Control Solution (TCS) using industrial computers, fieldbus networks, and distributive Input/Output (I/O) for control, automation, data acquisition, and analysis. This paper will discuss some of the control fundamental principles used by Technisys, Inc. (TI) to implement TCS.

Jan 1, 1998

By R. L. Loofbourow, Robert R. Miller

Deep, stable, unlined space promises secure, efficient, acceptable solutions to several current problems. With truly favorable conditions, it can be economic as well. The basic requirement is sufficient sound, tight rock at required depth. This and unusual surface requirements point to special testing. An objective is to describe conditions for planners, estimators and contracts. A first stage concept study needn't be prolonged but should overlook nothing significant. Although observations and tests on core are considered essential, time and expense can be cut by supplementing then with tests on walls of rotary or percussion holes. In some places initial drilling could be shallow.

Jan 1, 1981

By John J. Mancini

Elastomeric liner products have been used for over two decades in a wide variety of uses including pond liners, hazardous waste barriers, dam face rehabilitation and mining applications. Asphalt blended with polymers is enjoying renewed interest in the engineering community because of its durability, high yield attributes, fewer CQA steps due to seamless installation, and ease of installation and repair. As in other lining technologies, advancements in polymer chemistry and improvements in installation techniques have had dramatic impact on the quality of fluid-applied asphalt (FAA) membranes. Membrane 6, man­ufactured by Deery Oil, Inc. for over 16 years is a hot-applied polymer modified asphalt membrane that can be applied to a variety of substrates in a reinforced configuration or installed directly on an asphalt surface. By blending thermoplastic polymers with asphalt, very favorable stress/strain characteristics can be achieved (Chambers, 1980). Typically the membrane will yield under rel­atively low stress and also exhibit high elongation capability. In service applications where puncture resistance is a concern, fluid applied asphalt materials have the flexibility and com­pressive strength under heavy loading that leach pad designers may find attractive. Additional security is achieved if long term service life is important as in the case of radioactive waste con­tainment. The Department of Energy selected Membrane 6 over seamed liners for a surface barrier that must isolate and contain radioactive waste for 1000 years. Asphalt has a long history of use as a water-stop material and it is believed that this natural construction material combined with SBS polymers will per-form for a millennium. (Freeman, 1994) The process of installing Membrane 6 varies according to job size and the type of surface to be protected. Lining applica­tions on compacted substrates require the membrane to be applied to a scrim cloth (fig 1). Some early pioneers in FAA technology neglected this step and therefore never achieved per­formance levels that satisfied regulatory guidelines. The scrim provides a cohesive surface that promotes membrane flow while achieving high impermeability (2Xl0 '11).

Jan 1, 1996

By G. D. Hood, C. E. Jordan

The US Bureau of Mines investigated rapid froth flotation through more efficient bubble-particle collisions that improved the overall flotation kinetics. An in-line static mixer efficiently mixed the bubbles, water and ore, selectively attaching these bubbles to the hydrophobic mineral's surface. As the mixture entered the flotation chamber, the hydrophobic mineral was already attached to the bubbles and was quickly floated away from the remaining ore pulp. The rapid flotation system was evaluated for beneficiation with a western porphyry copper ore containing 0.67% copper and with a phosphate-bearing amine flotation tailings sample containing 9.5% P2O5 in a quartz matrix. Over 88% of the copper was recovered from the ore in a rougher concentrate containing 5.9% copper at a rate seven times, faster than conventional flotation. Sixty percent of the quartz in the phosphate-bearing sample was floated at a rate four times faster than conventional flotation. The unfloated product retained 80% of the phosphate in a 16.9% P2O5 concentrate.

Jan 1, 1994

By Neal Rackstraw, Mamo Meaza

Washington Metropolitan Transit Authority Section E8a consists principally of twin tunnels 1,713 meters (5,620 ft) long, excavated to a diameter of 6.35 meters (20.83 ft) using an open face shield, with a primary lining of four unbolted precast concrete segments expanded at the crown, and a full circle unreinforced concrete final lining with a finished tunnel diameter of 5.08 meters (16.67 ft). The tunnels, constructed in Cretaceous age sediments, are mostly in stiff to hard clay except for a few areas along the alignment that contain dense to very dense fine sand in the upper portion of the tunnel that created a mixed face condition. At two locations unexpected heavy water inflows produced very serious problems in both tunnels. Water flows in the interface area were generally more than 378.5 1pm (100 gpm) and reached as high as 2,649.5 1pm (700 gpm) in the mixed face ground. The nature of the tunnel inflows, the consequences, and the corrective measures adopted will be the subject of this paper.

Jan 1, 1991

By Reginald E. Reid

Mining on Bureau of Land Management (BLM) administered lands is affected by Federal laws and regulations requiring the mining industry to plan for the environmental consequences of surface disturbance. Regardless of the requirements for obtaining a claim, permit, lease or contract to mine, a notice or a mining and reclamation plan will be submitted and an acceptable environmental document must be prepared prior to mining. A bond may be required based on the results of the environmental evaluation, public interest and the operator's past history of compliance. In several areas, Federal requirements are different from California's requirements under their Surface Mine and Reclamation Act (SMARA). Therefore, the BLM is negotiating with the State in order to work out problem areas of responsibility and duplication of effort.

Jan 1, 1984

This paper presents the results of an investigation of the stability of the mass flow rates and average pellet size in the different streams of an industrial-scale balling circuit. The variables in this study include water content, drum speed and fresh feed rate. It was found that both the mass flow rates and pellet diameter are greatly disturbed when a change, positive or negative, in any of the variables takes place. For most of these disturbances to be damped don, a period of one hour or so is required. When a disturbance in the feed rate was made, the transient period extended to more than one and half hours (the duration of the experiment). It was observed that there is an interaction between the drum speed and moisture needed for producing an acceptable green ball product. The moisture content of the product pellets was found to be a function of the pellet size, with the larger pellets retaining a higher moisture content.

Jan 1, 1980

By L. Nahai

In an exchange of views with the Program Chairman for the Technical Session on Industrial Minerals and Investment in Foreign Countries, it was agreed that it would be more interesting to approach the problem of mineral investment in foreign countries in a more general framework and not confine it to industrial minerals. Therefore, this Bureau of Mines report is proposed to examine current attitudes toward investments in foreign mineral resources and restraints that they impose on investments necessary to assure supply for future global mineral needs.

Jan 1, 1976

By Betty L. Gibbs

Microcomputers are becoming more convenient to use at all levels of the business world, including the mining industry and mine offices. The state of the mining industry requires that we become more productive and innovative in our analysis of deposits and operations. With the help of computers, examination of options to increase productivity can be performed quickly and inexpensively. Effective use of the computer for designing underground workings combines the calculation power and speed of a computer with the technical expertise and judgment of the engineer. Computer programs can perform calculations in minutes that could take an engineer several months. The engineer must be on guard when using the computer for any calculation because it is very easy to assume the results produced by a computer program are always correct. The computer is a sophisticated calculator but cannot recognize logical errors nor transposition of numbers. Also some intuitive or obvious decisions made by an engineer are difficult or impossible to program effectively.

Jan 1, 1987

By Robert R. Munro

Traditional aggregate sources, that is the riverbeds, the alluvial fans, located relatively close to the developing urban centers are being foreclosed to mining. As the sand and gravel reserves are depleted, those production plants are unable to secure additional adjacent reserves and are being forced to close down. The sand and gravel industry, in many respects, is its own worst enemy. We promote development, we promote the paving of streets, the building of houses, and industrial and commercial centers, and because of economics, we tend to favor those developments located close to our operations. Thus, we encourage development by our neighbors who soon become our detractors. In general, urban development is not compatible with sand and gravel mining. The neighbors don't like the view of the pits or the quarries, they complain about the "dust", about noise, about trucking . . . in general, the neighbors are not happy being close to an aggregate source.

Jan 1, 1984

By Courtney Black, Paul F. Ziemkiewicz, Eberhard Werner, Matthew Daly, Joseph J. Donovan, Jeff Frazier

Injection of alkaline waste-lime slurry was performed at a West Virginia surface coal mine site, to attempt neutralization of acid springs by an alkaline recharge method. Deep trenching (>5 m) using an excavator yielded the most effective injection into the aquifer. Water from two springs, 90 m from the deep trench, showed 70%-80% reduction in acidity in response to injection. Neutralization persisted >170 days after treatment, with pH between 5.1-5.7 and metal acidity from 25-60 mg/L. A minor fraction of lime introduced was consumed. The sustained neutralization is attributed to reaction of acid water with subsurface lime, entrained below the wafer table by macropore infiltration. Characteristics of groundwater transport are critical in determining recharge structure location.

Jan 1, 2000

By Warren D. MacEvoy

INTRODUCTION Good ventilation bulkheads (stoppings) can be obtained only by conscientiously adhering to four basic principles: carefully selecting the site for the bulkhead, adequately preparing the site, properly constructing and sealing the bulkhead, and checking the results with a smoke tube before leaving the area. If all these guidelines are followed during each ventilation project, a poor job will result only from the use of improper materials and cannot be blamed on carelessness or oversight. SITE SELECTION A perfectly constructed bulkhead in the wrong location can be completely worthless. Conceivably, a bulk-head in the wrong location could cause dangerous ventilation conditions that are difficult to identify and isolate. If the suggestions herein are followed, a considerable amount of work, time, and material may be saved. Perhaps the single most important step is always to select the exact site for a bulkhead before starting construction. Although the latitude in selecting a site may be limited by instructions or operating conditions, it is common to find poor bulkheads built within a few meters (feet) of a site that would have been far superior but was overlooked during the planning process. The ideal site for a bulkhead should have as many of the following features and conditions as possible: 1) To provide a solid bulkhead, the selected site should be in firm and unbroken ground. 2) To minimize the amount of work and material required and to minimize the danger of later damage to the bulkhead, the site should have as small a cross section as possible. 3) The bulkhead site should not be encumbered by interferences such as pipes, wires, ditches, wire roof supports, trash, muck piles, etc. 4) The walls and timbers of the site should be free from oil, grease, or tar that would inhibit adhesion of the sealant used on the bulkhead. 5) Unless special precautions are taken, the site should not have water seepage, standing water on the floor, or water-carrying ditches. 6) To expedite construction of the bulkhead, the site should have reasonable access to transportation, supplies, communication facilities, and compressed-air lines. 7) The site should have a reasonably level floor, allowing direction of the bulkhead door swing to be reversed at a later time if so desired. In a steeply sloping location, it may be possible to open the door in one direction only. SITE PREPARATION Once a suitable site has been selected for the bulk¬head, it must be prepared properly. All site preparation work should be completed before starting any construction work on the stopping itself. Unfavorable site conditions can be identified during the course of thepreliminary site preparation, saving time, effort, and materials that otherwise might be wasted. The follow¬ing preparation steps help assure the construction of a good stopping: 1) If wire mesh has been used at the site, a strip 457 mm (18 in.) wide should be cut and removed from the walls and roof at the selected location. 2) The exposed strip of rock should be barred down thoroughly to provide a smooth surface. 3) All obstructing materials should be removed, including old timbers, pipes, rockbolts, wires, etc. If a conduit must cross the bulkhead area, it should be located or relocated away from the floor, walls, and roof to allow a 6.28-rad (360°) seal around the juncture between the conduit and the bulkhead structure. 4) All loose muck should be cleaned from the site and a trench about 152 mm (6 in.) deep should be dug from wall to wall in the floor. The trench must be wide enough to accommodate the entire bulkhead, including the posts. 5) The rock surfaces of the walls and roof should be cleaned with a wire brush to remove as much loose surface material as possible. Thorough cleaning promotes adhesion of the bulkhead sealant to the surfaces of the walls and roof, thus promoting an airtight seal. 6) It is quite difficult to seal landing mats that cross a bulkhead. If such a crossing cannot be avoided, the bulkhead should be placed between the end and the first hole in the steel so at least one side of the bulk-head can be sealed easily and completely. That may have to be done prior to actual construction if the end is located on the opposite face from the seal coating of the bulkhead. BULKHEAD CONSTRUCTION The three principal considerations in bulkhead con¬struction are the type of bulkhead, materials to be used, and construction method to be employed. For many projects, the bulkheads are specified by the requesting agency, with no latitude for independent choice of the type, materials, or construction method. In such cases, any deviations from the specifications, for any reason, must be approved in advance by the proper department or by the project senior ventilation engineer. Types and Materials When a choice of type, materials, or method is allowed, consideration should be given to factors such as cost, required useful life, proximity to blasting concus¬sions, availability of materials, direction of permissible air leakage, and degree of airtightness required. Other factors to be considered include the amount of time available, accessibility of transportation, potential for interference with operations or production, ambient water conditions, availability of connections to com¬pressed-air lines, etc. Despite the multitude of factors to be considered, most stoppings can be analyzed easily and the proper choices can be made without much difficulty. The four common classes of bulkheads utilized in

Jan 1, 1982

By A. J. Stewart, R. L. Shufflebotham, D. W. Ferguson, T. L. Page

The Inter-Island Tunnel is a 7.7 kilometer (25,160 foot) long by 3.5 meter (11.5 feet) diameter concrete lined tunnel through the Cambridge formation below Boston Harbor. Constructed as part of the Boston Harbor Project, this tunnel will bring untreated wastewater from the MWRA’s South System headworks facility at Nut Island in Quincy, MA to the new Deer Island treatment plant. A myriad of problems delayed the construction of the tunnel. These problems included salt water inflows of over 22,000 liters (5,812 gallons) per minute, a major fire in the access shaft, weak rock and soil collapsing on the tunnel boring machine, and hand mining operations.

Jan 1, 1997