Search Documents

By Wayne A. Sadik

The mine ventilation system of the Henderson Mine provides a case study of designing and maintaining high-quality respirable air in a large underground mine with over 200 units of diesel-powered equipment. This system was designed with concern for minimizing exposure to personnel of siliceous dust, diesel exhaust, smoke, and potential fire hazards while optimizing general environmental air quality throughout the multilevel/multiheading operation. As a relatively new operation, the Henderson Mine incorporates a modern ventilating plant and mine de- sign as well as state-of-the-art technology where appropriate. Two main ventilation shafts approximately 2,300 ft (701 m) in depth (one intake, one exhaust) will handle 1.8 million cfm (850 m3/s) of air circulated throughout 60 miles (97 km) of drifting, providing the ventilation requirements for more than 25,000 diesel horsepower (18,642 kw) underground.

Jan 1, 1980

By G. Roy, C. B. Pettersson, S. Nandagiri, D. J. Ivor-Smith

The Coastal Water Authority's 2,740mm/2,590mm (108 in./102 in.) pipeline, known as the Northwest Lateral Project, will transport raw water from an existing pipeline over 14.3 km (8.9 miles) to the City of Houston's East Water Purification Plant. The new pipeline crosses under Houston Ship Channel and Greens Bayou in tunnels at approximately 30.5m (100 feet) and 25.9m (85 feet) depths, which present unique experiences in tunneling under open bodies of water in the Gulf Coast's soft ground conditions. An earth pressure balance TBM is being used for the deep tunnel sections where the ground demonstrates high overload factors and variable conditions ranging from clays to silty sands. This paper discusses the design approach for the tunnels and shafts, ground conditions, constructability, and selection of the primary lining system.

Jan 1, 1989

By J. D. Miller, C. L. Lin

As the techniques and resolution for three-dimensional spatial analysis have advanced in the last decade, it is now possible to map in detail the microstructure of multiphase materials in three-dimensional digital space. In this regard, three-dimensional X-ray microtomography offers a unique imaging capability. Spatial resolution on the order of 10 µm can be achieved with the use of microfocus X-ray generators. Recently, a state-of-the-art cone beam X-ray microtomography system was installed at the University of Utah for the quantitative analysis of multiphase materials in three dimensions. This facility was designed to obtain 2,048 by 2,048-pixel reconstruction over a 10-mm diameter, while also allowing for the imaging of somewhat larger (40-mm) objects. The system is capable of handling high-density materials, even materials having a density as high as 8.0 g/cm3. This unique, one-of-a-kind instrument can be used to obtain three-dimensional spatial reconstruction for many applications, such as three-dimensional liberation analysis, pore structure analysis of particle beds during filtration and the air-void system of concrete structures. The utilization of X-ray microtomography not only allows for the quantitative analysis of multiphase systems but also allows, for the textural characterization and determination of phase continuity. This paper presents information regarding the current use of this new facility and a review of potential applications for the advanced analytical system. Key words: Cone beam X-ray microtomography, Three-dimensional analysis, Material characterization

Jan 1, 2003

By William H. Langer

U.S. Geological Survey (USGS) recently initiated the Front Range Infrastructure Resources Project. This is a multidisciplinary study along the Rocky Mountain Front Range from Pueblo, Colorado, to Cheyenne, Wyoming, and is designed to collect, compile, and analyze new and existing data on natural aggregate (stone, sand, and gravel), as well as water, and energy resources. To identify aggregate resources in the Front Range, a 1:500,000-scale reconnaissance map showing locations and quality of both bedrock and surficial sources of natural aggregate in the Front Range urban corridor was prepared by processing the digital geologic maps of Colorado and Wyoming. The first step of the process was to identify map units as either bedrock or unconsolidated material. Bedrock was classified according to type (i.e., limestone, granite, gneiss, etc.), which in turn was classified based on the suitability of the bedrock for use as crushed stone. Unconsolidated materials were classified according to relative age, with the older, more weathered materials being defined as less suitable for use as aggregate than younger materials. As a spin-off from the Front Range Project, the techniques developed for analyzing the Front Range geology have been modified and expanded to include all of Colorado and New Mexico. More detailed digital aggregate maps (1:24,000 scale) are being prepared in collaboration with the Colorado Geological Survey (CGS). Maps from the CGS "Atlas of Sand, Gravel and Quarry Aggregate Resources, Colorado Front Range Counties" show the distribution of potential resources of sand and gravel and provide general information about the physical properties of the resources. These maps are being digitized and merged into a single Geographic Information System (GIS) data base. In addition, the project is adding more specific information to the maps about deposit thickness, volume, and quality. This additional information is being obtained through field-characterization studies and modeling activities. The GIs data base can be displayed and queried using off-the-shelf software such as ArcInfo?, ArcView?, and Map Professional?. In addition, the USGS is developing a decision-support system to assist users in analyzing various land-use options on resource availability.

Jan 1, 1999

By Hisakazu Matsushita

1. Introduction This is a report on applications of the earth pressure type balanced shield tunneling projects executed under narrow streets on soft alluvial layers in Japan. Japan is a long island country surrounded by the sea. Steep mountain ranges run along the archipelago and numerous rivers originate from the mountains, leaving only limited areas of flat land along the upper and middle reaches of the streams. The majority of cities in Japan are on soft alluvial layers. Alluvium represents an extremely complex soil formation, sections bordering diluvium being characterized by sharp undulations. Various difficulties are therefore encountered in shield tunneling work undertaken in such ground conditions. Particularly, at work sites lying in an unstable, waterbearing layer with high permeability, shield excavation becomes utterly impossible, hampered by large amounts of underground water as well as land collapsing caused by the water. Even when work can somehow be accomplished by using chemical grouting or by lowering ground water level, which require extra expenses and time, undesirable effects such as ground surface settlement are unavoidable in projects undertaken in the past. The newly developed method allows safe and accurate tunnel excavation at normal speed and without giving any adverse effects on buildings above, even under such unstable ground conditions. An outline of this new method was announced at the "International Tunnel Symposium '78" held in Tokyo, and the method has since been employed in a number of tunneling projects in this country. This report provides further data on the new method with reference to some of those projects, explaining how it allows tunnel excavation with

Jan 1, 1979

By D. L. Schenk

The Navajo Mine is exclusively a multiple-seam surface coal mine located in the northwest comer of New Mexico. The property is situated entirely on the Navajo Indian Reservation. It is owned and operated by the Broken Hill Propriety Co. Ltd., of Melbourne, Australia. The mine began production in January 1963 with a long-term fuel supply agreement with the Four Corners power plant. The 2175 MW nominal generating capacity of the Four Corners powerplant consumes 7.2 Mt to 7.7 Mt/a (8 million to 8.5 million stpy) of coal. The Navajo Mine has estimated reserves totaling 1 Gt (1. I billion st) of strip minable coal. Only about one-third of that total is presently committed to the generating station. As development continued over the years, mining operations advanced into more complex geologic areas to satisfy the utility's demand for coal. To optimize the committed reserve and provide competitively priced coal to the customer, the Navajo Mine began developing a new pit in June 1986. The Dixon Pit boxcut development was completed in April 1987. About 6 hm3 (7.9 million cu yd) were stripped, uncovering 929 kt (1 million st) of coal. Strip ratio was 7.74:1 including 36.8% rehandle of prime yardage. This case study of the fourth production cut highlights a variety of dragline stripping techniques including highwall bench (overburden) side cast, intermediate highwall bench (parting-interburden) side cast and spoilside bench (partings-interburden) stripping methods. The Dixon Pit offers considerable challenges in the surface recovery of up to seven seams of coal within the 1432 m (4700 ft) of total pit length.

Jan 1, 1990

By Lynn B. Hales, Randy A. Ynchausti

There is a large economic driving force associated with improving metallurgical performance in mineral processing plants using process control. Because of this and other benefits, control systems of the future will develop towards more sophisticated user friendly computer based systems that use powerful software analysis and control techniques. Auto-tuning, adaptive control and process models will gain expanded use because of their transparent availability to the system designer. Control of individual unit operations will be optimized and coordinated through expert systems that monitor economic conditions and management directives and direct operations accordingly. Plant areas, considered cost centers for years, will be integrated into plant-wide control systems for economic control and optimization. New control hardware, process sensors, control strategies and software development tools will be presented, as well as an overview of the economics driving the continued development of advanced process control systems.

Jan 1, 1993

By Norm Steenson

Rapid excavation includes rapid support and is the central theme of this paper. Over the last few years, enormous strides forward have been made in the excavation and material handling aspects of underground excavation. However, the technology necessary to support these rapidly created openings has lagged behind the other aspects. This paper would attempt to bring you up-to-date on the progress made in bringing ground support using shotcrete into the same productivity rates as the other cyclic operations. Shotcrete has become an acceptable material for temporary and permanent support for undergound openings. However, coarse aggregate shotcrete has been an expensive construction material. It has been confined in the main to difficult ground conditions where conventional methods of support have proved to be even slower and more expensive than shotcrete. There are two main factors influencing the productivity of shotcrete equipment. (1) Structural shotcrete as opposed to gunite requires 40% to 45% rock minus 3/4" in the mix design. The equipment to handle such aggregate content has been difficult to develop on a volume basis owing to the attritional nature of the material which causes intense wear problems on

Jan 1, 1974

By Donald A. Dahlstrom, Soumitro Nagpal, Timothy Oolman

Bacterial oxidation of a pyrite/ arsenopyritic gold-ore concentrate was carried out with continuous flow operation in 14 liter (1.4x10-2 m3) mechanically agitated reactors. 02 and C02 uptakes were determined at varying residence times. Bacterial concentrations were measured using a protein assay. A sharp optimum in biooxidation rates was observed with increasing steady-state residence times. Growth of the bacteria and biooxidation of the mineral were both shown to be strongly dependent on dissolved 02 levels in the liquor.

Jan 1, 1990

By R. M. Ocampo-Franco

The line seven, as part of the development of the Subway Master Plan in Mexico City, will tunnel under different subsoil conditions of clay with high water content and low shear resistance located between 8 and 12m beneath the surface. Boulders in silty sand and gravel to a 40m depth underlay this stratum. Economics, scheduled time of construction, and the obligated interconnection with existing lines one and two determined the construction of the tunnels to have an overburden of 1.0 to 2.2 times the diameter. In the north part of line seven there is a track of 251m length that was decided to attack with an open shield of 9.14m of diameter due to the characteristics of the sub-soil, minimum section needed as well as a minimal overburden, of 10.41m. The paper explains the construction procedure from the excavation stage to the reinforcement of the final lining obligated for the ground subsidence as a result of volumetric changes of a stratum of 4m thick of clay overlying the crown of the shield. Manuscript not received in time for publication.

Jan 1, 1983

By Robert L. P. Kleinmann

Mining has been a significant component of the Appalachian economy for about 200 years. The region continues to be adversely affected by the environmental degradation associated with these past activities. In addition, companies today are being denied permits at sites where acid generation appears likely. And air emission limitations at power plants now threaten the economic health of many moderate- to high-sulfur coal mines. Thus, when considering the environmental impacts of mining coal in Appalachia, it is important to consider abandoned and active mine issues. For example, abandoned mines generate acidic, iron-rich waters that adversely affect more than 6,400 km (4,000 miles) of rivers and streams in Appalachia. In contrast, operations that were active after the enactment of the 1977 Surface Mining Control and Reclamation Act (SMCRA) cause little water pollution. However, the costs of water treatment at such sites exceed $1 million a day. Even where water quality is not dimished, water supplies can be affected by mining. Subsidence-induced fractures can lower water table elevations or drain a surface stream dry. Subsidence can also cause damage to surface and subsurface structures.

Jan 1, 1995

By Peter J. Tarkoy

The art of predicting rock excavating machine performance has become increasingly detailed and refined. Researchers using laboratory experiments and machine manufacturers using field observations have identified and defined mechanisms of failure, rock and tool interaction, and relevant design principles affecting them. Concurrently, practitioners have developed index tests which reflect rock properties relevant to machine performance. Empirical relationships between index properties and machine performance (penetration rate, cutter consumption, and machine utilization) have been established from past experience and are currently used throughout the industry. Contractors have used such relationships for estimating throughout the world. The detail in which geological, geotechnical, test, and project data, empirical relationships, and construction experience are utilized, is limited by time constraints imposed by the bidding period. To fully utilize all available data, methods of analysis, and construction experience, a simple computer program was developed for a microcomputer costing less than $7500. As a result, 1. machine performance predictions are detailed & reliable, 2. construction alternatives may be examined, 3. anticipated conditions & performance are graphically, documented & easily comparable to those encountered, and 4. results include a listing of assumptions & results of performance analyses & a graphic performance summary.

Jan 1, 1979

By Leo Wagner

In relation with the construction of the Sölk power station in Steiermark, Austria, tenders were called in October, 1976, for the construction of the 12-km "Donnersbach collector tunnel" by "Steirische Wasserkraftund Elektrizitäts AG". The specified showed both conventional blast tunneling as well as mechanical excavation with a tunneling machine, diameter 3.55 m. Total construction time from the date of the invitation to tender was given as 4 years. Part of the project was the construction of a concrete circular tunnel lining 20 cm thick. In 1977 the contract was awarded to "Arbeitsgemeinschaft Donnersbach", a joint venture formed by two companies, G. Hinteregger & Söhne, Salzburg, and G. Hinteregger, Bregenz. It provided for the project to be carried out with a tunnel boring machine. GEOLOGICAL DATA The entire tunnel was to be bored through a complex of the garnet mica schist group of the Wölz schists formations. These range from highly quartz-bearing to quartzitic mica schists, with thick, discordantly interstratified beds of marble and dolomite. In the western sector the axis of the collector tunnel intersects the bedding at an angle of 30° to 40°, in the eastern sector the bedding is about

Jan 1, 1979

By Bernard Amadei, Michael J. Robison

The purpose of this paper is to present the results of 102 mu1tiaxial tests conducted on cubical specimens of Indiana limestone using the mu1tiaxial apparatus available at the University of Colorado at Boulder. These tests include (1) uni-axia1 compression and tension, (2) bi-axial and tri-axial compression, (3) biaxial compression- tension and (4) tri-axial compression-compression- tension. The applicabi1ity of existing failure criteria to predict the strength of the tested materia1 is discussed.

Jan 1, 1986

By A. T. Yu

As a nation, we have been known as perhaps the most wasteful in history. From the perspective of engineers and builders on the other hand, planned obsolescence and demolition did beneficially pave way for growth and provided environment for new businesses. Recent economic recession and intense competition from overseas, however, have drastically changed the economics. The high cost of capital and the demise of indiscriminate plant expansion have totally altered the way we conduct our business and run our operations. As a response to increasing demands for better efficiency with little or no funding available, everyone is forced to make do and do better with whatever little he has. Today it nay not be an exaggeration to state that modification of existing facilities may have finally emerged as a way of life. This paper will outline examples of how several companies have effectively modified existing facilities to do more and do it efficiently without having to demolish everything and/or to spend a fortune.

Jan 1, 1985

By Peter Greenhalgh, W. Baguley, R. P. Riley

The traditional impeller system for aeration and suspension of slurries, e.g., in bacterial oxidation plants, is the vertical flat blade turbine (VFBT) . This type of impeller is energy-intensive, which results in a heavy-duty design of shaft, gearbox and drive. The VELMIX bio-reactor development programme is designed to evaluate the use of the new generation of hydrofoil impellers which consume less power and thus have poten­tial for capital and operating cost savings as well as being possibly less damaging to the bacteria. The early tests on pyrite oxidation in a 300 litre laboratory pilot tank using the Thiobacillus ferro oxidans bacteria, showed that hydrofoil impellers had superior charc­teristics to the VFBT impeller and to air­ agitated pachucas, with lower energy input. The geometry of the sparge _ring was found to be very important in optimizing the system.

Jan 1, 1990

By Jean-Michel Rendu

In most circumstances, the traditional methods of. ore reserve estimation for large undulating sedimentary deposits, such as coal and iron formations, do not allow the accurate prediction of grade for mining blocks. The problem is Particularly accute when the mining blocks are small with respect to the thickness of the geological zones in the deposit, and when there are significant grade changes between the foot-wall and hanging-wall of these zones. A simple geostatistical model has been developed, which takes into account the grade changes not only in the direction of the geological strata, but also in the direction normal to these strata. The genesis of sedimentary deposits and the resulting geological properties of these deposits were considered in the development of the model. The model has been successfully applied to the evaluation of a large coal deposit. Eventhough some practical difficulties have been encountered, for example when part of a geological zone was missing or had not been sampled, these difficulties have been .resolved. Both the theory and its practical application are presented in this paper.

Jan 1, 1979

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 Mark L. Bricker

The Jim Bridger Coal Mine, operated by Bridger Coal Co., is located in Sweetwater County, WY about 56 km (35 miles) northeast of Rock Springs. Bridger Coal is a joint ven¬ture between Nerco Coal Corp, the operator, and Idaho Energy Resources Co. The permit boundary encompasses more than 81 km'- (20,000 acres) on the western side of the Continental Divide. Since the mine began opera¬tions in 1974, it has produced about 82 Mt (90 million st) of coal while moving about 344 hm3 (450 million cu yd) of virgin earth. Annual production averages 4.5 Mt to 6.4 Mt (5 million to 7 million st) of run-of-mine coal. Coal is consumed on-site by the Jim Bridger Power Plant, a 2000-MW generating station. Electricity is transmitted to the Pacific Northwest power grid that includes Oregon, Idaho and northern California. Geology The mine is located on the northeast flank of the Rock Springs uplift. This is a broad, asymmetrical anticlinal feature about 97 km (60 miles) long and 56 km (35 miles) wide with a north-trending axis. This uplift separates the Green River Basin to the west and the Great Divide and Washakie Basins to the east. Precambrian rocks on the apex of the uplift are estimated to be 5200 m (17,000 ft) above the Precambrian rocks in the Green River and Washakie Basins. Normal faults with generally less than 30-m (100-ft) vertical displacement cut through the uplift. The dip of strata on the flanks is generally between 3° and 15°.

Jan 1, 1991

By Wen-Long Cai, A. Frederick Banfield

This paper investigates, through case studies on a porphyry copper and a coal deposit, the differences and relevances between an approximate production schedule approach, i.e., the best case and the worst case schedules and a practical production schedule approach. The comparisons were with regards to: 1) choosing an optimum ultimate pit size, 2) determining processing capacities, 3) selecting 'optimum' cutoff grades, and 4) blending. The comparison criteria was to maximize the project net present value. Conclusions were drawn based on the study results.

Jan 1, 1996