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By Prakash M. . P. E. Donde

1. INTRODUCTION The Washington Metropolitan Area Transit Authority (WMATA) has often taken a leading role in introducing innovative construction technologies to build its transit system. Most recently, Contract Section E-5a, which included Fort Totten Station and Tunnels was constructed utilizing the New Austrian Tunneling Method (NATM) in soft ground. Along with the station and tunnels, two permanent shafts were also constructed in soft ground employing the NATM technique. This project is located within the District of Columbia on the Greenbelt Route. The subject of this paper is to discuss the unique method of construction of these two shafts, and explore the benefits of applying the NATM technique to the construction of deep shafts. The design of the shafts was performed jointly by Jenny Engineering Corporation of Springfield, New Jersey, and Mayreder Consult of Linz, Austria. The designers also provided construction support services and a resident NATM expert at the site during construction. The construction of the project started in April 1988 by a joint venture of Mergentime Corporation and H. T. Construction, a subsidiary of Hochtief Company from Germany. This $48.7 million construction project has been completed. 2. SUBSURFACE CONDITIONS The two NATM shafts are located primarily in Cretaceous-age deposits that are over 100 million years old. These deposits are intermixed and lenticular in nature

Jan 1, 1993

By Levent Ozdemir

The advantages offered by mechanical mining have been demonstrated in the underground mining of coal, evaporites and other soft minerals. Mechanical mining and the advancements in automation technoloogies have been the principal drivers towards the realization of enhanced productivity in soft rock mining. For past two decades, emphasis has been placed on developing mechanical mining technology for hard rock applications, to achieve similar productivity improvements and cost reductions. The benefits of mechanical mining are numerous, particularly in an industry where market conditions continue to dictate higher production and lower costs while maintaining high safety standards. Other benefits of mechanical mining include reduced ground support and labor requirements and the elimination of blast and diesel fumes. These benefits further make this technology an attractive alternative to drill and blast for hard rock mining. Mechanical mining is conducive to full implementation of remote control and automation technologies that are under development to achieve further productivity and safety improvements in underground mining. Mine development has been the main focus area for mechanical miners by manufacturers and mining companies. Potential applications include ore body access, haulage and ventilation drifts, undercut and exploration drifts. The economic use of this technology in mine production is still considered many years away. It would need a major technological breakthrough that would make mechanical rock fragmentation competitive with the large-scale, low-cost production blasting operations.

Jan 1, 1998

By James C. Puckett

The mining industry finds itself in the middle, between the need to increase production of our energy resources and the necessity of minimizing the environmental impact. Using the recent past as a guide, the mine planning engineer's function will continue to increase as further coal quality constraints are made upon the production staff. The engineer will need to make use of all available tools in order to provide timely answers to the complex "what if" questions that arise. This need to consider many alternatives is bringing about a rapidly increasing acceptance and utilization of the computer. In the areas of data handling, mineralization modeling, and production simulation, the computer is an effective tool for the mine planning engineer. Described herein is a coal data storage and analysis system developed to provide timely answers to the "what if" questions for an operating strip coal mine in Montana. The characteristics of a computerized coal data base and coal quality planning system are outlined in this chapter. The system has been developed for use at a particular coal mine; however, it has applicability to coal mines in general. Fig. 1 is a flow chart showing the functional relationships of the system. There are three main file types: the drill-hole data base, the boundary file, and the zone file. The purposes for which each file is organized are illustrated on the flow chart.

Jan 1, 1979

By E. Grygiel, J. Haynes, T. McNider

Jim Walter Resources Blue Creek No. 3 Mine was opened in one of the most gassy coal beds in the United States. Although face ventilation requirements exceeded 14,000 cfm (6 .6m3/s) air, continuous miner sections experienced an unacceptable frequency of frictional ignitions. Modifications offered primarily by the U. S. Bureau of Mines such as diffuser fans, water spray fans, and slow speed cutting motors were used with little success. However, laboratory tests conducted at the U. S. Bureau of Mines indicated that an increase in bit attack angle from 50° to 55°-57° significantly reduced the chances of the bit causing a frictional ignition. An experimental miner drum was built using this concept coupled with a new bit designed by the Bureau and manufactured by Hughes Tool Company that better protected the bit steel shank with a carbide cap. It was installed on a continuous miner and placed in an area of the mine prone to ignitions. 50,000 tons (45,500 metric tons) of coal were cut without a frictional ignition. When the miner was withdrawn for rebuild and a machine with an unmodified cutting drum placed in service, two ignitions occurred before 10,000 tons (9,100 metric tons) were mined. Other machines have been rebuilt and are in service, and to date none have been known to cause an ignition.

Jan 1, 1987

By N. Colvin, J. W. Gulyas

HISTORY The Surigao Nickel Refinery of Marinduque Mining and Industrial Corporation is located on Nonoc Island off the northwestern coast of Mindanao in the Philippines. Nonoc Island is part of the Surigao Mineral Reservation which had been identified as early as 1912. Initial interest in these deposits was due to their iron content, and their value as a nickel deposit was not seriously entertained until the late 1950's. The Philippine government undertook extensive test pitting and sampling programmes at that time and in the early sixties Marinduque became involved in helping to establish firmer ore reserves. Evaluations of the test pitting programme indicated reserves of 75,000,000 tonnes of ore averaging 1.22% Ni, 0.1% Co and 38.5% Fe. The Philippine government called for bids on the reservation in 1962 and Marinduque and Sherritt Gordon carried out some feasibility studies for the recovery of nickel from the deposit. However, it was not until 1968 that Marinduque was granted proper authority to exploit the Surigao deposits. Marinduque and Sherritt then entered into an agreement which allowed Marinduque to utilize a process developed by Sherritt for treating lateritic ores. During 1968, a 25 st/d pilot plant was erected in Fort Saskatchewan, Alberta for the purpose of modelling all process steps. A 10,000 tonne ore sample was sent from Nonoc as feed stock for the pilot plant.

Jan 1, 1979

By John E. Urosek, Jack E. Tisdale

The Mine Safety and Health Administration (MSHA) has developed a Mine Ventilation Bleeder and Gob Training Course. This three day course is designed to increase the knowledge and understanding of bleeder ventilation systems. It discusses concepts, designs, plan approval, inspection and evaluation of bleeder systems. This paper will introduce some of the material contained in that course, focusing on the inspection, examination, and evaluation of bleeder systems. The regulations addressing the use of bleeder systems are found in Title 30 Code of Federal Regulations (30 CFR) Section 75.334. The examination requirements are found in 30 CFR Section 75.364. Section 75.364 de- scribes specific locations where examinations are to be made and specific information to be gathered at those locations. The required locations and information will be discussed in some detail with examples and illustrations. These weekly examinations for bleeder systems are designed to monitor the parameters of the bleeder system and to evaluate its effectiveness. Over time, conditions can develop in the bleeder system that affect the ventilation and lead to hazards such as methane accumulations. The hazards of methane accumulations need to be understood as such accumulations can contribute to mine explosions. The importance of additional information gathered by the mine examiner that can assist in evaluating the performance of the system will also be discussed.

Jan 1, 1997

By Mark S. Stagg, Michael J. Nutting, Douglas R. Barlet

Single-row bench blasts at a reduced scale in the field were used to study the effects of delay time on fragmentation. Nine shots with a spacing of 21 in. and a burden of 15 in. (S/B = 1.4) and nine shots with a spacing of 30 in. and a burden of 15 in. (S/B = 2.0) were completely screened to determine particle size distributions. Delay intervals between holes ranged from 0 to 45 msec, corresponding to effective delay intervals ranging from 0 to 36 msec per foot of burden. Each shot was instrumented with strain and pressure gages to measure in situ blast dynamics and to evaluate interactions between blastholes. Finer overall fragmentation was produced for shots with delay intervals between 1 and 17 msec per foot of burden. Only for shots within this optimum delay range was it observed that the strains induced by stress waves constructively interacted with strains induced by gas pres- sure from an earlier detonated hole. Coarsest fragmentation resulted at delay intervals less than 1 msec/ft, where stress waves from each hole were observed to interact destructively, and at delay intervals greater than 24 msec/ft, where no inter- action between holes was observed, indicating a condition that can be considered as the firing of single hole shots independently.

Jan 1, 1986

By L. Tondo, W. Lim

The high pressure grinding rolls (HPGR) is a relatively new technology which offers the potential benefits in energy savings, circuit simplicity and improved product characteristics in minerals processing applications. Over 300 machines are now operating world-wide, but most of these are used for grinding cement clinker, and relatively few are used in conventional mineral processing. One of the rea- sons for its current limited use in the minerals processing industry is that design, scale-up and flowsheet assessment procedures are seen to be relatively immature and untested. This has reduced confidence in the potential application of the technology. To help rectify this situation an industry funded research project was undertaken, one of whose aims was to develop and prove a mathematical model of the HPGR and a scale-up procedure. Data were collected from tests using laboratory, pilot and in one case a full scale unit (2.2m diameter). A range of feed types were tested including quartz, limestone, kimberlite, bauxite, iron ore and gold ore. These data were then used to develop models of the size reduction performance, power draw, throughput and operating gap for a wide range of pressures, feed sizes, and roll speeds. This paper describes the models that have been initially developed and illustrates their accuracy using some of these data.

Jan 1, 1998

By Richard Meriwether Smith

Mining-related earthy bodies in contact with the atmosphere are now counted, generally, as minesoils. Because soils within this broad category are extremely young the influence of parent material is stronger than in older soils, where climate, organisms, and topography have had time to interact with near-surface rocks to form more distinctly differentiated profiles. Understanding of minesoil properties and processes is aided by definitions of rock types in terms of chemical, physical, and mineralogical characteristics that are, with some degree of consistency, translatable into soils. Geological correlations based on age or sedimentary sequences are helpful if they assure details of mineralogy and lithology, but our pedologic objectives demand that any conflicts involving rock types must be resolved in favor of distinctions having strongest implications for soil properties after mining. Chemically this approach emphasizes accounting of potential acid-base status, plant nutrient availability by adapted and calibrated extraction procedures, and absence of biotoxins. Physically it anticipates particle sizes, shapes, and arrangements in readily pervious soil profiles that will favor plant growth with desired levels of moisture and oxygen. Concurrently we are considering soil property suitability for uses other than growth of plants. Above all we need to be able to predict pedogenic processes in the particular environment, including rate as well as direction of chemical and physical change.

Jan 1, 1974

By S. K. Kawatra, T. C. Eisele

Coal-cleaning operations commonly produce a fine-waste stream containing a considerable amount of coal. The recovery of this coal is normally not economical because the coal is mixed with large amounts of difficult-to remove clay slimes and is often heavily oxidized or contaminated. Conventional froth-flotation machines cannot, in a single flotation stage, produce an acceptable product from such material, and even flotation columns often have difficulty cleaning this type of feed. A new type of flotation column was designed specifically to deal with these problems, and a column of this design was installed and tested in a coal-cleaning plant in Ohio. The feed coal tested was the plant&apos;s tailings-thickener product. The coal was 80% -176 µm and had a heating value of 8401 Btu/ lb. The coal contained 39.8% ash, as fine clay, and 2.83% total sulfur. Because previous attempts at conventional flotation of this type of material had been abandoned, plant personnel believed that the coal was too heavily oxidized and contaminated for flotation to be effective. However, by using the new column it was possible to recover up to 85% of the calorific value in a product containing < 11 % ash, and it was possible to recover 60% of the calorific value in a product containing <8% ash. In addition, the bulk of the pyritic sulfur was also rejected from the coat.

Jan 1, 1996

By J. H. Bassarear, J. D. Vincent

General. Copper, the first metal used by man, today is the third in consumption after iron and aluminum. Compared to these it is relatively rare, with less than 0.01% of the earth&apos;s crust copper, 8% aluminum, and 5% iron. Nevertheless. our modern civilization is heavily dependent upon copper because of its high conductivity and resistance to corrosion, ease of working, durability, wide range of properties by virtue of its readiness to form alloys with other metals, and its attractive colors and texture that make it so desirable for many crafts and arts. These attributes explain why copper is chosen for a long list of uses, including electrical wiring, switchgear, and bus bars; piping, roofing, and siding; and manufactures of brass, bronze, and other alloys. The fact that copper ore is mined in nearly all parts of the world is significant. Its importance is shown in Table I, which gives figures on world production from 1968 to 1977. In the Free World, North and South America and Africa are preeminent. The table also shows the generally upward trend of production in this period; accurate figures for 1978 and 1979 from the same source are not yet available (1980), but it is certain that major environmental, economical, and political factors continued to disturb the industry in those years and into 1980.

Jan 1, 1985

By V. B. Achanti, A. W. Khair

This paper deals with the effects of various bit geometric parameters on the failure characteristics of rock material. Improving the rock-cutting efficiency of continuous mining machines has proven to be an interesting research topic during the last few decades. In the current study, an automated rotary rock-cutting simulator, duplicating a continuous miner, was used to study these parameters in the laboratory. The improvement of bit performance in terms of its life, cutting efficiency, dust production and energy consumption has drawn widespread attention. Research has demonstrated that optimizing bit parameters can result in efficient fragmentation of rock. Indiana limestone rock material was used in this study. The bit tip angle, bit tip size, bit spacing, depth of cut and cutting velocity of the rotary drum were varied to investigate the failure characteristics. The cutting pressure, penetrating pressure and the depth of cut were monitored on the simulator during the cutting process. Airborne dust and settled dust were measured for each experiment. Then, the specific airborne dust and specific energy were determined for each type of bit. Triaxial tests were carried out to correlate the failure angle of the rock in the static case to the dynamic cutting process failure. The physical and mechanical properties of the rock were also determined to assess their influence on the wear characteristics of each bit.

Jan 1, 2000

By A. English, Edward Martinez, L. A. Haas, N. W. Johnson, Harrison Copper, M. E. Tawil, C. C. Harris, G. V. Jergensen, D. Halbe, M. P. Amsden

Declining US ore grades along with skyrocketing energy, materials, labor, and regulatory costs underscored the urgency for technological innovation in the mineral processing area. Re¬liance on the scale-up and automation of unit operations was the sector&apos;s primary battle plan. Debate continues on the upper size limit of concentrating plants and whether process controls should be centralized or distributed in the mill. In the materials handling area, the economics of large-scale and mobile systems, particularly conveyors, were well documented in the literature. Comminution, the most costly and energy consuming area of the processing flowsheet, saw improvements in process controls and liner designs. The trend toward larger grinding units stalled somewhat during the year owing to some operational problems at commercial plants. Research and development of apparently less expensive physical separation processes-that also boast recovery of cleaner and more environmentally acceptable products -gained momentum during the year. Because of escalating capital cost requirements for new plant capacity, the year saw a greater interest by mill designers to re-examine existing capacity. The focus here is clearly to modify or retrofit unit operations with more efficient components as an alternative to installing more costly new equipment. The problems facing the processing sector during the 1970s can be expected to continue in the decade ahead. Technological gains from scale-up and process controls appear

Jan 5, 1980

By Harry M. Edenborn, Richard W. Hammack

Experiments were done to determine if a mushroom compost-based sulfate reduction system could be used to treat nickel-contaminated mine waters. Sulfate reduction systems were established in columns containing acid-washed mushroom compost. Simulated mine waters containing 2000 mg/L sulfate and 50 to 1000 mg/L nickel were adjusted to pH 4.5 and pumped through the columns at flow rates between 15 and 25 mL/hr. During the first nine days of operation, virtually all influent nickel was removed in the columns by sorption and ion exchange mechanisms. The nickel removal rate then dropped to 18 to 30 mg Ni/day (7.8 to 12.8 nmol/ g-substrate/day), probably due to low sulfate reduction rates. When sodium lactate was added to the inflow, a sustained and seven-fold increase in the nickel removal rate was observed. Bacterial sulfate reduction rates measured in mushroom compost-based wetlands exposed to coal mine drainage are 2 to 20 times faster than the rates observed in this study. Low sulfate reduction rates in the columns may have been due to the inhibition of microbial activity by high nickel concentrations and the removal of labile organic compounds from the mushroom compost substrate during acid-washing. Results of this study indicate that bacterial sulfate reduction can effectively treat nickel concentrations up to 500 mg/L if labile carbon is nonlimiting.

Jan 1, 1992

By W. Belobraidich

Kennecott&apos;s Ray mine is located about 145 km (90 miles) north of Tucson in the Mineral Creek mining district of central Arizona. Mining in the district started in the late 1800&apos;s. The Ray mine itself was first mined by under- ground methods in 1911 and was changed to an open-pit operation in 1952. Mineralization is complex and includes sulfide, silicate, and native copper mineralization, as well as minor amounts of molybdenite. Sulfide ore, mined at Ray, is shipped by rail to Kennecott&apos;s concentrator and smelter at Hayden, 32 km (20 miies) away. Silicate ore, mostly chrysocolla, is processed near the mine in a vat leaching-electro- winning plant. The mine consists of two sulfide areas: (1) the West pit and the Central pit (the original Pearl Handle pit) and (2) a silicate area on the northeast perimeter of the Central pit. The pit now is over 304 m (1000 ft) deep and approximately 3048 m (10,000 ft) long. Roads within the ultimate pit are limited to a grade of 10%, while those outside the pit are limited to 8%. The mining equipment consists of 40 Wabco 1094 (120-st) haulage trucks [ranging from 109 to 227 t (120 to 250 st)], 12 electric shovels [ranging from 6 to 23 m (7 to 25 yd)], and 3 11-m (12-yd) Dart production loaders.

Jan 1, 1979

By Jeffrey M. Listak, Gregory J. Chekan

The U.S. Bureau of Mines, in an effort to improve coal conservation and utilization is currently investigating longwall panel layouts to maximize coal recovery and minimize interactive problems in multiple-seam operations. When longwalling coalbeds in descending order, the transfer of stress from overlying gate roads is a major design constraint affecting pillar stability in the lower mine. The lower mine gate road pillars must be properly designed to withstand the additional load transfer if gate roads are superpositioned in successive seams. The Bureau&apos;s MULSIM/NL model was used to analyze load transfer mechanics for superpositioned gate road pillars. Analysis of Longwall Pillar Stability (ALPS), which is an empirically based design method for longwall gate road pillars, was used to calibrate model input parameters. The attributes of both the MULSIM/NL model and ALPS were combined to develop a modified method for estimating pillar stress for multiple-seam cases. The modified method uses a multiple-seam (MS) factor to estimate the stress on the lower mine gate road pillars when superpositioning is practiced. Numerical analysis shows that the MS factor is dependent upon the interburden thickness and pillar width and is presented in a series of graphs relating these two parameters. Several examples are included to illustrate the use of the MS factor for estimating lower mine pillar stress and resulting stability factors.

Jan 1, 1992

By J. Brent Hiskey

INTRODUCTION Metal electrodeposition processes are of fundamental technological importance to a number of fields. Electrorefining, electrowinning, electroplating, and electrogalvanizing have all been the subject of intense study for over a century. More recently, electrochem- ical deposition has played a critical role in advances in microelectronics and lately has been an enabling technology for the production of certain nanostructured materials. Electrometallurgists have most frequently been concerned with the structure and morphology of massive deposits. For example, in metal recovery steps such as electrorefining and electrowinning, deposits demonstrating adherent coarse-grained characteristics are most desirable. In the case of electroplating, a bright fine-grained, tenacious and strongly adherent deposit is required. The fabrication of microelectronic devices and the production of nanoscale structures such as nanoparticles, nanowires, and nanorods requires a keen understanding of early stage deposition effects. The initial stages of metal deposition, usually referred to as electroclystallization, are fundamentally linked to nucleation and growth phenomena. Early stage deposits are typically very ordered. Whereas, bulk metal deposition structures are much more ran- dom. In both cases, the discharge of a metal ion at an electrified interface is represented by simple cathodic reduction as follows: [ ] Me(H2O)xn[ ] is a hydrated metal ion residing in the bulk solution and Me is the metal atom occupying a crystallographic lattice position. A similar reduction reaction can be

Jan 1, 2005

By B. K. Parekh

The International Symposium on Comminution was organized at Camborne School of Mines, Cornwall England. Papers covered the fundamental and practical aspects of comminution in the mineral industry. Although comminution equipment design has not changed fundamentally during the last 50 years, methods of control and optimization have improved considerably. A simulation model for batch ball milling in the rotating mill was developed as a step toward continuous simulation of ball and autogenous milling. New concepts in jaw crusher technology design and the concept of a 1.6- x 2.1-m (66- x 84- in) jaw crusher with open feed throat has resulted in power savings. The use of cone crusher technology in comminution circuits with particular reference to machine design, plant flowsheet and control figuration has been reported by Boliden Allis, of Sweden. The Whiten steady state crusher model form has been used to develop a quantitative model of 2.1-m (7-ft) cone crushers. This was done by incorporating liner age (wear) and liner length as variables on the selection of particles for breakage and thus on the product size distribution. Another paper by Lira and Karetsky discussed the development of a model based on a multisegment ball mill developed by Whiten and Kavetsky. It is capable of simulating the performance of a coarse grinding ball mill of a given diameter, ball size and mill speed.

Jan 1, 1991

By L. Alan Weakly

The purpose of this paper is to present a viable method of reinforcing rock pillars by utilizing fully grouted reinforcing steel and a cement - fly ash mortar. Although the fully bonded bolt concept is not new, as exemplified by the present widespread use of resin bolts within United States mines and by the use of cement grouted reinforcing used as back pins in the Kiruna Iron Ore Mine in northern Sweden, (1) (2) the method of stabilizing mine pillars with fully bonded reinforcing is new. This method, called the "grout-rebar system", was first incorporated at St. Joe Minerals Corporation’s Fletcher Mine in December of 1972. The system was used on an emergency basis before extensive research on the mechanics of the system could be completed. Since December of 1972, however, approximately 206 pillars have been reinforced at Fletcher and the system is currently being used on a regular basis at two other St. Joe mines and at two competitor mines in the area. Basically, this paper is a case study of the efforts, research and results of utilizing the grout-rebar system, on a selective basis, at the Fletcher Mine. In addition to information about the system, this paper will explain in detail the three rock mechanics instruments developed by St. Joe and used to measure and monitor rock movement to validate the grout- rebar system.

Jan 1, 1977

By J. A. Ryder

Compressed air is a relatively inefficient yet very convenient vehicle for transmitting mechanical energy. It is inefficient when compared to, say, hydraulic or electric energy systems since compressor and pneumatic machine efficiencies are quite low (in the range 20-65%) and reticulation losses can be quite high unless adequate pipe diameters are used to minimize friction drops. It is convenient in that capital and maintenance costs of pipes and machines are exceptionally low, the equipment is flexible and lightweight, the technological level is simple, the form of the energy supply is intrinsic- ally safe, and as an additional minor but psychologically important benefit, it provides a ready source of cooling and air supply for emergency use in deep hot mines. It is for these reasons that compressed air is a premier source of energy for many forms of underground equipment, in particular hand or rig-mounted rockdrills, some forms of rock- handling equipment, and a host of minor applications including agitators, small-lift pumps and temporary f am installations. In a typical S. African deep-level gold or platinum mine, compressed air generation accounts for 15% of the total mine electrical energy bill - more than is used for hoisting. In these mines it is not uncommon for over 100 km of underground compressed air piping to be installed, primarily to supply handheld rockdrills.

Jan 1, 1979