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Ten years ago, only 3% of Consol's underground coal production resulted from using the longwall mining method. Today, that figure has grown to 45% and has helped the Pittsburgh-based concern fuel an upswing in productivity. The company reported that productivity at its underground mines, excluding labor strike periods, increased 24% between 1978 and 1981. Last year, an additional 8% increase was achieved. Efforts such as improved safety, training, engineering, and maintenance programs as well as the closing of unproductive mines has contributed to these gains, according to Joseph M. Richards, Consol's executive vice president of operations. But, Richards adds, a great part of the credit goes to longwall mining. What is Longwall Mining? To fully appreciate the advantages of longwall, one needs an understanding of how mining is done by other methods. For instance, in both conventional and continuous mining, rooms or tunnels are dug in the coal seam. Pillars of coal are left standing to support the roof as mining moves forward in the seam. In conventional mining, a slot is cut in the base of the seam and holes for blasting are drilled. After blasting, the coal is loaded. A more efficient method - continuous mining - uses a machine that combines cutting and loading. Longwall mining, by contrast, works backwards from the end of a panel. Two parallel sets of tunnels (development panels) are cut into a seam with continuous mining machines, then connected with a set of crosscuts at the far end. Min¬ing then proceeds back toward the entrance. Longwall mining employs some very productive machines. Large drum shearers, for example, run on a track along the length of the coal face for some 150-180 m (500-600 ft). The shearers cut the coal which falls onto a conveyor system or pan that also runs the entire length of the face. The longwall crew works under a roof of heavy steel supports called shields. As the coal is removed, shearers, pans, and shields are moved forward by hydraulic rams. The roof is allowed to collapse behind the shields. In addition to increasing production, longwall mining is considered to be safer because the miners work under strong steel shields. New designs have made them more rugged and maintenance free, as well as more stable on soft mine floors. Early roof supports, called chocks, had gaps in the roof canopies. The new roof shields now cover the entire working area and are better able to prevent roof material from falling into the working area, thereby improving safety and productivity. Longwall mining also results in a cleaner product in many mines. If the first layer of rock over the coal seam is thin, it might have to be removed with the coal in a room-and-pillar operation so a

Jan 11, 1983

By James J. Kabat, James A. McDonald

Impregilo/SA Healy JV recently completed this Project using the first slurry shield TBM’s in the United States. The Project used two TBM’s to mine 18,000 feet in sands, gravels, and silty alluvial materials under the Willamette River and downtown Portland, Oregon. This paper discusses alignment and geological conditions, equipment selection and plant setup, and tunnel excavation means and methods, parameters, and results. Extensive hyperbaric operations were required and will also be discussed.

Jan 1, 2007

By P. D?Elia

Following a study by NIOSH on the availability of teams in the U.S. as well as existing training sites and their capabilities, the Penn State University, leaders of the Pittsburgh Section of SME, providers of mine rescue equipment, and industry sponsors united to establish and make fully functional a student mine rescue team at Penn State University. With the growth of MERD and mine rescue competitive events at Missouri S&T, the Mine Training and Technology Center in PA, and at Colorado School of Mines Edgar Mine, a critical mass of effective training venues were made available to help student teams progress and develop mine rescue skills. The challenges to be met in creating and developing a student mine rescue team will be discussed. The rewards from this type of effort will be the quick capability of graduates from mining engineering programs to be involved in not only mining operations, but industry mine rescue teams and other leadership roles as well.

Jan 1, 2012

By S. C. Chelgani

The Thor lake deposit is a world class resource of rare earth (REE) metals and minerals in Canada. Development work to optimize a REE mineral recovery process flow sheet is underway, however, given the ore mineralogy; the developed reagent scheme is relatively complex. As part of a research project, micro flotation tests were conducted on a feed sample in order to examine factors affecting stream partitioning. SEM-EDX was performed to evaluate variability in grain composition between streams (concentrate and tails) and TOF-SIMS surface analysis was used to determine statistically significant differences in surface species particularly related to potential activation (or depression) of the examined mineral phases. SEM-EDX analysis reveal that the concentrate has a significantly higher proportion of REE bearing grains (carbonates and phosphates) relative to the tail (almost none were identified). Spectral fingerprinting by TOF-SIMS has allowed for the identification of all reagent species investigated. Reagent signal intensity discrimination on test stream mineral surfaces was observed by the TOF-SIMS analysis using reagents at plant concentration levels. TOF-SIMS analysis confirmed that REE bearing grains reporting to the concentrate are doing so in response to collector attachment whereas grains reporting to the tail are doing so in response to a lack of collector and/or in combination with the presence of the depressant. The surface analysis of gangue phases reveal a similar reagent discrimination; the signal intensity of collector species was significantly higher on the concentrate samples relative to the tails while depressant species were significantly enriched on the surface of the gangue phases in the tail samples. A detailed evaluation of the surface species representing the various reagents used in flotation scheme revealed a distinct competitive relationship between two of the reagents. The surface analysis identified that when used in concurrently, there appears to be a negative feedback resulting in a significant reduction in loading for several of the collectors on grains reporting to the concentrate. An evaluation of the effect of reagents on REE mineral in pilot plant is currently under way. Key words: Rare earth minerals, Flotation, Surface chemistry, TOF-SIMS, SEM-EDX

Feb 27, 2013

By R. E. Mclvor

This is an update of an original dissertation on this topic by Lavallee, McIvor and Stolovitch (1992). A step-by-step, technical procedure used to measure and improve the performance of plant grinding circuits was adapted into a training program. ?Systematic Design of Instruction? was applied to: ? Determine if training was a suitable way to deliver this new technology; ? Define the technical content of the program; ? Select program specifications based on learner and context characteristics; ? Design, create and test prototypes of the training modules; and, ? Establish a process for plant implementation. The training program covers numerous skills that are extremely valuable for plant personnel, not only in the grinding area, but also for many other parts of the plant. This paper describes how new skills are brought into the workplace through designed instruction can be an effective alternative to hiring during severe skilled labor shortages.

Jan 1, 2008

By David S. Yang, Osamu Taki

The innovative Soil-Cement Mixing Wall Technique, developed independently in Japan, consists of mixing in-place soils with cement grout using multi-axis augers and mixing paddles to construct overlapping soil-cement columns. The applications of overlapped soil-cement columns include cutoff walls for groundwater control and structural diaphragm walls for excavation support. The special features of this technique include water tightness, versatile strength design, and efficient installation in subsurface materials varying from clayey soils to cobbles or soft rocks. Through the introduction of two recent subway projects in Japan, this paper presents the design parameters, construction procedure, quality control and performance of soil-cement wall for excavation support and groundwater control.

Jan 1, 1989

By Charles A. Bankston, John C. Rowley, Robert J. Hanold, Joseph W. Neudecker

The basic concepts and processes of soil and rock melting as applied to excavation technology are reviewed. The electrically heated, small diameter prototype penetrator development sequence is presented. Emphasis is placed on the different methods of handling the fluid rock and soil melts and their significance in providing new solutions in hole support and debris handling problems. The refractory materials requirements, penetrator life and electrical heater technology are presented. Consolidating penetrators, which form stable glass-lined holes in low density rocks and soils, require no debris removal and will find applications in horizontal holes for utilities, cables, and pipeline installations. Extruding penetrators are being developed to make holes in dense, hard rocks. Melt is conditioned into a variety of debris forms, i.e., glass rods, pellets or rock wool, selected to match appropriate debris handling systems. Unique use in drilling into very hot rock or magma for geothermal exploration or production wells is projected. Some of the results of laboratory and field tests of these devices are compared with theoretically derived operating performance. Coring-consolidating penetrators for geological sampling in alluvium are projected to larger diameter self-propelled and guided coring devices for prospecting along proposed tunnel alignments. Application to the melting of annular shafts for pipeline support piles in difficult conditions such as permafrost has been scoped. Conceptual design studies of large diameter tunneling equipment have indicated the system contributions and economic aspects of rock melting relative to material comminution, wall and roof support and materials handling.

Jan 1, 1974

By A. Martikainen

Field tests concerning a fog mesh method for fog removal are discussed. The first tests were performed at the Pyhäsalmi Mine, Finland. As this study gave promising results, further studies were completed at the Orivesi Mine. The results of these most recent field tests are presented and the two studies are compared. The Orivesi test set consisted of four materials. These included air filter fabric, fibrous filter fabric, a plastic greenhouse mesh, and an aluminium mosquito net. The variation of the Orivesi results was more noticeable than what was found previously. The best fog removal effect of all tests was achieved with the aluminium mosquito net, while the plastic green-house mesh performed worst. The humidity reduction by aluminium net was more profound than any of its precedents. More mesh materials will be tested in the near future.

Jan 1, 2007

By Richard H. De Voto

The McDonald gold project and two satellite gold deposits near Lincoln, MT were discovered in the early 1990s. They contain at least 307.9 t (9.9 million oz) of gold and 933 t (30 million oz)of silver. The McDonald gold deposit alone contains 223.9 t (7.2 million oz) of gold reserves that can be open-pit mined and processed by cyanide heap leaching at a projected cash operating cost of $6.10/g ($190/oz). The deposit is predominantly oxidized with no chance of acid production. It can be mined, operated and reclaimed with minimal permanent environmental disturbance other than the creation of an open-pit filled with a fresh-water lake that would support trout.

Jan 1, 2000

By John Kinneen, Sunghoon Choi, Arne Fareth, Edward S. Barboe, Kyle R. Ott

A new water treatment plant is to be constructed for a portion of the water supply system of New York City. The project includes construction of new water conveyance tunnels crossing perpendicular and sub-parallel to the existing pressurized water tunnel at two locations. A study was conducted to evaluate the impact of new tunnel construction on stability of the existing tunnel and hydrojacking potential in the surrounding rock mass. This paper introduces a practical approach to evaluate tunnel interaction, expressed in terms of rock-liner interaction, stress-induced stability and hydrojacking failures. A simple method to evaluate hydraulic and mechanical properties of concrete liners and jointed rock mass is also presented.

Jan 1, 2007

By Lennart Mukka

The Kiruna Mine in Sweden currently has three ventilation systems. The first two (a new and old system) serve the production areas. The third system is used for the facilities on the former main haulage level 775. That area includes offices and workshops for load haul dumpers (LHD) and drill rigs. The third ventilation system also covers the crushing and haulage on level 1045. At the present time, the total airflow for the mine is 1,600 m3/sec(3.4 million cfm). The current system serves the levels above the 775 level. The new one is for the levels between 775 and 1,085 m (2,540 and 3,560 ft), which are needed for the new ore body. When all of the production is below level 775, the old ventilation system will be closed down.

Jan 1, 2002

By J. D. Morgan

Introduction In 1986, the US economy passed the $4 trillion mark. However, the value of domestically processed materials of mineral origin fell slightly to $240 billion. The value of metals produced from US ores was unchanged at $5.6 billion, as was recycled scrap at $4 billion, while the value of industrial minerals rose slightly to $17.9 billion. Consumer demand strongly affects mining and the US economy is relatively saturated with longlived products. Moreover, in recent years there has been a steady increase in consumer, mortgage, and federal debt, inhibiting new purchases of goods. Motor vehicles and housing are major traditional markets for mineral materials. However, the 242 million US citizens already possess 170 million licensed motor vehicles and 92 million dwelling units. In 1986, domestic motor vehicle production fell 3%, to 11.3 million units, while new housing starts rose slightly to 1.8 million units. Nearly all mineral commodities move relatively freely in world trade. As detailed in Figs. 1 and 2, in the last three decades world production of major mineral materials has greatly increased. At present, substantial excess productive capacity exists not only in the US but also in many other countries. Consequently, the US mineral industry is encountering increasing competition from other sources, along with increasing competition from newer, engineered materials. For example, US production of plas¬tics has risen from 900 kt (1 million st) in 1950 to 22.7 Mt (25 million st) in 1986 - on a volume basis significantly greater than steel. Plastics, too, are mineral-based materials, some 7% of petrochemicals going to their manufacture. 1986 saw increased calls for protection. But President Reagan, in his 1987 State of the Union Message and Economic Report to the Congress, reaffirmed adherence to a policy of free and fair trade. However, he stressed the need for increased efforts to open foreign markets to US exports and to increase competitiveness of US industry US imports of mineral-based minerals in 1986 were valued at $40 billion and exports at $24 billion. Strategic minerals As detailed in Fig. 3, imports supplied a significant proportion of total US consumption of several important materials, including many classified as "strategic and critical." There were no changes in stockpile policy during the year. Congress debated the President's 1985 proposals to reduce stocks of World War II-type materials and to focus more on high technology materials needed for the cutting edge of future military material. But no final action resulted. However, Congressional concern about apartheid in South Africa did result in increasing pressure to limit imports of South African minerals. Meanwhile, the National Critical Materials Council in the Executive Office of the President intensified its efforts to be better able to advise the President. The Defense Production Act provides authority for priorities and allocations, supply expansions, voluntary agreements, and

Jan 5, 1987

By Paul Richardson

This paper will review several projects completed during the period from 1976 through 1984 which have been carried out utilizing big hole drilling concepts. The projects discussed will be from various industries to demonstrate the extent that big hole drilling methods are being used along with the current state of development. There will be a discussion of projects planned for the future where big hole drilling methods are the only technology being considered. Also included in the discussions will be an overview of the most recently completed heavy oil recovery project. During the next decade, big hole drilling methods will be used more and more in all industries where underground access is required. The safety, speed and economics associated with shaft sinking using drilling methods are becoming more and more recognized and the technology is rapidly becoming an accepted shaft sinking method.

Jan 1, 1985

By Faruk Oksuz, Phillip L. Covell, Martin Doll

A series of difficult ground conditions causing high groundwater inflows and hazardous gas intrusion abruptly halted the construction of a 6.4-meter (21-foot) finished diameter and 1,890 meters (6,200 feet) long tunnel planned to serve as a 4-millioncubic meters (1-billion gallon) per day capacity river outfall for treated wastewater. Some 808-meters (2,650-feet) section of the constructed tunnel, TBM, and all other tunneling equipment were completely flooded with hydrogen sulfide laden artesian groundwater. The subsequent pumping and tunnel recovery efforts were unsuccessful and the tunnel was abandoned. In the end, the construction contract was terminated and options to redesign and reconstruct the project were re-evaluated to maximize the use of already constructed tunnel facilities such as the construction access and inter-mediate shafts and six outfall diffuser shafts in the river.

Jan 1, 2007

By J. Gustavson, E. Mallard, F. Pirkle

The Sales Comparison Approach to estimating the value of a mineral property must always be attempted1 . In addition to other parameters, the approach depends heavily on the availability of transaction data. The consideration for the mineral property must be in form of cash, cash equivalent or other consideration. In other words, “What dollar amount did the property sell for?” Mineral properties are generally real estate, albeit frequently buried deeply under the overlying surface real estate, unless the property may be a quarry. In some states, transactions must be recorded in county courthouses, and the sale consideration must be included. In such cases, the appraiser’s job is made easy. In other locations, the sale considerations are withheld in the courthouse data; but occasionally a local transfer tax is collected and recorded. Again, the appraiser’s job is made easy by back calculation with knowledge of the legislated transfer tax percentage. The worst problem occurs when the consideration for a mineral real estate sale is totally withheld. That may occur in so-called nondisclosure states. A recent map2 of ten non-disclosure states in red is shown below. For the full color code, please refer to the footnote

Mar 2, 2022

By S. J. Schatzel, J. D. Addis, V. Gangrade, L. L. Chasko, C. A. Hollerich

A ventilation study using tracer gas was conducted at a western US coal mine. The objective of the study was to evaluate the movement of longwall face air exchanges between the face and worked-out area and to document the presence or absence of face airflow pathways between these locations. The mine operator uses a bleederless longwall ventilation system with a back return and a blowing mine ventilation system. The study was conducted on an active panel and included both underground and surface monitoring sites. The study used sulfur hexafluoride (SF6) released as a slug on the longwall face and in the front of the gob inby the face. The velocity of the tracer gas movement in the gob was 0.019 m/s (3.7 fpm). The rate of movement for the overall tracer gas slug averaged about 0.0091 m/s (1.8 fpm). A separate tracer gas test initiated with the release of SF6 into the legs of the first shield showed the existence of more than one pathway of face air in the general direction from the headgate towards the tailgate corner. Maintaining adequate ventilation air on longwall faces is important for worker safety and for the dilution of methane emitted from the face and caved gob. A more detailed characterization of longwall system air and gas movement allows a mine to better assess its ventilation design for controlling gas on the face and in the gob.

By Akihiro Higashide, Roy H. Patten

The DOT Tunneling method combines two conventional earth pressure balance shield machines in an overlapping cylindrical arrangement. The method allows two tunnels to be driven simultaneously with mini¬mum cross sectional area. Two full size trials, one configured horizontally and one vertically stacked, were successfully completed employing the DOT method. The method was then utilized for the new transportation system. The goggle-shaped DOT machine, 9.36 m high by 15.86 m wide, is the largest earth pressure balance shield machine in the world. This paper includes a general description of the DOT tunneling method as well as a history of its development.

Jan 1, 1995

By James M. Barker

No commodity agreements now exist for sulfur and a lack of reference to sulfur commodity agreements exists in the literature. Law (1975) made a passing reference to sulfur as one of a group of commodities where "there have been additional control efforts of various types." Clearly, sulfur was a candidate, at least conceptually in the past, for some form of commodity agreement and the following discussion centers on the world sulfur market of the early 1980's in this context. GENERAL THEORY OF COMMODITY AGREEMENTS The upsurge in demands for commodity agreements seen in the last decade or so stems largely from agitation by the less developed countries (LDC) for better economic treatment by more developed countries (MDC). Several economic factors, real or imagined, adversely affect the LDC's as follows (MacAvoy, 1977): 1) variable demand in MDC's causes wide fluctuations in commodity prices which hurt the economies of commodity producers, who are often LDC's although consumer economies may also benefit from more predictable prices; 2) a general decline of commodity prices relative to the price of manufactured goods which hurts commodity producers in their balance of trade while their stocks and overcapacity rise; 3) instability of LDC economies enhanced by the above factors lowers internal stability, inhibits foreign investment, and retards economic growth; and 4) a lack of self respect when dealing with developed countries o, following the OPEC lead, LDC producers want the stature related to cartel market power.

Jan 1, 1985

By D. J. Pyra, J. Kudelko, Korzekwam W.

Polkowice region (Lower Silesia, Poland) is an area, where the copper mining activity started about 40 years ago and new technologies were applied. There are 3 underground mines, 3 processing plants, tailings pond (the biggest one in Europe), pipelines for flotation waste transport, railways. Although new technologies were applied during the copper ore exploitation, the environment in this area were polluted mostly by dust containing copper, lead, zinc and arsenic. Estimated values of heavy metals in polluted soils were compared to the natural contents of this metals. The geochemical background for Polkowice area was defined. The pollution zones occur around mining facilities. Copper ore exploitation and processing is planned for the next 20-40 years depending on market situation. After mines and other facilities closing the most important problem will be sustainable development of this area. To evaluate the scope of revitalization activities the analysis of recent soil environment condition will be necessary as well as forecasts for pollution migration. Geostatistic methods used also in mining will be very helpful for this task.

Jan 1, 2005

By William H. Langer

The annual consumption of sand and gravel aggregate in 2006 in the Phoenix, AZ metropolitan area was about 76 Mt (84 million st) (USGS, 2009), or about 18 t (20 st) per capita. Quaternary alluvial deposits in the modern stream channel of the Agua Fria River west of Phoenix are mined and processed to provide some of this aggregate to the greater Phoenix area. The Agua Fria drainage basin (Fig. 1) is characterized by rugged mountains with high elevations and steep stream gradients in the north, and by broad alluvial filled basins separated by elongated fault-block mountain ranges in the south. The Agua Fria River, the basin?s main drainage, flows south from Prescott, AZ and west of Phoenix to the Gila River. The Waddel Dam impounds Lake Pleasant and greatly limits the flow of the Agua Fria River south of the lake. The southern portion of the watershed, south of Lake Pleasant, opens out into a broad valley where the river flows through urban and agricultural lands to its confluence with the Gila River, a tributary of the Colorado River.

Jan 2, 2010