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By Duk-Won Park

Since geologic anomalies are one of the governing factors of instability of underground openings, it is extremely important to know in advance the locations and extent of these anomalies such as faults and weak zones. At an underground coal mine in the Black Warrior Basin, core drilling was conducted to find a fault in an area where they were planning to locate longwall panels and possibly a shaft. Core logging did not provide sufficient information to delineate the exact location, strike, and dip of the fault. However, a high resolution reflection seismic study successfully solved this problem. This experience proved the seismic exploration technique could be used for premining coal exploration by reducing drilling costs and providing more accurate and detailed information about geologic anomalies.

Jan 1, 1988

By J. P. Rider

Along with increased production from longwall units has come the likelihood of increased worker noise exposures. In recent years, equipment has become larger, more powerful, and noisier than its predecessors. For these reasons, the Mining Division of the National Institute for Occupational Safety and Health (NIOSH) is investigating worker noise exposure on longwall faces and researching possible solutions to reduce this exposure. Part of this research effort involves studying the effect of covering the underside of longwall shields with acoustical material to reduce reverberating noise along the face. Experiments using acoustical absorptive insulation to cover the undersides of the shields, shearer body, and the shield supports were conducted at the full scale simulated longwall test facility located at the Pittsburgh Research Center. Sound levels were recorded every l.5 m [5 ft] along a 15.2 m [50 ft] section of the simulated face for all of the conditions tested. The analysis of the data indicated that a 2.0-3.0 dBA noise reduction was achieved between the shearer drums and a 4.0-5.5 dBA attenuation was attained upwind of the headgate drum.

Jan 1, 1997

By Andrew Cushing, Joe Carvalho, Jon Hurt

"INTRODUCTIONThe shales of the Greater Toronto Area (GTA) have been known to experience time-dependent deformations (TDD); those initiated by excavation-induced stress relief which progress with time as a function of rock porewater salinity, access to freshwater (or air) of lower salinity, clay and calcite content, and the buildup of swelling pressures within the rock mass. These deformations can induce long-term pressures on shaft walls and tunnel linings, especially if the permanent works are constructed soon after excavation, with very little time delay. This paper presents measurements of time dependent deformation of recent shaft and tunnel projects constructed in the GTA, and draws conclusions regarding the main influences on the TDD. The key input parameters for the numerical predictive model are critically assessed. Projects which are discussed include the Billy Bishop Airport Pedestrian Tunnel, Hydro One Midtown Tunnel and Hanlan Feedermain (Contract 3).MECHANISM OF TIME DEPENDENT DEFORMATIONExplanation of MechanismThe Georgian Bay Shale unit consists of typically moderately weathered to fresh, grey to dark grey, fine to very fine grained fissile shale interbedded with slightly weathered to fresh grey, fine grained calcareous siltstone and limestone interbeds. There are two distinctive features of the shale in the Greater Toronto Area (GTA). One is a high horizontal stress regime, and the second is long-term time dependent swelling behavior which develops when the following factors occur (Lo and Micic, 2010):• Stress relief of the rock mass• Outward salt concentration gradient from pore fluid of the rock to the ambient fluid• Availability of fresh waterThe swelling is a consequence of the reduction in confined stress in the rock which occurs upon excavation in combination with a differential gradient in salinity between the saline rock porewater and freshwater or even humid air. Osmotic and diffusive processes result in a decrease in the salinity of the rock porewater achieved by an overall increase in the water content, resulting in volumetric expansion of the shale rock over time. The development of this time dependent deformation (TDD) relative to the time"

Jan 1, 2016

By R. K. Rajamani, R. Verma

In ball milling the rates of breakage vary primarily with the size distribution of powder in the mill. Using an approximate solution to the batch-grinding equation, the acceleration and deceleration of breakage rates of all individual size classes are determined when the grinding environment is varied. Experimental results with limestone and copper ore show time-dependent breakage rates under both dry and wet grinding conditions. The effect of grinding additives on breakage rates is also studied. In general, breakage rates increase for coarse sizes and decrease for fine sizes with an increase in the fines present in the mill. Such variations have strong implications in closed-circuit grinding.

Jan 1, 1992

By A. Moergeli

The Swiss are currently building the world’s longest tunnel, the 35-mile long Gotthard Base Tunnel. At Sedrun, for the first time in tunneling, four Roadway Support Machines will drive through most difficult ground, supporting variable diameters of up to 13 m. The machines are prepared for their first deployment. At Amsteg, two Hard Rock TBMs have successfully crossed a known fault zone by applying full circle steel arches and shotcrete immediately behind the cutter head. Comparisons between Drill& Blast and Hard Rock TBM are shown.

Jan 1, 2005

By Ch. Apostolaki

Eighty samples from Roman wall paintings from ancient Corinth were studied by means of optical and scanning electron microscopy coupled to an energy dispersive analyzer, X-ray diffraction and image analysis techniques. The goals of the study were the identification of the exact nature of the pigments and the technical features of paint application (binding medium, adherence to plaster, thickness of the pigment layer), which would provide evidence about the painting technique (fresco or secco). The main plaster is calcitic with secondary calcite as a cement binder to the primary calcite grains. All pigments, except Egyptian Blue, were naturally occurring ochres or pigment minerals, such as limonite, goethite, hematite for yellow, brown and red hues, cinnabar for red hues and celadonite for green color. The presence of specific elements such as Ni and Cr or minerals such as olivine, in the yellow, brown and red pigments, gave an indication about the provenance of the original pigments, which seems to be from Cyprus. The black color was represented using charcoal. It seems, finally, that for the pigment application the fresco technique was used, while secco is also apparent.

Jan 1, 2006

By Asa Weber

With continuing pressure from stockholders not only to maintain but to increase mineral revenues, producers have increased plant capacity. Depressed mineral prices have accentuated the trend toward higher production rates to maintain consistent cash flow, and these same trends have promoted the development of large-scale processing equipment. In addition to the need to handle increased throughput, larger flotation equipment can result in decreased capital-equipment and operating costs. The development of larger column and conventional flotation equipment relies, in part, on suitable scale-up procedures. To properly scale-up large flotation cells and columns, certain constraints and design parameters must be taken into consideration, including velocities in the vessel, residence time, solids suspension, and lip loading. This paper will review the design constraints and scale-up criteria for WEMCO® flotation cells. Scale-up criteria are augmented with computational-fluid- dynamics analyses and high-speed imaging techniques, as well as multiple regresesion analysis of in-plant operational data.

Jan 1, 1999

By K. -A. Björkstedt

INTRODUCTION Strassa lies in the central part of Bergslagen, a tradi¬tional mining district, on the eastern side of the Stora Valley at an elevation of about 200 m above sea level. A railway siding runs between the mine and the Stora railway station from which there are railway connections to the shipping port and iron and steel works in Oxelosund, about 224 km away. The distance to the provin¬cial capital Orebro is about 60 km. The climate is typi¬cal for this part of central Sweden and is illustrated by the diagram of monthly precipitation and temperatures for the years 1968-1975 (Fig. 1). HISTORY There is no certain information as to when the Strassa mine was first worked, but it is known from sur¬viving accounts of mine inspectors that there were smelt¬ing works in operation in nearby villages in the 12th century. An example is the Gusselhytta ore smelting works, 10 km south of Strassa, which dates from this period. Around the year 1540 there were two smelting works in Strassa, the Upper Karberg and Lower Karberg works. Ore for these smelters was probably taken from Strassa and from the adjacent Blanka mine. In the year 1624 Strassa is mentioned by the painter Jons Nils Krook in an account of the iron mines in the Linde mining district (Linde Bergslags Jarngruvor). Several mines were listed in the area, the deepest being about 30 m. An impressive power installation is mentioned in 1639, including a piston system of lashed poles for transmit¬ting power from the Stora River to the Strassa fields. Its length was 2670 m. Common ground comprising about 20.2 km2 (5000 acres) of forest was allocated in 1689 for the furtherance of mining operations. Until the beginning of this century only the rich cen¬tral parts of the ore body were mined and these yielded, after handpicking, lump ore suitable for smelter feed. An example of the ore grades from these early times is an analysis of ore from the "Big Mine" (Storgruvan) from the year 1873: 48.5% Fe, 0.008% P, and 0.06% S. This same year a total of about 18 000 t was ex¬tracted from the Strassa mine. OWNERSHIP The mine was owned and run until 1874 by a min¬ing association made up of 119 so-called "bergsman," who were homesteaders often engaged in agriculture and timber-cutting as well. In that year the Strossa Grufvebolag (Mining Co.) was founded. In 1906 it was con¬verted into a joint stock company, the Strossa Gruveaktiebolag. This was acquired in 1907 by Metallurgiska AB for the implementation of Gustav Grondal's beneficiating and briquetting methods, for which the Strassa ore was well suited. The same year saw the completion of a new ore dressing plant with an annual production of 46 000 t of ore concentrate. In 1911 the mine passed to new hands, and in 1913 it was purchased by an Austrian company. Extensive new installations were made and in 1915 a new dressing and briquetting plant was completed with twice the capacity of the old one. In 1917 the Strassa mine was acquired by Granges. Be¬cause of unfavorable business trends and technical diffi¬culties, mining operations were brought to a close in 1923. Pumping kept the mine free of water until 1933 but it was completely filled ten years later. Up to 1950 the surface buildings and installations remained intact but the large dressing and briquetting plant burned to the ground in that year. Today only the machine shop re¬mains from this earlier period of operation, now housing parts of the Mineral Processing Laboratory. The decision to take up mining operations again was made in 1955 and construction work began the follow¬ing year. Of the old installation, only the "southern shaft" could be used for some development drifting after it had been completed with a new headframe. Other¬wise, all the buildings and installations required for the operations had to be rebuilt. New installations ready by 1960 were office and personnel facilities, a new shaft and headframe, a sorting and concentrating plant, a macadam plant, settling basins, pump stations, and a railway and yard with transport equipment. The instal¬lation was completed with two plants

Jan 1, 1982

By J. A. Organiscak

Water spray applications are one of the principal means of controlling airborne respirable dust in coal mines. Since many coals are hydrophobic and not easily wetted by water, wetting agents can be added to the spray water in an effort to improve coal wetting and assist with dust capture. In order to study wetting agent effects on coal dust capture, laboratory experiments were conducted with three wetting agents used by the coal industry on -325 mesh sized Pocahontas No. 3 coal dust. Significant differences in coal dust sinktimes were observed among the three wetting agents at water mixture concentrations of 0.05%, 0.1%, and 0.2%. The best wetting agent as identified by the coal dust sink test was only tested at the lowest 0.05% water mixture concentration and was found to have a negligible effect on spray airborne dust capture. Water spray airborne dust capture results for all three wetting agents tested at a 0.2% water mixture concentration showed that all three wetting agents exhibit similar but small improvements in dust capture efficiency as compared with water. These results indicate that the coal dust sink test may not be a good predictor for the capture of airborne dust. Additional research is needed to examine if the coal dust sink test is a better predictor of wetting agent dust suppression effects during cutting, loading, conveying, and dumping of coal products by comparison to airborne dust capture from sprays.

Feb 27, 2013

By A. D. Davis

Limestone-based technology for arsenic removal from water is an innovative and promising method. The technology offers the potential for low-cost disposal of a stable waste product after arsenic removal, either in an ordinary landfill or by encapsulation in concrete. Leaching research described in this paper shows that the limestone waste, after encapsulation in concrete, passes the Toxicity Characteristic Leaching Procedure (TCLP) test. Leaching was less than 0.05 mg/L, which is 1/100 of the U.S. EPA?s standard for disposal of arsenic in a landfill. Disposal of arsenic-enriched waste is critical for commercial viability of arsenic-removal technologies. Low-cost disposal gives the limestone-based method an advantage that could help communities meet the new maximum contaminant level of 10 parts per billion for arsenic in drinking water. The ability to recycle the waste material in concrete could add a significant economic benefit, further reducing overall costs.

Jan 1, 2009

By P. Schmieder

"The close vicinity of mining companies to other sites that are used for commercial and residential purposes or to areas under conservation as well as the fact that the people become more and more sensitive to emissions have led to a negative attitude towards mining operations in the neighborhood. It is above all the use of drilling and blasting techniques that give rise to objections, in the course of which demands for more environmentally-friendly production methods have been voiced. It is in this context that production methods without the use of explosives are considered as an option. After all, the use of such production methods is the only alternative for some quarry operators. The question is what are the true benefits of these techniques and what is the relation between a possible improvement of the environmental effects on the one hand and the technological potential as well as the costs on the other. It is intended to assess the mining techniques for solid rock in their entirety. This paper will therefore look at the aspects for assessing mining techniques in the context of their environmental impact and the costs."

Jan 1, 2005

By M. B. Mooiman

It has recently been discovered that the pH at which gold can be extracted from cyanide solution with primary, secondary, and tertiary amines can be increased 2 to 5 pH units by the addition of modifiers. Under these circumstances gold can be extracted at pH values from 9 to 11, commensurate with the pH range found in cyanide leach liquors. The selectivity of the amines and amine/modifier combinations for AU (CN)[-2] over other metal -cyanide complexes is presented and discussed. In addition, potential applications for the solvent extraction of gold from cyanide solutions are discussed.

Jan 1, 1983

By Giin-Fa Fuh, Sally A. Shoop

An instrumentation program was developed based on the results of an analytical study of the geomechanical effects of longer longwall face lengths. Boundary element simulations showed that longer face lengths can cause in- creased face convergence and an increase in the shear stresses in the immediate roof. Empirical design methods predict that longer faces will cause little effect on abutment stresses as long as the roof caving is well behaved. On this basis, a longwall face instrumentation program was designed with emphasis on the interaction between face support and ground response for optimizing face conditions. At a 600-foot (183 m) face, five midface shields and two headgate shields were monitored with vary- ing hydraulic pump pressure. The instrumentation included six convergence rods with linear potentiometers to measure canopy-to-toe convergence; fourteen pressure transducers to monitor leg pressures; and two portable data loggers. Similar instrumentation will be in- stalled on a 750-foot (229 m) face for comparison. The results from the 600-foot (183 m) face indicate that a ground reaction curve, as determined from the relationship between the sup- port set pressure and the roof convergence, can be used to optimize the support pressure to control convergence, the key element to ground stability in the face area.

Jan 1, 1986

By Keith A. Yarborough

INTRODUCTION The National Park Service (NPS) conducted a research program from mid-1975 to early 1978 to measure alpha radiation levels in natural caves which it administers. Subsequently, a long-term management program was developed which has conducted routine monitoring of radiation levels and has computed employee exposure accumulations in certain NPS caves. The overall program: research and management; was undertaken to evaluate the possible health hazard to cave visitors, interpreters, researchers, maintenance personnel, concessions employees and other workers and to protect their health. The results of this work have been reported extensively elsewhere (see References 1 through 3, 5, 6, 9 through 13, and 14 through 26). This paper deals with the relation of radon gas and daughter produced radiation levels to the cave air flows which mobilize them. These flows are a function of interior cave and exterior ambient air temperatures and pressures and of the cave's geophysical configuration. The low-level, ionizing radiation is produced by minute concentrations of radon and thoron gases which emanate from within caves. Because of confinement, the radiation levels are often appreciably higher than in surface atmospheres. Subsequent radioactive disintegration of the gases into their ionized "daughter" products, which are particulates, permits distribution of the alpha radiation throughout a cave system. The extent and character of this distribution depends upon the particular cave and the air flows which it produces. Thus, the alpha radiation serves as a "tracer" to describe the flows. The flow analysis is divided into two parts: 1) A qualitative description with respect to the two basic geophysical cave types over both long-term (annual) and short-term (diurnal to weekly) periods. 2) A quantitative description of the unsteady, uniform and non-uniform, one-dimensional, incompressible motions for both influent and effluent air flow situations in both basic geophysical cave types. A part of the qualitative description presents "Special Measurement" data: Tsivoglou [vs.] Kusnetz working levels, Tsivoglou individual daughter levels and free ion concentrations, radon gas concentrations, and equilibrium ratios. A great deal of important work has been carried out by Mr. Bobby C. Carson, Cave Radiation Technician at Mammoth Cave National Park, Kentucky. He reports these findings later in this conference (Ref. 6). Some of his results have been used here to establish the cave air flow analysis. Other National Park Service personnel have made measurements at others of the caves for which data are reported here. All of this work and cooperation has been vital to the success of this research program. It is very much appreciated. THEORETICAL FLOW DESCRIPTION Previously reported research (See Ref's. 20, 21, 23 and 25) has established the qualitative relationship between the alpha radiation in caves and their natural air flows. The radiation serves as a representation of these air flows. Changes in radiation with time represent changes in the main forces which produce the air flows. The quantitative data have substantiated that [all caves in which the primary cause of air flow is due to temperature produced gravity (density) gradients and also having minimal man-made disturbances, experience seasonal variations in airborne alpha radiation. The radiation levels increase in summer but decrease in winter], based upon seasonal air movements through each cave system which occur naturally. Two general types of physical cave configurations which control the air flows have been identified as: 1. Those which go up into a hillside or mountainside: Type I ("Upside-down" = USD). 2. Those which go down into the earth; Type II ("Right-side-up" = RSU). These act to control the air flows seasonally. The summer increase in Type I caves is due to increased air flows, whereas in Type II caves it results from stagnation or reduced air flows. This seeming paradox is explained by the physics of the air flow regime in each cave type and has been detailed elsewhere [Ref's. (20), (22) through (25)]. It[ i] true, in general, that air flow decreases airborne radiation in the [immediate vicinity] in which it occurs. Any paradox results from subsequent distribution throughout the case as to [ how] the air moves through a cave [system] with respect to time and space. Exceptions to the cave air flow "rule" are: 1. Caves in which pressure gradients and pressure fluctuations [predominate] in producing the air flows. 2. Caves in which man-made effects and management practices are superimposed on the natural air flow regime. Man-made disturbances which can alter the natural cave air flows are tunnels, elevator shafts, bore holes, sealed and closed portals, etc. If these are not properly sealed, the natural air flows which they change will totally alter the distribution and seasonal variations of the alpha radiation levels. These exceptions may act separately or in combination.

Jan 1, 1981

By S. Sener

In this investigation, the changes in the grindability of both ulexite and colemanite related with the different structural modifications created by the heat treatment were examined with respect to work index (Wi). The effects of the heat treatment temperature and time on grindability index were also investigated. It was observed that, heat treatment significantly affected on the grindability of ulexite. The work index of original ulexite was found 7.11 kWh/shton and decreased to 3.5 kWh/shton level within 200-480°C for 60 minutes. On the other hand, the work index of original colemanite was found as 6.48 kWh/shton and no appreciable change was observed when heated up to 320°C. Thermally assisted comminution can be used to improve the grindability characteristics of ulexite. Besides, the different behaviour of ulexite and colemanite under heat treatment can be used for their separation. The artificial mixture of ulexite and colemanite could be separated with over 90% recovery by utilizing their different grindability characteristics by thermal treatment, semi-autogeneous grinding and screening.

Jan 1, 1999

By K. Zabrusky

Epithermal vein systems are often modeled as simple, discrete high grade structures within low grade host rock. However, geologic setting and structural preparation influence how such vein systems form. In structurally complex areas, veins may follow several structural trends and occur on a variety of scales. Geologic and grade modeling within such complex structural regimes can be difficult as individual veins cannot be delineated from host rock based on grade alone. Structurally complex areas require a different approach than traditional discrete vein modeling. Presented herein is a study of a structurally complex area that hosts vein mineralization to be mined underground. All veins could not be modeled discretely, so an alternate approach was needed. Major structures were modeled using surface and underground mapping and were then used to create a structural trend for the area. This trend was used to guide 3D grade shell construction. The grade shells replaced 3D vein solids for grade estimation in order to mitigate the influence of high grade samples. Structurally guided grade shell construction offers a more effective modeling method than discrete vein modeling in deposits that are structurally complex.

Feb 23, 2014

By S. D. Bearden

The world's barite reserve base is adequate for at least 100 years at the current consumption rate. China, India and the United States are expected to remain the leading producing countries, and the United States will continue to be the largest consumer. None of the known substitutes for barium sulfate are expected to impact existing applications. World production in 1995 was 4.41 Mt (4.86 million st), which is about 50% of capacity. Consumption is directly proportional to hydrocarbon well installation activity. Imports are expected to continue to supply more than half of the US requirements.

Jan 1, 1997

By Martin H. Stanczyk

Under the Solid Waste Disposal Act, the Bureau of Mines initiated several accelerated in-house research programs to develop new and improved methods of proper and economic solid waste disposal. The program being conducted at the Bureau' College Park Metallurgy Research Center is concerned with eliminating the current waste of valuable materials in municipal refuse by developing low-cost methods for reclaiming and recycling the metal and mineral values contained in incinerator residues. Each year the United States must collect and dispose of in some manner or other, about 150 to 200 million tons of municipal solid wastes. The monetary output for this service ranks third among public services, exceeded only by the costs for schools and roads based on population growth projections and materials use patterns, the quantity of refuse generated by the early 1980's may approach 300 million tons annually. Currant estimates indicate that only 10 to 20 percent of the total municipal refuse generated is disposed of by incineration. If all refuse were properly incinerated the residues would contain more than 11 million tons of iron and nearly a million tons of mixed nonferrous metals including aluminum, copper, lend, zinc, and tin.

Jan 1, 1969

By R. Vance, C. Cho, N. Mardi, Z. Qian, K. Prisbrey

One problem with the application of neural networks to the multivariable control of mineral and extractive processes is determining whether and how to use them. The objective of this investigation was to compare neural network control to more conventional strategies and to determine if there are any advantages in using neural network control in terms of set-point tracking, rise time, settling time, disturbance rejection and other criteria. The procedure involved developing neural network controllers using both historical plant data and simulation models. Various control patterns were tried, including both inverse and direct neural network plant models. These were compared to state space controllers that are, by nature, linear. For grinding and leaching circuits, a nonlinear neural network-based model predictive control strategy was superior to a state space-based linear quadratic gaussian controller. The investigation pointed out the importance of incorporating state space into neural networks by making them recurrent, i.e., feeding certain output state variables into input nodes in the neural network. It was concluded that neural network controllers can have better disturbance rejection, set-point tracking, rise time, settling time and lower set-point overshoot, and it was also concluded that neural network controllers can be more reliable and easy to implement in complex, multivariable plants.

Jan 1, 1998

By Terry L. Logan, Arfon H. Jones, James C. Seccombe

Deeply buried coal seams [greater than 3000 ft (914 m)] are difficult and sometimes hazardous to test and complete due to coal sloughing, formation pressure anomalies and coal fine generation. Data collected while stimulating two deep coalbed methane wells located at the Gas Research Institute/Resource Enter¬prises, Inc. "Deep Coal Sean Project" test site in the Piceance Basin, Colorado, is presented in this paper. A single thick coal seam was completed openhole in each well. Core data, reservoir data, in-situ stress measurements, and pre-stimulation calibration test data were collected at the site to use in the design of the fracture stimulation treatments for both wells. A nitrogen foam fracture fluid treatment was selected for the first well and a linear gelled water for the second well. Treatment pressures were monitored with a downhole quartz pressure transducer. Atypically high treating pressures were observed, possibly indicating coal fines plugging at the fracture tip or increase in fluid viscosity caused by interaction of the generated coal fines with the fracturefl uid. In addition, a comprehensive fracture diagnostic effort was employed during the fracturing of the second well; namely, triaxial borehole seismic, seismic televiewer, hydraulic impedance monitoring, gamma ray log (in conjunction with radioactive additives in the sand), and temperature log. The results indicate a vertical fracture was created parallel to the face cleat as expected.

Jan 1, 1986