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By N. Oswald

As coal mines age and become more developed, ventilation modeling becomes more important for the planning and continued operation of the system. Numerous studies have been performed and presented that address the collection of data and measurement of airway friction factor and resistance per unit length values. However, a quantitative analysis of the resistance for stoppings in coal mines for different construction materials and methodologies has not been adequately addressed. In order to develop an accurate/realistic ventilation model both airway resistances and stopping resistance values need to be determined. Over the course of the past two decades Mine Ventilation Services, Inc (MVS) has measured the resistance of stoppings of various construction types in mines throughout the world. An analysis of this data is presented in this paper along with a discussion of measurement methodology.

Jan 1, 2009

By J. K. Mokka, P. D. Rao, H. K. Lin

Extensive exploration has resulted in delineation of a massive sulfide district on the north flank of the east-central Alaska range. The district covers approximately 400 mi2 and contains numerous stratiform, transposed and some replacement type sulfide deposits ranging in size from less than 1 million st to 20 million st. Five types of ores were sampled for the study. Mineralogical analysis revealed that the minerals are too fine grained for conventional grinding and beneficiation. Hydrometallurgical studies were conducted using ferric chloride as a lixiviant. Ore microscopic studies as well as electron microprobe analyses of minerals in the raw samples and leach residues explained the low recoveries for certain elements as well as sources of impurities that need to be eliminated from the process streams.

Jan 1, 1992

By M. J. Laurila

Utilizing data compiled from a drilling program and bulk samples taken from a coal reserve, flowsheet performance for a coal preparation plant can be calculated using a desktop computer. Sets of equations defining material balances involving coal preparation plant unit operations are employed to depict plant performance. Techniques are discussed for interpolating washability data and extrapolating size distributions and other critical data to expand on oftentimes limited sets of quality data to a useable data base from which projections can be made. Simulation of flowsheets can be done for a number of different conditions and configurations while still remaining in a limited working memory capacity of 32,000 bytes. Presented within this paper are several pertinent examples.

Jan 1, 1982

By Landy A. Stinnett

Coal mines in the United States are the most productive in the world in terms of efficient labor employment. This is because of an abundance of workable coal beds, large infusions of capital, improved management practices and continuing competitive pressures. The standard unit of measurement for labor productivity is expressed as tons/manshift, although for underground mines, operators often refer to tons per machineshift. Articles written concerning labor productivity generally focus on measurement techniques, safety considerations, application of technology and training. This article will illustrate by example the impact of labor efficiency (or inefficiency) on the ultimate selling price of coal, f.o.b. mine site. During the past several years, the coal industry has seen significant improvement in labor use. Figure 1 shows the trends in productivity for all active mines in the United States from 1985 through 1994. Productivity in 1985 was 20.1 t/manshift (22.1 st/ manshift). This factor has increased almost linearly throughout that period to 37.5 t/manshift (41.2 st/manshift). This is a 7.2% annual compound growth rate.

Jan 1, 1995

By Jaroslaw Drelich

This report briefly reviews the measurements and interpretation of adhesion forces measured between microscopic probes and substrates having micro- and nanoscaled roughness characteristics that were recently conducted at Michigan Tech using atomic force microscopy. The laboratory study concentrated on both rigid and deformable materials, with the probes larger than the size of roughness features of interacting surfaces. For such systems, a detailed surface characterization in terms of roughness parameters, asperity size and shape, and spacing between asperities, as well as analysis of deformation of materials is required. Analysis of the experimental data can be done with theoretical models, which are suitable for rough surfaces and therefore allows to normalize the measured forces. Alternatively, loading of the probe during adhesion force measurements can be managed properly to control deformations of the nano-scaled surface irregularities. Controlling the deformation reduces and even eliminates the effects of nano-roughness on the probesubstrate contact area, promoting conditions described by the contact mechanics models for the sphere-smooth substrate system.

Jan 1, 2005

By Michael D. Balen

The plate-glass windows in the bus were cracked and mud-coated. Nevertheless, they afforded an excellent view of the many head-on collisions we narrowly avoided along the route from the Magadan airport to town. Apparently the driver thought the left side of the road was smoother than the right side, for he drove in the wrong lane at all possible times, even in the face of oncoming traffic. As far as we could tell, neither side of the road was any better than the other. Either way, we had to hang on just to stay in our seats. We careened past trucks and pedestrians, nearly always in the face of impending disaster. When the bus finally pulled into the parking lot of the Okean Hotel in Magadan, we had to thank the driver, not only for safely delivering his passengers, but also for the lasting first impression he gave us of the Russian Far East.

Jan 1, 1995

By W. R. Dengler

In Canada, most of the rock being broken in underground metal mines is being done by using traditional drilling and blasting methods. Despite advances being made in hardrock boring and other, more exotic techniques, Dynatec believes that the traditional methods will prevail for many years. It is also believed that modest research efforts expended on the traditional methods will result in substantial financial benefits to the mining and rock tunneling businesses. Dynatec has pursued productivity improvements through the use of long rounds in shaft sinking and lateral development. The concept of longer rounds was developed by Dynatec on the Craig Shaft Sinking Project (RETC, 1991). This technology was subsequently used to sink the two shafts at Aur Resources with great success. The development of a Long Round Jumbo for tunneling is a natural progression of the long round technology developed for the Craig Shaft. The Dynatec Long Round System has been patented in the United States and South Africa, with additional patent applications pending in Canada and Australia.

Jan 1, 1993

By R. A. Pindred, M. P. Lam

Cyanide is a conventional lixiviant for gold extraction but its' toxicity is a major concern for the environmentalist. There are many alternative non-cyanide lixiviants, such as thiourea, thiosulphate, chlorine and hypochlorite etc., which may reduce environmental sensitivity. This paper will discuss the leaching characteristics of gold in hypochlorite leaching solutions. The dissolution of gold in a hypochlorite solution not only depends on the concentration of the hypochlorite but also on other variables, such as hydrochloric acid, sodium chloride and temperature. The dissolution rate of gold in hypochlorite solution is much faster than other lixiviants. Due to the interference of impurities, gold extraction from an ore under ambient conditions requires large quantities of reagents. However, refractory gold ores may be successfully pressure oxidized in an autoclave at reasonably low reagent levels. Gold extraction to the pressure oxidation leach solution is rapid and complete in one stage, thus eliminating the need for further cyanidation.

Jan 1, 1990

By Henry P. Ehrlinger III, Latif Khan, John M. Lytle

The primary purpose of this project was to produce and test coal concentrates made from coal preparation plant waste fines for use in a slurry-fed gasifier. Concentrates from several individual waste streams were examined to determine their amenability as feedstock for a slurry-fed, slagging, entrained-flow gasifier. The tests included analyses of the plant feed and product, material balances, and estimates of gasification reactivity and of pumpability. The following preparation plant fines were examined: • fresh rejects produced in a plant processing underground- mined Springfield Coal • fresh rejects produced in a plant processing underground- mined Herrin Coal • fresh rejects produced in a plant processing surface-mined Springfield Coal and Herrin Coal • Five-year old impounded fines rejected during processing of underground mined Herrin Coal. At high coal recoveries the Btu content of the concentrates was greater than the Btu content of the utility product from the plant. The coal recovered from fines was found to be entirely acceptable for gasification and pumping without additives.

Jan 1, 1995

By G. D. Criswell, F. Palkovits, J. M. Johnson

A paste technology investigation was completed for non-pozzolanic fly ash from Units 3 & 4 of PPL Montana’s Colstrip Steam Electric Station. The purpose was to assess the feasibility of converting from dilute slurry deposition of ash products to a system using thickened or paste ash to reduce excess water storage in the impoundment, reduce seepage losses, and increase storage efficiency. The investigation included laboratory and field testing to characterize the rheological, geotechnical and dewatering properties of the ash products, an assessment of potential seepage reductions and an evaluation of potential for increased ash storage capacity by modifying impoundment operating procedures. The studies concluded that the conversion project was feasible, cost effective, and permittable. Critical facilities for the conversion project are currently under construction.

Jan 1, 2004

By James J. Snodgrass, David E. Siskind

The Bureau of Mines investigated the effects of vibrations from underground blasting in four rock types to define blast parameters that affect vibration amplitudes and to establish means of predicting expected vibration levels. Previous studies of surface blasting indicated that charge weight per delay period had a major influence on vibration amplitudes. Dividing the distance from the blast by the square root of the charge weight scaled the effect of various charge weights, however, and allowed vibration data for a particular site to be represented by a propagation equation of the form v = K(D/W ½ )-n (1) where v = particle velocity, D = distance from the blast, W = maximum charge weight per delay period, and K and n = empirically determined site constants. For square-root scaling, particle velocity and acceleration data from the underground sites appear to follow a similar propagation law. The subsurface data are in good agreement with those of the surface studies and provide a basis for engineering estimates of vibration amplitudes in many different rock types.

Jan 1, 1974

By Roshan B. Bhappu

In situ mining and extraction is one of the Frontier Technologies that is destined to play an increasingly important role in the recovery of metals and minerals in the future. This premise is based on increasing costs of labor and energy, increasing awareness of environmental considerations and decreasing ore grades in the United States. Up to now, in situ mining has been successfully applied to a few favorable situations for the extraction of some evaporites, copper and uranium. However, because of its unique technical, environmental and economic advantages, this versa tile technology will find broader applications for the recovery of above commodities as well as for others which are currently extracted by hydrometallurgical means. This paper traces the development of in situ mining and extraction; stresses its dependence on interdisciplinary science and engineering; discusses its theoretical, practical and economic aspects; and finally presents potential applications of this Frontier Technology.

Jan 1, 1985

By D. Krzyszton, P. Czaja

Mining explosions in rocks originate stress waves of great intensity, which crush the surrounding rocks and are then propagated as a seismic wave. Seismic waves are the cause of dynamic loading of pillars and their subsequent destruction. In calculating safe dimensions for inter-room pillars, not only the stresses conditioned by overburden pressures should be taken into consideration, but also the dynamic stresses caused by explosion. This is of particular importance for pillars with great specific acoustic impedance which have been destroyed mainly by the reflected seismic wave. It is possible to take dynamic loading into consideration in the calculation of pillars when the parameters of the propagation wave, the dynamic elastic constants of rocks, the strength properties of rocks, the strength properties of rocks subjected to dynamic loads and the parameters of the blasting charge are known. An example of the calculation for the safe width of an inter-room pillar subjected to the seismic effect of an explosion is given and the possibilities of reducing the dynamic loading of pillars are discussed.

Jan 1, 1982

By J. Stachurski, N. A. Abdel-Khalek

The objective of this investigation was to compare the results of countercurrent, column cell flotation vs. conventional (mechanical) cell flotation for the cleaning of a sulfur ore (-0.5 mm, 27.43% S) and its discrete size fractions. The tests were carried out using diesel oil as a collector and alcohol as a frother. Generally, column flotation produced concentrates of higher grade. For example, column cell flotation produced a nonwashed concentrate of 65.3% S with a recovery of 84.1%. However, conventional cell flotation produced a rougher concentrate of lower grade (57.0% S) and higher recovery (92.5%). At a superficial-wash water velocity of 0.265 cm/sec, the column product grade increased to 76.4% S, with a slightly lower recovery (80.3%). However, a concentrate with a similar recovery but a lower grade (74% S) than that of the washed product was obtained after three cleaning stages with the conventional cell. The column gave superior results for the flotation of fine and ultrafine particles.

Jan 1, 1994

By Bernard Lippe

The successful construction project is one in which the component construction operations are completed within the scheduled time and cost parameters. Most construction projects, however, are subject to delays and/or disruptions which adversely affect the time (start, duration, and completion) and cost aspects of the project. DELAYS Delays fall into two categories: Compensable Delays for which the contractor is entitled to contract time extensions and additional money as compensation for the extra expenses generated by the delay or obstruction to job progress, and Non Compensable Delays, for which the contractor may or may not receive an extension of time but no additional compensation. Compensable Delays Compensable delays may take the form of holds or suspensions on all or certain segments of a project by the owner, failure of the owner or his Engineers to approve shop drawings, cuts or material samples within a reasonable period of time, failure of the Owner or his Engineer to properly coordinate the job, discovery of design deficiencies in the plans and specifications which prevent the continuation of construction until

Jan 1, 1974

By Allan E. Hall, Kuda R. Mutama

Jet fan (ductless fan) ventilation in underground mines and tunnels is a subject requiring further attention. At present there are no accepted procedures or guidelines for this type of ventilation. The main reason has been the absence of sufficient general data, which has hampered the development of rules. There is great potential for using jet fans in terms of both effectiveness and economics because they eliminate the need for ventilation tubing. In the present studies a procedure is described and results are presented from a jet fan modeled in a square section wind tunnel. The major purpose of the studies was to provide fundamental data on jet fan performance after it was realized that previous work had been limited and too site specific. The jet fan position in relation to the tunnel walls was varied in order to study the influence of confining walls on entrainment rates and the resulting aerodynamics. A clearer understanding of the fundamental principles of jet fan applications was obtained.

Jan 1, 1995

By G. A. Achilleos

The insufficiency of Boolean Logic and ?hard? decision making to represent and manage spatial data in set with their spatial errors comprises a remarkable difficulty for widely accepted estimation procedures, in realistic planning of space geometric problems and management through a GIS. Fuzzy logic as well as other theories such as the theory of Probabilities, Bayesian theory etc., contribute substantially towards this direction. Data are accompanied by their accuracy and are managed through the applications and modules of Spatial Analysis, aiming to access a decision with known accuracy and fuzziness. As it concerns the cases of waste sanitary landfill sites designing, which are based on the construction of a bank, the problem shown by this paper, seems to be quite serious. The determination of the theoretical waste disposals body in the landfill is based on an uncertain Digital Elevation Model (DEM). As this model is a result of a procedure enclosing errors and inaccuracies, it is for certain a non - error free model. Thus, the geometric computation of the excavation quantities and the waste disposals solid body volume, misquotes the expected standard theoretical computation and imports the need to decide and set a risk level for the project.

Jan 1, 2005

By E. J. McGuire, E. W. Brickle

INTRODUCTION Several recent technological improvements - largely by the convey-or industry - have increased the importance of inclined shaft construction for developing mines where ore deposits are relatively shallow. With these newer systems, long conveyor haulages are economically feasible, allowing mine owners to justify the expense of the inclined shaft or slope. What this actually means is that they can now take advantage of the versatility this construction offers. For example, haulage capacity can be changed by conveyor additions or replacements; equipment can be trammed to and from the surface quickly without costly breakdown and re-assembly; and a walkway is available for workers in the event of an emergency. Now, another innovation may accelerate this type of construction, the use of tunnel boring machines or "Mechanical Moles" to dig the slopes. While conventional. drill and blast methods have been used previously to build inclined shafts, the tunnel boring machine technique offers greater production rates, higher safety and a better, much cleaner bore. McGuire Shaft & Tunnel Corporation of Ft. Smith, Arkansas recently started such a slope project - the first ever bid by a contractor based on the use of a "Mechanical Mole".

Jan 1, 1997

By J. P. Barbosa, R. V. V. Araújo, R. B. E. Trindade

Bromide stabilizes the auric or aurous ion by forming a stable complex in acidic aqueous solution. The oxidizing agent normally used for the process is bromine, which is a corrosive liquid with high vapour pressure. This is, in fact, the main reason why it has not found acceptance yet as an industrial oxidant for gold. Ferric ion with hydrogen peroxide and/or sodium hypochlorite have already proved to be effective oxidants for the dissolution of gold from a rotating disc in a bromide-containing aqueous solution. In the present work, preliminary tests with four selected ore samples were tested to evaluate the dissolution of gold with the same system already tested with the rotating disc (Br-/Fe3+/H2o2/NaCIO). Compared to the conventional cyanidation, results were superior in one instance only. The major obstacle seems to be the maintenance of a suitable potential to allow the complex formation. However, the studied system may be interesting, is in some situations it may yield better results than conventional cyanidation; therefore, further investigation seems to be worth doing.

Jan 1, 1995

By K. A. Natarajan, J. M. Modak, B. Saha

Nonliving waste biomass consisting of Aspergillus niger attached to wheat bran was used as a biosorbent for the removal of copper and zinc from aqueous solutions. Copper and zinc uptake by the biomass obeyed Langmuir isotherms. The binding capacity of the biomass for copper was found to be higher than that for zinc. The metal uptake, expressed in milligrams per grain of biomass, was found to be a function of: •the initial metal concentration (with the uptake decreasing with increasing initial concentration), •the biomass loading (with the uptake decreasing with increasing biomass loading) and •pH (with the uptake increasing with increasing pH in the range of L5 and 6.0). The metal uptake was significantly affected in the presence of a co-ion. The uptake of copper by the biomass decreased in the presence of zinc and vice versa. The decrease in metal uptake was dependent on the concentrations of metals in the two-component aqueous solutions. The effect of copper on zinc uptake was more pronounced than the effect of zinc on copper uptake.

Jan 1, 1997