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By S. Bhattacharjee, S. K. Singh, R. K. Galgali

A method for the preparation of zirconia- toughened mullite using dc plasma is presented. An indigenously developed 50-kW thermal plasma reactor is used for the preparation of zirconia-toughened mullite using a dissociated zircon and alumina mixture. Both XRD and SEM studies of the product confirmed the formation of mullite and zirconia. The zirconia grew as equiaxed grains of uniform size (~5 µm) in a mullite matrix.

Jan 1, 2002

By Anthony Busigin, Stephen Pogorski, Colin R. Phillips

The precision of radon daughter measurement techniques is a complicated function of uncertainties arising from concentration and flowrate fluctuations during sampling, counting statistics and many other factors. Optimization of a measurement technique requires that all these uncertainties - not just counting statistics - be considered. In this work, the optimization procedure of Busigin and Phillips (1980) is tested against Monte Carlo experiments for the case of the modified Tsivoglou method.

Jan 1, 1981

By Richard J. Frechette

Final reclamation of mine tailings impoundments typically involves addressing the broad issues of surface stabilization and water management. Surface stabilization includes immobilizing the tailings particles and providing long-term protection of the containment facility. Water management typically includes provisions for handling both the external water (rainfall and runoff) and the internal water (pore fluids). Wet tailings disposal facilities, and sites with limited access and steep topography, present challenges to implementing effective surface stabilization and water management plans. This paper presents a generalized discussion of the approach to tailings impoundment reclamation based on project experience.

Jan 1, 1995

By D. Zaharaki

In the present experimental study the geochemical stability of inorganic polymers was studied by immersing them in various solutions (distilled water, seawater and 0.5N HCl) for a period of 7 months. Inorganic polymers were synthesised by mixing ferronickel slag with kaolinite, potassium hydroxide and sodium silicate solution. The cement like paste was heated at 80 °C for 48 hours and left for curing at room temperature. Their structural integrity was assessed by compressive strength testing after subjection to freeze-thaw cycles as well as high temperature heating. XRD studies were carried out in order to identify new formed phases and provide useful information regarding the progress of the mechanisms involved.

Jan 1, 2008

By J. Alton Burks, James P. Rider

The ability to accurately predict the sound field is essential for the estimation of probable worker noise exposure. For this reason, the U.S. Bureau of Mines is researching computer- based analytical techniques specifically geared to calculate the spatial variation of sound pressure levels within common mining environments. Initial modelling efforts describing the user interface, the simulation of energy acoustics, and the graphical representation of sound pressure levels are presented in this paper.

Jan 1, 1993

By Cheng Zhengbing, Sun Baoqi

This paper summarizes several chemical purification methods used for producing high-pure industrial minerals These methods, mainly including alkali melting, acid leaching, oxidation-reduction bleaching, are respectively used to eliminate the impurities such as silicates in graphite and diamond, ferric oxides in quartz sand or other valuable silicate minerals, colouring impurities in kaoline, barite and other minerals which are required to have a high-whiteness. The fundamentals of the chemical purification methods and some practical examples in China are introduced in the paper.

Jan 1, 1995

By V. L. Zajakowski, J. D. Gargulak

The current political climate has forced multinational cement manufacturers to consider technology that minimizes GO, emissions. Along with this environmental issue, individual manufacturing facilities are under constant pressure to increase productivity and lower costs. The use of processing or functional additions can help address these difficult demands by maximizing the extender content in blended cements. Recently, cement standards have been modified such that additions can be employed to improve quality. By using these "cement performance enhancers," the cement manufacturer can maximize extender content of cement thus optimizing plant economics, while meeting local quality standards and minimizing greenhouse gas emissions.

Jan 1, 2003

By C. A. Wiggins, J. M. Kennedy

The Benbrook Connection tunnel forms approximately 6,666 m (19,560 ft) of17,678 m (58,000 ft) of raw water pipeline connecting Lake Benbrook with the Rolling Hills Water Treatment Plant. This connection is designed to minimize costs to the owners, the Tarrant Regional Water District, for providing raw water to its’ various clients. The geological formations through which the tunnel passes and the design requirements resulted in some-what unique applications of initial ground support systems which were modified by the con-tractor to optimize the mining operations. The pipe sections, fabricated in 12 m (40 ft) sections, are concrete lined and coated steel pipe. Construction of the work shaft and tail tunnel was also modified to suit the contractors methods. A Lovat universal TBM was chosen to excavate through the various rock types. The pipe sections will be transported using beam carriers.

Jan 1, 1997

By R. L. Lewis

The White Pine Mine is a large underground copper mine located in the Upper Peninsula of Michigan. A numerical ground water flow model of the White Pine Mine was constructed to evaluate potential engineering controls that would reduce the rate of mine-water discharge after closure. Of the passive controls evaluated, the placement of bulkheads within the mine workings was predicted to offer the greatest benefit, reducing the rate of discharge by as much as 35%.

Jan 1, 1997

By S. S. Peng

Horizontal stress is an important factor that contributes to roof failure during longwall entry development, especially when the immediate roof is weak. In this paper, the effects of stress angle between the maximum horizontal stress and entry development and stress ratio of the maximum to minimum horizontal stresses on the stress distributions in the weak immediate roof of a three-entry system are analyzed using the finite element method. The results have confirmed that stress angle has a significant influence on the stress distributions. Generally, the three-entry system is in the worst stress condition when the stress angle is about 60° to 75° . The stress ratio has also some effects on the roof stresses.

Jan 1, 2000

By R. A. Metz, Isaac Vera, Hans Ruge

The El Soldado copper mineralization occurs as relatively high-grade irregular ore bodies with assay contacts and with frequent inclusions of barren rock. The sampling methods must be timely for production grade control purposes, as well as accurate and inexpensive. Sampling techniques evolved from sampling dump cars at the haulage level to sampling Scooptrams at the loading pockets. These methods were abandoned in favor of sampling production blastholes. Several sampling alternatives are discussed. These involve the selection of optimum volumes and sampling frequencies while taking into consideration geological parameters and statistical analyses of sampling data.

Jan 1, 1992

By Andrew M. Garvie, William W. Plotnikoff, Eugenia Y. Kuo

Water infiltrating the surface of waste rock dumps transports pollutants into the environment. Lysimeters have been used to quantify the infiltration rate. To date their design has been guided by modeling under steady-state conditions. Recently a two-dimensional finite element code has been developed to model the response of lysimeters to time-dependent infiltration rates. It was used to investigate the response of lysimeters installed in a waste rock dump and subject to a monsoonal rainfall pattern. The results are presented and compared with field data.

Jan 1, 2000

By Robert M. St. Louis, Janet M. Edgecombe

The Mercur Mine's autoclave is an alkaline pressure oxidation system, operating at 220°(428°F) and 3061 kPa (444 psig) (total). Up to 725 metric tons (800 st) of ore, grading 2.02 g per mt (0.059 oz/st) Au and containing 1 to 2% sulfide sulfur, are treated daily in this circuit. A mineralogical and chemical investigation was initiated to locate the cause of lower than anticipated gold recoveries. Greater than 70 wt. % of reduced sulfur is oxidized; therefore, the autoclave is operating at specification. The low recoveries were attributed to increased concentrations of organic carbon in refractory ore. Activated carbon concentration in the attached CIL circuit was increased from 15 to 40 g per 1, leach temperature held below 21°C (70°F), and carbon flow changed to counterflow. These measures resulted in gold recovery improving from 75 to 82%.

Jan 1, 1990

By John R. Twining, Michael D. Lawton, Ross A. Jeffree

The Finniss River system in tropical northern Australia has received 'acid-drainage' contaminants from the Rum Jungle uranium/copper mine site over the past 4 decades. Following mine-site remediation that began in 1981-82 the annual contaminant loads of sulfate, Cu, Zn and Mn have declined by factors of 3, 7, 5 and 4, respectively over 1990-93, compared to the 1969-74 pre-remediation loads. Comparison of the frequency distributions of contaminant water concentrations over these pre- and post-remedial periods have shown varying degrees of reduction in the highest levels following mine-site remediation, that are consistent with reductions in their annual-cycle loads. Among the three selected major metal contaminants the reductions in maximum water concentrations are most pronounced for Cu. The demonstrated reductions in the highest water concentrations of all four contaminants are also associated with previously reported ecological improvement in the Finniss River system, compared to the benchmark of environmental detriment established in 1973fl4, prior to the beginning of remediation at the mine site.

Jan 1, 2000

By Jamai Rostami

Mining, perhaps more than other industries, has been under pressure to achieve higher productivity, while reducing costs and environmental impacts. This has encouraged a move toward large-scale operations and greater integration and automation of systems. Mechanization is being used increasingly to raise production and reduce labor requirements. Yet, while transportation, ventilation and other activities have benefited from this trend, mechanization of rock excavation (for development and production) has lagged. The switch to a mechanized excavation system can be complex, requiring a thorough study of operational and cost benefits to be successful. To justify the high capital cost of mechanical mining equipment, production rates and the true costs of machine mining must be accurately estimated. To evaluate the cost effectiveness of mechanical mining for a particular operation, the total production cost (capital and operating) must first be estimated. This requires a reliable estimate of the production rate of the candidate mechanical excavator. Previously, the variable nature of rock caused performance prediction of these machines to be more an art than a science. Additionally, some of these machines are highly sensitive to operator skill. They all depend on their backup systems. The effects of interaction with the overall mining operation can be difficult to forecast. And a new system must surmount psychological barriers before it can become truly operational.

Jan 1, 1994

By J. Finch, J. Yianatos, N. W. Johnson, R. Espinosa-Gomez

A method of determining the maximum concentrate solids rate or carrying capacity is described for given column operating conditions. The method requires alteration of the feed rate of solids to the column at a fixed residence time by manipulation of the % solid of the column feed pulp or the bias rate. The carrying capacity was measured for five streams at the Mt. Isa Mines Pb/Zn and Cu concentrators. As a potential scale up parameter, the mass of solids per unit time per unit column cross section (Ca, g/min.cm2) is explored. Ca is tentatively related linearly to the 80% passing size (d80) of the concentrate. For d80 < 15 pm Ca was less than 4 g/min.cm2 (8 lb/min.ft2) which makes it a critical consideration in scale-up for such fine feeds. An alternative carrying capacity parameter, mass of solids per unit volume of gas Cg was not as useful as Ca since Cg varied inversely with gas rate.

Jan 1, 1988

By Simona Markic

With the aim of environment protection the program package HOMOGEN is used for realizing the planning and noxious components control in the coal produced. Using the program package PRIPREMA the division in levels and transformation (Hermite polynoms) in the N (0,1) distribution are made. By separated kriging 50 m x 50 m blocks are estimated on the levels and detailed distributions of the estimated component content are obtained. The face - longwall face is built in the blocks estimated in this way, and the direction of mining is determined. Using the stochastic simulation the distribution of the estimated production component (e.g. sulfur) on the face is obtained. Simulating the production of all faces in operation the distribution of the estimated daily mine production component is obtained. The estimated depot component is obtained in the same way. This procedure is used in the short-term planning of the estimated component movement for a given period in advance, and also in the daily production control in the case of changing conditions, e.g. the increased atmospheric pressure. The technology is successfully applied to the Velenje Lignite Mine Slovenia.

Jan 1, 1992

By Abou Saghafi

In order to investigate the design parameters of a future longwall in a thick coal seam a numerical model of gas emission from the goaf area was developed. A Longwall goaf was modelled as a collection of different size coal blocks. For each coal block the partial differential equation of gas flow was independently solved. In developing the flow equations, both pressure-driven and diffusion driven gas flow regimes were considered. The total gas emission rate was calculated by integrating the gas release from each individual coal block over the whole goaf area. The main output of the computer program are gas flowrate from goaf and residual content of caved coal in the goaf as a function of distance from the face. The model was applied to a longwall face driven in a thick seam where large volumes of coal in the roof were to be left behind the face. The gas contained in the coal was mainly CO, with a high desorption rate. Simulations were under- taken to quantify the effect of size of the caved coal on the flowrate from the goaf. The flow properties of coal, such as diffusivity, permeability and coal swelling due to gas adsorption, were directly measured on coal samples from the seam.

Jan 1, 1996

By H. R. Weischedel

The art of wire rope inspection has advanced rapidly over the past decade. Present electromagnetic (EM) wire rope inspection instruments provide an important and often vital element of wire rope inspection. Some instruments are easy to operate and offer simple and clear data interpretation. Simultaneously, wire rope inspection and retirement standards are becoming simpler and more lucid. Future guidelines will he easy for inspectors to apply and for rope operators to fulfill. The thrust of evolving regulations is clearly toward periodic EM inspections supported by visual inspections. These development sallow even moderately skilled personnel to perform EM inspections of wire ropes. Therefore, it is now possible and cost effective for wire rope users to have EM and visual inspections performed by in-house personnel. In-house EM inspections have many advantages and offer an excellent return on the initial investment. Since EM inspections can detect rope deterioration in its beginning stage, wire rope users recognize that they are an effective preventive maintenance tool. For instance, the early detection of wear or corrosion allows immediate corrective action. This can easily double, or even triple or quadruple, the service life of a rope.

Jan 1, 1991

By Y. S. Kim, A. Bailey

A feasibility seismic refraction and reflection field survey was conducted at the U. S. Borax Company open-pit mine, Boron, California by the writers during the weekend of March 13 and 14, 1976. This field survey was carried out as a preliminary investigation primarily for the purpose of evaluating and establishing the ability of such geophysical techniques to locate and outline the subsurface openings of the old room-and-pillar mining under the present open-pit. The value of such knowledge about the old underground workings is directly related to the safe and economical operation of the open-pit mine for the company. Although mine maps of the old underground workings are available at the mine, the extent of roof and wall cavings and the present condition of the old underground openings are unknown. Owen and Suhler (2) are the first investigators who used electromagnetic methods, Pulse-Echo System, and electric resistivity measurement to solve the problem without success. A few years later, Herzig and Owen (1) attempted to solve the problem with application of earth resistivity measurement method with unfavorable results. The U. S. Borax Company carried out an extensive study for slope failure problems of the open-pit with application of dipmeter measurements. However, the slope stability study was not correlated to the old underground openings lying under the present open-pit (3).

Jan 1, 1977