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By William J. Gregg

Mechanical testing results on oriented Devonian gas shale core throughout the Appalachian basin show a preferred fracture direction perpendicular to bedding. The preferred direction is generally parallel to the Allegheny Front, but is only coincidentally parallel with in-situ stresses in some areas of the basin. The strength of the preferred orientation of induced fractures decreases with distance from the Front. It is suggested that strain related to Paleozoic deformation is responsible for this mechanical fabric and thus the direction of induced fractures in laboratory tests may not be of use as indicators of in-situ stress orientations as previously suggested.

Jan 1, 1986

By Terry A. Ring

Sand bed filters are used to remove large and small particles from liquid streams. The large particles are removed by the straining action of the filter bed and the small particles are removed by particle deposition on the surface of the bed particles. Particle deposition, while being essential for the filtering action of colloidal particles, is not the only process that occurs in the filter bed. Other processes that occur are (1) the substrate becomes filled with particles limiting further deposition, and (2) some deposited particles are resuspended. The sum total of all these processes determine the performance of a filter bed.

Jan 1, 1982

By I. González, G. Lapidus, M. Teutli

The cementation kinetics of silver with aluminum particles were studied with model solutions under nitrogen atmosphere, varying the temperature, aluminum/silver ratio, pH and concentrations of thiourea and surface activator Recoveries were evaluated both by solution concentrations and by REDOX measurements. Tafel curves were determined for this system. The results showed the cementation process to be essentially independent of the pH and thiourea concentration. However, a strong influence was observed with respect to temperature, aluminum/silver ratio and the quantity of activator. There is evidence that the controlling step is the dissolution of aluminum oxide from the particle surface.

Jan 1, 1990

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

In many mining operations, particularly northern open-pit mines, large seasonal variations in grinding slurry temperature can occur. It is shown in this paper that this temperature shift can cause a winter-time loss in autogenous grinding efficiency of as much as 20% if it is not controlled. Laboratory experimentation indicates that much of this effect is due to increases in slurry viscosity as the temperature is decreased. An additional effect may result from changes in rock strength upon freezing, for which possible mechanisms are discussed. However, no effect clearly resulting from rock strength changes has been definitely confirmed.

Jan 1, 1992

By H. Kandemir, G. Neeling, P. A. Spencer

Gold extractions from three refractory sulphide concentrates have been increased by bacterial oxidation with T. ferrooxidans prior to cyanide leaching. Arsenopyrite, pyrite and stibnite were the major sulphide components associated with gold in the concentrates examined. Kinetic oxidation tests were conducted for each concentrate by monitoring iron and arsenic levels in leach slurry. A correlation has been established between the level of bacterial oxidation and gold extraction from cyanide leaching of oxidised residues. High levels of bacterial oxidation have been achieved in approximately 8 days at pulp densities of 20-25/ w/v solids, resulting in 70-90% gold extraction.

Jan 1, 1987

By M. E. Kuchta

Research is currently being conducted at the Colorado School of Mines in the use of high-pressure water for scaling down loose rocks in underground mine openings. In addition to improved miner safety, the adhesion strength of shotcrete applied to rock surfaces treated with high-pressure water is also increased significantly, resulting in improved overall support capabilities of the shotcrete layer. Test results show an increase in adhesion strength by a factor of four on a concrete test wall cleaned with water at 21 MPa (3,000 psi) as compared to a surface cleaned at 0.7 MPa (100 psi).

Jan 1, 2003

By R. L. Grayson, Y. J. Wang

An application of material requirements planning (MRP) to coal mine inventory control is presented. MRP is an efficient material control system that integrates the production planning and inventory management functions. Net material requirements are determined from the production forecast utilizing bill of material files, the inventory status file, and the purchase order status file. Net requirements are computed for each period in a specified planning horizon, and purchase orders, offset by lead time, are initiated routinely to ensure timely receipt of materials. The MRP system is especially useful in production-inventory systems in which con¬sumption of materials is directly production dependent.

Jan 1, 1987

By James G. Sampson

The discarded phosphatic clays from mining operations have historically been stored behind earthen dams for long periods of time before any reclamation was accomplished. In efforts to expedite the dewatering and reclamation of the clay ponds, the phosphate industry explored alternatives to conventional clay disposal practices. One alternative, employed by CF Industries, Inc., combines the clay and the discarded sand prior to disposal behind earthen dams. The sand encourages the clays to 'give up' trapped water more readily resulting in enhanced consolidation behavior. This paper provides an overview of the sand-clay mix process including the reclamation of sand-clay disposal areas.

Jan 1, 1992

By R. Sawyer, M. Sadler, M. Holdworth

Greens Creek is a high grade Ag/Au/Pb/Zn deposit located in southeast Alaska. Maximizing the Net Smelter Return revenue from the fine grained mineralization is a dynamic process given changes in metal prices, smelting terms, ore grades and flotation characteristics. This paper discusses the evolving concentrate production strategy, and how it is affected by such factors as ore and concentrate specifications and by market conditions. Also described is the development of an on-line computer program that provides the mill operators with real time NSR data and a means for optimizing Net Smelter Return.

Jan 1, 2002

By Regina N. Tempel, Laurie S. Balistrieri, Lisa L. Stillings, Maggy F. Lengke

The Dexter pit lake, within the Tuscarora volcanic field in Elko County, Nevada, formed after closure of the Dexter mine. Mineralogy at the Dexter mine is related to widespread feldspar, silica, and chlorite alteration. Major mineralogy includes quartz, alkali feldspar, albite, phlogopite-biotite, hornblende, iron-titanium oxide, chlorite, kaolinite, smectite, illite, and sericite, with lesser amounts of calcite, zircon, apatite, and rutile. Trace element geochemistry is characterized by high levels of As, Ba. Cr, Cu, V, Zn, B, Zr, Li, and U. Detailed mineralogy and geochemistry are required for geochemical models to accurately predict trace element concentrations in pit lake waters.

Jan 1, 2000

By Walter J. Johnson, Robert L. Chufo

A unique non-contracting coal thickness measurement technique has been developed to measure both the dielectric constant and thickness of a coal seam as part of a sensor array supporting an autonomous coal mining machine. The sensor measures the reflection of an electromagnetic signal from the coal/shale interface. Underground measurements of coal 6- in thick with a dielectric constant of 4 have been confirmed. Measurements were also made of a 31-in thick coal pillar for application of the sensor to highwall mining. The electromagnetic measurement technique, the data reduction process and field test experience will be presented.

Jan 1, 1992

By Kirk Conway, Richard L. Unger

The U. S. Bureau of Mines conducted a research project to analyze the design of underground mining equipment with respect to ease of maintenance and maintainer safety. The work included a review of maintainability design literature, an analysis of maintenance related accident data, field reviews of equipment designs, and interviews with mine maintenance personnel and equipment manufacturers. Based on the findings, a set of maintainability design recommendations have been prepared. The final recommendations document includes maintainability engineering information for equipment designers, as well as a buyers' guide to aid purchasers of mining machinery in evaluating the maintainability of equipment.

Jan 1, 1992

By K. Professor Heiskanen

The improvement of grinding circuit efficiency is a constant industrial requirement. It has often been connected to the improvement of classification. The paper discusses some operational aspects of hydrocyclone classification. A hydrocyclone should be operated close to roping but should not with high density slurries go to roping. Unfortunately roping is not well understood and roping models for controlling hydrocyclone operation are not adequate. The paper discusses also some ways of improving the classification in terms of bypass and imperfection. The last part of the paper discusses the effect of bypass and imperfection on circuit performance.

Jan 1, 1997

By Harold E. Goetzman, Blair R. Benner

The U.S. iron ore industry is located primarily in Northern Minnesota and Michigan's Upper Peninsula with one additional small plant in Missouri. There are currently some 10 plants operating that produce about 48 million tons per year of pellets. The major reagent use occurs in the three general areas of: flocculation, flotation and pellet additives. Minor areas of usage are for corrosion inhibition and dust suppression. Current practice as to types of reagents, consumption, and method of application are reviewed. The interaction of reagents with other parts of the process are discussed. Also included is a discussion of future reagent needs.

Jan 1, 1994

By A. G. Wylie

The dimensions and shape both airborne and bulk amphibole-asbestos fibers are different from those of both airborne and bulk of cleavage fragments of the amphiboles. These differences are related to the mineralogical properties unique to the habit of asbestos, including the fibrillar structure, small fibril widths and distinctive crystal-lographic faces of fibrils. Criteria for distinguishing amphi-bole cleavage fragments from amphibole-asbestos include mineralogical properties observable in bulk samples and the dimensions of particles collected on air filters. It would be it very helpful to the mining and mineral industry lf these properties were recognized in the regulation of asbestos.

Jan 1, 1987

By T. Brady, J. Johnson, J. Whyatt, B. Pariseau, M. Stahl

An elastic-viscoplastic material model allows for time- dependent rock mass motion in proportion to excess stress above the elastic limit. The model produces rounded stair-step curves of displacement vs. time that are similar to those obtained from recent borehole extensometer measurements made in the central portion of the Ross Shaft pillar at the Homestake mine. The work in progress, including two- and three-dimensional finite element analyses using the UTAH2/3 codes, indicates that the model is a step towards more realistic safety and stability analysis, but that inclusion of rock mass damage may be desirable.

Jan 1, 2000

By Husheng Li, Zhongli Wu

This paper discusses the fundamental strategies adopted in the simulation package FIRES developed for ventilation simulation under mine fires. These fundamental strategies include (1) fire characteristic curves specifying the development of a mine fire with time, (2) simulation of fume spread in a ventilation system, (3) determination of the aerodynamic effects of mine fires on flows; and (4) dynamic simulation of flow state under mine fires. The major functions of the simulation package are also addressed. The package has been used to simulate an experiment of mine fire. A comparison is made between the simulation results and the measured data.

Jan 1, 1993

By Heinz Hoberg, Fred Ulrich Schneider, Rudolf Diegel

The risk of contamination of dumped tailings and ground water by coal flotation reagents has been investigated by using the 14C-radiotracer method for adsorption and desorption measurements. The results indicate, that a high amount of the reagent components adsorbed on the tailings if there was no coal in the pulp. In coal flotation however a competitive adsorption behaviour could be observed, with the effect that only a low quantity of reagents adsorbed on the tailings. Mobilization tests showed, that only small quantities of reagents could be desorbed by rinsing water. Therefore the contamination of ground water should be low.

Jan 1, 1995

By J. A. Frew, G. I. Orrock, R. M. Glen

The zinc flotation circuit was sampled to provide sized information on its metallurgical performance. A good balance was obtained and the roughing, scavenging, cleaning and regrind sections were assessed. Substantial losses of sphalerite occurred in all sizes. The limitations were poor recovery in the cleaning section which resulted in substantial recycling of 15-30µm sphalerite and iron sulphides, and inability to float +38µm sphalerite in the roughers. Regrinding increased sphalerite recovery by 7% with no loss in grade. Liberation measurements enabled balances for six size fractions to be calculated and the role of liberation on the metallurgical performance was assessed.

Jan 1, 1993

By Kotaro Ohga, Kiyoshi Higuchi, Zhang Xun Tao

In Japanese coal mines, drivage works of in-seam gate roads are mainly carried out by blasting methods. Changes of methane concentration in gate roads are recorded by centralized monitoring systems in general. To obtain useful information from the recorded data, authors analyzed changes of methane concentration for 3 hours after blastings. As a result, the changes of methane concentration with time can be divided into five distinct patterns. It is thought that appearance of the each pattern depends upon the geological conditions of the surrounding of the headings. Therefore, we attempted to confirm such observations by simulations using mathematical models.

Jan 1, 1989