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By G. J. Lindenburg, T. L. Wilson

The Velvet uranium mine is located in the Big Indian district of the Colorado Plateau. The uranium ore body lies within the lower Triassic Chinle Formation, and the ore is associated with west-south-westerly trending fluvial sand systems. Exploration and mining are directed by longhole drilling and radiometric sampling. Results of the gamma probing, face scanning, and geologic mapping guide mining decisions and planning. Three people are directly involved with the geologic procedures: two geologists and a mine supervisor. The two geologists map, do rib scans, and direct longhole drilling. The third man involved, the mine supervisor, has last minute directive action based on shot hole probe data.

Jan 1, 1992

By G. L. Mowrey

In addition to developing various types of coal interface detection systems, the U.S. Bureau of Mines is actively involved in developing a coal rib thickness monitoring system for high wall mining applications. One particular system that appears to show promise uses a ground-penetrating radar system to detect the coal-air boundaries of coal ribs. Based on preliminary laboratory and field tests, results indicate that this method can be applied successfully in highwall mines to maintain a constant rib thickness. The coal seam should be relatively clean in the vicinity of the antenna (e.g., have minimal partings or dirt bands) for best results.

Jan 1, 1995

By B. K. Slone

The depth at which it becomes more economical to use slope access as opposed to box-cut access for near-surface coal reserves, termed "transition depth," can be established for a given coal property by considering cost estimates for those parameters that determine respective access method. Fourteen parameters that influence access cost were identified and ranges determined. A Transition Depth Formula was developed to permit determination of the better method of accessing a reserve, given such information as highwall slope, road width, total bench width, pit dimensions, road grade, belt component costs, pumping costs, and cost of overburden removal and reclamation. In most cases, in Appalachia, studies indicate that the transition depth ranges between 20 and 30 m.

Jan 1, 1998

The Waste Isolation Pilot Plant (WIPP) is adding a third fan to operate in parallel with, and supplement, its two existing main fans. An engineering analysis conducted in 1995 identified the need for improved system availability and efficiency. The WIPP, located near Carlsbad, New Mexico, is a U.S. Department of Energy (DOE) Carlsbad Area Office facility designed to permanently dispose of U.S. defense-generated transuranic waste in a deep bedded salt deposit. Engineers at the WIPP performed a feasibility analysis for either modifying, supplementing, or replacing its two main mine fans. Since the centrifugal fans were installed in 1988, multiple operational and performance concerns have been identified. A comprehensive engineering study was conducted (K. McDaniel, et al., 1997) to: identify and quantify operational concerns, evaluate possible alternatives, and recommend an optimum solution. The study indicated that adding a third single-duty centrifugal fan similar to the two existing fans, and equipping that fan with Inlet Van Controls (IVCs) was the best choice. This alternative provided the most desirable combination of operational readiness, and improving system performance. The fan installation project accommodates several operational and scheduling constraints. WIPP is scheduled to receive waste in May 1998. This milestone is proceeded by an operational readiness review. Fan installation could not be allowed to compromise the WIPP's ability to declare facility readiness and had to minimize operational disruptions during the system tie-in. All engineering for the project is completed and physical modifications started in July 1997. The project will be completed in early 1998.

Jan 1, 1998

By M. Canty

An innovative biological treatment system designed to detoxify cyanide and nitrate and immobilize metals from cyanide leach operations is described. A pilot-plant demonstration was conducted to detoxify cyanide and immobilize several metals from a process stream at the McCoy/Cove Mine. Testing was performed under the EPA's Mine Waste Technology and Superfund Innovative Technology Evaluation Demonstration Programs. This technology was successful in detoxifying cyanide and effective in removing metals. The pH was consistently neutralized and nitrates were successfully removed. Results show that biological treatment can offer an innovative, cost-effective alternative for the treatment of mining wastewaters.

Jan 1, 1999

By D. R. Babich, E. R. Bauer

Noise-Induced Hearing Loss (NIHL) continues to be a concern of the mining industry. A new noise standard (30 CFR, Part 62) is aimed at reducing NIHL in mining through engineering and administrative noise controls. However, the difficulty and expense of implementing engineering controls can make administrative controls an attractive alternative for reducing worker noise exposure. Over the last three years, the National Institute for Occupational Safety and Health (NIOSH) has conducted worker noise exposure surveys in underground and surface coal mines and coal preparation plants. The surveys revealed numerous possible administrative controls and an approach to implementation and analysis. The surveys have shown that worker dosimetry, time-motion studies, and equipment noise profiling are important aspects of effectively utilizing administrative controls. A description of the approach for selecting, implementing, and evaluating administrative controls, and a list of administrative controls, are reported.

Jan 1, 2004

By M. J. Shulman

The exploration geologist is frequently confronted with the problem of allocating his resources, i.e., exploration effort, among various areas. Although geologic, financial and logistic considerations influence the allocations, no objective criterion is usually given which determines the optimal allocation. Maximizing the gain in information, subject to the constraint of a limited exploration budget, is used as the objective criterion to allocate reconnaissance effort. The information function, I(x), quantifies the expected gain in information, where x is the scale of exploration. To calculate the information function the following data are necessary: 1. The probability that an area contains a target must be estimated. 2. For each scale of exploration, four probabilities must be estimated: the probability that an anomaly is produced by the target; the probability that an anomaly is not produced by the target; the probability that an anomaly is produced by a barren area (false signal); and the probability that an anomaly is not produced by a barren area. Alternatively, the barren area can be replaced by other targets. To illustrate the allocation model, the optimal number of line kilometers/line spacing per area is determined for an aeromagnetic survey for iron in Egypt.

Jan 1, 1985

By Marcie A. Greenberg

The Fence Lake Project is located in the Salt Lake coal field, an extension of the San Juan Basin. Geologic formations exposed in the Project area range in age from late Cretaceous to Quaternary. Coal is encountered in the Moreno Hill Formation (upper Cretaceous). Salt River Project (SRP) followed the basic textbook approach for the exploration, regional appraisal, detailed reconnaissance, detailed surface appraisal and three dimensional sampling (physical exploration). SRP is exploring this property as a potential fuel source for the Coronado Generating Station. Therefore, for the physical exploration stage, the quality sampling program was designed from a utility company viewpoint to determine possible impacts to the Station. Exploration drilling was completed in spring, 1982; September, 1982, and summer, 1984. Engineering, environmental, and land acquisition studies were added in the Summer, 1984 Program to more closely evaluate the potential Fence Lake Project coal supply option for the Coronado Generating Station. Studies, including drilling, are ongoing-at this time.

Jan 1, 1984

By Adam Levy, Thomas Novak, Sampurna Arya, Joseph Sottile, Kozo Saito

The use of a woven wire-mesh screen as part of a flooded-bed dust-scrubbing system is very popular in the underground coal mining industry. It is used in combination with a demister (mist eliminator) to remove dust from the dust-laden air. A study was conducted to measure the pressure drop across a flooded-bed wire-mesh screen at different airflow rates in onephase (dry) and two-phase (wet) conditions. Two empirical relationships between pressure drop and air velocity were developed for dry and wet conditions, respectively. In both cases, the form of the empirical relationships was found to be similar to relationships given by Sabri Ergun for high velocity non-Darcy single and multi-phase flow through porous media. The experiments were repeated on a reduced-scale model of the wire-mesh screen, and the pressure-velocity relationships obtained from the full-scale prototype experiments were tested. The test results show validation of the full-scale empirical formulas on the small-scale model with an insignificant variation. This paper presents the empirical equations for pressure drop across the wire-mesh screen in dry and wet conditions. Researchers can use these equations as a tool to predict total pressure drops for wire-mesh screens of different scale sizes.

By C. J. Bise

Safety training requirements differ from mine to mine due to changes in the demographic characteristics of the workers or changes in job and organizational characteristics. Accordingly, a microcomputer-based procedure has been developed to assist mine trainers is determining if undesired worksite performances result from lack of knowledge or skill, which are trainable categories, or from categories that are considered to be non-trainable (such as equipment limitations or management procedures). A special effort was made to understand the psychology of worker behavior by analyzing worker reactions to various organizational and job characteristics.

Jan 1, 1995

By K. Dagdelen

The definition and shortcomings of traditional cutoff grades are discussed. The concept of optimum cutoff grade policy which maximizes the Net Present Value (NPV) of annual cash flows coming from a mining project is introduced within the basic framework outlined by K. F. Lane. Several examples are used to demonstrate the shortfalls of cutoff grade policies obtained by various heuristic optimization techniques. An algorithm to obtain an optimum cutoff grade policy which maximizes the NPV of a project is given and described in detail.

Jan 1, 1993

By J. Girard-Dwyer, T. Camm

Direct costs such as medical, legal, administrative, and worker’s compensation costs, property damage, lost earnings, and lost benefits are typically used to compute the economic impacts of occupational injuries. However, there are also a number of less obvious, indirect costs that substantially contribute to the overall loss costs. In fact, for every $1 of direct costs an estimated $3 to $5 of indirect costs are also incurred. This paper presents a systems approach that incorporates engineering, economics, psychology, and sociology in order to evaluate the total value of investments in safety. By studying the interrelated system comprised of the injured worker, their family and coworkers, as well as the organizational structure that was the setting for the incident, a methodology can be developed that will more accurately capture the true costs of mine injuries.

Jan 1, 2004

By D. R. Taylor

The use of clay granules as carriers for pesticides dates from the early 1940's and by the present day represents a business conservatively estimated at between 200 -300 thousand tons / year in the U.S. alone. Aside from economic and specific target pest efficacy advantages, the use of clay granules as pesticide carriers also delivers a number of environmental benefits which will be reviewed. Topics to be discussed will include: I) drift control (versus liquid sprays), 2) mobility (in the environment), 3) worker safety, and 4) transportation (spill) safety.

Jan 1, 1999

By James R. Jones

The tempo of air pollution control regulations has increased dramatically in the past few years. Because coal mining operations are frequently located in remote areas away from urban developments, specific regulations applying to coal mines have received lower priority and are thus only now being promulgated and/or enforced. Therefore, many mine operators are not yet familiar with the regulations and the impact upon their method of operations. Few have been faced with an inspector on the property sighting them for specific violations. Several of the Mid-western states are just now requiring permit applications to be submitted.

Jan 1, 1973

By N. Arbiter

The theoretical analysis of tumbling mill energetics and performance has largely neglected mill dimensionality, and, in particular, the importance of the length/diameter ratio. This is in spite of the fact that practice varies substantially in this area: geographically, for semi-autogenous and autogenous mills, as between North America and South Africa/Scandinavia; historically, for overflow ball mills, for which the L/D ratio has increased significantly from the earliest small mills to/the largest mills currently. The present study is concerned primarily with the influence of the L/D ratio on the design and operation of overflow ball mills; on the occurrence of the overload phenomenon; and on the limits, if any, it may impose on mill capacities because of critical pulp axial velocity limits. It will be shown that the shape face or is of major importance in this area; and that its adjustment to the extent that this is practical should remove the diameter limitations previously postulated for this mill type.

Jan 1, 1990

By Ehsan Alavi, Glen Frank, Michael DiPonio, Mike Mooney, Lisa Mori

"A study was conducted on the N125 project in Seattle to investigate the use of apparent density as an assessment tool for the effectiveness of soil conditioning. The formation of an air bubble as well as the plugging of cutterhead and excavation chamber can be a result of improper soil conditioning. Both air bubble formation at the top of the excavation chamber and developing plugging issues can be identified by analyzing the apparent densities in the excavation chamber. In this study, apparent densities less than unity were observed in the upper portion of both northbound and southbound TBMs, suggesting the presence of an air bubble. Apparent densities greater than the in-situ soil density were observed in the lower portion of the excavation chamber. Particularly high values of apparent density were coincident with clogging observed at multiple locations along the alignment. The combination of less than unity upper chamber apparent density and very high apparent density in the lower portion of the chamber are related, and indicate the inability of the TBM to effectively condition and mix the soil in the chamber.INTRODUCTIONProper soil conditioning in EPB tunneling offers many advantages to the quality and productivity of the project. There are few operational parameters that can be used to assess the soil conditioning performance such as advance rate, torque, thrust, chamber pressure signature, etc. One of the other parameters that potentially can be used is the apparent density. The apparent density of the material in the chamber was introduced by Guglielmetti et al. (2003) as the vertical chamber pressure gradient calculated from the physical relation between the horizontally measured chamber pressures and the vertical distance between the pressure sensors. Guglielmetti et al. (2003) introduced apparent density as a measure to ensure the excavation chamber is filled with material. To guarantee face stability the authors suggest to keep the apparent density over a certain limit so the material is able to transfer effective stress to the virgin soil, and thus provide support of the excavation face. They implemented this method at the Metro project in Porto, Portugal.Comparing the vertical gradient of the horizontal chamber pressures to the densities of excavation chamber samples, Bezuijen et al. (2005) discovered that the gradient is not necessarily representative of the muck density. They assumed that the yield stress of the muck as well as the adhesion between the muck and the cutterhead and bulkhead material have an influence on the vertical gradient during mining (Bezuijen et al. 2005, Bezuijen & Talmon 2014)."

Jan 1, 2016

By P. A. Schmitz

The characteristics of gold leaching from carbonaceous matter by sodium cyanide, and sorption of gold cyanide to carbonaceous matter in autoclaved and non -autoclaved gold ore from Barrick Goldstrike Mines Inc. (BGMI), Nevada, was investigated. Much greater gold cyanide complex sorption was observed for the carbonaceous matter in high preg-robbing ores relative to the low preg-robbing ores. This observation corroborates previous reports that have attributed observed preg-robbing behavior to the carbon in the ore. Gold cyanide complex sorption was found to be reversible for carbonaceous matter from low preg-robbing ore, but was irreversible for carbonaceous matter from high preg-robbing ores. Autoclaving the ore appeared to enhance the sorptive behavior of the carbonaceous matter from both high and low preg-robbing ores.

Jan 1, 1999

By A. Wahab Khair, Negendra P. Reddy

INTRODUCTION The continuous mining machines which were introduced in the 1950's now account for more than half the production of coal from underground mines. Unfortunately, these continuous miners which were designed for increased productivity have also increased the concentration of respirable dust in mines. Inhalation of this respirable dust by miners causes the Coal Worker's Pneumoconiosis (CWP). Concern for CWP increased in the United States following a 1963-65 survey that showed definite x-ray evidence of CWP in 9.8 percent of working miners and in 18.2 percent of nonworking miners in the Appalachian bituminous coal region (Breslin and Niewiadomski, 1982). One of the major objectives of the Federal Coal Mine Health and Safety Act of 1969 was the prevention of CUP. This law initially limited the daily average exposure of coal miners to 3 mg/m3 of respirable dust. However, following the results of a probabilistic model developed by Jacobsen, et. al. in 1971, the limit was reduced to a mass concentration of 2 mg/m3 unless quartz content exceeds 5 percent, a rare occurrence in mines. Based on x-ray categorization prior to death it is believed that the mass concentration in the respirable fraction is a parameter of primary interest for hygenic evaluation of dust exposure. Elorgan, Burgess and Jacobson (1973) suggested that the quantity of inhaled dust, although influential is not the only aspect of exposure which is significant in producing CWP. Miners working in higher rank coal (anthracite) mines are more susceptible to CWP (Morgan, Burgess and Jacobson, 1973). This also confirms the findings of the British (Bennett, Dick and Kaplan, 1979 and Hurley, et. al., 1979) and Germany (Reisner and Rubock, 1977). Based on the cy to toxicological evidence Reisner and Rubock (1979) suggested that when coal properties are similar, increasing quartz and mineral content increases toxicity. David, Ottery and Le ?oux (1975) examined that as the severity of the CWP increased the retention of the coal dust content in the pulmonary region remained the same, while that of quartz content increased significantly . Leiteritz, Baur and Bruckman (1971) studied the various components of coal dust and showed that coal particles comprised a smaller fraction of the mass of fine dust than did particles , of quartz and minerals. It is ironic that quartz and mineral matter both comprise smaller fractions of the higher rank coal dust (Dodgson, et. al., 1971 and Dwiggins, 1981). Results of a recent research revealed that quartz or any other mineral examined had no strong or consistent effect on the incidence or progress of CWP (Attfield,

Jan 1, 1986

By C. Dirscherl

"Declining ore grade, leading to increased material transport and plant throughput requirements, is one of the major challenges in the current mining environment. This is accompanied by rising energy and labor costs, decreasing plant productivity and the requirement for highest plant availability. Siemens’ answer is the latest gearless drive technology for grinding and conveying. Gearless drive solutions are surpassing the mechanical limits of conventional drive systems serving to utilize the principle of economies of scale. By elimination of various components of the drive train, the maintenance activities and spare parts inventories are reduced. The advantages are culminating in the incomparable availability of the Siemens’ gearless drive technology of 99.46 to 99.71 percent — as confirmed by real operational data from the Antapaccay Mine in Peru. It was the first plant worldwide to use gearless drives for both applications.The gearless principleThe principal idea behind a gearless drive system is to reduce the number of components and diversity of parts, especially those components that are at the edge of current manufacturing or power limits are eliminated. The used equipment provides the possibility to scale up and increase the power transmitted to the driven machine. This finally results in a possible increase of throughput respectively transported or processed material.In order to apply this principle of simplification, the components of a conventional drive system are examined. They consist of:• Driven equipment (mill, conveyor, slurry pump).• Components altering the rated speed (gearboxes, girth gear/pinion).• The electric motor.• Starting devices for the motor (VSD, CCV, LRS, clutch), which are necessary because a direct across-the-line start of high power motors with load would result in a significant drop in the line supply voltage.• Alternatively a variable speed drive (VSD) or cycloconverter (CCV) to utilize the possibility of speed variation during operation.• The electrical supply system (cables, switchgear, transformers, protection equipment)."

Jan 1, 2015

By K. J. Shoop

An analysis of an iron ore processing plant showed that its performance was affected by seasonal temperature variations, resulting in reduced grinding efficiency in the winter months. Laboratory and pilot plant studies were conducted to determine the cause of the observed loss of efficiency at lower temperatures. Experiments were divided into two groups: 1) Drop testing, which was performed to determine the effect of brittleness and frozen pore water on the breakage characteristics of the ore. 2) Wet grinding, which was further divided into laboratory tumble tests and pilot plant scale tests. Laboratory tumble tests were performed to determine the effect of temperature on the grinding of iron ore. This was done by varying the percentage of fines and percentage of metamorphic clay material added to the iron ore grinding charge. The pilot plant scale tests were conducted as a scale-up of the laboratory tumble tests and to determine the effect of temperature on slurry rheology, and how this changing rheology affected the grinding of iron ore. The combined results of drop testing and wet grinding were used to make some predictions of the performance of plant scale autogenous grinding. In drop tests the breakage characteristics of the iron ore had no noticeable change in size stabilities for dry and water saturated samples over the temperature range studied (-25°C to 25°C). The effect of frozen pore water was not observed due to the low apparent porosity of the iron ore. The addition of fines to the test charge caused a decrease in the amount of new fines produced for both the laboratory tumble tests and pilot plant scale tests. The production of fines further decreased when tests were performed at the colder temperature. The increased energy consumption at lower temperatures was dominated by rheology phenomena. The addition of metamorphic clay material to the iron ore test charge resulted in more fines being produced in the laboratory tumble tests. This was due to the metamorphic clay material grinding easier than the iron ore. This caused an increase in the amount of fines in the mill, which in turn, would prematurely slow down the grinding of iron ore because of an increase in the viscosity of the slurry.

Jan 1, 1995