Search Documents

By Hamid Maleki

Mine seismicity is influenced by the mechanical properties of both near-seam strata and overburden/underburden and the prudent selection of mining methods and mine layout designs, utilizing sitespecific structural setting of the mines. The importance of adequate data collection, monitoring, and prudent structural designs has long been recognized and utilized in many U.S. operations with adequate engineering resources. In this paper, two case studies of historic seismic events and contributing factors, in deep coal and trona mines with overburden thickness exceeding 1,500 ft, are reviewed using observations and analysis. By back analyzing the overburden response in a historic room-and-pillar coal mine, the overburden collapse mechanism associated with a 3.3 magnitude seismic event is reviewed as well as the need for improvements in designs including panel and barrier pillar widths. Similar high-order seismic events were also experienced in trona mines of the Green River Basin during 1990s, interrupting room-and-pillar mining and creating ground control concerns. Efforts to improve structural mine designs are described in this paper leading to stable and productive operations for decades following the high-order seismic events in both coal and trona case studies. These efforts included improving room-and-pillar extraction layouts and utilizing properly designed longwall mining techniques that were verified using long-term geotechnical instrumentation. The study mines are located on the Wasatch Plateau (WP), Utah and in the Green River Basin (GRB), Wyoming. More recently, in Utah’s East Mountain alone, Energy West Mining Company (EWMC) has extracted some 165 million tons of coal without any significant incidents. Overall, favorable geologic conditions and prudent mine layout designs are key elements to this successful experience in both single- and two-seam layouts. Utilization of conservatively designed longwall mining technique in the GRB has been geotechnically stable, using reported experience in 15 panels and monitoring results in the Northwest (NW) District with measurable longwallinduced seismicity being rare. These studies demonstrate a considerable amount of progress that has been made within the last four decades in the application of longwall mining technique, integrated monitoring, and analyses for the verification of structural designs in mines in the United States.

Jul 1, 2023

By M. Jaramillo

The expanded west pit of the 15 Mta (13.6 stpy) El Cerrejon mine will eventually reach a maximum depth of 270 m (890 ft). Slope-stability evaluations indicated that this depth, combined with structural complexities, would create a serious risk of footwall instability. Stabilization calls for anchoring the footwall by the installation of 9- to 33-m- (30- to 108 ft-) long multistrand steel cable bolts. For each of the 15-m- (50-ft-) high mining benches, a row of bolts is installed with variable horizontal spacing, depending on the dip magnitude. Cable bolting is now standard operating practice, and an estimated 11,800 bolts will be installed during the life of the mine. Results to date have been satisfactory in terms of the stability condition of the bolted slopes.

Jan 1, 1997

By Rob Dorey

The disposal of mine waste continues to be one of the main controlling factors in the economics and feasibility of project development. Particular to gold and precious metal mining, waste disposal is further complicated by the environmental and political implications of the use of cyanide. Regulatory compliance criteria have partially dictated and can be anticipated to further dictate the approach and methods of tailings disposal. To develop practical, economic, and environmentally acceptable tailings disposal systems within these criteria requires the use of common sense approaches and the application of available technology. Waste disposal is typically considered during the pre-feasibility stages of project evaluation. At this time, the main emphasis is on the economics and practicality of extracting the metal values from the ore. Frequently, the result of this is that the nature of the tailings and the ability to dispose of the tailings is prejudged. It is also frequently the case, however, that during the feasibility stage and project permitting, the requirements for tailings disposal become paramount.

Jan 1, 1998

By K. N. Han

The adsorption of gold onto activated carbon in iodide solutions was studied. The adsorption rates were determined as a function of temperature, salt concentration and pH, as well as activated carbon concentration. A kinetic model was developed for the adsorption. The adsorption rate was believed to be controlled by a combined mechanism of film diffusion and pore diffusion with the film diffusion having the most significant effect. Experimental findings were in good agreement with the model developed. The apparent activation energy was found to be 14.9 kJ/mol.

Jan 1, 1995

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 B. K. Baird, P. C. Satchwell

The application of cutoffs during and after pit optimization is examined for a lower-grade multi-metallic copper deposit. Pit optimization requires calculation of the net revenue associated with each mining block, incorporating parameters such as metal prices, grades and expected recoveries, mining and processing costs, smelting and refining charges, and penalty element and royalty charges. Sensitivity analysis during pit optimization reveals which of these parameters have a significant effect on the total contained resource tonnage and total contained non-discounted revenue in the optimized pit. The cumulative effect of changing several of the more significant parameters is investigated. Application of a copper cutoff grade to a block inside the optimized pit could result in the less than optimal extraction of the resource. A block with copper grade below the applied cutoff could be economic due to the presence of other metals. Conversely, a higher copper grade block may be sub-economic. The relative merits of applying a copper grade cutoff, “equivalent grade” cutoff and dollar value per ton cutoff to blocks inside the optimum pit are discussed.

Jan 1, 1999

By D. C. Moore

The decision to proceed on a "fast track" construction project is not" without risks as well as rewards. An understanding of some of the risks prior to start of the project will maximize the rewards. This paper describes the research, development, procurement, engineering and construction of the Asamera Minerals cannon Mine concentrator. This fast track project was accomplished in 20 months. Special attention is paid to the risks encountered and the steps taken to ameliorate them.

Jan 1, 1988

By D. W. Ashman

Today the electrolytic zinc industry is facing unprecedented environmental pressure and low metal prices. Zinc plants have to decide how they will dispose of iron residues in an environmentally friendly way without major capital expenditures. Only low-cost producers will survive, so companies must continuously improve to stay competitive. Therefore, the challenge of the process engineer is to find innovative solutions to the industry's problems. This paper reviews the status of electrolytic zinc processing and provides some insight into how the industry will respond to the pressures facing it

Jan 1, 1993

By Gerald H. Luttrell, Jaisen N. Kohmuench, Michael J. Mankosa

A new separator, known as the Hydrofloat cell, has been developed to overcome limitations of traditional flotation cells in recovering coarse particles. In this process, small air bubbles are introduced into a hindered "teeter" bed of fluidized solids to create light bubble-particle aggregates that can be separated based on differences in density. Laboratory tests conducted with coarse phosphate feeds indicate that the Hydrofloat cell is capable of increasing BPL recoveries by nearly 20% over conventional flotation methods. Based on these encouraging results, a pilot-scale Hydrofloat cell was fabricated and installed at a central Florida phosphate plant. Test data collected using the pilot-scale unit suggest that the BPL recovery of the plus 35 mesh plant feed can be increased by more than 40% through the application of this new technology. This improvement is particularly beneficial due to the very high grade (-73% BPL) of the plus 16 mesh particles in the Hydrofloat concentrate. This article describes the theoretical basis for the development of the Hydrofloat cell and provides an overview of recent laboratory and pilot-scale test results.

Jan 1, 1999

By X. Wu, M. Karfakis, E. Topuz

The generalized ventilation network problems encompassing both natural and controlled splitting networks, is formulated using a nonlinear nonconvex programming model, which has not yet been solved satisfactorily. This paper presents a methodology which can deal with the problem. The proposed methodology converts the nonlinear problem into a linear problem, by using special ordered sets of variables, and optimizes it by a modified branch and bound technique. The global optimality of the methodology and its applicability to different cases are investigated

Jan 1, 1991

By R. L. Grayson, M. P. Miano, S. Yuan

Matching the productivity gains of continuous mining machines with the increasing performance levels achieved by longwall units has required creative thinking to assure that development is completed in time for uninterrupted longwall production. By using management information systems to coordinate support operations, the most productive planning decisions can be made. This paper focuses on the role of computer technology tools in achieving improved productivity from both longwall and continuous miner sections. The primary emphasis is on the planning process and the methodology developed to guarantee the best allocation of management and manpower resources.

Jan 1, 1995

By Don Opacic

The disposal of sludges and other similar industrial wastes is a major problem. Liquid wastes from industrial operations, when treated, produce significant volumes of sludge which are difficult to dispose of, because of the chemical and physical properties of the sludge. In the mining industry sludge is produced from various water treatment operations, in particular mine drainage neutralization. Waste water from coal preparation plants also produces a sludge however the sludge is in fact a slurry containing clays, coal fines and coal impurities. In many areas the disposal of these sludges is producing a serious problem. Mine drainage sludge consists of a variety of hydrous iron oxides, usually ferric oxides, contaminated with other neutralization products such as calcium sulfate. The volume of sludge from mine water or mine

Jan 1, 1973

By C. Bazin, D. Hodouin

Dynamic experiments were performed in a continuous open-circuit 40x40-cm ball mill using a pseudo-random binary sequence of the feed rate and measuring the variations of the discharge particle-size distribution. The impulse response is calculated by a cross-correlation technique. Then a model involving a discrete transferfunction and a time-series stochastic equation is calibrated using maximum likelihood methods. Based on this empirical model, a minimum variance controller with constrained input is designed and its performances are compared, by simulation, to the performances of a conventional PID regulator.

Jan 1, 1987

Jurist, educator and historian Neil Reynolds will be the keynote speaker at the National Mining Hall of Fame's 11th annual induction banquet on Sunday, Oct. 11,1998 at the Pointe Hilton Resort in Phoenix, AZ. Reynolds is Municipal Court Judge for the City of Leadville, CO, home of the National Mining Hall of Fame & Museum, and a fifth-generation resident of the community. His family staked mining claims on nearby Mount Massive in 1862. Judge Reynolds is a fulltime faculty member at Colorado Mountain College, Chairman of the Lake County Historic Preservation Advisory Board and practices law in Leadville. In announcing the speaker, Board Chairman Richard Moolick said seven inductees into the National Mining Hall of Fame will join 138 mining greats previously honored in the annual ceremonies. This year's inductees will be enshrined by Thomas Falkie, president and chief executive officer of Berwind Natural Resources of Philadelphia, PA. Moolick also announced that Jeffrey Clevenger will be the master of ceremonies for the induction banquet. Clevenger is executive vice president of Cyprus Amax Minerals, Englewood, CO and president of Cyprus Climax Metals, Tempe, AZ. A cocktail reception at 6:30 p.m. will precede the black-tie (optional) dinner, to begin at 7:30 p.m. For additional information, contact Esther Mellott at 719 486 1229. Here are the biographies, then, of this year's seven inductees to the National Mining Hall of Fame & Museum.

Jan 1, 1998

By Robert H. Marshall

The application of simulation to production planning at a large, complex open-pit mining operation proved to be challenging and enlightening. The mine is divided into two separate pits and several dump areas which are served by the same truck fleet. The operating system consisted of shovels of two different sizes, wheel loaders, and a fleet of three different truck types moving material from seven source locations to ten dumping sites. The interconnecting haulroad network included many common segments. There were operating constraints unique to the system, such as: traffic rules; manpower limitations; shovel, material-type, and destination priorities and production limitations; and a unique, non-centralized dispatching method for truck distribution. The truck distribution was further constrained by the matching of trucks to shovels, loaders, and destinations by truck type. The gathering and transformation of input data as well as the evaluation of results and validation of the model were also challenging. Despite a high level of sophistication in production reporting, some input data were neither readily available nor backed by field observation. As a result, many innovative techniques had to be used to develop realistic input data and to validate the simulation results. Nevertheless, this case study definitely proved the feasibility of applying computer simulation techniques to short and long range mine planning and budgeting at a large, complex mining operation.

Jan 1, 1982

In conjunction with steady increases in production levels, long-wall operators have applied greater quantities of ventilating air to control respirable dust and methane gas. As a result, air velocities greater than 7.6 m/s (1500 fpm) have been measured on longwall faces. Operators have expressed concern over the potential entrainment of respirable dust at these high-velocities, especially during shield advance as dust falls from the shield canopy directly into theair stream. Laboratory tests to simulate dust liberation by shield movement were conducted at the Pittsburgh Research Laboratory of NIOSH in a wind tunnel designed to study dust entrainment in high-velocity airstreams. Dust was introduced into the tunnel to determine dust concentration as it relates to entrainment, dilution, air velocity, and particle adhesion. Airborne dust samples were obtained by iso-kinetic sampling using BGI cyclones to quantify respirable dust concentration at the various air velocities. Laboratory tests were con-ducted at velocities ranging from 2.0 to 10.1 m/s (400 to 2000 fpm),and significant differences in airborne respirable dust levels were measured. This research is being conducted to provide fundamental information on the entrainment characteristics of respirable dust at high air velocities, which will subsequently lead to solutions for shield dust control. A discussion of the test procedures and results are presented.

Jan 1, 2004

By Mark S. Stagg, Michael J. Nutting, Douglas R. Barlet

Single-row bench blasts at a reduced scale in the field were used to study the effects of delay time on fragmentation. Nine shots with a spacing of 21 in. and a burden of 15 in. (S/B = 1.4) and nine shots with a spacing of 30 in. and a burden of 15 in. (S/B = 2.0) were completely screened to determine particle size distributions. Delay intervals between holes ranged from 0 to 45 msec, corresponding to effective delay intervals ranging from 0 to 36 msec per foot of burden. Each shot was instrumented with strain and pressure gages to measure in situ blast dynamics and to evaluate interactions between blastholes. Finer overall fragmentation was produced for shots with delay intervals between 1 and 17 msec per foot of burden. Only for shots within this optimum delay range was it observed that the strains induced by stress waves constructively interacted with strains induced by gas pres- sure from an earlier detonated hole. Coarsest fragmentation resulted at delay intervals less than 1 msec/ft, where stress waves from each hole were observed to interact destructively, and at delay intervals greater than 24 msec/ft, where no inter- action between holes was observed, indicating a condition that can be considered as the firing of single hole shots independently.

Jan 1, 1986

By José A. Matar Ibañez

Geologic terranes in Argentina include potential mineralized environments from localized younger Precambrian cratonic outcrops through Paleozoic sequences, generally in the northwest or under younger cover, to the Mes[o] zoic-Cenozoic Andean Systems in western and southern Argentina. Argentina is self sufficient or nearly so in many metallic, nonmetallic, and energy commodities, and exploration in each of these categories is ongoing. Present production of precious metals (silver and gold) is important, and many recent discoveries of base metals, precious metals, alloy metals, and other mineral categories have been made. Economic trends, geologic environments, and commodity types important in actual exploration are described, and it is emphasized that extensive areas showing attractive alteration, geochemical, and geological anomalies, especially of porphyry, cordilleran vein, and epithermal characteristics, remain to be fully evaluated.

Jan 1, 1986

By Robert A. Jankowski, Jonathan Kelly, Edward F. Divers

Results for the first underground test of the ventilated drum in a U.S. coal mine are presented. Tests were conducted by the Bureau of Mines through a contract research program with Foster-Miller, Inc., to evaluate dust control effectiveness in a western mine and for gas control in a full scale laboratory facility. The ventilated drum is designed to reduce the amount of dust from cutting by drawing dust-laden air from the cutting zone through twelve water- powered "dust capture" tubes built into the shell of the shearer drum. High pressure water up to 1 12.48 kg per cm2 (1,600 psig), released from sprays, induces maximum airflow of 1.89 m3/sec (4,000 cfm) from the face side of the drum and provides cleaning for respirable dust and improved methane dispersion. At the gob side of the drum a deflector plate, attached to the cowl arm, turns the water spray and a proportion of the cleaned air back into the cutting zone. More than 50 ventilated drums have been installed to date in England, and their tests carried out on fixed height and single-ended ranging drum shearers have shown reductions in respirable dust of 60-80 pct, as compared with conventional wet cutting. The U.S. test on a double drum shearer showed slightly lower reduction.

Jan 1, 1987

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

Flotation tests were carried out on six coal samples of different rank as well as their oxidized samples. A mixture of diesel oil and alcohols was used in these tests. Surface oxidation caused a distinct decrease during flotation recovery with some improvement in the grade. The reduction in the recovery increased with increasing concentration of the oxidizing agent. The floatability of low rank coals was affected by oxidation to a higher degree than the floatability of medium and high rank coals. The recovery-size curves of oxidized samples were similar in shape to the recovery-size curves of non-oxidized coals.

Jan 1, 1991