Search Documents

By Peter J. Conroy

Introduction Most subsidence monitoring to date has been surface monitoring to develop empirical relationships of the magnitude and extent of subsidence effects. Federal regulations are forcing a better understanding of subsidence. Empirical methods of subsidence prediction may not be adequate, since the empirical relationships may not be valid between or even within coal fields. A better understanding of the mechanics of subsidence is required in order to develop and verify analytical models. This paper presents some of the results of surface and underground monitoring in longwall faces of a coal mine. The seam thickness in these mines ranges from 5 feet to 6 feet at depths of 600 to 1100 feet.

Jan 1, 1982

By Gerald H. Luttrell, Rick Q. Honaker

A coal preparation plant incorporates a variety of solid-solid separation processes that operate in relatively independent parallel circuits. Studies have shown that total plant performance can be optimized by selecting circuit cutpoints that maximize total clean coal yield irrespective of the performance of individual circuits. Although the optimum cutpoints can be determined using simulation programs, these mathematical routines require detailed washability data and empirical partition information that is not often available to plant operators. In addition, routine fluctuations in the washability characteristics of the plant feed make this approach impractical to implement in industrial facilities. As an alternative, practical optimization criteria can be developed for plant operators through a fundamental understanding of scientific principles involved in coal cleaning operations. This article provides an overview of the most important optimization criteria and presents several industrial case studies that illustrate the financial benefits of this practical approach m plant optimization.

Jan 1, 2005

Iron ores may be upgraded by flotation of iron oxides or siliceous gangue using either cationic or anionic collectors. The electrostatic mechanism of adsorption can account for the complex chemistry involved. In industrial practice, only cationic silica flotation is used at present in North America. Some of the seemingly paradoxical phenomena of cationic silica flotation behaviors in meeting the demand for low silica concentrates are reviewed.

Jan 1, 1989

By Betty L. Gibbs

Computer software for mining applications has been in development since before 1970. These packages cover tasks from exploration data management through final reclamation planning. These programs were originally written in Fortran and have evolved into colorful, user-friendly packages. Programs that produced printed symbol maps now show color, three-dimensional image of an ore deposit on a computer screen. Pictures can be rotated and looked at it from all directions and layers can be peeled off to show other parts of a model. Computer users have also evolved. In the early Fortran days, users had to learn computer operating systems, have someone punch data cards, set up run files and wait a day or so to find out if there was one little mistake somewhere that caused the program not to run. With today's technology, users sit at their desks in the office, key in some data, read other data from digital files and build a model within days, rather than weeks or months.

Jan 1, 1999

By James R. Piper

Cumulophyric feldspars, of varying morphology, carry myrmekitic quartz interstitially between microperthitic feldspar lamellae. The size, coarseness, and morphology of these crystals, together with concordant foliation features constitutes evidence that they are a product of primary crystallization, formed prior to eruption from a vent. These crystals occur preferentially along 2 - 5 mm thick tan, vesicular to compressed alteration bands intercalated with more densely welded light grey bands. In perlite with quartz at or below a 0.1% threshold, megascopic feldspars are less than 1%. Perlite with quartz above this level has megascopic feldspar concentrations >3%, typically in the 5-20% range.

Jan 1, 1991

By Robert A. Jankowski, Charles Babbit, Natesa I. Jayaraman

The Bureau of Mines, together with Foster Miller Inc., has developed a compact, high pressure scrubber system for continuous miners. Powered by water energy alone, it can move up to 1.4 m3/s (3,000 cfm) of air and scrub a significant amount of the dust in the air. Full- scale model and underground trials showed excellent performance. Operated at 8.3 x 10[3] kPa (1,200 psi) and 38 L/m (10 gpm), the scrubber has reduced operator and return dust concentrations by more than 50 pct. This paper describes the full-scale model development, system fabrication and underground evaluations of this novel and inexpensive scrubber.

Jan 1, 1989

By Ron L. Schmiermund

The Ferris-Haggarty underground mine was abandoned circa 1910, and portal discharge has since resulted in degradation of a trout fishery in the receiving waters of Haggarty Creek. Although tunnel discharge varies dramatically in volume throughout the year due to infiltration of snowmelt, compositionally it is a nearly constant low-TDS, pH-neutral, low-sulfate, copper-silicate dominated water. Between infiltration events, components of ARD accumulate in unsaturated, oxygenated environments within upper workings and are delivered to the main haulage level by the subsequent annual snowmelt flush. Mixing with non-ARD mine waters results in neutralization, dilution, and precipitation of amorphous copper carbonate and silicate phases. These mechanisms, combined with variations in the water balance, control the composition of the portal discharge. Understanding the chemical and hydrologic control mechanisms was critical to the design of a passive treatment system to decrease effluent copper concentrations.

Jan 1, 2000

By Hans Skretting, Abraham A. Dor

This paper briefly reviews the historical development of the Rotary Kiln-Electric Furnace Process, which was first applied commercially to the treatment of qarnieritic ores in New Caledonia in the mid-fifties. It describes various technological improvements introduced, since, in industrial plants or developed in pilot facilities where a wide variety of nickel oxide ores has been treated success- fully over the years. Major categories of ores are characterized. The effect of their physical and chemical properties on their performance in the electric furnace is discussed. The relationships between ore composition, ferronickel grade and slag composition are analyzed and their effect on slag and metal tapping temperatures, nickel recovery, and electrode voltage are discussed.

Jan 1, 1979

By Jeff Hussey

Since 1955, Gaspe Mines has produced 150 Mt (165 million st) of ore averaging 0.9% copper. The ore was mined from two open pits and from underground workings. In 1994, four exploration drill holes discovered a buried porphyry/skarn copper-molybdenum (Cu-Mo) deposit at depths of between 1,000 and 1,700 m (3,280 and 5,580 ft) below the top of Porphyry Mountain. The mineralization and alteration associated with the Porphyry Mountain quartz monzonite does not outcrop. Prior to 1997, about 19,500 m (64,000 ft) of drilling in 12 drill holes had outlined 200 Mt (220 million st) grading 0.73% Cu and 0.08% Mo. Mineralization occurs as veins and disseminations of chalcopyrite and molybdenite.

Jan 1, 1998

By J. D. Miller, J. Hupka

Environmental applications of the air-sparged hydrocyclone (ASH) technology are presented. The original ASH design used porous sintered steel or porous polyethylene tubes as spargers. To diminish/prevent plugging and to reduce pressure head loss in the gas path a wire screen sparger and new hydrocyclone design have been developed, which allows for wide application of the technology to solve environmental problems and to be used as a chemical reactor. Field and laboratory trials have shown that the ASH technology might be preferred for the stripping of volatile organic compounds WOC) from contaminated water. The ASH has also been developed for absorption of SO2, toluene vapors, and for the recovery of cyanide.

Jan 1, 2005

By D. A. Day, H. L. Marsh, P. J. Stephens, C. A. Wiggins

Lightweight cellular grout backfill behind pipe-in-tunnel has been gaining increased acceptance in the tunneling industry and has proved to be both practical and economical. Two successfully constructed projects, the Upper Scioto West Interceptor Sewer (USWIS), in Columbus, Ohio and the Benbrook Pipeline Tunnel Project in Fort Worth, Texas will be discussed. The projects represent two different but successful applications of lightweight cellular grout backfill. The USWIS placed the grout behind precast reinforced concrete pipe, in water bearing limestone, and in close proximity to residential water wells. The Benbrook Project placed grout behind 6,096 meters (20,000 feet) of steel pipe from just two locations, eliminating major surface disruption typically associated with the placement of pumped concrete.

Jan 1, 1999

By Arthur J. Borst, Joseph P. Gildner

In a recent National survey, Seattle topped the list for having the worst daily traffic congestion. To address this problem, Sound Transit is planning to build 40km (24 miles) of light rail, including ten kilometers (six miles) of twin tunnels with four subway stations 40 m (130 ft.) to 65 m (210 ft.) deep. The overall schedule is very aggressive and Sound Transit is preparing four separate heavy civil construction contracts for simultaneous underground construction. Three of these contracts are being considered for design-build. Final design will start in March2000 and all underground construction must be completed by the end of 2005.

Jan 1, 1999

By D. X. Tang, G. Wilson, Y. Luo, S. S. Peng

Knowing the location of voids/fractures in roof rock will be greatly helpful for roof support design. The drilling parameters obtained during normal roof bolt installation cycle provide a fast and economic way for determining void location in roof rock. In this research, feed pressure and rotation torque are found to be good indicators for identifying the voids, based on the results of a series of laboratory experiments. A set of computational rules has been developed to locate voids in mine roof using the measured roof drilling parameters and implemented in MRGIS, a software package developed to allow mine engineers to make use of the large amount of roof drilling parameters for predicting roof geology properties automatically. Anew feature, 2D map+3D figure display, is also added to MRGIS.

Jan 1, 2004

By Thomas R. Yanske, Jonathan E. Carmack, Lyndon M. Clark

In order to maximize the extraction of high grade pillars at The Doe Run Company, artificial pillars are created using cemented rock fill (CRF). CRF pillars aid extraction of pillars in two ways. One is to offer back support for the immediate area where pillars are being extracted. The second is to increase the post failure residual strength of pillars surrounded by backfill. The CRF is produced using a combination of minus 1.0 m run of mine (ROM) rock and minus 5 cm crushed rock. Depending on the operation the CRF slurry is either produced in an underground or a surface batch plant. The slurry and rock are transported to the fill area by truck where they are mixed and placed in 1 m lifts. To reduce the amount of CRF needed, fill fences are constructed around the perimeter of the CRF pillar. Within these fences ROM CRF is placed in lifts until within 0.6 m of the back after which minus five centimeter CRF is slung tight to the back utilizing slinger trucks. In constructing these artificial pillars a number of set procedures have been established to ensure that the work is done both properly and safely.

Jan 1, 2001

By R. P. King

Direct observations of intergranular fracture during comminution are very difficult to make. The best indirect method is based on the measurement of interphase area before and after comminution. If intergranular fracture does not occur, the interphase area should be conserved during comminution, but it should decrease if significant amounts of intergranular fracture occur. The interphase area per unit volume can be determined by image analysis from measurements on sections of the unbroken ore and on sections through the particles after comminution. However, the measurements must be corrected for the effects of image resolution on the measured phase and particle perimeters. A correction procedure was developed, and the true interphase perimeter per unit volume was measured before and after comminution in a sample of chromite-serpentinite ore and two samples of Witwatersrand pyritic quartzite. The pyritic quartzite showed no significant evidence of grain- boundary fracture while the chromite-serpentinite showed a significant decrease in interphase area per unit volume of chromite, indicating that intergranular fracture occurred.

Jan 1, 1992

By Angela Binder, Oliver Langefeld

"The future of mining will be characterized not only by the application of modern technology, but also by the harmonization of economic, environmental and social issues. These areas set major future challenges which are complex and demand extensive knowledge. As an example, mining of highly complex orebodies for the supply of often critical raw materials, needs to consider technically demanding and cost-intensive extraction issues. The amount of tailings, which need to be stored, increases with the amount of ore mined. Therefore, the negative impact on environment and society increases. Hence mining becomes expensive with regard to all three aspects: economy, environment and society. In view of a sustainable mining practice this challenge should be used as an opportunity. The positive impact should be maximized for present and future generations. The objective is to create and use the mining openings in an optimum way related to sustainability. The approach of Blue Mining, which focuses on energy and ergonomics in the field of Sustainable Development, enhances the closure planning by recommending subsequent usage of such openings for energy storage. The approach fosters among others the implementation of the 7th Goal for Sustainable Development defined by the United Nations with the assurance of access to affordable, reliable, sustainable and modern energy for all. The usage of underground storage increases the stability of solar and water power usage, which are otherwise unreliable. Blue Mining embeds these issues in the main planning effort long before groundbreaking. This approach involves experience from past and current projects. This paper introduces the concept of Blue Mining with respect to post-mining utilization of a mine for energy storage. Methods and perspectives are presented with examples covering best-practices and lessons-learned."

Jan 1, 2017

By Michael J. Shulman

The DEAREX knowledge acquisition and engineering system is a teaching and exploration tool designed to facilitate the under- standing and development of expert systems by explorationists without the aid of a knowledge engineer and without recourse to expert system languages. To fulfill its objective, the DEAREX system considers the selection of exploration methods in desert areas. The system consists of three parts: 1. A tutorial which introduces the basic and selected advanced concepts of expert systems, 2. A sample program illustrating how an expert system works and can be used, and, most importantly, 3. A knowledge acqusition and engineering program which enables users to develop their own expert systems. The tutorial provides a brief and concise introduction to expert systems, a 10 rule exploration example which defines, explains and illustrates the basic concepts and design of expert systems, and a glossary of expert system terms including cross references. The sample program is a larger, self contained example of an expert system with some commentary illustrating addition- al expert system concepts and the role of the knowledge engineer in particularizing rules and ascertaining the knowledge base. Restricting itself to the selection of exploration methods in desert areas, the knowledge acquisition and engineering program questions the user and converts the answers into an expert system. Questions pertain to geology, infrastructure, availability of instrumentation, personnel, etc. Additional information may also included. In conclusion, some salient points concerning knowledge engineering toolkits, shells and knowledge acquisition capabilities such as contained in DEAREX are discussed.

Jan 1, 1992

By B. J. Arnold, B. W. Parker

Rosebud Mining Company added a classifying cyclone/spiral concentrator circuit addition to its McVille Preparation Plant, Freeport, PA, in mid-2002. This paper will describe the plant addition, which was implemented fully by plant staff, and review improvements in cleaning plant performance and economics.

Jan 1, 2003

By Andrzej Wala

Constantly increasing demand for energy materials and metal ores brought about tremendous progress in mining techniques which are characterised by a high degree of mechanization and concentration of works. One of the recent trends in underground mining mechanization is connected with an application of heavy machines with diesel engines [l],[2]. The introduction of diesel engines in mining all over world caused not only improvement in economic conditions but also the necessity to prevent contamination of air in the mine by toxic agents in diesel exhaust emissions. A generally used way of eliminating exhaust gases is proper ventilation of the cross cut by means of providing permanent exchange of air that would guarantee in every point of the cross cut and in every moment the decay in concentration of exhaust gases beyond threshold limit [3][4][5][6][7][8][9][10]. The present paper is an attempt to define a mathematical model describing the changes of concentration in cross cut face to which fresh air is distributed by ventilators and tubes in a forcing way. Obtained model should offer its practical adaptability to engineering calculation of the amount of fresh air needed for diluting and eliminating exhaust gases beyond threshold limit. Justness of these models has been confirmed by investigation of the growth of nitrogen dioxide concentration in air environment in some cross cut faces of Kiirunavaara iron ore mine in Kiruna (Sweden).

Jan 1, 1980

By M. T. Holroyd

Digital computer applications to minerals exploration remained largely an experimental alternative to manual techniques until well into the 1960's. Due to the high cost of computer time, and the lack of digital data and appropriate software, the most favoured applications in the early days were computationally intense tasks - those which produced the most results with the least demands for programing and data input, e.g. forward modeling. When large digitisers and plotters became affordable, the computer took over simple labour intensive tasks such as data transcription, and when software caught up, more complex tasks such as contouring. Digital data acquisition systems and superminicomputers made total computerisation of geophysical compilation and cartography possible and affordable. Applications continued to develop into areas of much greater logical complexity. Software, the new labour intensive process, still lagged behind. The microcomputer made computer applications potentially available everywhere to everyone. Desk-top micros as powerful as the minis of ten years ago can take on any geophysical exploration task currently done by computer - when the software becomes available.

Jan 1, 1989