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By Roger Mourich

As the Powder River Basin coal industry has grown, many changes have occurred in the coal market, the economy and the Basin's methods of dealing with competition in the coal mining business. This article notes the mines that have changed to draglines as the major overburden-stripping tool. The Powder River Basin is defined as those mines within a 97 km (60 mile) radius of Gillette, WY. Mines to the north and south of this area - Decker, Spring Creek, Glenrock - have used draglines more extensively. The reasons for the conversions to draglines at each mine, and the specific timing of these changes, were different. However, the driving factor was economics. As coal production increases, strip ratios increase and coal sales prices decrease, mines must find ways to deal with rising costs and falling revenues. The primary method used has been conversion of overburden stripping to dragline operations. Stripping ratio equals the bank cubic yards of overburden removed for every ton of coal mined.

Jan 1, 1994

By Lars Lövgren, Jörgen Jönsson

Heavy metals may be retained within deposits of sulfide minerals under oxidation and in the nearest recipients of drainage water by sorption to secondary iron precipitates. The extent of sorption is strongly influenced by solution pH and presence of complexing ligands, such as sulfate and natural organic acids. Desorption of metals and organidinorganic anions to recent secondary Fe precipitates, collected at the Kristineberg mine, Sweden, has been investigated under different geochemical conditions. Elemental composition and structural characterization (X-ray powder diffraction) indicate presence of schwertmannite. While metals such as Ni and Pb were fractionally desorbed from the precipitates under acidic conditions, oxyanions, e.g. arsenatdarsenite and sulfate were desorbed preferably under alkaline conditions. In a separate study the adsorption of NOM onto synthetic goethite was investigated. NOM adsorption showed a strong pH dependence, 95% was adsorbed at pH 3 and 40 % was adsorbed at pH 9. Addition of 2 mM of sulfate desorbed about 10 % of the adsorbed NOM.

Jan 1, 2000

By James W. Mahar

The following paper summarizes our observations on building response to mine subsidence and techniques for mitigation of building damage. The subsidence cases are located in Illinois. The general description of the geologic and mine conditions are primarily for those sites. Data on building response and mitigation measures were collected under grants supported by the Abandoned Mined Lands Reclamation Council (AMLRC) of Illinois and the U. S. Bureau of Mines, in Twin Cities, Minnesota. Case histories include pit and sag subsidence primarily beneath abandoned room and pillar mines. The majority of the paper deals with structures affected by sag subsidence. Most of the structures are one and two story homes. The first section of the paper summarizes the typical geologic and mining conditions at the sites. Building response to pit and sag subsidence follows the first section. Emphasis is placed on the behavior of concrete and masonry foundations, and wood frame and masonry superstructures. The third section describes mitigation techniques used to prevent or minimize building damage. A summary of the observations and critical parameters is given at the end of the paper.

Jan 1, 1982

By Y. FUJII, E. CHANDA, J. KODAMA, D. FUKUDA, M. NISHIHARA, Y. NAKAYAMA, P. SINKALA

This paper describes a creep damage model that was proposed to clarify the rockburst mechanism for the Mufulira underground copper mine in Zambia. Cumulative rock damage was evaluated for the edge elements of each sidewall of the mining drives based on normal stresses by the 3-D displacement discontinuity method (DDM) (Crouch and Fairhurst, 1973). The rockburst occurrences were well hindcasted.

Jan 1, 2023

By J. W. MacDonald

Two coal mine shafts recently completed in Franklin County, Ill., afford experience and accomplishment to warrant review, These shafts provide access to a tract with a potential recovery of one hundred million tons. This work provided the initial sinking by other than a contractor's organization since 1918. Four additional shafts required during the interim were sunk under contract arrangement with others. Supervisory contact and inspection afforded experience to govern planning and conduct of the recent work.

Jan 1, 1960

By Philip-Mark Spanidis, Christos Roumpos, Francis Pavloudakis

This paper presents a quantitative research (QNR) methodology, collaboratively conducted with a group of mining experts, to assess the knowledge management (KM) landscape in the Greek mining industry. The methodology involves a framework for structured data collection using questionnaires, statistical analysis, discussion on critical methodological aspects, and interpretation of results focusing on key aspects of interest for designers of KM systems. The paper concludes by summarizing the methodology’s outcome and proposing perspectives for further research.

Aug 1, 2024

By T. P. Harrington

Research efforts are just beginning to identify the acoustic signatures of very short pulses of sound associated with the fracture of single particles in an autogenous mill. This presentation will discuss the anticipated correlation between these data and the fundamental mechanisms of rock fracture It is hoped that further tests will help identify what design and operating parameters influence the acoustic spectra, determine whether different minerals have different spectra and correlate product particle size distribution with acoustic spectra.

Jan 1, 1980

By R. E. Greuer

The design of mine fire emergency plans requires that the contamination of mines by fumes, and the mutual interaction of fires and ventilation systems be pre-calculated. Several computer models were developed by the Bureau of Mines for this purpose during the last decade. The models advanced in sophistication from the transient-state simulation of fume concentrations for the early stages of a fire to the steady-state simulation of airflow rates, concentrations, and temperatures for fully developed fires, and finally to the complete transient-state simulation of fires and ventilation systems. The principal features of these models are described.

Jan 1, 1989

By M. Manrique, S. A. Pirzada, P. R. Taylor

A thermal plasma-assisted laminar flow reactor was used to evaluate the kinetics of converting alumina to sodium aluminate in flight. Free energy minimization calculations were used to determine experimental conditions. The experimental variables included alumina particle size, alumina/sodium nitrate molar ratio, temperature and residence time. A mathematical model for the conversion was developed and validated. Experimental and mathematical results are presented.

Jan 1, 1998

By Janusz Cygankiewicz, Marian Branny, Józef Wactawik

The paper presents mathematical model of concealed fire. We consider a porous medium (goaf, coal fissures) through which air flows. The set of equations is constituted by transient, two dimensional mass, momentum and energy balance equations with sources describing oxygen loss and heat generation caused by coal oxidation. Paper presents several examples illustrating the phenomenon of spontaneous heating in goaf areas behind longwall faces.

Jan 1, 1997

By Jiang Shuguang, Zhang Huicheng, Wang Xingshen

Based on the experience about determination of properties of the main fan in mine shaft, this paper relates at length how to reasonablly select test system, test methods and test instruments, how to appraise the reliability of determination results, and how to effectively control the adjusted air etc. The merits and demerits of the two methods of determining air with Nine- Anemometer and Pitot meter are compared.

Jan 1, 1991

By Nick Karlin

Dragados USA is constructing the LA Effluent Outfall Tunnel, a 7-mile, 18 ft internal diameter effluent discharge tunnel, utilizing a 21.6 ft (6.585 m) Herrenknecht Mixshield TBM. This paper highlights the means and methods used for TBM launch from a 55 ft diameter shaft excavated in wet with diaphragm wall support of excavation. This included SEM excavation of jet grout blocks for starter and tail tunnels, temporary concrete structures and steel installations, TBM sealing system, umbilical management for TBM hydraulic, electric and bentonite circuits as well as complex segment delivery logistics. The many launching challenges were overcome thanks to the innovative approaches from the project team.

Jun 13, 2023

By Y. Akin, M. Hancer, M. S. Celik, J. D. Miller

Flotation pulps with boron minerals such as colemanite and borax using primary amine collectors, e.g. dodecylamine, exhibit collector precipitation above a critical pH depending on the amine concentration. This was earlier attributed to the formation of a mine hydroborate. However, results from this current study indicate that the precipitate is dode-cylamine, rather than dodecylamine hydroborate. A systematic study involving solubility, zeta potential, microflotation, adsorption, and surface tension measurements is presented to elucidate the role of a mine precipitates in boron flotation systems.

Jan 1, 2000

By Donald E. Warnken

The Study concerns the estimation of fair market value (FMV) of non-producing mineral rights. Two approaches to value are used and the values determined by each are compared. The Study area environment is unusual. The tectonics is visible on surface rocks throughout much of the study area. The effect on mineral values in the exposed areas has been compared to areas where the tectonics is not visible.

Jan 1, 2005

By K. A. Lewandowski

Heap leaching efficiency is reduced by poor solution flow characteristics (channeling and ponding), which result from compaction and fines migration. Agglomeration of the ore can prevent compaction and immobilize fines, but copper leaching requires an acid-resistant binder to stabilize the agglomerates. Until now, there has not been a satisfactory way to evaluate whether a binder was effective, other than squeezing a handful to see if it ?feels right.? Procedures have been developed to quantitatively determine whether a binder produces agglomerates that can withstand compaction in an acidic solution, and have identified several binders that will provide sufficiently compaction-resistant agglomerates for copper heap leaching. Keywords: Copper heap leaching, Binder performance, Compaction

Jan 1, 2010

By Guillermo V. Borquez

The economics of open pit mine design are dictated by three basic elements: cut-off grade, stripping ratio and slope angle. Although these elements are functions of a number of independent parameters, they are interrelated through their influence on the overall economics. The optimum slope angle is the most uncertain element to determine, because rock mass properties are difficult to obtain. However, for preliminary estimation, the slope angle can be determined from the relationship between the probability of failure and the safety factor. The economics of the slope selected will depend on a profit versus risk judgment. In this paper, the author will present an actual case of application of this postulate.

Jan 1, 1977

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 J. Alvarez, S. Helle, U. Kelm, M. Pincheira

The principal geological and mineralogical characteristics of Chilean porphyry copper deposits are described. Elevated contents of fine grained ore and gangue material may cause copper losses and pose problems or render useless the flotation process. Examples of chalcopyrite and bornite size distributions are given. The state of the art of mineralogical and mineral chemical characterization in Chile is evaluated permitting analyses to lm and nm level by lacking the regular use of direct surface analysis.

Jan 1, 1998

By J. P. H. Steele, M. U. Ozbay

As mining operations progress toward tele-mining and autonomous procedures, the need for machine performance monitoring increases. Presently, through a combination of vision, sound, and other subjective observations, an operator attempts to optimize the mechanical excavator’s operation. As the operator is moved away from the face in the case of tele-mining or completely removed for autonomous operation, the qualitative sensory input is lost. This lost information must be replaced with quantifiable sensory input. Chip formation detection may be a suitable replacement sensory input. Chip formation can be predicted with high confidence (>80%) through the analysis of the load waveform associated with the bit/rock interface.

Jan 1, 2002

By Colin J. Booth

Hydrogeological impacts of active longwall mining were studied at two sites in Illinois. At the site with the more transmissive sandstone aquifer, aquifer permeabilities increased an order of magnitude due to subsidence. Piezometric levels declined with subsidence due to increased porosity, and ahead of mining due to a transmitted drawdown. Levels recovered rapidly at first and fully over two years. At the site with the less transmissive aquifer, impacts were similar except that recovery has been limited. Local aquifer enhancement through increased yield can occur, but only where the aquifer is transmissive enough for recovery.

Jan 1, 1986