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By Gordon T. Clark, Stephen H. Gleaton

This paper discusses the conceptual design of cut-and-cover tunnels currently being considered as one of the replacement options for the earthquake damaged, elevated double-deck highway and seawall built in downtown Seattle 50 years ago. The 4.8 km (3 mile) long, 6-lane improvement consists of 1.6 km (1 mile) of at-grade roadway with aerial interchanges, 1.6 km (1 mile) of large two-level cut-and-cover tunnels along the Elliott Bay waterfront, and retrofit of the 50-year old, 1.6 km (1 mile)long Battery Street tunnel and north transition to grade. Construction of deep cut-and-cover tunnels, in complex glacial geology overlain by hydraulically placed fill immediately adjacent the existing sea wall, will require extensive use of concrete diaphragm walls, ground improvement and dewatering. The potential liquefaction and lateral spreading of the fill materials in this active seismic region pose significant design challenges and risk.

Jan 1, 2003

By J. P. Rider

The number of extended cut mining systems has increased significantly in coal mines over the last decade, and there is a constant push to extend the face ventilation systems to even greater setback distances. The need to maintain airflow at setback distances of12.2 m (40 ft) and beyond requires that methods for delivering intake air to the face be improved, or alternative ventilation techniques be implemented. The emphasis of this research effort was to examine various techniques to improve the distribution of available air at the mining face in order to reduce face methane levels. A study was conducted comparing the performance of a jet fan, used in conjunction with a machine mounted scrubber, with blowing curtain ventilation in a 27.5 m (90 ft) heading. In addition, a second study was performed on blowing curtain systems examining how scrubber flow, intake air velocity, and curtain setback influence face methane concentrations. Results showed that when the heading advances to a depth of 27.5 m (90 ft) blowing curtain systems were more efficient at diluting face methane levels when compared to a jet fan. Also, increases in scrubber flows and curtain velocity resulted in lower face methane concentrations for blowing curtain systems at 9.2 and 15.2 m (30 and 50 ft) setbacks.

Jan 1, 1997

By E. Fidler

A recent headline in the Wall Street Journal declared, "trendy management schemes very often fail." Many of the management techniques addressed in the accompanying article are associated with quality management including reengineering, benchmarking, total quality management, and employee empowerment. The article made the point that executives, employees, and customers who are involved in such programs rate the effectiveness of these programs very low, and the programs often fail. Yet, we all know of companies that have made significant advances in their operations using these same quality management practices. Why do a few succeed while many fail? History has shown that the companies that successfully carry out quality management programs have two things in common: 1) Strong leadership committed to the success of the program. 2) A comprehensive plan for carrying out and maintaining the program. Stated another way -the reason many companies fail is the lack of committed leaders and inadequate planning. It is ironic that the title of the Wall Street Journal article is "The Best Laid Plans."

Jan 1, 1994

By Isabel F. Barton, MarkD. Barton, Christian A. Rathkopf

Molybdenite is the world’s principal source of rhenium (Re), a critical element in multiple high-tech applications. However, the Re contents in molybdenite vary by orders of magnitude on scales ranging from single grains to whole deposits. In order to better understand the systematics of this variation and what geochemical factors control molybdenite Re concentration, and hence overall Re resources, we examine global patterns in molybdenite Re contents through a compilation of > 3000 measurements of Re in molybdenite from > 700 mainly ore-bearing moderate- to high-temperature hydrothermal systems of different types. Our results are similar to but expand on those of earlier studies. Rhenium concentration in molybdenite has a lognormal distribution and varies systematically with type of geologic system, intrusive lithology, and Mo grade. The lowest-Re molybdenite occurs in greisens (geometric mean 1 ppm ± a multiplicative standard deviation of 9), quartz vein-hosted W-Sn deposits (2 ± 5 ppm), unmineralized granites and granodiorites (12 ± 8 ppm), intrusion-related deposits (24 ± 8 ppm), and porphyry W-Sn deposits (16 ± 11 ppm). Rhenium is most enriched in molybdenites from volcanic sublimates (23,800 ± 5 ppm), with skarn Fe and Au (560 ± 5 ppm and 540 ± 3 ppm respectively) and porphyry Cu and Cu-Au deposits next (470 ± 4 and 430 ± 7 ppm respectively). Among porphyries, skarns, and quartz vein-hosted deposits, Re is most highly concentrated in molybdenites from Cu and Au systems and its concentration decreases systematically through Cu-Mo, Mo, Sn, and W deposits. In nearly all cases, molybdenites from systems associated with intermediate igneous rocks contain more Re than molybdenites from systems of the same type with more felsic rock associations. The disparity between Re contents of molybdenite in felsic and intermediate systems is largest for porphyries, quartz vein-hosted, and skarn deposits and is near zero for subeconomic or barren granite and granodiorite Mo systems; felsic intrusion-related deposits have slightly higher molybdenite Re than their equivalents associated with intermediate intrusions. In most systems, molybdenite Re content does not correlate with metal grade, but may have an inverse correlation with Au grade in intrusion-related deposits (based on a small number of data points) and does exhibit a strong inverse correlation with deposit Mo grade. Dilution of Re through larger amounts (higher deposit grades) of molybdenite explains about 40% of this correlation, but the relative enrichment of Re in molybdenite from low-Mo deposits must also reflect some selective enrichment of Re/Mo in porphyry Cu systems compared to porphyry Mo systems. We found no evidence for secular increase or other systematic temporal variation in molybdenite Re content. The data regarding the use of molybdenite Re content as a proxy for mantle influence are ambiguous. Nearly all observed empirical correlations can be traced back to differences in redox state and sulfide concentration, the two geochemical factors identified here and by previous experimental work as the controlling influences on Re mobility under hydrothermal conditions. Hydrothermal systems with reducing conditions (W- and Sn-rich) tend to have low molybdenite Re even though compiled whole-rock data indicate that their source rocks have as much or more Re as those of more oxidized systems (e.g., Cu-rich). Vapor-phase exsolution, crustal assimilation, and mixing with external fluids may all enrich molybdenite Re concentrations in individual deposits and deposit types, but their extent and importance in overall hydrothermal concentration of Re is uncertain. Thus, it appears that the available molybdenite Re resource in an ore deposit largely depends on how the deposit’s redox and sulfidation conditions have varied over time and space during the timespan of hydrothermal activity. Oxidized, high-sulfide conditions tend to concentrate Re in molybdenite, whereas reducing conditions tend to leave Re dispersed at low concentrations in the bulk rock.

By C. D. Hebert, T. Gregor, M. Ghazi, G. J. E. Kramer

This paper describes the recent application of gasketed, precast concrete segmental lining design that has improved tunneling productivity and quality. The speci?c segment arrangement includes: six-piece ring with equal 60 degree gasketed segments, juxtaposed key and counter-key segments, trapezoidal and parallelogram shaped segments, inclined and skewed radial joints and plastic circumferential joint connectors. This allows rapid, but accurate ring erection, reducing mine cycle times. The design avoids cruciform joints, minimizes potential gasket damage and eliminates the need for separate left and right ring molds. The implementation on the Los Angeles ECIS and NEIS sewer projects is described.

Jan 1, 2003

By D. Marcus

A methodology was developed wherein. the increase in compressive strength, mineralogical changes and pore water composition were all studied simultaneously as a function, of moisturized spent shale curing time. From these results the relationship between the nature of cementation process and the composition of pore water was established. Heavy metals were entrapped in the cementing constituents and the pore water became mainly a solution of alkaline sulfates. While the specific data are applicable only to the material studied, the methodology and general conclusions are useful for evaluating the environmental factors in spent shale disposal and expected leachates composition.

Jan 1, 1984

By L. E. Murr

Solution flow in leach dumps and heaps or in columns of representative rock has been the subject of only limited studies. This is a regime involving unsaturated flow in semiconsolidated rock with a wide size distribution. Even the concepts of continuous flow systems are fairly recent, and have evolved from the search for better methods of operating industrial chemical reactors. (1-3) Waste rock consolidation and permeability play a key role in solution flow characteristics. Harris (4) suggested that bulk density variations in a leach dump could alter the particle-to-particle contact, and that large particle aggregates could act like single, large particles . In the limiting case where the bulk density approaches that of the undisturbed, consolidated rock, the entire waste unit would behave as a single particle. Roman (5) treated the phenomenon of bulk density and its effect on consolidation in terms of lixiviant flow paths or solution channeling in leach dumps. Like Harris, he assumed that no solution moved through particles or particle aggregates associated with zones of high bulk density. Solution flow paths are thus effectively separated by particle regimes, creating solution channels in the waste body. While some attempts have been made to describe solution flow in leach dumps and related systems by utilizing computer model approaches and laboratory- scale simulations (5,6), there have been no direct, large-scale observations of solution movement in channels or of the actual channel sizes and distributions within a waste body. This paper describes a series of experiments involving large-scale, controlled waste leaching tests, conducted over a period of several years, and aimed at providing some direct observation of the changes in waste consolidation and permeability, the size and distribution of solution channels, the movement of such channels with continued solution application, and other features relating to solution flow during the leaching of low-grade waste. These results are then combined with mineralogical information to explain observed leach behavior.

Jan 1, 1981

By Yung Sam Kim

The study of ultrasonic-wave propagation in substances has been remarkably advanced in recent years in most engineering and science fields. The main object in studying the velocity of ultrasonic-wave propagation in solids, is to determine dynamic properties of these materials. The present paper, however, presents some other possible applications of ultrasonic-wave propagation in the study of rock mechanics as follows: Investigation of the mechanism of microseismic activites of geologic materials, (a) at initial or low stress level, (b) at final or fracture stress level, and (c) under fatigue loading condition. Also, correlations among stress level, density, and the velocity of ultrasonic-wave propagation in rocks are discussed in this paper.

Jan 1, 1973

By L. C. Raymond

Good afternoon. I have entitled my talk "Investment for Progress," implying thereby a spark of friendly competition by private enterprise with such government-inspired foreign aid and investment programs as the Alliance for Progress. While the subject of foreign investment is hardly a new one, the perpetual flux of the political and economic surface of this earth we inhabit makes it forever timely and forever interesting. Especially do tremendous opportunities for international investment constantly present themselves to the mineral industry, and just as often must the industry approach these opportunities with a great deal of investigation and caution. This is not to say that the mineral industry--no less than any other industry--should be unenthusiastic about the foreign scene, but like everyone who proposes to put his money where his hope is, it should consider all the factors and weigh the possible disappointments as well as the rewards.

Jan 1, 1964

By S. R. La Brooy, P. C. Earley

Gold and Resource Developments NL (GRD) operates the Macraes Gold Project in East Otago in the South Island of New Zealand, treating a carbonaceous, refractory sulphidic gold ore. The ore is concentrated by flotation, then reground, followed by CIL cyanidation, to minimise loss to the preg-robbing natural carbonaceous material. As the mine has progressed there has been some variation in the preg-robbing nature of the ore, with average overall gold recovery generally in the range 70- 75 %. The Macraes Gold Project has been operating since 1990 and still has an estimated 11 year mine life, which has stimulated the continuing drive to enhance gold recovery. Testwork in 1994 showed there was no improvement in CIL gold recovery after conventional acid pressure oxidation of Macraes Gold Project flotation concentrate. Hence roasting was initially considered as the preferred option to improve gold recovery, being the only established technology to deal with both carbonaceous preg-robbing and sulphide encapsulation. However Newmont Gold Company pressure oxidation technology, as used at Twin Creeks in Nevada, has proved to be applicable to the Macraes Gold Project concentrate. Pilot scale testwork has shown that both roasting and pressure oxidation could achieve similar CIL gold recoveries on the concentrate. However, capital cost, simpler arsenic stabilisation, the ability to operate autothermally at a lower concentrate sulphur grade and simpler environmental consenting factors, has tipped the balance in favour of pressure oxidation. Overall average gold recovery is expected to improve to approximately 84% with adoption of pressure oxidation. GRD has appointed Minproc Limited as EPCM contractor to install pressure oxidation at the Macraes Gold Project, together with upgrading the existing flotation and grind circuits at a cost of NZ$ 30M (US$ 16M). Construction is 60% complete and on schedule for 1 October 1999 start up.

Jan 1, 1999

By E. Steel

The asbestifom habit is most commonly developed in certain amphiboles and chrysotile, but other minerals may also crystallize with this unususual habit, The habit may be characterized by 1) a fibril structure, single or twinned crystals of very small widths (generally less than 0.5 inn) which have gram with a common fiber axis direction but which are disoriented in the other crystallographic directions, 2) anomalous optical properties, primarily parallel extinction, 3) unusual tensile strength, 4) high aspect ratio, and 5) flexibility. In addition, there is evidence to indicate that some amphibole asbestos may have unusual surface properties.

Jan 1, 1979

By Z. T. Bieniawski

Geomechanics signifies the science and engineering of soil and rock materials and of rock masses. It is a field of professional practice and research that draws heavily on the elements of soil and rock mechanics. Geomechanics contributes to a number of disciplines: mining engineering, civil engineering, geological engineering, petroleum and natural gas engineering, and engineering geology (including the elements of geohydrology and geophysics). These disciplines are involved in the design and construction of such projects as mines, tunnels, foundations for structures, excavated rock slopes, dams, shafts, boreholes, oil reservoir wells, underground storage facilities for oil and gas, and hazardous waste repositories. Geomechanics allows us to improve both our environment and our quality of life. In the context of this Handbook, the scope of geomechanics is discussed mainly from the point of view of applications to mining engineering. However, the coverage of the subject mate¬rial is so comprehensive that it is relevant to other disciplines as well. Section 10 covers the field of geomechanics in a structured fashion, beginning with the fundamental principles and leading into practical applications in mining engineering. Throughout the treatment of the subject, knowledge of geologic conditions is assumed since this is discussed in other sections of the Handbook. An important feature of this section is a series of practical examples illustrating the various aspects of geomechanics. Since geomechanics is concerned with both soil and rock mechanics, Chapter 10.1 introduces the fundamentals of soil

Jan 1, 2008

By J. C. Cawley

Improvements in today's maintenance practices are mandatory as more complex and productive machines evolve in the mining industry. By keeping machine reliability high, through improved maintenance procedures, overall mining costs can be reduced. The Bureau of Mines is investigating diagnostic maintenance systems for underground mining machinery. A hydraulic expert diagnostic system and an electric motor predictive diagnostic system have been designed and installed on a Joy 16CM continuous miner. An electrical diagnostic system has been designed and installed on a Joy 14CM continuous miner. Each system is functionally described and the relative merits of expert diagnostic systems versus algorithmic diagnostic systems are discussed.

Jan 1, 1991

By Dan Brunner, Scott Thomson, Ben Lyddall, Duncan Thomson

Geosensing is used in oilfield drilling in conjunction with geophysical tools to support characterization of rock properties, geology, and reservoir conditions. This technology is now available to the mining industry and has been successfully applied to underground in-seam directional drilling in Australian coal mines for geologic exploration and methane drainage. The system utilizes a range of drill rig and wellhead mounted sensors which, combined with analytical software, produce real-time data from which 3D spatial features can be accurately modelled significantly in advance of mining. This innovation greatly expands on the information obtained from current in-seam directional drilling practices and provides for improved characterization of coal seams, including soft and weak zones, locations of geologic discontinuities, and analysis of formation flow. This paper provides a description of the geosensing system and the interpretation of actual data from long in-seam directionally drilled methane drainage boreholes at mines in Australia, and discusses how this system increases the value of directional drilling as an exploration tool for the coal mining sector, and the evaporite and hard-rock mining sectors where directional drilling is also applied.

Feb 1, 2024

By Chris Crowl

Employee involvement does not directly correlate to performance improvement. A key ingredient is the introduction of new Human Resource Systems that promote both performance improvement and employee involvement. Many organizations have tried to use employee involvement as the ''fixer" of performance issues-and seen their performance deteriorate further. They failed to realize that the entire human resource strategy must be connected to the goals of performance improvement and that greater employee involvement is only one tool in that strategy. So what are Human Resource Systems? These are systems that all managers use to get work done. Most of us are familiar with basics such as planning, assigning work, checking progress (auditing), completing assignments. We also commonly think in terms of staffing, training, compensation, or corrective action. All of these are human resource systems. All must be designed to support what you are trying to accomplish with your people. We call that the Human Resource Strategy. Let's examine one part of a total strategy intended to support more employee involvement at Kennecott Utah Copper-the hourly job structure. The design of hourly jobs directly affects how many employees of different capabilities are required to get the work done. It begins to answer some fundamental questions: • What are the roles and accountabilities of each employee? Do they have enough information to make decisions, to take responsibility for their work?

Jan 1, 2004

By David Lynn Passmore

The reliability of mine operators reports to the Health and Safety Analysis Center of the U.S. Deparetment of Labor of days lost from work by injured miners is .267.

Jan 1, 1985

By Robert C. Freas

While on the surface limestone marketing may appear mundane, it has continued to provide a series of challenges beyond the realm normally envisioned with this industry. This paper presents a case history of a mature and well-established quarry company that has attempted to keep pace with an ever-changing economy. It examines the impact of socio- economic and technological factors on the company's marketing efforts, and looks at the role of both short and long range planning. The realities which have had to be faced and how product requirements have been kept in balance with production restrictions are also discussed.

Jan 1, 1981

By Gunnar Thaning

The iron ores mined by LKAB in the north of Sweden have excellent beneficiation properties. This gives LKAB a favourable position as regards the production of low silica pellets for direct reduction. LKAB have concentrated on developing and marketing grades of pellets for the Midrex-Purofer-HyL process group, i.e. such D.R. processes which are carried out in a shaft furnace or a static bed using reformed natural gas as a reducing agent. The paper deals with properties and quality demands of iron ore pellets for such processes. Matters such as the effect of the residual magnetite in the fired pellets on the degree of metallization, the amount and composition of the slag phase in the pellets, the mechanism of the disintegration during reduction, the state of swelling of the pellets during the conditions prevailing in these processes, the importance of the porosity, the improvement of the reducibility and lowering of the sticking tendency of the pellets by small additions of suitable additives and the influence of the pellet size are discussed. A special test procedure for D.R. pellets has been elaborated by LKAB. Thus, three metallurgical properties are routinely determined separately, namely reducibility, reduction strength and sticking. The test methods are described. Finally the present and future LKAB pellets for direct reduction are presented with respect to chemical analyses and metallurgical properties.

Jan 1, 1978

By David J. Dunn

Mill liner design is an important factor in grinding. Testing and selection of the optimum liner profile for a given set of mill operating conditions can improve mill capacity, liner life, and liner wear rate At a time when mill avilability is at a premium, production costs are going up, and lead time for mill liner castings is a year or more, the mill liner that grinds best, lasts longest, and costs least is a necessity for economic mill operation. In testing four mill liner profiles for 13' x 12' overflow ball mills, Climax found that an improved design increased mill tonnage by 3 tons per hour while reducing finish grind by 1.7% + 100 mesh, reduced liner wear rate, and almost doubled liner life.

Jan 1, 1976

By J. E. Feddock

To succeed in today's competitive coal market, coal companies must continuously improve production and lower cost. However, the coal industry's historical management practices must change to remain viable? The practices of the current day efficient coal mine manager are reviewed and examined using W. Edwards Deming's definition of management. The statistical tools, including Pareto Charts, Control Charts and Scatter Diagrams, which identify the problems management must approach differently to increase productivity at a coal mine, are discussed.

Jan 1, 1993