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By R. J. Hickson

From 1993 through 1999 Cyprus Amax Minerals Company successfully completed eight major construction projects around the world. Six greenfield mines were brought into production, an ongoing operation was completely modernized, and an environmental issue was appropriately remediated. The projects stretched over three continents, from arctic Russia to the Atacama Desert, from 16,000feet to sea level, from city suburbs to remote wilderness, from a low of $130 million to over $1 billion. Open pit and underground; mill and leach; gold, copper, molybdenum, and coal were all encompassed. The breadth of diversity experience from these projects inspired Cyprus Amax to create a “best practices” project management protocol, to steer corporate expansion into the next millenium. This paper summarizes those best practices, while high-lighting project management pitfalls to avoid.

Jan 1, 2000

By S. J. Schatzel

Coal mine longwall face ventilation is an important component of the overall mine ventilation system. Increases in the production rate due to higher capacity mining equipment tend to increase methane emission rates from the coal face, which must be diluted by the face ventilation with a minimal opportunity for assistance from additional control equipment (i.e., surface boreholes). Increases in panel length, in some mines approaching 6,100 m (20,000 ft), and panel width provide additional challenges to face ventilation designs. Face ventilation can also be affected by communication with the methane-laden gob gas reservoir. Except in a two-entry system, belt air cannot be used to ventilate the face in the US, except in limited cases. This relatively recent requirement has further challenged the mining industry in maintaining adequate longwall face ventilation. To assess the effectiveness of current face ventilation practices, a face monitoring study was combined with a tracer gas test on a longwall face. The study was conducted at a US mine operating in a thick, bituminous coal seam with some self-heating tendencies. Multiple gob gas ventholes were located near the face and produced a small portion of ventilation air in their production flow. Initial results show that emission rates on the longwall face showed a very limited increase in methane concentrations from headgate to tailgate despite the occurrence of methane delays during monitoring. Increases in methane concentrations in the tailgate entry in the vicinity of the longwall face T-junction appeared to be produced primarily by gas flow from the gob, not from increased emissions from the face. Barometric pressure variations were substantial over the course of the study and varied on a diurnal basis, as is typical of many mining operations. Suggestions are forwarded for reducing longwall face methane concentrations.

Jan 1, 2012

By Judy B. Jones, Bradley A. Crenshaw, Theodore DePooter

This paper reviews groundwater issues leading to a secondary grouting program at the Chattahoochee Tunnel that was implemented subsequent to the contact grouting program. The secondary grouting program was developed based on infiltration data, geology, and testing programs. This paper includes a brief description of the geological features encountered, as well as describing the grouting program. The success of this grouting operation has been quantified by several methods, and is presented to help others project the costs and benefits of this type of program. Review of initial results and refinements of techniques are also discussed.

Jan 1, 2005

By Ellsworth R. Spencer

An assessment of U.S. western hardrock miners? noise exposures was conducted as part of a multi-year National Institute for Occupational Safety and Health (NIOSH) survey of noise exposures in each sector of the mining industry. Noise from selected mining equipment and operator noise exposures were measured, analyzed and tabulated for dissemination to the participating sites and are being used to direct NIOSH research and interventions to address the greatest noise hazards. Eighty-two noise dosimeter measurements were obtained, along with time-motion studies as the miners operated hardrock mining machines. Of the operators, 96% had daily noise doses that exceeded the U.S. Mine Safety and Health Administration?s (MSHA) permissible exposure level. The average gold miner dosages while operating the following equipment were: haul trucks - 261%, load-haul-dumps (LHDs) - 235%, single boom drills - 221%, bolters - 214% and dual boom drills - 163%. The worst exposure level was a silver miner with a daily dose of 873%. Time-motion data showed that this miner?s exposure accumulated most rapidly while operating a jackleg drill. These results will be used to help prioritize noise control development by NIOSH and other partners.

Jan 3, 2010

By S. Frimpong

Shovel excavation constitutes a significant component of production costs in any surface mining operation. This makes shovel loading an important cost center that needs to be improved to lower production costs. Optimization of tool design will improve energy efficiency in earthmoving operations. However, modeling the soil-tool interaction is a complex process due to the fact that forces for excavating particulate material are functions of many variables. The magnitude of this resisting force depends not only on the type of soil but on the size, shape and orientation of the cutting element. Moreover, part of this complexity is attributed to the fact that the behavior of the material during excavation is not yet well understood. For the past five decades, researchers have mostly used the passive earth pressure theory to study the soil failure patterns around a cutting tool and to develop force prediction models for design optimization with some success. Although the force models developed from the passive pressure theory have been successful to some extent, they can hardly be extended to a general case because of the underlying assumptions and simplification of tool shapes. This paper aims at reviewing some of the existing empirical and analytical methods of cutting and excavation tool modeling with a focus on their merits and limitations. The paper also explores the use of numerical methods, specifically the discrete element method, for dealing with the unresolved aspects of soil dynamics in excavation.

Jan 1, 2011

By K. Norrena

Grade control in open pit mining requires the specification of dig limits that account for mineral grades, economic costs, and selectivity of mining equipment. Visual identification of ore rock types is ideal, but this is not always possible in lower grade disseminated deposits where ore/waste contacts are not visually discernible. In this case, conventional grade control practice consists of a two-step procedure (1) create a map of mineral grades at some selective mining unit scale, and (2) determine practical ore-waste boundaries or dig limits on the basis of the gridded block grades or assay information. This procedure is laborious, depends on a subjective assessment of where the boundary should be, and may be economically sub-optimal. We pose the determination of dig limits as an optimization problem and solve that problem with the technique of simulated annealing. Simulated annealing has the unique advantage of being able to combine multiple non-linear constraints into a single objective function. We use maximum profitability and the ability of the equipment to mine the proposed dig limits as constraints in the determination of optimal dig limits. We require a map of expected profit for eah block. Geostatistical techniques are recommended, for mapping expected profit but not necessary. Geostatistics will provide a quantification of the uncertainty in the grades within rock types using all available blasthole samples and exploration drilling. Some variant of L-optimal estimation or kriging can be used to determine the block-by-block classification that is economically optimum. We also need the expected profit for each block. It is unrealistic to assume free selection, that is, each block cannot be extracted independently of its neighbors. The optimal balance of ''accepting dilution'' and ''wasting ore'' is achieved to maximize profit subject to equipment constraints.

Jan 1, 2001

By J. D. Morgan

In the first half of the year, lessening of cold war tensions was welcome. But Iraq's invasion of Kuwait in the second half led to the Persian Gulf War in January and February 1991. This caused an oil shock that dampened the economy. So the US gross national product rose only 0.9% to $5,463 billion (US billion = 109). The buildup of military forces in the Persian Gulf area focused greater attention not only on petroleum but also on other strategic materials. The Department of Defense continued to review stockpile goals and to upgrade several mineral materials. In addition, the Bureau of Mines continued to maintain the standby Emergency Minerals Administration. The Defense Production Act, which authorizes priorities, alloca¬tions and supply expansion, lapsed on Oct. 20. So the Selective Service Act of 1967 became the authority for assuring that orders of the armed forces and defense atomic-energy programs were given priority treatment. Consumer demand strongly affects mining worldwide. US citizens carry significant debt, and large stocks of housing and consumer goods are already in place. Some 250 million persons have 188 million licensed motor vehicles and 100 million dwelling units. Consequently, new car production fell 11 %, to 6.1 million units. Truck and bus production fell 8%, to 3.7 million units and new private housing starts fell 13% to 1.2 million units.

Jan 1, 1991

By Bruce Clements

The Bagdad mill, located near Bagdad, AZ, was built in 1977 with a designed mill capacity of 36.3 kt/d (40,000 stpd). An autogenous mill-ball mill crusher (ABC) grinding circuit was chosen. The original mill contained three independent grinding circuits. Each contained one 9.75m-diam x 4-m-long (32-ft-diam x 13-ft-long) fixed-speed autogenous mill, a4.7-m-diam x 6.7-m- long (15.5ft-diam x 22-ft-long) ball mill and one 2. 1-m-diam (7-ft-diam) short head cone crusher. Total installed power per grinding circuit was about 8.4 MW (11,350 hp), with 5.9 MW (8000 hp) in the autogenous mill, 2.2 MW (3000 hp) in the ball mill and 261 kW (350 hp) in the crusher (Fig. 1). The autogenous mills were designed to be able to operate semi-autogenously. However, they were never converted to semiautogenous grinding (SAG) mills. As a result of this design, only about 4.1 MW (5450 hp) of the designed power is used in the autogenous mills. The grinding circuits are closed, with 2.4 x 6 m (8 x 20 ft) double-deck vibrating screens. A series of conveyors re- turn screen oversize underneath the mill coarse ore stockpile to feed the crushers. Variable speed belts feed the crushers and control power draw. Crusher product reports directly to the tail end of the autogenous mill feed belt (Fig. 2). A magnetic sensor detects tramp iron in the autogenous mill-crusher circuit.

Jan 1, 1992

By M. Radwan, S. Shimada, S. Z. El-Tawil, K. A. El-Barawy, Y. Miyamoto

This study presents the results of synthesizing monolithic siliconoxynitride, Si2N2O, ceramic from a mixture composed of reclaimed silicon and natural desert sand by using the nitriding combustion synthesis method. Single-phase Si2N2O powder was prepared by the combustion of a mixture composed of silicon and pulverized sand in 3 MPa nitrogen gas. The combustion reaction completed in 2 min and the combustion temperature reached 1577°C.The as-synthesized Si2N2O powder is agglomerate of fine particles with sizes < 5 µm and has various morphologies; rod-like and irregular crystals, irregular kinking, hollow crystals and grown pseudo-hexagonal prismatic crystals. Porous Si2N2O compacts (24.5–47.1% porosities) were fabricated from the synthesized Si2N2O powder at different calcia-alumina additives (5–20 wt%) by normal sintering at 1500°C for 1 hr in N2atmosphere.They showed superior oxidation-resistance at high temperatures up to 1500°C in an oxidizing atmosphere of Ar/O2/H2O(70/20/10 kPa).Near-full dense Si2N2O compacts were also successfully fabricated from the synthesized Si2N2O powder with 5 wt% oxide additives by using the spark plasma sintering at 1600°C.DenseSi2N2O had good mechanical properties (18.7 GPa Vickers hardness, 3.3 MPa.m1/2fracture toughness and 363 MPa strength) and excellent chemical and oxidation resistance.

Jan 1, 2004

By Takuji Yamamoto

High-speed TBM excavation requires rapid ground assessment ahead of excavation, particularly in complex grounds. The Tunnel Reflector Tracing technology (TRT) developed by authors, uses seismic reflections to produce volumetric images of ground anomalies. To further minimize interruption in the TBM excavation the authors modified surveying technique switching from cable (wired) to radio (wireless) data acquisition system. This paper presents the outline of the Wireless TRT system, and compares the results for the wired and the wireless surveys. The comparison shows that the wireless system offers high precision data, is more efficient and economical and significantly less intrusive in tunneling operations.

By F. Freme

Coal production in the United States increased in2004 by 36 Mt (39.7 million st) to end the year at 1 Gt(1.11 billion st), according to the U.S. Energy Information Administration (EIA). This was a 3.7-percent in-crease from 2003’s 971.6 Mt (1.07 billion st) (Table 1).(All percentage change calculations are done at the short-tons level.) Although U.S. coal consumption rose in 2004, not all coal-consuming sectors had increased consumption for the year. Coal consumption increased in the electric power sectors by 1 percent and declined slightly in the other industrial sector, while coking coal consumption dropped by 2.4 percent. U.S. coal exports rose for the second consecutive year, while coal imports again increased to record levels. Coal stocks declined during the year, as electric generators used their stockpiles to helpmeet increased demands and missed shipments. Coal producers used their stockpiles to supplement their production levels.

Jan 1, 2005

By W. G. Pariseau

This contribution focuses on the role of stress analysis for mine planning and the selection of suitable computer programs for the task with special emphasis on coal mine pillars. In this regard, barrier pillars that defend a set of five main entries at the Crandall Canyon coal mine in central Utah were formed during extensive longwall mining north and south of these main entries. Numerical analysis for ground control guided the mine planning and permitting. Retreat mining of pillars led to disastrous events August 6 and 16, 2007, with the loss of nine lives. A most difficult lesson taught by the Crandall Canyon tragedy is the need for education in the selection and use of computer programs for pillar design. Much of this contribution is taken from a report prepared for the Mine Safety and Health Administration (Gates, et al, 2008). Details appear in Appendix Q of the report (Pariseau, 2008). The Crandall Canyon mine is about 16 miles west of Huntington, Utah, in the Wasatch Plateau coal field. Geology of the Wasatch Plateau is described by Doelling (1972) as gently dipping Cretaceous sandstones, mudstones, coal seams, and shales. Joint systems are present in strata above and below coal seams where cleat systems are present as described by Hucka (1991). Several major fault systems transect the field and form grabens with 450- 760 m of drop. One such structure is Joes Valley fault that crosses the Crandall Canyon mine. Mines in the Wasatch Plateau are generally developed from outcrops in steep canyon walls. Overburden increases rapidly as mining progresses into the plateau; mining depth varies with topography between 450 and 600 m in the region of interest. A stratigraphic column derived from a borehole into the mine is shown in Figure 1. There are 11 layers in the column.

Jan 1, 2011

By S. J. Stokowski

Abstract An extensive drilling and laboratory testing program indicates that a construction aggregate resource is present within the Oligocene Sombrerito Formation limestone, southwestern Dominican Republic. The first part of the testing program included the collection, photographing and geologic logging of diamond drill cores to allow lithologic subdivision of the strata into potential quarry layers. The primary lithostratigraphic units are: I- (youngest) approximately 10 m of white, dense marine limestone II-approximately 5 m of white, interbedded dense and chalky marine limestone III-more than 2 m of tan, chalky, calcitic dolomite. Unit I is often altered by lateritic weathering and/or dolomitization. Unit II is often altered by dolomitization. The cores were individually crushed by quarry layer into coarse and fine aggregate sizes for chemical and physical analyses: specific gravity and absorption, MgSO4 soundness, sand equivalent, Atterberg limits of the minus #40 mesh fraction, and LA degradation. The unaltered portion of Unit I is suitable for all construction aggregate uses. Unit II is best suited for crushed stone base. Each of the non-weathered units decreases in coarse-aggregate yield and quality with depth and diagenetic dolomitization. Dolomitization typically causes about 5% lower yield of coarse aggregate, a sand equivalent of about 20 units below the original value an increase in absorption of about 3%, an increase in the LA of up to 13%, and a decrease in the average five-cycle MgSO4 soundness of about 17%.

Jan 1, 1991

By J. E. Bernick, J. Davies

This paper describes the design and construction of a 22.86 m (75 ft) long jacked tunnel, which was successfully installed, despite difficult mixed face conditions at Metro-North’s Westport Station, in Connecticut in the fall of 2003. The tunnel utilized what is believed to be, the first application of a steel grillage system within the United States. This grillage was installed before the jacking started and allowed the tunnel to be jacked under four live railway tracks, which included the Acela high speed line, without affecting train operations. The clearance between the top of the tunnel and the rails was only 0.9 m (3 ft).

Jan 1, 2005

By C. P. Mangelsdorf

Introduction The use of frequency of vibration measurements to determine tension has long been accepted by industries that use electrical or stranded cables of wire ropes in their operations. In contemplating how to determine the tension in chords of a roof truss, it seems almost inevitable that a similar approach should be investigated even though there are some important dissimilarities in physical behavior between a chord of a rod-type Birmingham truss and a stretched wire rope. While the dominant feature of both types of behavior is the existence of tension, the bending resistance of the vibrating truss chord cannot be ignored. And it is common to have attached to the chord, pieces of hardware (turnbuckles, extension sleeves, wedge boxes) that represent concentrations of mass not usually found in a vibrating wire rope. Analytical solutions to the problem of vibrating wires or beams can be found in the literature on vibrations (Timoshensko, 1955; Den Hartog, 1956). But in every case, at least one of the ingredients of the vibrating truss chord is missing. The presence of axial tension, or bending resistance, of concentrated masses and of end conditions peculiar to truss chords is a combination that appears not to have been dealt with before, although the techniques for dealing with it are commonly known. The purpose of this note is to report the results of a project to measure and calibrate such frequencies. The work was conducted by the University of Pittsburgh under the sponsorship of the US Bureau of Mines. Field observations Tests were conducted on 24 different truss installations. The first 18 trusses were installed in shale roofs above Kentucky No. 9 seam and Illinois No. 6 seam. The remaining six were placed against the competent sandstone over the Pocahontas No. 3 seam in West Virginia. Chord tension was determined by two electrical resistance strain gages, in series, applied diametrically opposite to one another on the rod before tensioning. Due to the combined effects of inexact gage placement, rod bending and residual torsion in the chord due to tightening, errors in tension as high as 1780 N (400 lb) were reasonably possible. Due to faulty soldering or damage, three of the first 18 trusses and one of the final six were rendered completely unreliable. In addition to strain, the first natural frequency of vibration was observed to the nearest 0.1 Hz. Dimensions recorded included the span between contact points at the bearing blocks (Fig. 1) and the locations and amount of excess rod and rod gap at the wedge box and turnbuckle, respectively.

Jan 9, 1985

A glance at the accompanying table reveals that for the first time in many years the industrial minerals field did not post significant gains in production. Gypsum, cement, sand and gravel, and crushed stone production-which are very sensitive to construction industry performance-barely managed to stay even, or in fact, declined slightly. Even barite production, in spite of increased oil and gas drilling, was off 5% in 1979 from 1978. Domestic fluorspar production continued to decline while imports, primarily from Mexico, South Africa, and Spain, rose 11%. Worldwide production of iodine (which is used primarily as a catalyst, animal feed additive, and in ink and colorants, stabilizers, pharmaceuticals, photographic film, and disinfectants) grew about 9% on a worldwide basis-from 10.75 Tg to 11.16 Tg. This does not include US production. The two US producers increased demand as apparent domestic production increased about 5%. Increasing energy costs and the transportation situation have had a prohibitive effect on the industrial minerals field. The critical shortage of railroad cars, according to consultant Neil Johnson, is due to several factors: • High capital investment rind interest rates needed to build new equipment, • Accidents, obsolescence, and failure to repair equipment reduced car availability, •Reduction in some train schedules due to fuel economy, and •Increased turnaround time as a result of new safety regulations. Railroad rates have increased an average of 7% per year for the past 10 years. Last year&apos;s increases were about 11.1% due to fuel costs and surcharges. Truck shipments have increased their penetration in certain areas of the southeast because of the shortage of box cars and the producers&apos; demand for quick shipment. Some producers report a 15-20% increase in truck use. In the feldspar-mica area, which formerly made most shipments by rail, trucks are now used for about half the shipments. Marketing prices, as expected, increased due to higher costs for energy, power, labor, and supplies used in production. Estimated average price increases were about 10% which, in many cases, did not cover increased production costs. These factors-rising energy costs and the critical transportation situation-resulted in an unsatisfactory year for industrial minerals. Stanley J. Lefond Cnntrihuting Editor

Jan 5, 1980

By H. Do, R. Yoon

Mineral flotation is effective over a relatively narrow particle size range of approximately 10 to 100 µm. If the upper particle size limit can be increased, however, a run-of-mine ore may be coarse ground, and only the middlings are ground further to achieve required grades. This will result in significant energy savings and increased throughput. In this communication, methods of increasing the upper particle size limit will be discussed on the basis of a flotation model that can predict flotation from both hydrodynamic and surface chemical parameters. An example of increasing flotation recovery by control of a chemistry parameter is given.

Jan 1, 2007

By John E. Tilton

During the past several years — much to the delight of producing firms and countries — copper prices have surged from under $1 to more than $3/lb. Anyone familiar with the industry also knows that since the early 1970s the long-run trend in real copper prices has been significantly downward. This sharp contrast between short-run and long-run trends raises the issue of the forces behind these developments. What has been driving short-run prices up and long-run prices down? Simple economics suggests that it is all a matter of supply and demand. When demand is rising faster than supply, prices will rise and vice versa.

Jan 1, 2006

By Refik Elibay, Lawrence A. Williamson, George D. Barnes

Under an extremely aggressive schedule, final design of 13.5 km (8.4 miles) miles of 8.2 m (27 ft) diameter deep rock tunnel, 322 ML/day (85 million gallons / day)submersible pumping station and associated facilities were accomplished ahead of a federal court mandated consent decree schedule. Challenges overcome by the project team in enabling timely completion of the construction documents will be presented. Discussion includes evolution of final design, consideration of future O&M requirements, and risks identified for construction and operations, together with measures to manage and proactively prepare for such risks.

Jan 1, 2005

By Birger Schmidt

INTRODUCTION Conceptual design of the first Exploratory Shaft (ES-I) for the Nuclear Waste Repository in Basalt (NWRB) began in July 1981; detailed design began in February 1982, and was largely completed by December (RKE/PB, 1983). The intent was to begin shaft construction by January 1983. The site had been prepared at that time, a construction manager selected and on board, the starter hole excavated and lined, and steel casings were under procurement. Government policy changed, however, and construction was halted before the drill rig started turning. Construction is now planned to begin in 1988. ES-I is a part of the site characterization program for the NWRB. The shaft will be used to develop production data and related information relative to drilling shafts at the site near Richland, WA, and to provide access to the repository horizon for site characterization and testing. The early program called for one shaft and some 330 m (1000 ft) of drifting. The program has since expanded to include a second shaft (ES-II) and more extensive drifting and testing. Currently, both shafts are planned to be 1.8 m (6 ft) in finished diameter, but studies are underway to determine if the second shaft should be larger. The drilling method was selected for shaft construction primarily because it offered a significantly shorter construction period than conventional shaft sinking using freezing and grouting. The finished drilled shaft will be lined with a continuous steel lining. Personnel are safer during construction with a drilled shaft than with a conventionally sunk shaft. The drilling method

Jan 1, 1987