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By W. Clark Ashby

Productivity is a fascinating concept. Like motherhood or apple pie, we know it as a good thing. Just what it means is not so clear. To a coal miner we assume it means tons of coal hauled from the mine. To the company president it means profit after capital, labor, and other costs have also been reckoned. To the government economist it means output in a balance of payments. What does it mean to the biologist, and can reclamation really be productive? In this paper we discuss productivity from a biological viewpoint, give some yield data for various types of reclamation plantings, and discuss how our demand for or acceptance of differing kinds of productivity is tied up in bigger questions of land use, environmental stability, and resource allocation.

Jan 1, 1981

By M. Dale Slade, Gordon S. Bird, Robert S. Kelly

Gallium scrap is obtained from many different sources, therefore each lot received has to be evaluated and then processed accordingly. Some of the problem areas are separating small amounts of gallium from large concentrations of iron, eliminating trace amounts of gold, silver, copper, germanium, tin, and zinc from gallium, and having the flexibility to process each lot of scrap individually Following gallium from the raw scrap material to the final seven nines pure product requires stringent quality control and excellent analytical capabilities.

Jan 1, 1983

By James B. Meredith

The European Economic Community (The Common Market) is now shifting from I a coal oriented to an oil oriented economy. The proportion of energy supplied by oil has increased from only 13% in 1950 to 38% in 1962, and will approach 50% by 1970. In the past five years Common Market petroleum demand has in- creased 15% per year compared with only 3% per year in the United States. This rapid shift to oil can be explained by looking at oil's competition, First; there is simply not enough other energy - European coal, natural gas and hydro-electric power - to meet the demand, Secondly, oil?s primary competing energy in the Common Market is coal, and Community coal is high-priced - it costs more than two and a half times as much as U. S, coal at the pithead. The third reason for the shift to oil is consumer preference for the ease of handling, convenience and cleanliness of liquid fuels. As these reasons suggest, much of the shift to oil and the resulting growth in demand would have occurred whether or not the Common Market organization had existed. On the other hand, the Common Market has stimulated the use of oil by causing a higher rate of energy consumption, and oil has been the beneficiary of most of this growth.

Jan 1, 1963

By E. Bakhtavar

All parameters influencing the decision for selection of a suitable extraction method were first selected as the base of this study. Then these parameters were categorized in two main groups. The first group of the parameters includes ?geomechanical and inherent characteristics of the dimension stones? such as hardness, RQD, compressive strength, joints plane orientation and spacing, and water content. The second group was named ?technical and economical parameters associated with the investor?s objectives? like for example extraction capacity (production rate), blocks recovery, mechanization, capital investment and operational costs. Finally, the influences of all mentioned parameters on the selection of the most applicable extraction methods have been assessed and discussed.

Jan 1, 2012

By Cheng Ang, Yun Bai, Zhi Liu

"This paper presents a conceptual design of an innovative tunnelling method named the Ring Pipe Jacking Method (RPJ) which is conducted by the Ring Pipe Jacking Machine (RPJM). The RPJM consists of a double ring shell which forms a ring section where small interlaced cutter heads or several micro tunnelling machines are assembled to cut soil. Similar to the conventional pipe jacking method, the RPJM also needs a thrust system, a slurry transport system, and a control system. To satisfy the need for large/super large or special section tunnels in future, the RPJM is designed to reduce sharply the excavation face to the annular section, thus enhancing the face stability. Part of the innovation is that the RPJM uses modular cutter heads or micro-TBMs which can be reused. The typical double shield shape can be easily changed by reinstalling the modular cutter heads. Modularity allows the tunnel to be cut in any cross-section shapes, ranging from a circular tunnel to a rectangular one. INTRODUCTION The demand and requirement to utilize urban underground space is rising with the rapid social development in recent years. It is necessary to reduce excavations of the urban ground surface to ensure smooth traffic in cities. Therefore the conventional open cut construction method for underground tunnels can no longer satisfy the need of practical engineering, and it is taken over by trenchless technologies .The Pipe jacking method is an important trenchless technology and is used more and more frequently to install underground pipelines, but the present pipe jacking method still has many problems. For example, it is not suitable for installing large-diameter tunnels and it also has difficulty in construction of short radius curved tunnels. This paper presents a conceptual design of an innovative pipe jacking machine named the Ring Pipe Jacking machine (RPJM) and introduces the correspondent Ring Pipe Jacking Method (RPJ) which can be applied to construct large-diameter tunnels. Furthermore, technical characteristics and superiority of the ring pipe jacking method are analyzed in this paper."

Jan 1, 2016

By Yiming Sun, David Tsztoo, Rick Nolting, Adam M. Wirthlin, Rebecca Fusee

"Excavation and initial support of the New Irvington Tunnel presented significant challenges, including rapidly changing ground conditions, heavy ground loads, and squeezing. Such behaviors were anticipated from historic tunneling records of the adjacent Existing Irvington Tunnel, and extensive site investigation, but clearer understanding of their actual extent and causes has resulted from convergence measurements, observations of ground behavior, initial support monitoring and detailed geologic mapping. Time-dependent movements, documented hours to months after excavation in clay-rich rock and in moderately to intensely fractured rock, identified squeezing areas, allowed classification by currently-used predictive methods and added to the list of lessons learned in tunneling such ground. INTRODUCTION In March 2003 the San Francisco Public Utilities Commission (SFPUC) authorized funding for the $4.6 billion Water System Improvement Program (WSIP) to repair, replace, and seismically upgrade its water system. The program consists of 35 local projects located within San Francisco and 48 regional projects located in several counties from the Sierra foothills to the San Francisco Bay Area. The New Irvington Tunnel (NIT), a key component of the WSIP, is located east of Fremont in Alameda County, on the east side of San Francisco Bay. The NIT is a new 18,660 foot (5,689 m), redundant tunnel, 190 to 670 feet (58–204 m) offset from, and subparallel to the Existing Irvington Tunnel (EIT). Built between 1928 and 1932, the EIT was constructed with an unreinforced cast-in-place concrete lining and is vulnerable to damage in the event of a major earthquake along the two closest active faults. The Hayward Fault is located less than a mile west of the tunnel, and the Calaveras Fault is located half a mile east of the tunnel. Although the alignment does not intersect these faults, the shaking and sympathetic displacement along secondary faults that cross the tunnel alignment are potential hazards. The NIT provides a seismically reliable water transmission facility capable of withstanding earthquake damage and maintaining continuous water service after a major earthquake. The NIT also adds system redundancy and provides for operation flexibility of running water through both tunnels, or through one tunnel while the other is out of service for inspections and maintenance."

Jan 1, 2016

By James Barker, Jacques Renault, Chris McKee

Previous XRD work by us (McKee, Renault, Barker; 199Oa, 1990b) showed that by using pressed powder briquettes and a peak deconvolution technique, quartz in perlite can be routinely determined at <0.1 wt. %. In the present report, we discuss two additional methods of standardization: 1) chemical determination of quartz in silicate standards and 2) addition of a large amount of quartz to an unknown mixture. The first method applies the concept of mass balance and is sensitive to the analysis of silica and a monitor element. The second minimizes mixing errors; its equation is non-linear and is derived from the two component case with unequal mass absorption coefficients treated by Klug and Alexander (1974).

Jan 1, 1991

By S. K. Mishra, S. B. Kanungo, D. Biswal

An attempt was made to beneficiate low-grade, high-phosphorus manganese ores of the Garividi-Garbham region of Andhra Pradesh, India, by using wet high-intensity magnetic separation (WHIMS). The distribution behavior of both mass and chemical constituents in different size fractions of a typical highly weathered ore sample was studied to obtain information about the liberation characteristics of various chemical constituents. Magnetic separation indicated that in the +208-µm size fractions, P and acid insolubles were concentrated in the magnetic fractions. However, in the -208-µm size fractions, P and acid insolubles were concentrated in the nonmagnetic fraction because of a lower recovery of the magnetic fraction. Variations in field intensity between 1.3 and 1.75 T had little effect on the recovery and the grade of concentrate. The results also demonstrated that phosphorus was associated with all three major constituent phases, namely, oxides of Mn and Fe and aluminosilicate gangue minerals.

Jan 1, 2000

By J. Andres, M. Cross

"Freeport-McMoRan’s Sierrita operations has two natural gas-fired molybdenum roasters for converting molybdenum disulfide into molybdenum trioxide. When these roasters were compared to other similar units within the company during a benchmarking exercise, it showed that increased throughput from the roaster units at Sierrita was possible. A team of site metallurgists, technical experts from other sites, and engineers from the Climax Technology Center was formed to study the potential in more detail. The team investigated many parameters in the roaster, including temperature profiles, roaster chemistry profiles, rabble and drop hole patterns, and operational strategies. The results of these studies and the associated throughput improvements are described in this paper. INTRODUCTION Molybdenum, a vital component for the steel industry, is typically found in nature as molybdenum disulfide (MoS2). MoS2 is typically recovered via flotation processes and is purified through leaching processes. While molybdenum disulfide is a commercial product, it is not the form of molybdenum that the steel industry requires. They require molybdenum in the form of molybdenum trioxide, MoO3. There are multiple ways to refine molybdenum disulfide into molybdenum trioxide. The primary method is the oxidation of molybdenum disulfide in a multiple hearth roaster. The chemistry of converting molybdenum disulfide to molybdenum trioxide is very favorable at increased temperatures, oxidizing the molybdenum through a range of exothermic reactions to ultimately produce MoO3. The chemical reactions that occur in molydenum roasting occur in three zones. These three zones correspond with four different reactions."

Jan 1, 2015

By J. Korak

Belt conveyor systems, long the standard transportation technique in soft-rock open-pit applications, are encountering growing interest in the hard-rock open-pit sector as economic factors force companies to seek an alternative to costly truck haulage. A general review of mine conveyor systems is followed by detailed analysis of the mobile and semi-mobile in-pit crushing plant essential to successful use of mine conveyors. A final section presents case studies of three crusher-conveyor systems handling overburden, copper ore and granite.

Jan 1, 1985

By E. A. Adey, C. Baciu, P. Whitbread-Abrutat, M. Varul, T. Ejdemo, R. K. Shail, F. Wall

Responsible mining requires stakeholder engagement throughout all operational stages and after mine closure. By assessing the current and anticipated future socio-economic and environmental impacts, a company can maximise the positive impacts they can have on a community, whilst minimising any negative impacts. Despite the current emphasis on companies maintaining effective stakeholder relations to gain their ‘social license’ to operate, findings of the present study reveal a wide variation in community expectations, with different degrees of ‘acceptability’ evident across seven sites in Romania (Rosia Montana), Sweden (Kristineberg), the United Kingdom (Cornwall), Bosnia Herzegovina (Vihovici) and Russia (Karabash, Gay and Mednogorsk). These variations reflect the current status of mining within a community, as well as its socio-economic background and the nature of existing engagement with mining companies already operating in the region.

Jan 1, 2011

By Jian Liu

The dissolubility of a natural sphalerite (ZnS) in the entire pH range was theoretically calculated, and its practical dissolution in an aqueous solution at different pH values in an inert environment, together with its surface properties after dissolution, was fully investigated. The results of the investigation indicate that the total concentration of Zn (CZnT) decreases significantly with the increase of pH value, while the pH value is set below 8; however, it reverses when the pH value reaches 8. Such a tendency is similar to that of the theoretical calculations, although the experimental CZnT were much higher than those of the theoretical calculations. The X-ray photoelectron spectroscopy (XPS) of the sphalerite surface after its dissolution under alkaline solution shows that a polysulfide (Sn 2-) surface layer with a binding energy (BE) value of 162.96-163.25 eV is present on the surface, and the percentage of Sn 2- increases significantly with an increase in pH value; the undissolved and dissolved sphalerites under the acidic solution have a negligible difference in S2p peaks. The surface S/Zn ratio of all dissolved sphalerites shows a marked Zn enrichment and S deficiency. An atomic force microscope (AFM) view of the sphalerite surface, after its dissolution under the alkaline solution at a pH of 12, shows that the surface is significantly different in morphology from that of the undissolved one.

May 1, 2012

By Jerry C. Tien

Without a doubt, the scope of China?s coal boom has been nonstop. Despite the world economic slowdown, China?s year-on-year gross domestic product (GDP) jumped 10.3 percent year-on-year in 2010, boosted by a faster than expected 9.8 percent expansion in the fourth [ ] quarter. And, the first quarter of 2011 expanded another 9.7 percent. According to a frequently cited statistic, the country is building two mid-sized coal plants each week. This amounts to a yearly increase equivalent to the entire power grid in the United Kingdom. China?s coal production was doubled in the last 10 years, from 1.044 Gt (1.15 billion st) in 1999 to 3.2 Gt (3.52 billion st) in 2010. This is 3.2 times the U.S. production (986 Mt or 1.085 billion st) and nearly half (46.3 percent) of the world?s total coal production (6.91 Gt or 7.6 billion st). This rapid increase of demand for coal has made China the world?s largest coal importer in 2009. With the economic situation improving, this trend is expected to continue.

Jan 1, 2011

By M. E. Gershon

Conventional methods of drill hole site selection are reviewed briefly. Two approaches using geostatistics are then discussed, both of which have been shown to yield improved results. Finally, a branch and bound algorithm is described which will select the best locations for drilling from a user specified number of possible drill sites. Two options are discussed. First, the user can specify a maximum drilling investment or a maximum number of drill holes and the program will select the locations yielding the minimum estimation variance. This amounts to getting the most for a given investment. Alternatively, a maximum tolerable estimation variance can be specified and the program will select the number and location of the drill holes to obtain the desired information at a minimum cost. Another benefit of the approach is the quantification of the tradeoffs between investment and information obtained.

Jan 1, 1985

By G. W. Riley, D. E. Pickett

HINDERED SETTLING CONCENTRATION In the free settling of mineral particles in a liquid, the falling particles are at a distance from each other so that no particle is affected by its neighbor. In hindered settling, the concentration of particles is sufficiently high so that each particle is affected by its proximity to other particles in the suspension. Richards and Locke86 have described the hindered settling phenomenon as the condition “.. where particles of mixed sizes, shapes and densities in a crowded mass, yet free to move along themselves, are sorted in a rising current of water, the velocity of which is much less than the free-falling velocity of the particles but yet fast enough so the particles are in motion." This is the condition normally encountered in mineral con¬centration processes. The well known Newton equation for free settling of coarse (ap proximately +10-mesh, 1/16-in. or -- 2000-µm) spherical particles is:87 where v," is free settling velocity, cm/sec; p&apos; is density of the fluid; p is density of the particle, g/cm3; d is particle diameter, cm; g is acceleration due to gravity, cm/sec2; and Q is coefficient of resistance, dimensionless, ~0.4. For the settling of fine spheres in water (approximately 150 mesh or 100 µm) the equation of Stokes pertains:87 where µ is viscosity of the fluid in poises and the other symbols have the same meaning as those in Eq. 1. For particles whose size lies between about 10 mesh (--2000 µm) and 150 mesh (100 µm), their settling velocity can be determined from experimental data. These data are available in convenient form in the text by Taggart88 based on the original work of Richards. Alternatively, a Reynolds number-coefficient of resistance plot may be used to determine the settling rate of such particles.87 The settling rate of spherical particles under hindered settling conditions can also be calculated from Eqs. I and 2 by replacing p&apos;, the density of the fluid, by p" the apparent density of the suspen¬sion. The concentration of particles in the fluid thus imparts an appar¬ent density to the composite fluid or suspension greater than that of the liquid alone, resulting in a buoyant effect on the larger particles. Particle shape affects the settling rate of both coarse and fine particles. The general effect is to reduce their settling velocities and the effect is greater for coarse particles and for those settling under hindered settling conditions than for fine particles or free settling ones. For two particles of differing densities but settling at the same velocity under Newtonian conditions, the ratio of their diameters from Eq. 1, called the free settling ratio is: where L signifies the lighter particle and H, the heavier particle. Under Stokesian conditions the exponent would be 0.5. For hindered settling conditions the fluid density p&apos; is replaced by the apparent density of the suspension, p", to obtain a generalized equation for the hindered settling ratio: assuming both particles settle in approximately the same regime. The free settling ratio as given by Eq. 3 has been called by Taggart88 the "concentration criterion" and is used to predict the effectiveness of any gravity concentration process (see Introduction to this section). Based on Eqs. 3 and 4, if two particles of densities pH and p,, settle at the same velocity, the diameter of the lighter particle will be larger than that of the heavier particle. For example, in the case of galena (pH = 7.5) and quartz (pL = 2.65) settling in water (p =1.0) under free settling, Newtonian conditions 3.9. Thus, a quartz particle nearly four times as large as a galena particle will settle at the same velocity. Any quartz particle just slightly less than four times the diameter of the largest galena particle may be separated from it. Under hindered settling, Newtonian condi¬tions in a suspension where p" = 1.65, dL/dH = 5.85 or any quartz particle just slightly less than about six times the largest galena particle may be separated from it. Reference to Eq. 4 indicates that a superior separation between two minerals of differing densities is favored by: (1) coarse particles settling under Newtonian conditions, (2) a large difference in (pa - PL), and (3) separation under hindered settling conditions where p" is high. Of course, there are practical limits to increasing p" excessively because at very high percent solids suspen¬sion fluidity would be lost and the hindered settling separation process defeated. Examples of hindered settling separators are the Dorrco-Fahren¬wald sizer,89 the Rheolaveur box 90 the Spitzkasten,89 and the Willoughby washer.91 These devices make a mineral separation on the basis of both specific gravity and size and all of them are essentially obsolete except for the Dorrco-Fahrenwald sizer and similar devices which still find application for the removal of coarse particles from a much finer particle assemblage and for preconcentration ahead of shaking tables. However, nearly all gravity concentration processes (jigs, tables, flowing film concentrators, heavy media separators) and many sizing devices (sizing classifiers, clarifiers, thickeners, hydrosepa¬rators) make use of the hindered settling phenomenon during the separation of particles. JIGGING Introduction In jigging, a mixture of ore particles, supported on a perforated plate or screen in a layer or "bed" with a depth many times the thickness of the largest particle, is subjected to an alternating rising and falling (pulsating) flow of fluid with the objective of causing all

Jan 1, 1985

By O. M. Johnson

Barite and bentonite are the two principal components of drilling fluid systems used in the petroleum industry for oil and gas well drilling with rotary-type rigs. Approximately 87 percent of the world&apos;s annual production of barite is used in drilling applications. Of the worldwide production of bentonite, an estimated 30 percent is used. The drilling fluid, or drilling mud, to which barite and bentonite are added, performs five distinct functions: Lubrication-The liquid phase of the drilling mud lubricates the drill bit, preventing premature failure of the cutting edges and bearings. it also helps to soften the formation being drilled. Cuttings Removal-A mud system must be able to carry rock cuttings broken loose by the bit up to the surface where they can be removed by mechanical or chemical methods. The fluid&apos;s ability to perform this function depends upon maintaining a proper balance between the rate of circulation of the fluid and the colloidal properties required to entrain the cuttings in the mud to prevent their settling to the bottom of the hole. Hole Stability-The pressure exerted by the mud against the wall of the bore hole prevents the collapse of the uncased portions of the hole. Downhole Information-The fluid characteristics of the mud should be such that good cuttings samples, cores and electric logs may be obtained to help evaluate a well&apos;s productive zones and potential. Control Oil, Gas and Water Flows-It is essential that a drilling fluid offset any pressure from naturally occurring formation fluids in order to prevent a potentially wasteful and dangerous blowout.

Jan 1, 1980

By Tom Ireland, Tony Rock

The proposed 1.83km long twin bore A3 Hindhead road tunnel planned for contruction in 2008 is being delivered under a Highways Agency Early Contractor Involvement (ECI) contract. The proposed construction methodology is progressive mechanical excavation of a horseshoe shaped tunnel with shotcrete installed close behind the face using robotic spraying equipment. The tunneling medium is a ‘soft rock’ sandstone for which there was little previous tunneling experience, requiring extensive geotechnical investigations and an innovative approach to lining design. A 240m long portal section though sandy material utilising a steel pipe umbrella is also required. This paper describes the development of the tunnel planning and design including the most recent developments in UK road tunnels, and the innovation included in the ‘permanent’ primary lining design.

Jan 1, 2007

By Morley H. Mathewson

The unprecedented demand for capital investment in the mining industry today has intensified management&apos;s interest in every known technique which will help to reduce operating costs and increase production. One proven approach leading to the accomplishment of this objective is well known in the mining industry and is gaining added prestige, particularly where keen competitive conditions exist. This approach is in the area of incentives applied to mining productivity. An investigation of many incentive plans now in use throughout the mining industry revealed a predominant number of conventional type plans, Most of these plans are designed to reward the hourly-paid employee on the basis of percent over and above a standard hourly or daily ton rate, By contrast, this search failed to divulge any incentive plan solely and independently developed for production management employees. This does not mean that such plans in the mining industry are nonexistnet, but it does indicate that production management incentive systems are scarce or are being kept under wraps.

Jan 1, 1960

By Albert Musschoot

The expanding applications of vibrating feeders for controlling the flow of bulk materials, and their adaptation for processing requirements, have developed considerable interest in stockpiling and reclaim systems. The general design of these units consists of a material transporting trough, or platform, driven by a vibratory force system. Design flexibility and variety is limited only by engineering ingenuity. The basic motion of the vibratory trough, or work member, is a controlled directional linear vibration that produces a material tossing or hopping action. Material travel speeds vary from 0 to about 30 m/min, depending on the combination of frequency, amplitude, and slope vibration angle.

Jan 6, 1981

By F. Ferella

In this paper several leaching tests were per-formed to optimize the leaching section of a hydrometallurgical process for the recycling of alkaline and zinc-carbon batteries. Zinc and manganese oxides were dissolved by an acidic-reductive leaching using sulphuric acid and oxalic acid as reductant. Leaching tests were developed according to a full factorial design. The operational variables were pulp percentage, sulphuric acid concentration, temperature and oxalic acid concentration. Additional tests were performed to evaluate the precipitation rate of Mn and Zn oxalates. Finally a hydrometallurgical process were proposed for the recycling of alkaline and zinc-carbon batteries, in which Zn and MnO2 are recovered from purified solution by electrowinning: Zn is recovered as metallic compound, while Mn can be recovered as electrolytic manganese dioxide (EMD), but recovery of further manganese compounds is possible with simple process changes.

Jan 1, 2006