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By B. A. Hancock

It is not at all surprising that causticized potato and potato derived amylopectin starch solutions performed much better than their parent starches. Some preparation is required to rupture the starch granules to effect the polymeric adsorption and interparticle bridging necessary for selective flocculation. In laboratory work comparing the deslime performance of causticized and autoclave cooked laboratory corn starch solution preparations, it was found that higher deslime weight rejections, with attendant proportionally greater iron unit losses, occurred with the causticized starch. These results may be specific to the ore involved but they do suggest that cooking and causticizing cause different starch granule rup- ture and/or starch breakdown, which have an effect on desliming response. I calculated from the data in the article that the slimes product grades were high - 24.3% and 20.3% Fe when 53.7% and 54.5% Fe concentrate products were obtained, respectively, in Table 4, and 21% Fe with a 62.6% Fe concentrate in Table 5 - using the natural tailings sample, which had a head of 34.3% Fe. It may be advisable for the authors to consider different starch preparations in future investigations. The combination of upgrading and selectivity results presented in Table 4 are not as good as the authors suggest. The authors' claim that a system has been developed to produce saleable concentrates from the Kudremukh tailings is quite disconcerting. There are many hurdles yet to be crossed before commercial application of selective flocculation becomes possible because differ- ences between the very small-scale laboratory tests conducted and commercial application are rather large. Among the many differences are varying circuit feed grades that will occur from use of tailings, the apparent face that much lower tailings grades will be encountered in practice (it is much easier to achieve a high concentrate grade with reasonable recoveries using 34.3% Fe tailings as in the study rather than 25.3% Fe tailings grades that the plant apparently averages), the hydraulic nature of the thickeners used in operations compared to the static system used in laboratory tests, the different size distributions that will be obtained from a plant closed grinding- classification circuit, and differences in water used in a plant operation and the laboratory. The authors wrote that it was necessary to overgrind to be sure that the coarse gangue would not settle with the iron oxide floccules. This situation is likely to be exaggerated in commercial operations where it is assumed cyclones would be used for classification. Because cyclone classification is greatly influenced by particle densities, there will probably be an even greater difference in size between the iron and gangue particles in the plant, which would make the gangue slightly coarser still in relation to the iron. This would make the selective flocculation-desliming separations using the procedure employed by the authors even more difficult and, using the dispersant system the authors employed, greater overgrinding would be required. To grind finer to minimize the coarse gangue in the flocculated iron oxides is quite inefficient and appears not to broach the problem. The actual problem appears to be insufficient dispersion of the ground pulp. In this situation, addition of a dispersant would likely be required to attain a sufficiently high pulp dispersion level to efficiently effect a selective flocculation-desliming separation. Although the very coarse particles would still have a tendency to settle with the floccules, it probably would be found unnecessary to overgrind as much as indicated. Use of an optimum combination of dispersant and pH modifying reagents may also significantly improve the selectivity of desliming. Additionally, although it is possible that sufficient dispersion may be obtained by pH control alone in some situations, it is quite probable that added dispersity was obtained in the reported work from using distilled water. It is research experience that distilled water enhances dispersion. In commercial operations it may not be expected that sufficient dispersion will be obtained by pH control alone, unless the water used in the process is by nature quite dispersive. Overall, a change in the Kudremukh tailings dispersant scheme appears necessary where a dispersant is used in conjunction with a pH modifying reagent. With this change, different dispersion-flocculation responses will result that would have to be further evaluated. Therefore, it is still an open question whether an efficient and effective selective floccula- tion separation using Kudremukh tailings may be obtained that will produce saleable concentrates.

Jan 1, 1987

By Johanna I. Wong, R. John Caulfield, Victor S. Romero

The existing Hetch Hetchy water system, owned and operated by the San Francisco Public Utilities Commission (SFPUC), serves 2.4 million people within the San Francisco Bay Area. The system has existing 1920s-era pipelines crossing under the Bay that are vulnerable to seismic damage from the nearby San Andreas and Hayward fault zones. The SFPUC plans to replace the pipelines with the first TBM-driven tunnel underneath the San Francisco Bay. The tunnel will be constructed using an Earth Pressure Balance machine. The new tunnel will pass under environmentally sensitive habitats and will be approximately eight kilometers (five miles) long with no intermediate shafts. The project challenges will include tunneling through a prominent buried bedrock ridge that transects the alignment and through soft soils under the Bay. Seismic performance criteria include maintaining service flows after a large earthquake on one of the active faults in close proximity to the project site.

Jan 1, 2007

By Robert E. Mead

During the past three years the New York Trap Rock Corporation has been restricting blasting operations to days when favorable atmospheric conditions prevailed. By favorable atmospheric conditions is meant the absence of temperature inversions or isothermals in the lower atmosphere or under 6,000 feet altitude. Strong wind and wind shear can also cause conditions unfavorable for blasting. As a result of this practice, there has been a marked decrease in the number of blasting complaints received. The New York Trap Rock Corporation operates four stone quarries on or near the Hudson River within 60 miles of New York City. The Company supplies approximately 7,080,000 tons of high grade, crushed and graded aggregate, rip rap and by-products to the New Pork City area annually, This stone is carried to the market by a fleet of company owned deck &cows which are moved by tugs of a subsidiary towing company. Stone from two of the quarries is diabase: and, from the remaining two, dolomite.

Jan 1, 1962

By Josef Martinsen

This paper describes two-lane dual motorway tunnels under construction in Bergen. The tunnels are part of a by-pass motorway system throuth the most congested area of the city of Bergen. The tunnels are unique due to their length, heavy traffic, longitudinal ventilation system and the use of a tunnel boring machine, or "TBM", to excavate through hard rock. The tunnels are being built by The Norwegian Public Road Administration and the TBM was delivered by the Robbins Company. The diameter of the TBM is 7.8 m and the tunnel profile is cut by conventional drill and blasting methods in the tunnel's lower half to attain a two lane motorway tunnel. This paper also describes proposed fjord crossings along the Norwegian west coast where the TBM may be used due to its great advantages in comparison to conventional drill and blasting methods.

Jan 1, 1987

By Drupad B. Desai, James G. Gallanes

A key component of the Inland Feeder Project is the Riverside Badlands Tunnel, a7.9-mile stretch subjected to high internal and external hydraulic pressures passing beneath highly eroded hills in a semi rural environment. The tunnel presented significant design and management challenges to the project team. This paper describes the formula for project success used to manage the design of this complex pressure tunnel, from team member selection to the completion of all contract documents, on schedule and below budget. The project team dealt with sensitive regional and local community issues and won the trust of the community. The team included participation by senior management and recognized experts from inception to finish. The team worked diligently to build quality into design and adopted a claims avoidance approach to management and preparation of documents.

Jan 1, 1997

By William L. Carter

Through your presence here this morning and your membership in the Society of Mining Engineers, you have shown that you are interested in keeping abreast of the latest technology and mining procedures, want to be part of the continuing progress made by those in your profession, and are looking for ways to participate in expanding your professional and personal experiences and skills. All of these factors are part of your continuing education, the need for peer identification or recognition, and the desire to make a specific contribution to strengthening your profession. However, you may be here with or without your company support and financial backing, unless you are self-employed. Whether you are here for the above reasons, or for many others, your presence reflects a recognition of the importance of participating in the organizational structure of your profession.

Jan 1, 1981

By A. Bruynesteyn

Procedures are discussed to determine if a waste material can become acid producing when left exposed to the environment. When wastes proves to be acid producing, methods are described that can be used to determine the characteristics of the effluents produced from a commercial size waste dump, taking into consideration that large quantities of pollutants can accumulate inside a waste dump during dry periods. The length of such dry periods and the quantity of rainfall greatly affect effluent characteristics.

Jan 1, 1980

By Richard H. Sillitoe

Gold is an important byproduct and, locally, coproduct of porphyry copper deposits, and possesses potential for discovery as the major metal in porphyry deposits in either island arcs or Cordilleran belts. Tungsten and tin occur as major components of several potentially bulk-minable porphyry deposits, as well as being byproducts from the Climax porphyry molybdenum deposit. Whereas porphyry tin systems are localized in Cordilleran back-arc settings, their tungsten counterparts appear to span a range of geotectonic settings, from Cordilleran principal arcs through back-arcs to rifts. Although silver is a common byproduct of porphyry copper deposits, it tends to be preferentially concentrated with lead and zinc on the fringes of all types of porphyry deposits and/or as late-stage superpositions; the latter situation could be of some interest in the higher parts of porphyry systems. As byproducts, rhenium, uranium, platinoids and magnetite are exploited occasionally, and rutile and the rare metals, such as tantalum and niobium, have merited consideration.

Jan 1, 1982

By A. Mai, J. S. Wakeman

The progress results of a pilot plant study on the effects of ball top size and other mill operating parameters are reported. Test series on taconite and quartzite crude ores using a 1.7-m diam primary mill in closed circuit with a vibrating screen indicate clear trends on the improvements of mill throughput and power consumption when using larger diameter balls. Possible effects on mill liner and ball consumption as well as future research plans are discussed.

Jan 1, 1987

By John C. Galloway, Heinz G. Leistner

ACKNOWLEDGEMENTS The investigations described in this paper were supported by contracts with the Defense Nuclear Agency (DNA) under direction of Lt. Col. John Galloway, and by Boeing Company research funds under supervision of James Wooster. Other engineers of The Boeing Company who contributed to the work of this investigation were Don Armitstead, John McAvoy, and Tom Day. INTRODUCTION In this paper, we are describing a current concept for placing intercontinental ballistic missiles (ICBMs) in sites deep underground to be used as a strategic Future Secure Reserve Force (FSRF). The objective of such concepts is to utilize soil and rock cover to protect high value strategic weapons from destruction by nuclear attack. The burial deep underground achieves two purposes. First, it imposes a miss distance upon the attacking weapon equal to the depth of burial minus any penetration capability the weapon might have. This tends to offset increasing accuracy of weapon delivery. The other purpose is to absorb as much of the weapon's energy as possible, thus reducing the effects of powerful weapons. This use of soil or rock cover over military facilities began with the development of man's capability to loft projectiles. Until recently, underground military installations, by their nature, performed defensive functions. Since they are not mobile and their weapons in the past had very limited range, an enemy would have to approach them before an engagement could take place. Thus, they were often used to control "choke points" on sea lanes as in the case of Gibraltar or

Jan 1, 1979

By J. Loredo

In some rural regions of Peru, artisanal gold mining is currently an essential activity as it provides an important source of income. In the Huanca region (Ayacucho Department) gold deposits are not attractive for mining companies due to their reduced size, but they have enough interest for artisanal mining because of the ease and low cost of mining operations. Artisanal gold mining represents an important damage for the environment, because operations related to amalgamation processes using Hg result in special environmental problems besides the typical ones commonly associated to all mining activities. A preliminary sampling has been made in soils, materials from tailing ponds and surface water of the Acarí River, at the site of the Huanca village, according to networks specially designed for the particular conditions of the area. Studies accomplished revealed high mercury concentrations in soils and tailings. Chemical analyses of soils directly collected in the area of the active or abandoned ?quimbaletes? show mercury concentrations ranging from 15.3 mg?kg-1 to 44.2 mg.kg-1. Mercury concentrations in soils decrease as a function of distance from the before mentioned sources. Water quality of the Acarí River that flows through the area does not present important changes as a consequence of the mining and processing operations.

Jan 1, 2006

By M. S. Walton

A conference attended by a limited number of invited participants was held last September in Denver under the auspices of the Underground Construction Research Council of ASCE funded by the National Science Foundation (RANN) to explore the problem of accelerating the transfer of advanced geophysical technology, used principally in the petroleum exploration industry, into more effective and widespread use in subsurface investigations for underground construction. There are technological problems, but technical difficulties and unfavorable ratios of benefits to costs are not the major obstacles. The problem centers on the complex way in which potential net benefits are translated into effective incentives to innovate for each actor in the complex web of individual, corporate and institutional entities involved in the planning, designing, building, funding, operation and ownership of major underground construction projects. The entities responsible for site investigation, design concepts and specifications do not directly bear the risks of unanticipated costs and failures, nor directly gain from savings. The conventional unit-price construction contract is strongly implicated in blocking innovation. Problems of risks and incentives, more than technical feasibility, must be solved before large investments in technical adaptation and adoption can occur.

Jan 1, 1974

By R. G. Graber

Field testing of GPS mining applications has confirmed the technical and operational viability of GPS for precise, centimeter-level positioning in harsh taconite environments. GPS hardware has provided consistent availability exceeding 90%, with precision in certain applications of ± 0.07 foot at 95% confidence levels. Despite these technical successes though, challenges persist in achieving effective GPS integration. These challenges include the acceptance of new job tasks by mine personnel, the capacity of typical mine data communications infrastructure and the need to design GPS interfaces for new mining equipment.

Jan 1, 1998

By Gail I. Bakker, Mark E. Smith, George Sintay, Allan Young

The Snow Caps mine was an open pit and conventional cyanide heap leach gold project located 10 Km east of Independence, California in the Owens Valley. The project is unique in that it is one of the first projects to go full-cycle, from design through closure, under California's Chapter 15 mine waste regulations adopted in 1984. The property was acquired by Sunshine Mining Company in 1985. During 1986, final design and permitting were completed and the facility was commissioned in 1987. Mining continued to mid - 1990, when the minable ore body was depleted, and heap leaching continued into early 1991. Rinsing of the spent ore was completed in 1991, and final closure will be complete in 1992. The spent ore will be left on the leach pad for its final disposition. The focus of this paper is the permitting and closure aspects of the project as required by California's Chapter 15, Article 7 regulations.

Jan 1, 1992

By Jack G. Pippenger

The Coteau Properties Co.'s Freedom Mine is a surface lignite mine that uses large draglines, trucks and shovels, tractor-scrapers and bulldozers to uncover a single coal seam. In 1989, a work order system was instituted to record data by equipment type, cost, productivity and distance. The system was also used to provide historical information to plan the most efficient and economic use of each equipment type in the mining operation. The Coteau Properties Co. is a wholly owned subsidiary of The North American Coal Corp. The company was formed in 1972 to supply lignite from its Beulah-Hazen coal reserve to a coal gasification project and an electrical generating facility located near Beulah, ND. The reserve consists of a single coal seam between 3 and 7 m (10 to 23 ft) thick. The overburden above the coal is predominately glacial tills and clays and ranges from 6 m (20 ft) to more than 60 m (200 ft) thick.

Jan 1, 1994

By C. Patrick

Annually, the U.S. coal industry generates and must dispose of over 200 million tons of coal refuse, expanding a major environmental problem. The purpose of this research was to investigate the feasibility of utilizing coal refuse as an aggregate in concrete. This paper reports on findings of the initial phases of a project to determine the viability of replacing traditional concrete blocks, used for under-ground ventilation stoppings, with refuse blocks. Refuse was collected from three active preparation plants in Eastern Kentucky and used as the primary aggregate for concrete cylinders. The refuse fell within ranges normally observed for size consist, moisture, and ash. Stress-strain analyses yielded compressive strengths of the refuse cylinders from 59% to 77% of the control group strengths. Low variability within groups while significant differences between groups were found. On-going determination of effects of weathering on the refuse cylinders is being conducted and will be completed in early 1995. The research results are favorable for the future direction of the overall project objectives.

Jan 1, 1995

By Yi Luo

Simulation of the multi-entry and multi-crosscut (MEMC) ventilation systems commonly employed in U .S. underground coal mines can be very tedious, due to the large number of crosscuts with stoppings to be represented in the network models. In order to reduce the amount of work needed to build the models, a common practice is to represent a number of crosscuts with one equivalent airway. However, this introduces certain errors into the simulation results. In this paper, algorithms have been proposed to simplify the ventilation networks of common MEMC systems encountered in panel development operations. The algorithms can be used to reduce a MEMC system into one airway with an equivalent resistance and to determine the airflow distributions in the system and the leakages through the stoppings.

Jan 1, 2011

By Sheldon P. Wimpfen

Man is a short time resident of the planet Earth. He does not have the memory to fully comprehend just what is going on. His span of knowledge can be related to the life of the world to see that this is the case. A museum at Grand Canyon features a geologic clock that compresses Earth's age of 4.5 billion years into 24 hours. Man's estimation of the earth's age has changed radically in the past half century. In 1930, one prominent geologist asserted that the age of the Earth was ". . . at least 600 million years." Later, physicists used radioactive clocks to conclude that the Earth's age was 1.6 billion years. More recently, geologists have found rocks in northwestern Australia estimated to have formed 4.5 billion years ago. As we learn more about what is underfoot, the estimate of Earth's age might change again. The Grand Canyon's 24 hour clock shows that the dinosaurs were the dominant life form for 165 million years. Then an event occurred that wiped them out about 65 million years ago. The prevailing theory is that an asteroid struck the Earth and generated enough dust to wipe out the vegetation upon which most dinosaurs fed. During Earth's existence, there have been at least 12 such mass extinctions - the worldwide disappearance of diverse animal groups. On a planet that has been around for 4.5 billion years and that may continue to exist for another 4.5 billion, it seems reasonable to expect that further mass extinction's will occur. According the Grand Canyon's 24hour clock, the 165 million year reign of the dinosaurs amounted to about five minutes. On that 24 hour clock, the world has been dinosaur free for almost two minutes.

Jan 1, 1993

By Peter N. Loncar

Most miners dream of finding a gold mine sometime during their mining careers, but not very often do such dreams come true. On the tenth day of September, 1962, our dream of finding gold came true when the results of the third drill hole were received. This was undoubtedly one of the most exciting days of our lives. Little did we realize then that this was the beginning of a major discovery destined to became one of the largest gold mines in the country. Discovering and mining gold is not entirely new, however, to Eureka. County a old Lynn Mining District in northeastern Nevada. Since 1900 there has been sporadic activity, mostly consisting of small lode mines and placers. These have produced totally about $300,000; and existence of our orebody would probably have remained unknown had it not been for the United States Geological Survey. The USGS extensively mapped the Roberts Mountain Thrust and published a paper indicating that mineral occurred along this fault and in some places was gold bearing. Utilizing this information, our Newmont Exploration geologists located an area in which: drills were brought in to test their theories. By keeping flexible in our thinning and working, we were able to bring a raw prospect to a producing mine with ore reserves of eleven million tons in a short three-year period.

Jan 1, 1965

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' 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', 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' 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