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By M. A. Vera

This paper proposes a simple two-parameter model for the typical inverse relationship between recovery and flotation concentrate grade. The model is based on the mineralogical limitations imposed by the material properties. One parameter (R*) describes the proportion of metal content which is floatable, and the other (b) is the rate at which the fastest floating particles are being contaminated by the other less valuable particles present in the mineral system. One significant feature of the recovery-grade curve is that initial recovery (i. e. R ? 0) is at the purest attainable mineral grade, (but as recovery rises the cumulative grade of the concentrate tends to the feed grade. The ideal recovery-grade curve for a particular mineralogical system can be obtained by release analysis: the release analysis curve determines the maximum or limiting separation efficiency. The model proposed in this work is similar to the linear recovery - cut-off grade model of Dell (1), but has the advantage of describing the whole curve.

Jan 1, 1999

By William D. Leech, Peter S. Buskirk

Virginia Electric and Power Company commencing in early 1985 will begin operating the Bath County Pumped Storage hydroelectric facility, presently the largest capacity installation of its kind. Six concrete lined vertical shafts, 3 ea x 44.0 ft (13.4m) diam x 330 ft (100m) and 3 ea x 28.5 ft (8.7m) diam x 740 ft (226m), comprise a portion of the three underground power conduits. The project team decided to employ the slipform over the conventional jump form method. This selection was based on the engineer's hydraulic design and the contractor's performance requirements. This paper presents the key elements of the shafts' successful slipform operations. The contractor achieved slip rates as high as 60 ft (18m) per day; and the owner received competent permanent linings as specified by the engineer. The authors describe the team's effort to progressively improve both concrete quality and placement rate.

Jan 1, 1985

By Vladimir Adamek

This paper describes the Bureau of Mines development of a novel subsidence prediction methodology suitable to the mining and geologic conditions in the Northern Appalachian Coal Region. It describes the computation of vertical and horizontal movements, inclination, curvature, and horizontal strains. The substance of this method is the separation of the effects of lithology by introducing a correlation between hypothetically homogeneous overburden and existing lithologic conditions, while providing for different mining conditions, i.e., underground geometry and overburden thickness. The effects of lithology have been expressed in the form of a variable subsidence coefficient within the subsidence trough. The subsidence coefficient is considered a constant for other predictive methods. Field data from 16 test sites at 11 Bureau longwall panel studies were used in the analysis. For each panel, the characteristics of the variability of the subsidence coefficient were defined. Regression analysis of the subsidence coefficients from all test sites on their locations relative to the edges of their respective panels yielded a third-degree polynomial equation. The results from additional longwall panel studies, not included in the regression analysis, were used to prove the validity of this method. To facilitate the use of this precalculation methodology, a computer program was written in BASIC for use on a personal computer.

Jan 1, 1987

By Trevor A. Moss

Installation of equipment and structures at mines often requires mine planners to evaluate unique loading and operating conditions. Consideration of these unusual features is required throughout design and construction and into operation. Most planners understand the necessity of employing sound civil, structural and mechanical engineering techniques to design these structures and equipment. However, the influence of geotechnical factors on the overall progress of construction and operation is less appreciated. Mine operators routinely perform exploratory drilling to define ore deposits. These exploration activities can be extensive and often include provisions for assessment of subsurface conditions as they relate to the mining operation - requirements for ground support. All of these factors are important to the economics of the mine and are well justified. Surface facilities are provided to access and service the mine, and they play an important role in the successful development and operation of a project. Headframes, hoist foundations and shaft collars, in particular, are examples of unique installations encountered at underground mine sites. The design and above-surface behavior of these facilities can be analyzed with the usual fundamental engineering practices employed throughout the engineering professions. However, near surface exploration for the purposes of assessing soil and rock conditions for foundations is often given a reduced priority and less consideration. This article provides an outline of the benefits and importance of performing such exploration. References here relate particularly to shaft headframes, hoists and shaft collars. But the issues raised apply equally to other installations of a similar nature, including milling equipment.

Jan 1, 1992

By Reinhard Gnilsen

Ground pillar control in soil and weak rock often represents a critical and sometimes a determining factor for mined underground civil structures. A concept is desirable that minimizes the restrictions possibly imposed by pillar control requirements on geometrical tunnel characteristics and on the mining operation itself. Conventional concepts are discussed and an alternative concept is introduced. This concept reduces pillar control requirements to ground control measures required with "regular" tunnels. The conventional model of pillar mechanics with potential yielding of a ground body in more than one direction, is then avoided. Due to the complexity of pillar mechanics, the level of engineered design furnished to the contractor is crucial to optimizing ground pillar control. Conventional versus alternative contractual arrangements for pillar control are described and their important role is illustrated. The concept introduced relates to principles inherent to the New Austrian Tunneling Method (NATM). However, tunnel projects using other mining concepts can employ alternative ground pillar control principles as well, if certain criteria are observed. Case histories in the United States and abroad are presented and the impacts from different concepts of ground pillar control are illustrated. The paper concludes by analyzing concept characteristics that can infer monetary impacts on both the owner and the contractor.

Jan 1, 1987

By Jack Parker

Pillar design ought to be a matter of matching pillar strength against pillar loading conditions to come up with dimensions that will cause the pillar to behave as required - to stand forever, or for a limited time, or to fail in a controlled manner. But something has gone wrong in recent years, seriously wrong. Pillar design practices have departed from reality. The laboratory and computer have taken the place of the mind. If the mind is put to work and such pillar design practices are examined critically, it becomes obvious that they deal with conditions that do not exist in a real mine. Time, effort and money are wasted, and the end results are incorrect and misleading. These questionable pillar design practices have been passed on from generation to generation over the past 30 or 40 years. The hope here is that we can return to reality as soon as the questionable practices are generally recognized. We could then go back into the mines and define how pillars really work, and mining safety, efficiencies and costs should improve. Let us take a close look at current textbook design practices and compare them to real-life conditions. Common sense might then prevail. (At this time, we will consider only mine pillar design, but similar scrutiny should be applied to design criteria for width of openings, floor conditions and roof support systems.)

Jan 1, 1993

By E. D. Attanasi

Exploration for non-fuel minerals has declined since 1988 as recessionary pressures have slowed growth in the industrialized economies. By most accounts, however, 1990 expenditures were still significantly greater than the low levels experienced in the mid-1980s. The Persian Gulf crisis introduced instability in energy prices and greater uncertainty into an already cloudy economic picture. As 1990 unfolded, the US savings and loan problems spread to the commercial banking system, leading to the failure of several major US commercial banks. The Japanese stock market also suffered significant losses as Japan's Central Bank raised interest rates. The Soviet Union experienced shortages of food and other basic items. Its government faces resistance to changes leading to a market economy. Individual Soviet republics also are seeking more control of their own destiny. The cost of German reunification, in terms of the capital required to bring the east's infrastructure and industrial base to western standards, also appears to have been underestimated.

Jan 1, 1991

By Charles H. Dowding

INTRODUCTION "On many projects, the tendency is to drop interest and support of the geological service as soon as it seems safe. That . . . is a short-sighted policy . . . It would be of further service perhaps to learn whether predictions were reasonably true to life." --C.P. Berkey, 1938 (3) This paper quantitatively compares predicted and encountered shear zone size and location and rock type for tunnels in the Colorado Mineral Belt. The Colarado Mineral Belt is composed of igneous formations with associated metamorphic rocks and faulting. As such, it represents the most complex of provinces for at-grade predictions (27). Shear zone and rock type data are assumed to be statistically homogeneous because of the common geology of the seven tunnels. It is often felt by geologists and engineers that the amount of information from which a geological model is created is so low that any statistical inferences are unstable. In other words, the addition of new data may drastically alter the means and variances suggested by the model. Therefore, predictions are rarely couched in quantitative statistical terms but modified with "probably," "most likely" or "possibly." Comparison of predicted and encountered data from past geological models will permit the "probably's" to be quantified and distilled from the art of geological prediction. To date, two other studies of the validity of predictions have been made (26 and 16). Together, these two studies indicate that

Jan 1, 1976

By W. A. Steingraber

This paper discusses the application of deep well disposal techniques to the problem of disposing of large volumes of low level radioactive wastewaters generated by the in situ uranium mining industry in Seth Texas. Data is presented on wastewater composition and volumes, geologic and hydrologic parameters of the disposal reservoirs, tell construction techniques, well operation, well monitoring requirements, and critical factors in evaluating the Safety and environmental impact of a deep injection well system.

Jan 1, 1980

By Philip U. Santacroce, James H. Meinholz

INTRODUCTION The Milwaukee Metropolitan Sewerage District (MMSD), is a special purpose sub-regional agency that provides collection and treatment services for sanitary wastewater for an area of 420 square miles (1088 km2) in 27 municipalities in the Milwaukee, Wisconsin metropolitan area. During its almost 75 years of existence, it has constructed 464 km of intercepting sewers, the majority in tunnel, and two sub-regional secondary wastewater treatment plants. The present program, the $1.7 billion Milwaukee Water Pollution Abatement Program, was started in 1977 and developed from ongoing internal planning, the Federal Clean Water Act and court judgments. Elements of the Program include improvement and expansion of the two treatment plants; rehabilitation of older in-place sewers; building new interceptors and relief sewers and providing capacity for high volume storage in approximately 32 km of deep, large diameter rock tunnels; reducing combined sewer overflow; and disposal/utilization of the solids that remain after the treatment process. The construction phase of the Program accounts for $1,105,900,000 within 335 separate construction contracts, 211 let to date, and covers a span of 15 years, starting in 1979 and running through 1994. Conveyance System construction cost is estimated to be $650,000,000 or about 60 percent of the total. Through December 1986, in terms of dollars, the total construction program is about 38 percent complete with Conveyance at 34 percent complete.

Jan 1, 1987

By Z. Eisenstein, H. Heinz

INTRODUCTION Contemporary underground transit systems often require cross sections which are not adaptable to shield tunnelling. Due to the frequently large dimensions of these cross sections, which are normally situated at shallow depths and in soft ground, full face advance is not feasible because of ground control and construction requirements. Ground deformation and face stability are controlled by "staged excavation", which consists of sequentially driving smaller, specially arranged, individual headings hence avoiding full-face excavation. Shotcrete is normally used for initial support and these tunnels are frequently described as applications of the New Austrian Tunnelling Method (NATM). Figure 1 illustrates the relative size of large cross section tunnels with respect to conventional shield tunnels. Within the scope of this paper, 'large' cross sections are defined as those whose continuous (i.e., without intermediate pillar support) cross sectional excavated area exceeds 60m2. This definition includes most double track highway, railway and subway tunnels, subway stations and some single track railway tunnels. Excavation schemes which have been more frequently used for continuous cross sections (i.e., with no intermediate pillars) are presented in Figure 2. This classification is an extension of that presented previously by Eisenstein et al. (1986). The symbols used for classifying the excavation schemes are formed by the letter T (for "type"), followed by a number, which represents the number of excavation stages fully embraced by a shotcrete ring, termed "cells" by Lessmann (1986). The numbers inside the cross sections in

Jan 1, 1989

Jan 12, 1951

By H. Barry Holt, Charles A. Bischoff

On November 15, 1990, President Bush signed the Clean Air Act Amendments of 1990. The new legislation is sweeping in its demands for cuts in smog, acid deposition, toxic air pollutants and ozone-depleting chemicals. The Amendments will siqnificantly alter air quality permitting and compliance and are estimted to cost billions of dollars to implement. This article provides an overview and summary of each of the eleven titles of the Amendments. It also addresses how the Amendments will be implemented.

Jan 1, 1991

By John A. DesLauriers, Hans J. Broennimann

INTRODUCTION The early record of tunnel excavating machines in hard rock tunneling has not been one to particularly brag about. We have all heard the stories of major difficulties when trying to break hard rock with machines at promised advance rates of several times that of conventional drill and blast. Unfortunately, sometimes this has not happened. It has been through this trial of the past generations disappointments that today's TBM's have evolved to their present high level of performance in a wide range of ground conditions. Today's machines offer much increased reliability and durability. This translates into high availability to the tunnel contractor. Although there still are occasional disappointments being reported, the state of the art is that reliable and predictable machine excavation of rock now is both a reality and well founded expectation. The most recent editions of Atlas Copco's MINI/MIDI Fullfacer, we feel, make a strong contribution to the reliable performance of todays TBM's---especially in small-size rock tunnels. This report will, 1.) explain the equipment and effect of rock both on the cutting technique and machine performance; 2.) list advantages of the non-circular shape, during and after construction; 3.) list applications in civil and mining industries; 4.) discuss North American experiences, performance and costs; 5.) list advantages over drill and blast and; 6.) discuss briefly lease arrangements.

Jan 1, 1979

By Charles T. Ford

Limestone neutralization of acid mine drainage has been proposed and examined as a method of treatment. However, limestones differ greatly in composition and structure. The reactivity of 14 selected limestones was studied, both by chemical and physical properties and by relative effectiveness in neutralizing synthetic and actual mine waters, and several guidelines for the choice of limestones are given. The particle size should be at least as small as 74 microns and preferably smaller. The most effective limestones are most nearly pure calcium carbonate. Stones which have a relatively low calcium con- tent but which contain calcite and have a large surface area are also effective neutralizers. Magnesite and dolomitic limestones are much less reactive. Disadvantages in using even the most reactive lime- stones for neutralization are indicated.

Jan 1, 1974

By Eugene F. Casey, John G. Ruggiero

INTRODUCTION Construction of tunnels in urban areas, especially reclaimed areas, pose many problems. The Red Hook Intercepting Sewer Tunnel, Contract 1A is a portion of the Red Hook Water Pollution Control Project located along the Brooklyn waterfront in New York City. This contract required the construction of a 2620 meter long (8600 L.F.), 3 meter (10-foot) diameter soft ground tunnel, eight Tunnel Manholes, nine Regulator structures, four Diversion and Tidegate structures and 765 meters (2500 L.F.) of branch intercepting sewers of diameters between .30 meters (12 inches) and 1.8 meters (72 inches). The construction contract bid price was $62 million with a duration of three years. The tunnel route crosses over five sets of operational twin cast iron subway tubes with clearances ranging from 4.3 meters (14 feet) to as small as 0.35 meters (14 inches). The route of the tunnel traverses historically interesting areas which have been reclaimed over the last 200 years. This paper is a case history describing the contractor's methods utilized to successfully advance the work through the above problem areas. LOCATION The Red Hook Intercepting Sewer Tunnel is located in the Borough of Brooklyn of New York City. The route is

Jan 1, 1981

By P. C. Guillaume

Global plant modernizations or expansions cannot be considered in the same light as any other industrial investment project. Relationships between the partners, relationships and communications with the client, structure and organisation of the teamwork, schedule of the work, and a lot of other tasks and missions devoted to external contractors have to be defined considering one fundamental input: an operating plant. For an engineering company expert in processing, like UM Engineering, such a context requires a specific approach as well as specific procedures able to efficiently challenge the generated constraints. First of all, even if a detailed audit had been conducted at the beginning of the conceptual engineering phase, new elements will be discovered during the preparation and realization of the project, and must be continuously integrated. Consequently, a close proximity to the site is necessary. This is one reason why UM Engineering, most often, works in partnership with a local engineering company. The second important point for the client is that the operation must not be interrupted during the realization. In order to make that possible, UM Engineering has defined a specific project structure and organisation, integrating on a permanent basis the operators (the "users") in the project teams. This paper presents the way UM Engineering copes with this type of "multi-constraints" context with reference to the recent copper cellhouse modernization under realization for the CCR Refinery of Noranda Inc. in Canada.

Jan 1, 1999

Australian continental crust has accreted and consolidated by thirds: 1/3 during Archean time, 1/3 during Early to mid-Proterozoic time, and 1/3 during latest Precambrian to mostly Paleozoic time. The progression of orogenic systems and the crustal consolidations they represent seem not fundamentally different in basic orogenic processes from better known Mesozoic-Cenozoic examples in that accretionary, continental margin, collisional, and intraplate intracratonic inverted and/or reactivated systems are all recognizable in the tectonic evolution ofAustralia.

Jan 1, 1995

By Robert G. Ditchburn

Dating seafloor mineralization at hydrothermal centres of submarine arc volcanoes is important for understanding deep-seated volcanic events that can produce deposits rich in base and precious metals. The activity ratios, 228Th/228Ra, 228Ra/226Ra (Bq.Bq-1) and 226Ra/Ba values (Bq.g-1) are used for dating barite- rich seafloor massive sulphide (SMS) in the age ranges 0.3 ? 12 years, 3 ? 35 years and 500 ? 15,000 years, respectively. Thus, the time elapsed to amass an economic deposit and, ultimately, its capacity for sustainable extraction, can be estimated. 226Ra/Ba and 228Ra/226Ra values have been measured in relatively young chimneys that were collected, 1998 to 2006, from hydrothermal sites at Brothers and Clark volcanoes (Kermadec arc) and East Diamante volcano (Mariana arc) to check these initial ratios, essential for calculating ages for older mineralization at the same sites, were not varying significantly. We found that the 226Ra/Ba value for fresh SMS mineralization at the Brothers NW caldera and East Diamante hydrothermal sites have been reasonably stable for 6 years and 2 years, respectively. At both sites, the 228Ra/226Ra value for fresh SMS has been stable for 5 years. This was established from young chimneys where the measured 228Ra/226Ra value could be corrected for radioactive decay using the age derived via the 228Th/228Ra method. However, long-term stability of the initial 226Ra/Ba and 228Ra/226Ra values has yet to be proven. These isotopes of Ra are used as a proxy for better understanding of the transfer of Ba from deep magmas to the seafloor, via the circulating fluids of the hydrothermal system.

Jan 1, 2011

By Nathaniel Arbiter, Brij M. Moudgil

Separating oil shale from waste material or into high- and low-grade fractions can have a major economic influence on the surface retorting process. Different shale rock components vary significantly in physical and surface chemical properties, such as specific gravity, color, and water wettability. Various techniques that use the differences in one or more of these properties have been proposed to preconcentrate oil shale before retorting. This article discusses some proposed techniques, such as gravity separation, sorting, and froth flotation. Retorting oil shale is the most common method for recovering oil from the rock. This process is accomplished either underground (in situ) or above ground (ex-situ or surface retorting). Both techniques have serious limitations, such as low recoveries in the underground method and the ability to process rich shales only in the above ground retorting method. Also, environmental problems are associated with both techniques. Some of these limitations could be overcome if feed to the retorts is of consistent grade. This could be achieved by selecting appropriate sites for in situ retorting and selective mining for surface oil shale retorting. Both of these, however, would have a serious economic impact on shale oil recovery. Obviously, little control can be exercised over preparing feed material in the in situ retorting process, but beneficiation of oil shale could definitely be advantageous in surface retorting, and should have positive influence on the overall economics of recovering oil from the shales. For example, preconcentration of mined shale could result not only in reduced costs for materials handling, but also in waste disposal costs, since waste characteristics before and after the retorting process are significantly different. Upgrading the oil shale might also allow substitution of alternate technology for retorting as well as extend the process to recover oil from marginal deposits. Also, the separated material may become a potential source for recovering other values from shale deposits. Overall, the incentives for preconcentration are to reduce costs and improve thermal efficiency of the recovery process. Oil Shale Properties Important to Preconcentration Oil shale is a carbonaceous rock assaying 5-30% organic material (kerogen) and 70-95% ash-forming minerals. Kerogen is soft, nonbrit¬tle or semi-brittle material, and generally forms a matrix between irregularly distributed mineral grains. Inorganic mineral mat¬ter-quartz, feldspar, dolomite, kaolinite, dawsonite, and nahco-

Jan 9, 1982