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By E. E. Krist

El desmuestre de un criadero tiene un buen número de finalidades. En la fase inicial es necesario definir los límites del yacimiento y el contenido o ley del mineral hasta el punto de que pueda ser establecido si es, de hecho, un yacimiento económico. Igualmente, las muestras tienen que ser generadas de forma tal que las evaluaciones geológicas y metalúrgicas puedan ser Ilevadas a cabo. Finalmente, cuando se conoce la suficiente información concerniente a la geología, mineralogía y metalurgia, puede ser desarrollado un método minero y su plan, y construidas las oportunas plantas metalúrgicas para procesar los minerales a medida que se encuentran disponibles1. Con las minas actuales grandes y complejas a cielo abierto los métodos de desmuestre único deberían de ser inadecuados. La perforación por diamante, la perforación por percusión, pozos subterráneos y galerías, juegan todos conjuntamente un papel parcial en la definición total del yacimiento. En la mina Twin Buttes, de la Anamax Mining Company, el desmuestre y la definición del yacimiento conducirán eventualmente a la existencia de tres plantas metalúrgicas de proceso y, quizá a, una operación de minería subterránea. Fue puesto en marcha un concentrador de sulfuros de 30.000 tons. por día en Septiembre de 1969 y una planta de 10.000 toneladas diarias de lixiviación de óxido fue puesta en servicio en Mayo de 1975. La finalidad de esta presentación es la de exponer históricamente el desmuestre del yacimiento que ha sido Ilevado a cabo en Twin Buttes, describir brevemente el criadero, y exponer los métodos analíticos corrientemente utilizados para ayudar al geólogo, al metalúrgico y al diseñador de la mina en sus respectivas evaluaciones.

Jan 1, 1982

By William A. Dupree, Mark J. Schultz, William J. Francart

Maintaining intake escapeways clear of contaminants from mine fires has been an issue for many years. Removing fire sources from these entries reduces the risk of contamination greatly. In recent years, concerns have been raised related to contamination of the intake escapeways by leakage when fires occur in adjacent airways. This paper discusses measured leakage rates for multiple stoppings at various pressure drops across stopping lines in a number of actual coal mines. Also addressed are methods for reducing the contamination risks for the intake escapeways, considering the ventilation system employed. The Effects of Air Leakage The effects of air leakage through ventilation controls has been well documented. While normal leakage is expected through stoppings, overcasts and other structures, abnormally high leakage results in an inefficient ventilation system and can increase operational costs for a mine. In addition, excessive leakage results in less control over mine ventilation airsplits. This may compromise the isolation of mine escapeways, and allow adjacent entries to be rapidly contaminated by products of combustion in the event of a mine fire. A study was conducted at ten mines in which air pressure and quantity measurements were taken near the active sections. The method used to construct the ventilation controls to separate airways was also noted. Stopping Construction Table 1 shows the type of stopping construction commonly used in the 10 mines included in this study. Main entry stoppings were normally built with mortared joints (wet stacked) with sealant applied to the high pressure side of the stopping. In most cases the entire face of the stoppings were sealed. In one case only the joints between blocks were sealed but the perimeters were sealed in all cases. Some mines also sealed the low pressure side of the stopping. Solid blocks were normally used for main entry construction and hollow blocks were sometimes used for longwall panel development. [ ]

Jan 1, 1993

By H. W. Seany

Over the years since the initial experiments with underground concreting were made in 1956, attesting to cope with the ground weight and pressure encountered in the development of a large-scale underground block caving system, the use of monolithic concrete linings has grown to include most of the primary development in the, mining area. Although the development cost of concrete linings is higher than either timber or steel-supported openings, the repair and maintenance costs are substantially lower, making concrete the most economical means of ground support. Other advantages are also apparent, in that concrete provides superior fireproofing, better ventilation, and a safer, cleaner working place.

Jan 1, 1965

By Thomas V. Durkin

About 1.41 kt (45.2 million oz) of gold have been ! produced in South Dakota since 1875. South Dakota's mining laws attempt to strike a balance between economic development and environmental protection. Mining is promoted as an industry while prevention of pollution is required along with reclamation of affected lands to a beneficial use. The South Dakota Department of Environment and Natural Resources' (DENR) system of "one-stop shop- ping" for environmental permits streamlines the permit process. It fosters quick resolutions to compliance problems and helps keep enforcement actions out of the courts. Paha Sapa means "Hills that are Black" in Dakota Sioux. Appearing dark from a distance due to a thick forest of Ponderosa pine, the Black Hills were gold to many people. The exact date that gold was discovered in the Black Hills remains debatable. An inscribed stone tablet found in 1887 near Spearfish recorded these words:

Jan 1, 1998

By Colin J. Douch

New Zealand has been a significant producer of gold for over a century. Total recorded production is over 850 tonnes. There were three major periods of production: the first and biggest was between 1860 and 1880, the second was between 1895 and 1920 and the third was between 1930 and 1945. After 1945 gold production fell continually until 1980 when the major upward adjustment in gold price led to renewed interest. There have been important new developments in each of the known gold-rich areas: Westland, Otago and Coromandel and exploration for gold in these areas and in previously unprospected regions has reached unprecedented levels. In Westland over 140 gold processing plants are each producing between two and six ounces a day from low-grade placers. A major gold dredging operation will soon be producing over a tonne of gold annually and other new dredges are proposed. There are still vast reserves of gold-bearing gravels in Westland and prospecting is continuing to reveal new resources. In the Reefton area there is renewed interest in gold-bearing quartz reefs which were the source of over a million ounces of gold between 1900 and 1951. New large opencast reserves are now defined.

Jan 1, 1988

By Tetsuji Hirato, A. J. Monhemius, Yasuhiro Awakura, G. W. Warren, E. Peters

An electrostatic pseudo-liquid membrane technique, in which extraction and stripping take place simultaneously in a single reaction vessel using an electrostatic dispersion, was applied to recover Ni(II) from aqueous 0.1 kg m-3 Ni(II)(as NiSO4) – CH3COONa solutions, and the Ni(II) ions were concentrated by a factor of 9 into an aqueous 1.0 kmol m-3 HCI solution using D2EHPA as an extractant at the applied voltage of 3.7 kV for the dispersion. When the process of ESPLIM proceeds favorably, the concentration of Ni(II) in the upper part of the organic phase of the reaction vessel is lower than that in the lower part. In addition, the concentration of Ni(II) in the organic phase of the extraction chamber is higher than that in the stripping chamber. For the stable operation of this process, the stripping rate must be greater than the extraction rate to prevent the excess accumulation of Ni(II) in the organic phase which leads to the poor dispersion of the aqueous phase.

Jan 1, 1993

By Anthony Edey, Leigh A. Readdy, Bruce A. Kennedy

Introduction Very little attention normally is given by the experts, or the public at large, to the fact that the majority of the oil that has been or will be discovered within the U.S. remains in the ground. The inherent limitations of oil production through surface wells, either by primary or secondary techniques, will result in a total of over 300 billion bbl of oil left in the ground after completing production by standard petroleum techniques in currently producing or producible fields. This reserve represents some two-thirds of the original quantity of oil discovered in place. Recent work by a number of groups has shown that there is strong economic justification for extracting this remaining oil by mining and processing techniques. Table 1, taken from 1977 API reports, demonstrates the oil left in place at the end of the con¬ventional petroleum production cycle in then-known fields within the U.S. Possible targets for oil mining operations include (1) oil remaining in place in fields and pools that have reached economic depletion by current petroleum production methods and that are not amenable to economic recovery by conventional petroleum industry techniques; (2) oil-or bitumen-saturated rocks not normally considered by the industry to constitute producible reservoirs, such as shales and diatomites; and (3) asphalt- and bitumen-impregnated rocks. Economically Depleted Fields A more detailed examination of the depleted fields shows that estimates of oil remaining in place after primary, secondary, and nondestructive tertiary recovery can vary widely. There is significant evidence, however, that more than half the estimated original oil in place (OOIP) remains in the reservoir after all petroleum extraction techniques have been applied. If one compares the sum of past oil production and estimated remaining producible reserves with the API estimate of total discovered OOIP as of 1975, it becomes apparent that for the U.S. as a whole, 67% of the OOIP will remain in place at the end of the

Jan 9, 1980

By Andrew Mackenzie, Paul Rantala

Data is now appearing in literature that indicates many current paste fill systems in Canada suffer from plugged lines and severe wear rates. Both of these conditions suggest: design problems with the pipe distribution system, backfill composed of poorly graded material and/or possibly poor operator practices. Problems that can be prevented in the design stage, but still may be readily solvable with current technology. However, if left untreated will lead to an increasing frequency of down time. The compatibility of the distribution system with the paste fill rheology is fundamental and essential for the reliable delivery of fill. Either many mine operators are not familiar enough with the technology to provide a critical review that could foresee problems down the road, prior to construction and or North American designers are not clarifying their designs to their customers. The objective of this paper is to highlight key concepts to mine operators with the purpose of better enabling a critical review of contractor's/consultant's designs. There is a great deal of understanding about the rheology of backfill over a range of pulp densities from hydraulic slurry to dense to paste. However, outside of deep mines (especially in South Africa) neither hydraulic or dense fill distribution systems have suffered the problems of paste fill. Paste fill is fundamentally different from hydraulic fill principally in its transportation characteristics. These differences have a direct impact on the design of the distribution system. By understanding the practical implications of these differences the operator can play a more active role in their design while better appreciating how to best operate their own system.

Jan 1, 2001

By J. Wes Blakely

In the mid-1950s the importation of foreign oil began to encroach on traditional coal markets such as railroad steam engine fuel, home heating, electrical generating plants, and others. Many of the smaller coal companies with substantial coal reserves subsequently found that they could no longer continue to mine economically and merged in various ways with larger established coal mining concerns. As the seats of top management and authority were removed from the mines to large metro centers such as New York, Pittsburgh, and Chicago, the more personal relationship between mine workers and management that had existed prior to these mergers began to be eroded and replaced by " remote control " mine management. The disappearance of this face-to-face contact of upper management with mine employees tended to create barriers blocking simple effective communications between coal mine management and labor. In examining the human relations aspects of the coal mining industry, many elements, some concerned with work and others not, have depicted the industry as almost devoid of good applied human relations and communications practices, and, in truth, little has been done to alleviate this situation. In past years many coal producing companies, with the exception of one of the largest, failed to adequately define the term "communications" as it applied to their companies, whether internally or externally. Internally many still place heavy reliance on written communications such as company-wide newspapers to do the job of communicating with their employees which they feel ought to be done. One company puts an inordinate belief in its company "newspaper" as the primary instrument to stimulate its work force into increasing productivity. Primarily aimed at the workers, who greatly outnumber the salaried administrative people, this publication mainly documents the fortunes of individual mine workers who are felt to have achieved something with their lives, e.g., a mine worker who had managed to put four children through universities, the philosophy behind this being to inspire other workers to achieve worth- while goals.

Jan 1, 1981

By E. Spyridonos

Sustainable development in the mineral industry requires a paradigm shift from purely economic to multi-objective decision-making, considering economic, social, environmental and governance criteria. The commonly accepted aim is responsible stewardship of non-renewable resources. State-of-the-art 3D geological and mine modeling software technology can contribute to meet this objective as reliable and accurate geological models form the basis for an optimum management. The benefits obtained by the application of computerized modeling are illustrated at hand of three studies. The examples cover global and local producers of industrial minerals in fully developed as well as development countries. They refer to different levels of planning, from initial resource assessment over long-term planning to the generation of rolling forecast for operative planning in a running mine.

Jan 1, 2003

Compared to alternative ways of dealing with coal fines, oil agglomeration has always been a commercial bridesmaid and never yet a bride. Yet interest is high in the process, as shown by a number of pilot plants in operation that are funded by industry as well as government. In the past in the US, alternative ways to handle coal finer than 100 to 200 mesh included flotation, or no treatment except dewatering, or discarding the fines as waste. There are now a number of factors that tilt the economics more toward fine coal recovery. Today, the cost of mining a ton of underground coal runs from $22-30, and discarding even 10% as unrecovered fine coal is a real economic loss. A number of attempts (notably by EPRI) have been made to quantify the effect of coal cleaning on utility boiler operations. Transportation and ash handling costs, frequency of unscheduled outages, fouling and slagging problems, and boiler tube erosion are all lowered by cleaning coal. The advantage of coal cleaning on these parameters has been shown, but the dollar amount varies with many assumptions and is difficult to pin down. The message to a utility, however, has not been lost and the trend toward cleaner steam coal is accelerating. This may lead to fewer installations that only wash the coarse coal, and add back the unwashed fine coal until a maximum contractual ash limit is reached. And, as the proportion of coal fines continues to increase by continuous and longwall mining, it may become impossible to clean the coal sufficiently without cleaning the fines. Flotation and oil agglomeration are the only processes that presently deal directly with cleaning the very finest coal fractions. Flotation has proven its effectiveness in cleaning blackwater and in separating fine coal from mineral matter. It has the achievable potential for far greater pyrite rejection than is now obtained in commercial preparation plants. While flotation will continue to be the predominant method for fine coal cleaning, there are conditions and opportunities where oil agglomeration can be a

Jan 8, 1980

By H. Ziock, J. Ruby, A. A. Johnson

Power generation systems that promote energy security and environmental benefits are highly desired and pursued by a number of government and industry programs. Gasification of coal, other fossil fuels, or biomass has the technical promise of high efficiency and low or zero emission. Gasification for the purpose of electrical power generation has been researched, developed and demonstrated over the last 20 years, but for many reasons is not viewed as economically competitive. This paper describes a coal-based gasification technology well suited to mid and long-term goals of secure, environmentally clean energy. The technology should be adaptable for use with other carbon-based fuels including biomass and a full range of fossil fuels. The new zero emission gasification process is sponsored by ZECA Corporation, a continuation of the Zero Emission Coal Alliance (ZECA). ZECA has completed process design and engineering to assess the viability of a concept originated at Los Alamos National Laboratory, and the creation of a business plan to define paths for advancing the technology toward a near-term goal pilot plant. The zero emission carbon (ZEC) technology includes hydrogasification, the production of hydrogen and the carbonation of lime with CO2. For the power generation base case, the hydrogen is used in high temperature coal compatible fuel cells to produce electricity and the carbonate is calcined to produce a pure stream of CO2for sequestration. This paper provides the status of work with the ZEC technology and the availability of crucial equipment, materials and required testing. Discussions are presented for future actions to accelerate the technology assessment, testing and demonstration of a ZEC plant. Brief remarks are provided on complementary projects dealing withCO2separation and gasification costs.

Jan 1, 2004

By David Rolley

The extended weakness of dollar-denominated commodity prices during the past four years has often been attributed to, among other factors, the strong rise in the value of the dollar, and many U. S. producers have hoped for a recovery in metals and minerals prices once the dollar weakened in foreign exchange markets. The recent turnaround in dollar strength may put this view to the test quite soon. Hence a review of the role of exchange rate changes in the determination of the prices of world-traded metals and minerals may be timely. This paper has three parts. Part I reviews the recent summary record of price movements in commodity and foreign exchange markets. Part 11 reviews the distinct ways in which exchange rate changes influence the supply and demand sides of a representative commodity market. Part III then more closely examines copper and aluminum prices to highlight the potential differences in the effects of exchange rate changes for commodities whose production is dominated by geology and commodities which are processing-dominated. The paper also contemplates the likely implications of these differences for commodity prices in the case of a decline in the trade-weighted dollar. The evidence suggests that the degree of recovery for dollar- measured commodity prices may be very different for differing goods. And it may be the case that some commodities whose prices appear to have been most affected by exchange rate influences may show the least recovery in response to a fall in the trade- weighted dollar.

Jan 1, 1986

By A. M. Marabini, G. Belardi, V. Alesse, E. Spaziani

The objective of this investigation was to verify the effectiveness of commercial and synthetic depressing agents in a complex oxidized zinc mineral flotation flowsheet using sodium sulfides and amine. The flotation tests were run on a finely-disseminated calamine ore grading 16.96% Zn and containing smithsonite, hemimorphite, cerussite, calcite, quartz and iron oxide, present essentially in colloidal form. The reagents used in the testing can be grouped into four classes: guar, starch, celluloses and acrylic polymers having various degrees of substitution and molecular weights. The depressants exhibiting the greatest selectivity towards the gangue (considered as a whole) are tripolyphosphate, polycarboxylic acids, methylcarboxylate guars and ethyl hydroxylic starch. In the rougher stage, the Zn recovery ranged from 70% to 80%, and the Zn grade ranged from 27% to 29%. In the Zn-Fe2O3 separation, the compounds ensuring the most efficient separation are the tripolyphosphate and the polycarboxylic acids. In the Zn-SiO2 separation, the compounds that exhibit the best separation efficiency are tripolyphosphate and guar of methylcarboxylic sodium salt. In the case of the Zn-Ca separation, methyl-carboxylic guar exerts the best depressing effect and does not adversely affect the Zn recovery. The separation provided by ethyl hydroxylic guar is also good, although not as good as the preceding reagent. Regarding the Zn-Al separation, the tripolyphosphate, the celluloses and the carboxylate guars are the best depressants. A hypothesis is advanced to interpret the depressing action of the most effective reagents.

Jan 1, 1995

By V. D. Ayurov, N. O. Kaledina

The coal mines monitoring should be based on the usage of simple and evident models, letting in the total unity to reflect a structure of organization of mine, system ability of its construction and specific character of its functioning. Such models are offered to create on the basis of extracted hierarchies of objects of mine. All objects of mine are broken on levels of technological hierarchy. For objects of each level of hierarchy there are made balanced models of entering and leaving material flows. Then these balanced models are coordinated among themselves by the help of the inter hierarchical relations. So the structured-qualitative characteristic of the object of monitoring, reflecting in a kind of the table structure of formation of material flows on mine, their intensity and measure of transformation is formed under transition from one level of hierarchy of mine to another. An example of real us- age of hierarchical balanced models on mine is given. The mathematical models of coal mine monitoring should reflect objective laws of their structural organization and functioning. Therefore under the constructing of mathematical models it is important such a way to reflect a structure of the mine organization, that in totality the models has been reproduction of system ability of its construction. The knowledge of the separate parties of functioning of mine, reflected in particular mathematical models, should "to be packed" in combined unity. Or else, they should be connected in system, convenient for recognition by the person. Considering the mine, the expert allocates multi-dimensionality of the objects of making its elements. He always has the knowledge of laws of development of mining work that is connected with pithy stratification of researched object. In dependence of sparial-temporary level of abstracting there are allocated the horizon, wing of a mine field, layer, panel, extracting face, longwall in coal mine. The human thinking on each of these levels operates with a set of concepts peculiar to him, characteristics, definitions.

Jan 1, 1996

By L. A. Puchkov, Mesentsev. V. K., I. O. Temkin

The problem of increasing underground mine ventilation efficiency is still of top priority. The complication of geological conditions with the depth of underground mining processes and reinforcement of requirements to technological and ecological safety are extorting the necessity of solving this complex problem with using of new information technologies. There exist different approaches to the ventilation problem. One of them, which the authors adhere to, is based on the concept of monitoring (under special mining and geological conditions-automatic control) of mining atmosphere and operative re-distribution of underground mining air among consumer , in accordance with the criterion of optimality [ 1.3 1. ] The set of tasks which should be decided in the frame of con- crete ventilation system depends on the peculiarities of deposit, technological schemes and so on. Nevertheless, some ventilation tasks such as: defining of ventilation network parameters; finding of dependence between these parametrs; operative redistribution of air streems, could be interpreted as universal ones. Main aspects of practical solving of different ventilation problems and their classification were investigated and considered in detail before [I ,2 ]. Some years ago we have began our investigations to develope quite simple and effective methods for decision of ventilation tasks on the base of neural network technology. It is well known that ventilation net, formed by various mine workings, is the main component of underground mining ventilation system. In general, network air distribution may be described by some functional F(Q,R,H), where Q- is a vector of air consumptions; H- is a vector of depressions; R- is a vector of airdynamic resistences. (Q,R,H) - are the informative entities , characterising every branch of the net. There exist some fundamental tasks which should be decided during the process of control of mining ventilation: calculating of natural air distribution Q = Q,{R, H,}, or Q = Q2(R, Q?}, where H, - is the maximal depression of the ventilation net, Q, - is the air consumption in the ventilation shaft; identifying of airdynamic resistance for some branches on the base either of air-depression removal or operative monitoring: [ ]

Jan 1, 1996

By George Aul, Richard Ray

Short-hole horizontal degasification systems have been utilized in Island Creek's Virginia Division mines since 1986. These systems remove methane from the coal seam in advance of longwall mining. Without an in-seam methane drainage program, methane liberation rates from the longwall faces may exceed 0.47 cu m/s (1,000 cfrn), requiring 47 cu m/s (100,000 cfm) of air for adequate dilution capability. Optimization of the degas systems has enabled methane liberation levels and the associated ventilation requirements on the longwall faces to be reduced by 50 to 80 percent. Since the inception of the first degas system at the Virginia Pocahontas No. 6 Mine, Island Creek has developed an overall methane drainage program designed to maximize gas production and minimize ventilation requirements for methane dilution. Gas production from the degas systems is affected by four main design criteria: (1) hole location, (2) hole length and spacing, (3) collection system capacity, and (4) time available for drainage. Drilling equipment and materials for the gas collection system are selected to meet the necessary criteria while minimizing manpower requirements. Benefits gained from reducing methane liberation rates from the longwall faces are fourfold: (1) improved safety due to lower methane concentrations in the face area, (2) fewer production delays caused by excessive methane concentrations, (3) lower fan operating costs resulting from reduced air requirements, and (4) enhanced worker comfort resulting from lower air velocities and less dust generation.

Jan 1, 1991

At first glance the staid Joralemon background does not seem to equate with the life of adventure that irresistibly called me for over 70 years. But my ancestors had their adventures too. My father's family were Dutch Reformed Protestants who had energy or daring enough to come to America to escape the Catholic persecution that followed the Massacre of St. Bartholemew. The first Joralemon came from Friesland to New Amsterdam m 1636, just after Peter Stuyvesant. My father's mother's family, the Berdans, were French Huguenots who came to northern New Jersey only a little later to escape the Catholic domination in France. Some say that the first Berdan to come to America was given all the land between the Passaic and the Hacken-sack Rivers by King James. Whatever, the Berdan family settled there and was able to make a scanty living by farming and selling their produce in Manhattan. The spirit of adventure in my mother's family was just as tenuous. Gamaliel Beaman was pastor of a shipload of Puritans who came to Massachusetts in 1636. Gamaliel's descendents were peaceful farmers and some ministers in New England and later New York State. They had got all of the adventure out of their systems in the long and dangerous voyage across the Atlantic to escape religious persecution. The Joralemons and the Berdans married into families that had been in America almost as long as they had. On my father's side the Berdans, Doremus, DeGreys, Vanderbeeks, and Varicks showed by their names their Dutch or French Huguenot stock. The only one who achieved any fame was Peter Varick, who was George Washington's military secretary during the American Revolution. After this he was nine times mayor of New York and was one of the founders of Kings College, later Columbia University. He was responsible for one of my few ancestral claims to distinction. When the Marquis de Lafayette made a fare-

Jan 1, 1976

By Robert J. Timko, R. Lincoln Derick

The Bureau of Mines evaluated the integrity of escapeways in a three entry underground coal mine. A center conveyor belt entry (secondary escapeway), was flanked by an intake (primary escapeway) and a return entry. Diesel equipment was used throughout the mine for material and personnel haulage. A carbon monoxide monitoring system, tied to a data recording computer on the surface, was deployed throughout the belt entry and at selected sites in the intake and return entries. Previously, the company had a fire of unknown origin in another mine, which prompted an interest in the performance of their escapeways. An initial, qua1itative evaluation was performed by burning approximately 14 kg of coal at the mouth of the intake entry. The first test was followed by a similar burn at the mouth of the belt entry. These initial trials showed a high quantity of leakage between entries. In several follow-up evaluations, simulated fires, using a tracer gas, were set in the intake and belt entries. Tracer gas concentrations were obtained in all entries at four different underground locations. The results of these tests showed that permanent stoppings could not guarantee isolated, contaminant-free escapeways.

Jan 1, 1989

The 1997 Rapid Excavation and Tunneling Conference (RETC) was held at the Mirage Hotel, Las Vegas, NV. The RETC is a biennial event jointly sponsored by SME and the American Society of Civil Engineers (ASCE). Conference attendance was 573 members, nonmembers and students, an increase of seven attendees from the 1995 conference in San Francisco, CA. Exhibitors occupied 51 booths at the Las Vegas RETC. The 1997 conference encompassed 58 presentations in 15 sessions. Participants were given details on achievements and advances that have resulted in new design solutions, alternative work practices and increased productivity within the industry. The page at the end of this article tells how to get your copy of the RETC proceedings, either hardbound or on CD-ROM. Or, if you wish, for the first time a CD-ROM is available with the complete RETC proceedings from 1972 to 1997. This two-disk, archival volume has key-word search capability, is in portable file format and is compatible with PC and Macintosh platforms. RETC program sessions included design and planning, ground support, tunnel boring machine (TBM) case histories, conventional excavation, new technology, difficult ground, geotechnical, shafts and raises, future/special projects, new Austrian tunneling method, international projects, soft ground case histories and water and gas. What follows are highlights of some of the RETC presentations.

Jan 1, 1997