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By X Dahe

SLon vertical ring and pulsating high gradient magnetic separators (VPHGMS) possess the advantages of high efficiency and high reliability in beneficiating weakly magnetic minerals. In recent years, models SLon-2250, SLon-2500, SLon-3000 and SLon-4000 have been developed. This paper gives several examples of their applications in oxidised iron ore and ilmenite processing flow sheets to improve iron and ilmenite recoveries.CITATION:Dahe, X, 2017. Recent development and application of SLon vertical ring and pulsating high gradient magnetic separators in the iron ore and ilmenite processing industries, in Proceedings Iron Ore 2017, pp 461–466 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By B. M. England, L. C. Mackey

Magnesia minerals are included in most iron ore sinter mixes to provide the MgO requirements of blast furnace slag. The properties of these minerals have an influence on the eventual sintering properties of the mixes. A detailed study was undertaken of serpentine and dolomite and the use of limestone, olivine and magnesite was also investigated. A consideration of particle properties indicated that as these materials calcine a reduction in size can occur together with cracking and changes in surface properties. These changes could affect the permeability of the sintering bed and sintering performance. Studies of sintering reactions showed that magnesium and calcium, formed from the calcination of dolomite, are extremely mobile before the formation of melt. Evidence suggests that the movement of these oxides into surrounding areas is via a solid-state diffusion process. The diffusion of Ca into the surrounding hematite particles is faster than that of Mg, resulting in the formation of dicalcium ferrite and magnetite or magnesioferrite, the last two subsequently being converted to dicalcium ferrite in the presence of Ca with removal of Mg from the structure as ferroan periclase. Studies of pilot-plant sinters indicated that reaction mechanisms formulated from the bench-scale studies were occurring in actual sintering processes. The differences in sintering reactions between dolomite and serpentine were considered to be the major cause of differences in the availability of lime for bonding phase formation. Pilot-scale studies indicated that the sintering properties of a mix containing dolomite could be improved by increasing the basicity of the sinter mix while keeping the MgO level constant

Jun 18, 1905

"The effective thermal conductivity (ETC) is one of the most important thermo-physical properties of porous media. Due to the lack of higher precision influence of temperature on thermal conductivity, we took 6 groups of experiments on rock samples (including igneous rock, sedimentary rock and metamorphic rock) under different operating temperatures from 20? to 50? by 7 acquisition points. The general equation of thermal conductivity drives the value of it increasing along with the decreases of the temperature. While in our experiments, it is easy to find a singularity among them for each sample. The experimental investigations we attempted to observe and interpret the alteration mechanism. According to the Heat Capacity Theory in solid state physics, this research gives the explanation about the “singularity” from 3 understanding of specific heat, average free path, and thermal conductivity. Our research divided the condition of the rock thermal conductivity into 3 different types. INTRODUCTION The effective thermal conductivity (ETC) is one of the most important thermo-physical properties of porous media(Huang & Han ,1988; Peierles ,1955). This parameter is necessary for analysis of heat transfer(Vaferi et al, 2014;Hans-Dieter & Rudiger,2003). It’s well known that a general equation for ?(T) was set by Sass et al. (1992) which based on the coupled effect of composition and temperature on the thermal conductivity(Jesse et al, 2013; Mongelli et al,1982).The equation was further successfully verified for other rock (Zumrud et al,2010;Abdulagatova et al,2009;Seipold& Huenges,1998).Thermal conductivity is also related to other physical proper ties of porous rock, such as thermal diffusivity, heat capacity(Brettmann et al,2011;Abuel-Naga et al,2008). It is well known that ETC and other thermo physical properties of rock materials are affected by various factors, such as temperature, pressure, mineralogical composition, porosity, stratification, size and shape of the components, and nature of pore fluid, etc. (Tiedje & Guo, 2014; Touloukian et al,1970).The understanding of heat transport processes still requires the knowledge of thermal properties of rocks."

Jan 1, 2015

By Peter Metcalfe

"Wireless communication in the mineral processing environment is not as simple as it is in the home or office environment. The correct design of a wireless network in the mineral processing environment can offer a more flexible and lower cost installation than the transitional fiber networks. However with the flexibility of a wireless solution, also comes some limitations. By reviewing the plant requirements along with weighting the wireless benefits and limitations it is possible to design a network that combines the robustness of a wired solution with the mobility of a wireless solution. This paper addresses some wireless design considerations and it looks at some real life examples in the following areas: •,Meshed wireless network for high levels of redundancy •,Wireless instruments (such as HART, Modbus and others) •,Portable devices for mobile operators •,Network monitoring for plant personnel (it’s no longer just for IT people) INTRODUCTION Typical networks used in the mineral processing environment consist of a fiber network infrastructure with industrial switches used to connect the network devices. These fiber networks can be redundant or put into a ring topologies to offer a higher level of availability. Fiber networks have the benefits of: •,Immunity to noise from power and grounding issues •,Ability to span long distances (2km for multimode fiber and 20km for single mode fiber) •,Maintainable “off-the-shelf” technology Fiber networks however have some drawbacks, such as: •,Relativity high initial installation cost for cable trays, poles, trenches and pulling and termination of cable. •,Fixed geographic topology, adding future fiber drops may be challenging and expensive. •,Mobile users are not considered. Integrating a wireless network with a fiber network can offer the best of two worlds, a reliable high speed backbone for mission critical activities and a wireless network for remote applications and mobile users."

Jan 1, 2014

By I. Marklund, W. Hustrulid

Sublevel caving is likely to remain the dominant system at both Malmberget and Kiruna for the foreseeable future. The sub-level interval has increased from 12 m in 1983 to 30 m, requiring more effective drifting and the development of a contour blasting technique to reduce requirements for rock reinforcement. Production drilling is mainly by hydraulic hammers or water-powered in-the-hole machines drilling 115 m diameter holes. Loading operations are undertaken 7 days/week with 15-25 tonne capacity electric shovels. Production has increased by nearly 70% since 1983 and productivity has risen threefold

Dec 1, 1995

The Peelwood district of New South Wales is located some 65 miles south of Bathutst on the Tuena-Crookwell road. A number of occurrences of lead-zinc-copper ore are known from this district but only three mines, Peelwood, Cordillera and Mt. Costigan, have achieved any significant production. The purpose of the paper is to describe the mineral composition of sulphide ores from these three localities.HISTORYNo published information on the geology of the Peelwood area is available. Came (1899) reports that, at the time of cessation of mining operations in 1888, the Peelwood mine had produced some 600 tons of copper metal and regulus, the Cordillera mine had yielded 9000 tons of ore at the recoverable grade of 2·5 per cent Pb, 2·5 per cent Cu, 90z/ton Ag and 1 dwtjto:p. Au, but that no production figures were available from Mt. Costigan. No further work was carried out on these properties until 1951 when the Electrolytic Zinc Company of Australasia instigated a programme of geological mapping and exploratory diamond drilling (Whitten, unpublished data, 1953). The Peelwood district was recently mapped by Mutton (unpublished thesis, 1960) from whom the following geological summary account was taken.GENERAL GEOLOGYAll rocks in the Peelwood area belong to a series of interbedded fine grained sediments and volcanics that are thought...

Jan 1, 1961

By Frank Rieber

THE study of earthquakes long ago developed the fact that by studying the travel times of the various groups of waves from the same earthquake, as received on seismographs at varying distances, major discontinuities in the earth's crust could be reasonably well defined. Using this original discovery, and adapting the mathematical methods originally devised in seismology for determining the depth below the surface at which such discontinuities occur, other investigators were able to develop a new branch of seismology which promises to be extremely useful in extending the boundaries of our information on local conditions below the earth's surface. As an outstanding example of the applications of this work, we have the so-called "seismograph" exploration of the Gulf Coastal region, which has resulted in the discovery of a large number of salt domes, from many of which oil fields may be developed. The original seismological investigations, from which different major discontinuities in the earth's crust were deduced, as well as these later successful experiments in locating salt-dome structures, involve relatively simple problems. In each case we are dealing with surface materials in which elastic waves will be propagated with a fairly definite velocity. Under this material we have something quite different, in which the elastic waves will be propagated with a much higher velocity. The transition from one medium to the other is likewise relatively abrupt. For example, in the Gulf Coastal region the sedimentary formations have a velocity of 6000 or 7000 ft. per sec., while the velocity of elastic waves in the cap rock of a salt dome may exceed 15,000 ft. per sec. Under such conditions, delineation of the formation is a relatively simple matter, and, furthermore, there is very little opportunity for ambiguous results.

Jan 1, 1928

By G. Paquet, E. Godin

"Since the mid fifty's, worlwide pellet production capacity has constantly risen (Fig. 1, Ref. 1 l. There was however at that time no real incentive to decrease production costs but only to produce as many pellets as possible. State of things changed with the iron and steel market recession, starting in 1975, and is currently leading producers to improve pellet quality and to reduce fuel and power consumption.At the Port-Cartier pellet plant, the energy needed for the induration of pellets ranks first in overall operating costs. An important step was made when starting admixing coke breeze in 1980. Oil prices justified the use of coke breeze as a direct replacement in terms of dollar/ton, however, while gaining expertise in using solid fuel a significant decrease in energy consumption was observed (Fig. 2, Ref. 2).In 1985, the ""Centre de Recherches minérales"" was commissioned to undertake research work to investigate the effects of further increasing coke addition to the pellet mix. The positive results of that work led to a 1,5% coke addition plant trial during the fall of 1985. Both laboratory and industrial results are discussed in this paper."

Jan 1, 1986

By J. M. Riley

This report summarizes Bureau of Mines experiments in purifying sulfate leach liquors, which were prepared from low-tenor beryl concentrates by modifying the Degussa process. The leach liquor was prepared from a beryl concentrate containing 2.7 percent BeO by (1) sintering the beryl concentrate with limestone in a rotary kiln at about 1,150° C. and by (2) treating the sinter first with sulfuric acid and then with water to form and extract beryllium sulfate. About 80 percent of the beryllium was dissolved. The resulting leach liquor contained 2.4 grams of BeO, 20 grams of Al203, and 6 grams of Fe203 per liter. The laboratory solution contained much more aluminum and iron than a solution derived from treating 10 percent BeO concentrate, which is the standard raw material used by industry. Tests were made to determine the behavior of the solution toward alum purification and limestone neutralization both of which were employed industrially in conventional Degussa procedure.

Jan 1, 1962

Nuclear power currently produces about 20% of the electricity in the US, with 104 nuclear power plants located in 31 states. The commercial US nuclear industry contributes over $4 billion annually to US workers in salaries and wages. 25,000 new jobs need to be filled in the next 5 years. There are over 30 new power plants under consideration by US utilities. The operating reactors use uranium oxide fuel enriched to about 4% U235 and fission is the process used to generate heat to form steam to drive the turbine generators. Nuclear energy is an important element in the US generation portfolio and represents the largest producer of nearly emission-free electricity. Most, if not all, of the operating plants will secure an extended 20 years of operation or more. The last plant constructed was ordered in 1978. New smaller, modular reactors are under design to provide less expensive, expandable generation options.

Jan 1, 2011

By L. C. St. Arnaud

"Open pit mines can produce large disturbances within regional hydrogeologic systems. The degree of disturbance and the consequences on the local environment depend on the size of the pit and on the physical setting of the mine. Comparisons and contrasts are presented for three Noranda base metal open pit mine sites.The Brunswick Mining and Smelting No 6 open pit has a surface area of 11 ha and a depth of 185 m. It is located within complexly deformed schists and meta-volcanic rocks. The massive sulphide and iron formations visible along the north and southwest walls of the pit generate acid drainage. Mining ceased in 1983, and the pit is presently being filled with waste rock and neutralized drainage water. Water balance calculations estimated a total fill up time of sixteen years. As the water level rises, leakage to groundwater could take place across a fault zone intersecting the pit.The Mattabi Mines F-Group pit has a surface area of approximately 3 ha and a depth of 50 m and is also set in meta-volcanic rocks and acid generating iron formations. Production at this site ceased in 1982, and the low pH pit water is neutralized and pumped into a nearby lake at least every five years. Major water inflows are from precipitation and groundwater. Groundwater mounds within adjacent high land surrounding the pit provide a natural hydraulic barrier to groundwater flow, except for the southeast side. As a consequence, the pit water elevation is being kept below the elevation of the nearby creek in which some of the pit water could drain.The Bell Copper open pit covers an area of 40 ha and is 270 m deep. With present ore reserves, the mine might be in operation until 1992. The geology around the pit consists of andesitic tufts, siltstones and shales, and the acid generation potential of the rock is relatively low. A recent hydrogeological study estimated fill up time by precipitation and groundwater to be in the order of 260 years.With increasingly more stringent requirements for mine closure, it is anticipated that more detailed hydrological and hydrogeological studies of open pits will be required to determine post-closure environmental impacts and the suitability of open pits for mine waste disposal."

Jan 1, 1990

By G. W. Jones

"INTRODUCTION In a previous reports results were given of a manhole investigation carried out over a period from June,- 1929, to July, 1930, in cooperation with the Edison Electric Illuminating Co. of Boston, Mass., to determine the general hazards of combustible gases and vapors in manholes and other underground openings owned by this company. Considerable time was spent in this initial investigation in developing a suitable detector for determining the range of explosibility of the gases found in manholes. About 17,000 tests have been made with the detector since the investigation was started and its utility has been verified and its accuracy checked, by having complete analyses made of such samples that showed combustibles present equal to or above 25 per cent of the lower explosive limit, and those found deficient in oxygen.The initial investigation made in 1929 and 1930 demonstrated that the detection, control, and elimination of combustible hazards in manholes can best be obtained by a close cooperation of the interested parties through a systematic and continuous inspection of manholes, under proper supervision.COOPERATIVE INVESTIGATI0N DURING 1931The investigation carried out during the year 1931 has been along lines similar to that conducted during 1929 and 1930. In the present investigation the Edison Electric Illuminating Cc. of Boston and the Boston Consolidated Gas Co., have cooperated with the Bureau of lanes. The Boston Consolidated Gas Co. serves a major part of the territory under discussion with gas, but the tests covered the Edison territory irrespective of the gam company furnishing manufactured gas. A test crew consisting of two men, one an employee of the Consolidated Gas Co. and one an employee of the Edison Electric Illuminating Co., has been continuously employed during the year in the testing of games in manholes served by the Edison system. The test crew was under the direct supervision of John Campbell, superintendent of the special service department of the Edison Electric Illuminating Co., and F. M. Goodwin vice president of the Consolidated Gas Co.As in the previous investigation, all manhole tests were given test numbers. The test data sheets on which the information regarding the tests were recorded were prepared in triplicate, one copy going to the Edison Company, one going to the Gas company, and the third to the Bureau of Mines at Pittsburgh. These test data sheets were then filed (1) according to the town, (2) the street location, and (3) the manhole number; in this way a complete record pf each manhole tested was immediately available. A specimen test sheet is given below."

Sep 1, 1932

By S. W. Stogran

"Chemical and limited biological monitoring of mine and mill effluents are being used by regulatory agencies to monitor and control discharges to the environment. Amendments to the Federal Fisheries Act may make it mandatory for mines to conduct Environmental Effects Monitoring (EEM) which will change the emphasis from monitoring effluents to monitoring impacts on receiving waters. The EEM amendments may expand the scope of present environmental studies to include: effluent mixing zone delineation; inventory and classification of resource, habitat, and historical receiving environment; effluent quality determination; chronic and acute bioassay testing; tissue analysis; benthic invertebrate monitoring; fish population surveying; fish tainting evaluation; and the evaluation of impacts on fish habitat, invertebrate communities and fisheries resources. The requirements for EEM have not yet been worked out by the mining industry and the government committee. Experience at Lakefield Research in conducting biological monitoring studies for the mining industry has shown that biological monitoring may be useful for assessing environmental impacts only if programs are planned and executed to collect relevant data, thus minimizing costs and maximizing effectiveness.IntroductionThe chemical monitoring of effluents and water bodies receiving effluents is common practice in the Canadian mining industry and has been used routinely by regulatory agencies to control discharges to the environment. Biological monitoring has also been used on a limited basis, primarily to augment chemical data collected. A number of regulatory bodies, primarily in Canada and the United States, have been incorporating biological monitoring into environmental regulations.Various forms of biological monitoring techniques have been used in Canada and the United States to help assess the impact of mining operations and effluents on the environment. Biological monitoring includes a wide range of activities, from monitoring metal uptake in individual organisms to examining the population dynamics in ecosystems. The most commonly employed biological monitoring techniques are the chronic lethality toxicity tests. Also becoming widely used are in situ and chronic toxicity tests."

Jan 1, 1994

By H. E. Pawson

"COMMON METHODS OF ELIMINATION: The four methods most frequently used to dispose of cyanide wastes are:1. Oxidation2. Dilution with water or with cyanide free wastes3. Acidification and dilution of resulting gas with air4. Alkaline ChlorinationMost operators practice a combination of the first two methods, allowing oxidation and dilution of cyanide waste in tailings ponds. Then, pond effluent is introduced to a stream for further dilution andoxidation which is expected to take care of the cyanide. This method oftreatment does work to a certain degree. Atmospheric oxidation in tailings ponds and in receiving streams chemically breaks down the cyanide radical to form carbon dioxide and nitrogen.2(CN) + 202 2 CO2 + N2The monetary advantage to this method is obvious to the operator but too frequently though, climatic conditions are ignored. Length of winter, and reduced flow of the receiving stream in summer, adversely restricts the result of this combined method. For those of us who rely mainly on dilution it would be wise to remember that 70 million pounds of water are required to dispose of one pound of sodium cyanide (1).The third method outlined involves addition of acid in a closed vessel and venting resulting gas to atmosphere with or without air dilution by mechanical means. Cost, safety and some form of secondary treatment to complete destruction of cyanide remaining in the solution usually make this method prohibitive.The alkaline chlorination method is the one most commonly accepted for treating cyanide bearing wastes since it is felt that cyanide is completely eliminated in this manner."

Jan 1, 1973

The offshore Maui gas/condensate field was discovered by Shell BP and Todd on Services Limited in 1969. Subsequent appraisal drilling and negotiations with the Government led to a development agreement, æThe Maui White Paper' being concluded in 1973. Part of this agreement provided for the Government to take a 50 per cent shareholding in the field. The field is comprised of a double domed anticlinal structure containing two gas reservoirs at depths ranging from 2700 - 3000 m. Water depth is 110 m. The development plan called for two standalone steel platforms to be installed sequentially over a period of some years depending on gas demand. The first platform (MPA) was put in place in 1976 but difficulties were experienced with piling and drilling of the 12 (later increased to 14) wells did not start until 1978. First gas was piped ashore late in 1979.

Jan 1, 1994

By C. Steve

ABSTRACT: In this paper, the stability evaluation and bifurcation criteria are presented for the Jinping arch dam structure. The bifurcation models in failure status of the arch dam are derived from the uniqueness of the controlling equation of dam behaviours, and the relative phenomena between positive definition of dam structural tangent stiffness and bifurcation are given in the paper. Then the structural collapse criteria for arch dam are discussed based on the energy mode. A stability criterion of dam based on the connection of yield zones is proposed according to the implementation of elasto-plastic FEM (finite element method) numerical analysis. In accordance with this judging method, nonlinear FEM analysis is used for Jinping arch dam. The failure process of the Jinping dam was simulated and yield zones were found under the overloading condition. Keywords: Stability evaluation, bifurcation, failure process, Jinping arch dam ZUSAMMENFASSUNG: In der Verliegenden Arbeit wird ein integrater geomechanisch Modellversuch fuer Jinping Bogenstaumauer Vorgesstellt. Die Bogenstaumauer liegt aut der komplizerten felsformationen. Der Zerstoerungsmechanismus, die Stabilitaetsfaktoren und die Interaktion zwischen der Bogenstaumauer und den Seiltichen. In der Vorliegenden Arbeit wird eine dreidimensionale finite element analyse fuer die seitlichen. Gestein sauflager mittels dem Bruchmodell Vorgestellt, da fuer Jiniping Bogenstaumauer angewandet wird. Ein Bruch mechanismus model einschliesslich der statistischen parameter der Gesteinfes tigkeit wird entauckeit. RÉSUMÉ: Das ce documènt a été faite une analyse d’elemt limité de trois dimensions dn fondement de construction de roche faisant appel au modéle de l’endommagemnet à fracture, analyse appliquée an fondement du bar ragevoute de Jinping. Ce documènt décrit le test de modéle géomecanique intégral pour le barrage-voûte de Jinping L’ampleur du modéle en question constitute l’une de plus importantes en China. Ils correspondent par faitement anx calculs des résultats.

Jan 1, 2003

By J. N. Murphy

The use of the National Science Teachers Association (NSTA) regional meetings as a forum to educate teachers on the role of minerals in our society has been immeasurably successful. Each year, on average about 3,500 to 4,000 teachers participate in each of the three regional NSTA meetings. At each of these meetings, nearly 2,000 teachers visit the “Minerals Coalition Booth” and receive free mineral samples and other educational support materials. Some rules of thumb for a successful booth at the NSTA are provided. Considering the level of effort for such a booth, are there alternatives? The NSTA also organizes a national annual meeting with attendance of about 20,000. All who have participated in a regional NSTA agree that the traditional approach of providing a mineral set and teacher materials for a substantial fraction of the 20,000 attendees is not feasible. Conceptual alternatives for minerals education at the national NSTA meeting are introduced and evaluated.

Jan 1, 2001

By Richard J. Mainiero, Michael J. Sapko, Marcia L. Harris

Since 1988, there have been thirteen documented incidents in the United States and Canada in which carbon monoxide (CO) is suspected to have migrated through near surface strata into structures or other enclosed spaces as a result of nearby trench blasting or surface mine blasting. From these incidents, there are thirty suspected or medically verified CO poisonings and one fatality associated with these incidents. To better understand the variables contributing to this hazard, the National Institute for Occupational Safety and Health (NIOSH) carried out a small- scale field study to identify key factors that may contribute to the migration of CO through the ground. NIOSH conducted single- hole heavily confined experimental test shots to measure the radial pressure pulse as it propagated through surrounding monitoring holes to determine if a relationship existed between the pressure pulse and resulting CO measurements afterwards. NIOSH also monitored blasts at an airport construction site. Following the detonations, the concentrations of CO, nitric oxide (NO), and nitrogen dioxide (NO2) were monitored for several days in the surrounding satellite holes. The peak CO measurements relative to distances from the shots were compared. Pressure histories and peak particle velocities (PPV) were measured at monitoring boreholes. It was found that the differential pressures recorded within the boreholes give some indication as to the likelihood of CO appearing, whereas the PPV measurements do not seem to be as good an indicator for potential CO migration. In this limited study, changes in barometric pressure had very little influence on removing the trapped detonation products, whereas applying a vacuum to the monitoring holes was effective in reducing the entrapped CO concentration.

Jan 1, 2005

By J. Thompson

Paper written on project work carried out in partial fulfilment of B. Eng (Mining Engineering) degree A study into the stability of strike gullies at TauTona mine was to be carried out. In reaching the conclusions to follow, a three-stage process was followed. ?A literature study as well as discussions with management and workers alike to gain their inputs and perceptions. ?An ESH Department survey into the history of transgression from proper mine standard in TauTona strike gullies. Unfortunately records were found to be scarce and obscure and the importance of better inter-departmental recordings cannot be stressed enough. ?An underground survey of 11 pre-selected gullies distributed in both the UCL and LCL reef horizons. This stage is to carry the greatest weight in the points to be brought forward in this report. The process highlighted and ranked the following areas as the most critical role players in the deterioration of strike gullies: ?Poor blasting practice ?Sub-standard siding depth and lead-lags ?Split sets ?Off line gully development ?Adverse geological features. The following has been suggested to the mine to help reduce strike gully instability. ?Where possible, maintain lead-lags below 7 m?else increase the siding depth to suit. ?Decrease the gully width standard to 1.2 m (especially in ?high risk areas?). ?Discourage drillers from drilling side holes in gully face blast pattern. This will allow for time in which tendon support can be kept up to date. ?Ensure split sets are installed 1 m behind the gully face so as to prevent opening up of fractures. ?Utilize the centre split set in the 1:2:1 pattern to maintain the proper gully line. ?When adverse conditions prevail, it is necessary to apply a special support plan not only to the panel face, but also (just as importantly) to the gully as well. Shotcreting of the gully hanging is a suitable long-term consideration for providing the additional a real coverage needed. List of Abbreviations [CL Carbon Leader M/O Mine Overseer UCL Upper Carbon Leader FOG Fall of Ground LCL Lower Carbon Leader H/W Hanging Wall ERR Energy Release Rate F/W Foot Wall WDL Western Deep Levels ESH Environmental Safety and Health ]

Jan 1, 2002

By Mohammad Irshad, Klaus Mussger, Harald Wagner

Despite the fact that the New Austrian Tunneling Method; NATM, has been used in the United States for the past 23 years or so, still considerable misconceptions exist in the industry about the nature of the method and its implementation. In the authors’ view its implications are usually not well understood. The paper provides an overview of the highlights of NATM usage over the past two decades to illustrate the point that NATM is now a well-established tunneling method in the U.S.A. Accordingly the thrust of this paper is on the more pragmatic aspects of the NATM technology usage as it concerns the Owners, Designers and the Contractors. Prior to examining the implications of NATM usage from the viewpoints of various stakeholders, it should be helpful to first briefly provide an overview of the history of the method as it was introduced and implemented on several key tunneling projects in the US, over the last 2 plus decades.

Jan 1, 2005