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By Nasri Munfah, Steffen Matthei, Vojtech Gall

"Conventional tunneling as defined by ITA WG19 is also known as the New Austrian Tunneling Method (NATM) or Sequential Excavation Method (SEM) was transformed in the US to deal with challenging tunneling conditions as an alternative to the more traditional tunneling methods. It is being used more often in urban areas, under difficult ground and ground water conditions, and with limited cover. Often the tunnel is of a large and non-uniform cross section in soft soils or weak rocks. The intent of using this tunneling method is to minimize impact on traffic and utilities and reduce disruption of everyday life of people and businesses. To meet these challenges, the industry developed technical approaches and implementation techniques and established sophisticated contractual relationships and collaboration in the field among various parties for successful implementation. This paper examines the development of conventional tunneling (NATM/SEM) in the US to deal with these challenges using recent examples such as Russia Wharf in Boston, Northern Boulevard Crossing, in New York, and Chinatown Station in San Francisco. INTRODUCTION / HISTORY Conventional tunneling or NATM/SEM is a concept that is based on the understanding of the behavior of the ground as it reacts to the creation of an underground opening. In its classic form the SEM/NATM attempts to mobilize the self-supporting capability of the ground to an optimum thus achieving economy in ground support. Initially formulated for application in rock tunneling in the early 1960’s, NATM has found application in soft ground in urban tunneling in the late 60’s and has since then enjoyed a broad, international utilization in both rural and urban settings. In the US the NATM/SEM tunneling method has been used successfully to address challenging tunneling conditions in urban areas. A large number of tunnels have been built around the world using a construction approach which was loosely termed NATM. During the years of discussions and the application of NATM a variety of terms have been used for the same construction approach. These terms were primarily aimed at describing the construction approach rather than the region of its reported origin."

Jan 1, 2016

By Michael R. Grubbs

In most resource recovery plants the incoming solid waste material is first shredded and then air classified into a light and a heavy fraction. The light fraction which contains mostly paper, cardboard, etc., can be used either as a fuel for power generation or in the production of new paper products. The heavy fraction which remains consists mostly of glass, ceramics, wood, ferrous metals and non-ferrous metals. The ferrous metals may be removed from the heavy fraction by conventional magnetic separators. After primary shredding, most of the glass and ceramic is fine in size and may be screened away leaving a residue of wood, cardboard, and non-ferrous metals. This residual heavy fraction is the input material for the separator described in the present paper. A new metal separator was recently reported by t. Schlömann1. The author described the theoretical relationships and presented results of tests on samples of the residual fraction of municipal solid waste. This paper describes the operation of the metal separator and develops the basic separation relationships controlling the process.

Jan 1, 1976

By B. Andersen

An accurate knowledge of Interactions among mineral particles and between such particles and dissolved and precipitated species Is Important in developing efficient separation processes. In this investigation interactions in Florida phosphatic clay waste, that are relevant to dispersion and selective reagent adsorption, the two main prerequisites for selective flocculation, were studied. Initial studies with artificial slimes, consisting of pure clay and phosphate minerals, showed dispersion of artificial slimes to be relatively easy. The problems that were encountered during selective flocculation of the artificial slime were due to unselective polyacryllc acid adsorption on clay, which was caused by the presence of multivalent calcium ions on the exchangeable cation positions on the clay surfaces. This problem could be solved by exchanging calcium for sodium, which reduces the interaction between the polymer and the clay surface. This procedure, however, was not successful for mineral mixtures. Natural slimes were found to be much more difficult to disperse. This was attributed to the presence of cementing materials such as humic substances and Ai and Fe (hydr)oxide precipitates. Selective removal of these cementing materials resulted in good dispersion and partial separation. Further increase in separation of natural slime is likely determined by the presence of calcium on the clay surfaces, as was found for the artificial mixtures.

Jan 1, 1992

By A.M. Wala

A new radioactive tracer method to measure airflow in inaccessible airways has been developed for situations when studies of the mine ventilation system are not possible using conventional flowmeters (anemometers). The new method has been tested in the ventilation laboratory at the University of Kentucky and in the Experimental Underground Coal Mine at the U.S. Bureau of Mines. This new tracer method has been utilized in leakage, dilution and flow velocity measurements in laboratory and field (mine) experiments.

Jan 1, 1996

By K J. Kidd

There is general understanding of hoisting systems throughout the mining industry. However, the relative importance of the various parameters influencing hoist selection and utilization is not completely understood. In order to determine if these parameters can be identified and prioritized, data covering 613 hoist installations were compiled. The 613 installations represent hoisting systems in 30 countries on six continents. This study compares data to historical trends, correlates design parameters in an attempt to identify underlying selection criteria, and comments on the apparent trends in recent developments in hoist design.

Jan 1, 1998

By Alessandro Boscaro, Daniele Martinelli, Cristina Gabriela Oñate Salazar, Daniele Peila, Carmine Todaro

"The wear phenomenon in TBM machines is not a simple issue, as many parameters are playing an important role on the consumption of the tools during a tunnel excavation. The action of the wear due to the contact with the soil can occur on the excavation tools, on the cutterhead, in the excavating chamber and on the screw conveyor. The test developed at the Laboratory “Tunnelling and Underground Space Center” of the Politecnico di Torino is aimed to reproduce the interaction between the tools and the excavated material, simulating the excavation conditions in terms of soil conditioning and water content. The test, which is not standardized, is studied to evaluate the wear in a global point of view. The present work starts by testing the influence of the use of chemical agents during the conditioning phase on the drop of the wear phenomenon, in terms of metal weight loss. 1. INTRODUCTION The wear phenomenon of the excavation tools used in TBM tunneling machines is playing recently a major role in the design stage of full-section tunnels in both soils and rocks. Concerning EPB excavation technology, the main issue regarding productivity is the wear of its components (Peila et al.,2012), which increases the so called dead time in the whole process. The friction generated between the components and the ground causes the consumption of the tools and other metallic components in contact with the ground, described as primary and secondary wear by Nielsen et al. (2006a). This leads to downtime, with risky and complicated maintenance operations (Peila and Schulkins, 2009), as occurred in recent tunneling works in Liguria (Italy). The study of this argument in granular soils is very delicate, as it encloses not only the properties of the excavation tools, but also the characteristics of the ground to be excavated (hardness, mineralogy composition, shape and dimension of the particles and moisture content). The penetration mechanism is based on the scraping of the ground, by mean of cutting tools, with its consequent consumption. Concerning the rocks, the excavation principle is characterized by crushing the rock mass matrix by applying high compressive stresses through cutting disks. In such a way, to avoid frequent downtimes and their consequent economic losses, it is very important to study this subject and therefore understand and forecast the durability of the components, in order to try to maximize the productivity of the machine by reducing the frequency of maintenance stoppings."

Jan 1, 2016

By Fabrizio Fara

The Ship Canal Water Quality Project (SCWQP) includes a 2.7-mile long, 18'-10" internal diameter tunnel which is located inWest Seattle. Tunneling in urban areas and soft ground conditions (Till and Till-like soils in Seattle) is associated with the risk of settlements, especially in presence of groundwater above the alignment. The Designer foresaw the use of soil improvement (jet grouting) outside of the launch shaft to mitigate the risk of flowing ground and to provide a redundant sealing. The Contractor proposed and ultimately successfully executed a different approach by using a “Steel Bell System” or Pressurized Can as described in this paper.

Jun 13, 2023

By Alastair R. Biggart

ABOUT BENTONITE TUNNELLING Much has been written and many learned papers given on this subject whose generic term is Slurry Tunnelling. This paper is about the particular form of slurry tunnelling known as the Bentonite Tunnelling System. This method. of tunnelling was invented by J.V. Bartlett of consulting engineers, Mott Hay and Anderson in 1964. The general principles are incorporated in British Patent No. 1083322. It was not until the early 1970's that serious experimental work was started to prove the technical feasibility of the process. In the U.K. in 1971 Edmund Nuttall Limited started on an experimental length of 3.8m diameter tunnel at New Cross in London. In Germany at about the same time Wayss and Freytag were starting on a 3.7m diameter collector sewer tunnel in Hamburg. In Japan early slurry tunnelling work was carried out in the 1960's. In the early 1970's a large number of slurry tunnels of various diameters were carried out in that country. This paper is being presented at a time when this system of tunnelling has become an accepted method throughout the developed world. As a result of the work carried out so far there is now a large amount of data existing regarding the effects on the ground in the immediate area of the tunnel, settlement at the surface and the ability of the system to cope with ground varying from clays to coarse gravels and containing large erratics such as granite boulders. The decade of the 1970's has therefore seen a very rapid pace

Jan 1, 1979

By R. F. Korcak

There exists a wide array of industrial by-products that can be shown to produce beneficial responses in the soil/plant environment. These materials range from clean coal technology residues produced in the generation of electric power, particularly those high in gypsum, to mineral 'fines' produced by the aggregates and crushed stone industries. A number of these materials will be examined in relation to potential nutritional interactions in soils and crops with emphasis on trace elements. The significance of utilizing these materials in agriculture as a component of sustainable agricultural systems will be discussed.

Jan 1, 1995

By C. V. Deutsch, O. Babak

A longstanding problem in geostatistics is that kriging usually assigns significantly greater weights to end samples in strings of data than it does to central samples. These weights are theoretically valid, but suboptimal estimates may result when there are geological trends in the variable near contacts, that is, large weights may be applied to samples that are systematically lower or higher than average. A number of ad-hoc corrections exist, each with pros and cons; none are fully automatic with a well-defined measure of optimality. A new method for estimation in a finite domain is proposed. This method is referred to as finite domain kriging. The method is based on kriging with a successively larger number of data. The total number of relevant data (n) is established, and then n kriging matrices are solved. The first matrix has the closest single data value (n-1 weights are set to zero); the second has the two closest data (n-2 weights are set to zero) and so on. The final matrix has all n data. The kriging weights used for estimation are the average of the weights from the n successive kriging runs. Each kriging run is optimal, yet with different smoothing and a different treatment of data at the end of the strings. The result is a set of weights that does not give undue influence to data values at the end of strings. The methodology is developed with examples. Cross validation shows that finite domain kriging outperforms conventional kriging.

Jan 1, 2009

By M. D. Flavel

My paper relates to bond's third theory of comminution and suggests work be used as a basis for designing crushing and screening plants, this will give more accuracy than existing methods, As stated in the abstract, this paper is only a synopsis of my official paper, many of the questions that might arise in this brief address will be answered by referring to the detail i n the main paper $ Because of the limited time available and the fact that many people here do not need to study the aspects of crushing and screening in depth, i will highlight-those sections of the paper which show how major capital, operating and energy cost savings can be achieved in the process, I will develop the theme in the following manner, Firstly, pointing out, why a new approach is needed to the fundamentals of crushing and screening, Secondly, by setting forth some theory to describe what we are trying to accomplish, Thirdly, by looking at important factors which need to be observed in designing plants and applying machines to comply with this theory, Lastly, i will put forth some ideas on how we might develop this theory to make the industry more efficient, At the outset, i have to say my approach to this process is entirely new, for those used to applying machines and designing plants on existing criteria, they will find this theory easier

Jan 1, 1977

By Giovanni Barla

This paper examines the application of gelatin mixture models to the study of factors such as gravity effects, tectonic and residual stresses, anisotropy, physical nonlinearity, time-dependent behavior of the rock mass and connectedness of the geologic space. The calibration technique of gelatin mixtures, proposed by Richards and Mark in 1966, is applied to the particular problem considered. Similitude relationships between model and prototype are discussed with reference to the constitutive equations describing the physical behavior of the rock mass. The interaction between two openings in a linearly elastic medium, under conditions of plane strain, is used as an illustrative example, with the view of describing the history of stress and deformation changes on the rock medium and lining around a slusher drift while undercuts are made in block caving.

Jan 1, 1968

By Paul H. Johnson

A field investigation was undertaken to study some of the. chemical and hydrological aspects of leaching an impermeable copper sulfide waste dump. Samples, obtained by means of a Becker pneumatic drill from Kennecott's Chino "J" dump, near Silver City, New Mexico, were analyzed for their moisture and soluble-salt content, Fe +2 , Fe +3, Cu +2 , and H in their interstitial solutions and non-water - soluble Fe, Cu, and S in their rinsed residues. Conclusions were drawn from these data concerning the overall chemistry of impermeable-dump leaching and the hydrological characteristics of the dump.

Jan 1, 1970

By Y. Luo, S. S. Peng

Several issues deserve further attention to improve subsidence prediction accuracy. These include: subsidence initiation and development over a setup entry area; subsidence development after face stop; and subsidence over chain pillar. An intensive subsidence monitoring program has been carried out over several longwall panels. A large amount of subsidence data has been collected, analyzed and solution techniques developed. In this paper, some of the measured data. data analysis techniques and the developed prediction methods are presented.

Jan 1, 1992

By O. J. C. Runnalls

Canada has played a significant role in the international uranium industry for some three decades. Although there have been many challenges in the past, the future offers a more extensive range of problems and prospects as Canada moves to expand its activities in all aspects of the nuclear fuel cycle. World uranium demand could grow to an annual requirement of 500,000 tons U308 by the year 2000. A substantial fraction of this material is likely to come from Canada because the country's reserves and resources are large, and because of a favourable geological potential for future discoveries. There has been a long history of association between the producing industry and the federal government, and it has provided the foundation for existing national uranium policies. Close industry-government association will be maintained and developed in future because of the anticipated rapid growth of the industry and the consequent need for continual refinement of government policies relating to exploration, mining, processing and export of uranium.

Jan 1, 1975

By W. G. Fischer

Trona ore at the Westvaco mine of FMC Corporation has been obtained by room- and-pillar methods since the mine began operation. The flat-lying, 10-foot bed of trona, Na2CO3 NaHCO3 2H2O, is covered by 1500 feet of weak shale and sandstone. Extraction of pillars on the retreat quite often throws large amounts of weight onto development workings. Weak shales in the roof and floor fail rapidly and the mine ribs slough to such an extent that mining often becomes very difficult. When this occurs efficiency goes down, costs go up, and the risk to men and machinery increases greatly. Difficult mining conditions in the early 60's forced a re-evaluation of all presently known mining techniques in bedded deposits. Many room-and-pillar mining plans' were compared with the system in use at that time, but none of them offered a better solution to the roof control problem. Longwall techniques were seriously considered, but machinery was not available that would cut the hard trona seam and still maintain the productivity obtained from room-and-pillar sections. Roof cones troy in the longwall methods appeared to be more satisfactory than that found in room-and--pillar techniques. It was therefore felt that a new technique using the longwall principle and based on rock mechanics should be tried rather than previously known pillaring methods.

Jan 1, 1966

By M. Brändström, R. Dube, J. Moyo, T. Perkins, G. Bermudez, L. Bartsch, C. Smith, R. Sorensen

The Kennecott Copperton concentrator is currently the bottleneck for the Kennecott operation and several projects have been initiated to increase throughput. This increase in grinding circuit throughput has resulted in a coarser grind size which has impacted flotation circuit recovery. Metso Outotec 300m3 forced air tank flotation cells are currently utilized in the rougher flotation circuit at the Copperton concentrator. Higher overall recoveries have been observed on the newer Outotec tank cells compared to the original 85m3 self-aspirated flotation cells they replaced. However, coarse particle flotation response on these large, forced air cells did not show encouraging results when compared to smaller previously installed cells. This coarse recovery loss has been attributed to the longer froth transport duration and transport distance on large cells (100m3 and larger). Cell manufacturers addressed the risks of additional coarse particle losses in large cells by installing concentric circumferential launders and crowders (also called center launders). These are designed to reduce froth transport time and distance in the last cells in rougher stages where low residual floatable minerals causes a lack of froth mobility. The center launders also increase froth crowding, which also helps to increase froth transport velocity and increases copper and molybdenum recoveries. A trial set of the center launder retrofits were installed on the last three tank cells in one of the parallel rougher flotation rows at Copperton. The launder retrofits were installed at the end of October 2020 and monitored until March 2021. This six-month trial showed statistically significant improvements in copper and molybdenum flotation recoveries through the rougher circuit.

Mar 2, 2022

By James R. Garvey

The impact of conversion on the coal industry can be summarized very briefly: We are going to have to mine an awful lot of coal. Fortunately, the United States has the coal reserves available, and given the right conditions, we can mine it. The coal reserves of the United States are enormous. If we consider them on the basis of proved reserves, using the standards of the petroleum industry--that is, resources mapped and explored and recoverable with present techniques at close to present costs--and compare that with the reserves of other fuels, coal constitutes 88 per cent of the proved recoverable energy resources of the nation. That includes oil, natural gas, oil shale and uranium, so long as the uranium is used in burner reactors. If we consider resources on the basis of "ultimate recoverable" reserves, that is, those resources which can be extracted with improved technology and at somewhat higher costs--and if we include those resources of all fuels not yet found but believed to be waiting discovery--coal still accounts for 74 per cent of the national total. We have built a hydrocarbon economy in which about 76 per cent of our total energy needs are supplied by petroleum and natural gas, and about 20 per cent by coal. Domestic resources of oil and gas are running dangerously low and, assuming a continued hydrocarbon economy, the 20 per cent supplied by coal may increase dramatically. We already import nearly a quarter of the petroleum we consume, and the chief source of additional imports seems to lie in the politically unstable Middle East. Natural gas is in even shorter supply, and the problems of importing it seem at least as difficult as those of oil. The fact is, the United States is already relying to an increasing extent on foreign fuel sources. There is an obvious national risk in making an important part of energy supply hostage to foreign governments of uncertain tenure and friendliness. There is also an economic risk--one of the chief reasons for last year's economic freeze was to try to correct the deficit in our balance of payments; it is obvious

Jan 1, 1972

By Rodolfo V. de la Cruz

The in-situ deformability of a highly jointed basalt rock mass was determined by two distinctly different methods: one, by the NX- borehole jack method where the displacements of opposing curved platens were related to the applied hydraulic pressures, and; two, by the modified Goodman jack method where the tangential strains on the borehole walls were related to the induced tangential stresses. The modulus obtained by the modified Goodman jack method were much higher than those obtained by the NX- borehole jack method. To explain the discrepancy, the influence of fractures and test variables such as depth, orientation, hole number and applied pressure on the calculated modulus of the rock mass were analyzed by factorial analysis and it was found that the orientations and depths of measurement has statistically significant effects. The in-situ deformability values obtained by non-linear regression analysis were also found comparable with other measurements and empirically predicted values for the basalt rock mass.

Jan 1, 1982

By P. J. Best

Due to its low mine production costs, competitive rail rates and low sulfur content, the Southern Powder River Basin (SPRB) now commands 30 percent of the U.S. utility coal market. In 1996, production exceeded 260 million tons, a growth of 110 million tons since 1989 and 15 million tons over 1995. Continued growth is expected as the second phase of the Clean Air Act Amendments (CAAA) looms. This growth will be the greatest in the southern part of the basin, where coal quality is higher. This article is an overview of supply and demand issues affecting markets for SPRB coal. It reviews the current markets for SPRB coal and addresses future prospects for market expansion.

Jan 1, 1998