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By Jamal Rostami, Wei Hu

Efficient performance of EPB TBMs in clayey ground is primarily dominated by the flow capability of the excavated muck in the cutterhead and screw conveyor. Currently, Consistency Index approach is used to evaluate clay clogging potential, but it does not include the effects of surcharge pressure on clay behavior. In this paper, a macro-scale soil rheometer is introduced to assess the clogging potential under various water content and surcharge loading conditions. The results show that, in addition to water content, surcharge pressure has clear impact on clay clogging too. In practice, Consistency Index chart can be refined to incorporate the impact of face pressure to better simulate the EPB tunneling conditions.

Jun 13, 2021

By W. C. Baver

Even before the energy crisis developed in the early '70's, considerable research world-wide was being directed towards the development of schemes to both reduce the energy requirements and to reduce air pollution emissions associated with the manufacture of glass. In many cases the sought-for solutions would benefit both objectives. If, for example, the glass batch could be consolidated into such compact forms as briquettes or pellets, they could be preheated in a moving-bed heat exchanger with the high-temperature exhaust gases from the glass furnace. Lower furnace temperatures would thus be possible with a corresponding reduction in heat losses and total fuel consumption. Moreover, the lower temperatures would also reduce the amount of nitrogen oxides generated in the furnace and emitted to the atmosphere. Many tests on consolidated glass batch have been run in many countries. In some cases, extended tests on production furnaces have also been included in the programs. For various reasons, however, none of these has proved to be economically attractive. The current, but temporary lull in the rapidly rising cost of energy which has been with us in recent years, has reduced the push for research for energy saving means for melting glass. A few of the current programs will be discussed. Since raw material requirements, primarily physical in nature, are affected by some of these schemes, these will also be considered.

Jan 1, 1986

By R. F. Pearce

The paper in based on laboratory and pilot plant investigations which led to the development of a series of processes for production of high purity metals from nickel-copper-cobalt mattes of a wide range of composition. The selection of ammonia pressure leaching or acid pressure leaching for various mattes is discussed. This is followed by discussion of various methods for leach solution purification and metal separation. The metals of high purity are produced by reduction with hydrogen from purified solutions. Examples are given of complete flowsheets for a number of mattes. Drawing upon those examples, general principles for the selection of the most suitable treatment process for particular material are outlined. Under certain circumstances, those processes may replace part of the pyrometallurgical treatment and all of the electrolytic refining steps which are customary in the treatment of nickel-copper-cobalt mattes.

Jan 1, 1959

By R. Schuerch, C. Cimiotti, M. Piemontese, N. Karlin, P. Perazzelli, P. Halton

The new Los Angeles, California JWPCP effluent outfall tunnel will transport secondary-treated effluent from the Joint Water Pollution Control Plant in Carson to White Point Manifold. The tunnel will be approximately 7 miles (11 km) long with a finished internal diameter of 18 ft (5.5 m). The TBM is designed to cope with high water pressure up to 10 bar. The geotechnical challenges are due to the heterogeneous subsurface conditions: in the first half of the alignment, the tunnel runs through soils with a low overburden under urban areas, and, in the second half, the tunnel runs through extremely weak, intensely faulted rock masses with high overburden. Following an overview of the project, this paper focuses on the northern portion of the alignment and presents a decision-making procedure developed during pre-excavation phase in order to cope with the expected heterogeneous conditions during mining. The risk assessment and the TBM operational design of the southern portion will be dealt with in a future paper.

Jun 13, 2023

By Dmitriy A. Malovichko

The general theory for the description of seismic sources is briefly discussed. The effect of excavations on seismic radiation is considered. Expressions for seismic source mechanisms in terms of the geometrical and mechanical parameters of source processes are provided for the following cases: fault slip and shear failure in a confined environment, dynamic stress fracturing around a tunnel, rock fall, landslide and sudden subsidence. A classification of seismic events in mines based on source mechanisms is introduced. The classification separates blast-, slip- and crush-type events. Various approaches of analysis of source mechanisms involving forward modelling and inversion are discussed. The following examples demonstrating the utility of source mechanisms in mining are presented: forensic analysis of damaging seismic events, assessment of the increase in the depth of failure for dynamic stress fracturing around tunnels and its duration, examination of the rockmass deformation regime, assessment of deformation around tunnels using crush-type events, identification and parameterisation of weak geological structures, stress inversion from slip-type events. Finally, the requirements for seismic data to ensure high quality source mechanism solutions are briefly reviewed and future challenges in the interpretation and utilisation of seismic source mechanisms in mines are speculated on.

Apr 26, 2022

By Robert D. Schmidt

The Cyprus Casa Grande Corporation has provided Bureau of Mines researchers with an opportunity to investigate the hydrology of leaching an in place copper ore deposit. Hydrologic investigations of underground in situ copper leaching are being jointly conducted under a cooperative agreement. The hydrologic concerns of leaching operations at the Casa Grande mine focus on maintaining adequate solution injection and recovery rates, and on distributing the injected leach solution effectively within the ore deposit. Hydrologic considerations underlying these concerns relate to the permeability of the oxide ore zone during leaching, the unsaturated condition of the deposit prior to leaching, and the constraints imposed on in situ hydrologic design by the underground mine setting. The investigation involves monitoring of flow and pressure conditions in 58 injection and recovery wells, estimating permeability conditions using a hydrologic model, and on-site testing of hydrodilation and airlift pumping. Transient, fracture-controlled permeability is determined to be the dominant hydrologic consideration. A statistical modeling procedure has been developed for estimating changes in permeability during leaching. Flexibility in well design and operation is essential for accommodating the changes in fracture permeability that occur during leaching.

Jan 1, 1990

By John E. Edkins

Metal sulfides, chiefly pyrite and mFnor sphalerlte zssociated with che Herrin (No. 6) coal member of the Pennsylvania Carbondale Formation, have been concentrated in a coal refuse deposit in southern Illinois. Oxidation of pyrite has produced highly acid waters with high concentrations of iron, zinc (up to 200 parts per million) and toxic trace elements that have leached downward to a water system perched on glacial drift. Chemical, petrographic, low-temperature ashing and x-ray diffraction were performed on cores. The data show that economic recovery of zinc and other trace metals is unlikely at this site. Energy (coal) recovery at the Superior Washer site is possible if resultant environmental problems are considered in the planning.

Jan 1, 1981

By John Sasadi

Several years ago I wrote a comprehensive paper 'entitled, "Future Trend of Bulk Carriers" dealing with the principle dimensions of vessels and how they can be predicted; then with loading and unloading of large carriers, especially considering various designs of "Self Unloaders". Since writing the paper, many large bulk carriers were basically built along the, predictions made. Maximum size today is in the 150,000 DWT class, with few exceptions, which are combination carriers (ore-oil) or OBO's (oil-bulk-ore) in the 200-250,000 DWT class in the same paper, many references were made cautioning engineers not to design ports which could be "obsolete tomorrow", however, these were not always followed. Nevertheless, during the past few years many modern ports were built signaling the beginning of a new area of "Super Ports". Super Ports can be built for various reasons, most important to provide transfer stations where bulk material is received from large carriers then transferred to smaller vessels or barges for distribution. Obviously, opposite movement of bulk commodities can justify the building of "Super Ports", however, these are not as difficult to build for many reasons. The Material Handling Industry has developed efficient means of unloading smaller vessels or barges with continuous-type unloaders and has mastered the art of storing, reclaiming, and moving large quantities of bulk material to high-capacity shiploaders. Nevertheless, the industry has failed to design and market efficient ship unloaders which in any way could match the presently attainable shiploading rates. For these reasons, it is considerably more difficult to build "Super Ports" for incoming rather than outgoing bulk materials with large bulk carriers. The purpose of this paper is to elaborate on problems affecting high-capacity, continuous ship unloaders, especially involving large bulk carriers. For better understanding, some references will be made to the smaller, continuous barge or ship unloaders, but only as the principles affect the larger units. Additional references will also be made to exploit the present "State-of-Art" of the grab

Jan 1, 1972

By Jr. Koch

Since 1882, world zinc production has increased. In contrast, United States zinc production rose until about 1915, but since then has remained nearly constant, with a slight tendency to decrease. Production from the Tri-State district, the largest early source of zinc in the United States, has gone down steadily; this decline has been balanced by a growth in the rate of other districts. These changes in United States production are due to economic, not geological, factors. Recent exploration has located large mineable ore bodies; additional deposits will undoubtedly be found in the strata-bound carbonate rock and volcanogenic environments. A statistical analysis of the exploration effort in the Middle Tennessee district indicates that new discoveries can be expected there. Thus, the United States is in an early stage of the production cycle for zinc. Of major mining districts in the United States, only the Tri-State is exhausted under current economic conditions; large zinc resources of low-grade material, which would repay mining at higher prices or improved technology, are known to exist in that district.

Jan 1, 1980

By J. E. Gebhardt, S. Chander

Significant advances have occurred in the use of electrochemical techniques for sulfide mineral flotation research. The techniques have been used singly or jointly with other characterization methods. When used in combination with other methods, the electrochemical methods provide a means to control the state of oxidation of the surface. Various analytical methods are employed for characterization. The methods that have been used include wetting, x-ray photoelectron and fourier transform infrared spectroscopies. The electrochemical methods include voltammetry and transient electrochemical techniques of galvanostatic polarization and AC impedance spectroscopy. The challenge for the future lies in the utilization of this knowledge in plant operations so as to increase the overall efficiency of flotation separations.

Jan 1, 1989

By D. G., Bosse&apos

Equipment choices for ultrafine grinding encompass several different types of dry and wet size-reduction devices. These need to be put into functional perspective for systematic analysis of capabilities and limitations versus processing requirements of the materials to be satisfactorily ground. Particle strengths plus maximum and average sizes are the primary variables controlling grinding action requirements and equipment options for efficient processing. These are fairly well understood and provide the starting point for decisions. Particle space requirements under dynamic processing conditions vary with particle shapes and size-distributions by as much as 30X. This additional major variable is not widely appreciated and does need adequate description to provide a firm basis for selecting processing compositions and procedures.

Jan 1, 1983

By R. J. Mirville

Flocculation is an important step in the treatment of coal preparation waste waters. The effects of polymer charge and molecular weight and solution pH and ionic strength on the adsorption and flocculation characteristics of a series of polymeric flocculants on some typical waste water constituents have been studied experimentally. The results indicate that the nature and extent of flocculation are strongly system-dependent. For the case of coal, both adsorption and flocculation behavior can be correlated with the polymer conformation in solution. For the mineral constituents, on the other hand, adsorption and flocculation depend also on the surface properties of the solid.

Jan 1, 1979

The Colorado portion of the Rio Grande rift is clearly defined physiographically from the south in the San Luis valley northward to the latitude of Leadville where sediments of the Dry Union Formation (Tweto, 1961) accumulated within the subsiding rift zone. To the north of Leadville is a system of faults active in the late Tertiary, including the Mosquito fault that offset a portion of the Climax mineralization (Wallace et al., 1968). Tweto (197B) describes remnants of Dry Union Formation against the Mosquito fault north of Dillon in the Blue River valley, so it is apparent that the rift and associated sediments extended well to the north of Leadville. Kelley (1952, 1954, 1956) and Chapin (1971) have noted in New Mexico that the Rio Grande rift is a series of en echelon basins, offset to the east, with constrictions connecting them (Fig. 1). In Colorado the structural basins are offset to the west. The net effect of all the rift zone basins in New Mexico and Colorado is an arcuate pattern (Fig. 1) abutting the Colorado Plateau and Sari Juan Volcanic Province on the west. The width of the rift system gradually decreases northward to about Leadville where rift definition is not apparent.

Jan 1, 1987

By R. L. Grayson, L. L. Probert

A three-year project focusing on the depth profiling of respirable coal mine dust particles using scanning electron microscopy coupled with energy dispersive X-ray analysis resulted in the development of statistically classified particle-behavior models. The models depict the changing silicon fraction for particles at 5-, 7-, 9-, and 11-keV accelerating voltages, thereby giving a clear indication of the nature of various types of mineral particles. This paper focuses on the results for respirable quartz particles sampled from five underground coal mines across the US. Through statistical analysis of results the relationship between the fraction of surface available quartz in respirable dust samples and coal rank is established for three Pennsylvania coal seams.

Jan 1, 1995

By D. G. Bosse

Equipment choices for ultrafine grinding encompass several different types of dry and wet size-reduction devices These need to be put into functional perspective for systematic analysis of capabilities and limitations versus processing requirements of the materials to be satisfactorily ground Particle strengths plus maximum and average sizes are the primary variables controlling grinding action requirements and equipment options for efficient processing These are fairly well understood and provide the starting point for decisions Particle space requirements under dynamic processing conditions vary with particle shapes and size-distributions by as much as 30X This additional major variable IS not widely appreciated and does need adequate description to provide a firm basis for selecting processing compositions and procedures

Jan 1, 1983

By D. L. Moellenberg

Under various state laws enacted mostly within the last 20 years, reclamation requirements and standards for hard-rock mining operations have been established virtually everywhere in the western United States. Unlike the uniform and detailed coal mine reclamation requirements under the federal Surface Mining Control and Reclamation Act ( "SMCRA" ) and state programs mode led after SMCRA, the various state law hard-rock mine reclamation requirements are based upon a variety of objectives, and therefore are subject to varying standards from state to state. While the diversity of reclamation requirements complicates the determination of what reclamation measures will be required at any particular mine, there are valid reasons for this diversity. There are dozens of different commodities mined in the United States, and mining methods are different for each commodity. Local natural conditions such as climate, precipitation, geology, hydrology, and biology vary widely across the county. Site-specific conditions also affect mining and reclamation methods. Also, factors such as economics, land use, and environmental protection issues receive different priorities in different states and communities within those states. State reclamation requirements in general provide the flexibility to consider site-specific circumstances, allowing operators to design and engineer the best reclamation measures for each mining site. To the mine developer or manager, reclamation requirements must be translated into design, operational, and closure measures for mine planning. Each of these measures must then be assigned additional costs to be factored into the economic decisions for a particular mining operation. On a broader level, reclamation costs must be factored into decisions such as where to invest in exploration and mine development. The purpose of this paper is to provide a summary of the state non-coal mine reclamation requirements in twelve western states. This summary comparison may be useful as a starting point in considering how local reclamation requirements will impact potential mining costs.

Jan 1, 1994

By C. E. Ekburg

Gold Quarry is a sediment-hosted, epithermal disseminated gold deposit located along the Carlin Trend. Gold, hosted by allochthonous Ordovician siltstones and cherts, is localized at the intersection of structures sympathetic to the major Good Hope and Gold Quarry faults. The magnitude of Gold Quarry was discovered in 1979 by surface exploration and by percussion holes drilled near the Maggie Creek orebody. Four years of development drilling delineated an open pit mineable gold deposit that contains 130 Mt (144 million st) of ore at an average 1.68 g/t (0.049 oz per st) of gold and includes a high-grade core of 46 Mt (51 million st) that average 2.64 g/t (0.077 oz per st) gold. Milling of the higher-grade portion began in 1985.

Jan 1, 1987

By D. Naden

Sulphuric acid leaching is the most common method of recovering uranium from its ores and in the following discussion various alternative low cost routes are investigated for recovering uranium from milled ore acid leach liquors. Historically uranium has been recovered from dilute impure leach liquors by packed bed ion exchange (IX), solvent extraction (SX) or a combination of both. All three process routes as commonly practised require complete separation of leached solids and liquids, as well as extensive solids washing in order to reduce soluble uranium losses to a minimum. Separation and washing are costly and often require equipment covering large areas of land. The size and capital cost of the post leach solids washing operation is controlled by the ease of washing the slimes fraction of the ore and the key to the problem of cost reduction, as many others have realised, lies in the ability to separate the slimes fraction of the ore from the more easily washed sands, to wash the sands in low cost equipment and to recover uranium from the slimes stream. Sands and slimes are usually defined in this context as the material larger than, and smaller than, 325 mesh (44 microns). The proposed flowsheets which minimise solid-liquid separation and washing have usually incorporated ion exchange (Refs 1,2,3), and resin in pulp is in fact practised in several mills in the USA (Ref 1). The resins used in these flowsheets and [cranium] recovery throughout the world have been strong base resins which load rapidly and are moderately selective for the uranyl sulphate complex anion over the range of pH which is conveniently achieved in an acid leach operation. Strong base resins are, however, not as selective as weak base resins and weak base liquid reagents owing to the adsorption of competing anions, some of which find their way into the product while others act as resins poisons. Ion exchange using strong base resins must therefore be followed by a more selective weak base SX purification step if pure yellow cake is required.

Jan 1, 1976

By G. M. Clarke

Minerals are certainly where they are found. The undemocratic distribution of the world's mineral wealth has created an incongruous inbalance: mineral-rich, scarcely populated countries supply highly-populated industrialised countries that in turn consume more minerals than they produce. This has been as much a generating force for colonisation, invasion, and war as religion, political ideals, or megalomania. The Industrial Revolution of the seventeenth century was born in Britain, a country with large domestic resources of coal, iron, lead, zinc, copper, tin, etc., as well as a large population. As consumption outstripped production imports filled the gap, particularly from its worldwide colonies. For example, when Canada was founded in 1867 more than 905 of its investments were British financed, and much of these were mineral-based. The British made similar investments in South East Asia, Australasia, the Caribbean, and elsewhere, as did the other industrialised Western European countries hungry for raw materials. Later the United States emerged as a leading industrial power, again due largely to its abundant natural resources. Consumption soon exceeded production and foreign sources were saught. American business went exploring abroad ant many a mineral resource was developed almost totally on the basis of the US market many .thousands of miles away. Closer to home, Canada was also an obvious target for the US with its rich mineral resource base, small population, and geographical juxtaposition, so much so that about the time of the 1914-18 War the US took over from Britain as the major investor in Canada, and this peaked in 1967 when the US accounted for 80% of the country's foreign investment. After the 1939-45 War Japan joined the ranks of the USA and Western Europe as industrialised powers, and they too searched the world for the deposits lacking in their homeland.

Jan 1, 1981

By L. J. Lindsay

Kaiser Resources Ltd. operates a coal mining complex in Southeastern British Columbia. A large surface mine, a conventional underground mine, and an innovative hydraulic underground mine are presently in operation. The products of these mines are fed to the Elkview plant. This coal has to be prepared to 9. 5% ash and 6'o total moisture for export from the port of Roberts Bank near Vancouver, British Columbia to Japan at a rate of 4. 5 Mltpy. The moisture requirement for the coal product was recently increased to 8. 0% total moisture. The entire operation has been described in various publications (1), (2), (3). Details of the venture will not be repeated in this paper. In this paper we hope to describe the modifications made to the original coal preparation plant in order to satisfy market requirements for quality and quantity of coal.

Jan 1, 1974