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By J. A. Lombardi

Innovative hard rock narrow-vein, longwall, and stope leach mining systems concepts are described and evaluated economically. The principal tool proposed for use in these systems for both mine development and production is the U.S. Bureau of Mines radial-axial splitter. The mining systems concepts are prefeasibility level costed and projected to be cost competitive for steeply dipping veins, 0.6-1.2 m wide, for horizontal tabular ores 2 m -5 m thick, and for leachable ores with greater than a 1.7:1 stripping ratio. In all of the systems the orebody, less swell, is retained underground for use as backfill.

Jan 1, 1994

By K. B. C. Brady, B. E. Scheetz, J. E. Cuddeback, T. W. Bergstresser, W. A. Telliard, S. C. Parsons, R. J. Hornberger

Two weathering procedures are being developed by the Acid Drainage Technology Initiative in cooperation with federal agencies(OSM and EPA). Objects are to: (1) standardize existing humidity cell and leaching column procedures; (2) improve test methods by maintaining a carbon dioxide enriched environment needed to optimize carbonate mineral dissolution, and quantifying particle size variables to evaluate reaction kinetics, and (3) provide flexibility in test method implementation consistent with EPA guidelines for Performance-Based Measurement Systems. Preliminary results indicate the CO2enriched leaching environments produce alkalinities that are similar to field observations and greater than the tests run under atmospheric PCO2. Leaching columns produce higher alkalinity than humidity cells.

Jan 1, 2003

Shallow ore deposits are mined by surface methods but a depth is reached in the case of most deposits after which underground methods are applied for the extraction of the remaining ore. The determination of this depth and its analysis is the subject of this paper. In order to determine transition depth from open-pit to underground mining on the basis of the allowable and economically feasible overall stripping ratios, an economic-mathematical equation is first introduced. Using the achieved equation and an analytical procedure on a particular two-dimensional hypothetical tabulate deposit, an effective formula is then established. The formula introduced here, together with the procedure adopted, could be used in all similar mining situations by the mining design engineer.

Jan 1, 2010

By W. Jacobi, F. Steinhausler, A. C. James

INTRODUCTION In 1979 the Committee on Radiological Protection and Public Health of the Nuclear Energy Agency (OECD) defined a programme of work needed to improve radon dosimetry and monitoring. A Group of Experts in this field was established by the NEA and at the first meeting of the Group the authors were designated an initial task with the following terms of reference:- To review dosimetry of radon, thoron and their daughters, and in particular:- - to examine analytical models for the assessment of dose to individuals who are exposed to aerosol mixtures of these nuclides; - to examine the state of knowledge of the characteristics of aerosol mixtures of these nuclides and other factors that influence the dose to the lung, and identify those parameters which should be measured for dosimetric purposes in radiological surveillance programmes; - to identify areas where further study or research are needed. In this presentation we attempt to examine, with these objectives, the relationship between exposure to radon and thoron daughter aerosols expressed in terms of the working level month l (WLM), or its SI equivalent, and dose accumulated by sensitive tissues of the lower respiratory tract. Over the past two decades many attempts have been made to calculate the lung dose equivalent to l WLM exposure in mine atmospheres, usually in terms of the maximum dose to basal cells in a small part of the bronchial tree. The calculations have employed variously detailed models of airway anatomy, aerosol deposition, ciliary clearance and dosimetry of tissue at the bronchial surface, and are well reviewed elsewhere (Walsh, 1970; UNSCEAR, 1977; Jacobi, 1977; Fry, 1977). They agree in the conclusion that basal cells in segmental bronchi (between about the third and fifth bronchial generations) receive the highest dose, although estimates of this dose differ by more than an order of magnitude, ranging from about 0.2 to 12 rads per WLM (2 mGy to 120 mGy). The most critical parameters of these models are the assumed depths of basal cells below the bronchial surface and the fraction of the WL carried by free ions. When more realistic values of these parameters are substituted (Jacobi, 1977), the dispersion in calculated maximum doses to basal cells is reduced to give a much smaller range from about 0.3 to 1 rad/WLM (3 to 10 mGy/WLM). The parameters and methods employed in these various models, however, remain too diverse to infer the sensitivity of the dose conversion to practical variations in aerosol characteristics and the additional factors determining lung deposition and clearance. We have therefore taken the approach of developing newer models (Jacobi and Eisfeld, 1980; James et al, 1980) that can encompass the range of available experimental data on the physical and biological behaviour of radon and thoron daughters and also accommodate the different interpretations that can be put upon them. We have paid particular attention to the averaging of dose over tissues of equal sensitivity in the lung

Jan 1, 1981

By G. H. Gronhovd

The U.S. Geological Survey estimate of the total remaining reserves of lignite in this country as of Jan. 1, 1967 was about 448 billion tons. This represents 27 percent of the total coal reserves on a tonnage basis and about 17 percent on a thermal basis. Approximately 98 percent of these reserves are in a vast lignite field located in western North Dakota and eastern Montana. This field also extends north into the Canadian province of Saskatchewan. Despite these large reserves and relative ease of mining by stripping operations, lignite production historically has accounted for less than 1 percent of the national total. This is largely due to the fact that the lignite deposits are located in an area that has no large centers of population and the economical radius of transportation is limited by its relatively high moisture and low heating value. Commercial utilization of North Dakota lignite for power production became firmly established in the mid-1920's with the development of the first successful lignite-burning equipment. Most of the early lignite-fired boilers were equipped with spreader stokers, but as the size of the plants increased, pulverized-coal firing became the more popular method, and with few exceptions, the plants built during the past 15 years are pc-fired.

Jan 1, 1968

Anhydrite-based dam constructions, which have been implemented successfully in other geological formations, were investigated with regard to their suitability in salt mines. The laboratory investigations show that anhydrite-based building materials with suitable additives bind safely in spite of the high temperatures in salt mines which normally pre-vent hydration. The dependence of the compressive strength, swelling behavior, porosity and permeability upon the choice and ratio of binding material components and additives was determined. Based on the results of these investigations, a pilot-scale experiment was carried out at the GSF Research Mine Asse (Germany) using a mixture suitable for the prevailing conditions

Jan 1, 2004

By D. Antonov

The physical and mechanical properties of coal play a important role in the planing and design of coal mines. However, due to the complexity conditions in situ and the influence of unknown factors, it is hard for people to evaluate the physical and mechanical properties of coal directly. In this research, uniaxial compressive stress was used to change the attribute of coal samples, and the ultrasonic measure technique was used to evaluate the physical and mechanical properties of coal. The results of laboratory test showed that there was a strong relation between uniaxial stress and velocity of ultrasonic wave. Sensitivity analysis with numerical simulation was used to define the relation between the physical-mechanical parameters of coal and ultrasonoc wave. With the dynamic analysis module of FLAC, three elastic and plastic models were built to model the coal samples. The modeling parameters were changed pro rata, and the correlation of coal and ultrasonic wave properties were summarized and presented. The result from this research will be base for further analysis of caving behavior of coal.

Jan 1, 2010

By Michael Fehler, Hidenshi Kaieda, Leigh House

Hydraulic fracturing has gained in popularity in recent years as a way to determine the orientations and magnitudes of tectonic stresses. By augmenting conventional hydraulic fracturing measurements with detection and mapping of the microearthquakes induced by fracturing, we can supplement and independent1 y confirm information obtained from conventional analysis. Important information obtained from seismic monitoring includes: the state of stress of the rock, orientation and spacing of the major joint sets, and measurements of rock elastic parameters at locations distant from the wellbore. While conventional we1l 1ogging operations can provide information about several of these parameters, the zone of interrogation is usually limited to the immediate proximity of the borehole. The seismic waveforms of the microearthquakes contain a wealth of information about the rock in regions that are otherwise inaccessible for study. By reliably locating the hypocenters of many microearthquakes, we have inferred the joint patterns in the rock. We observed that microearthquake locations do not define a simple, thin, planar distribution, that the fault plane solutions are consistent with shear slippage, and that spectral analysis indicates that the source dimensions and slip along the faults are small. Hence we be1 ieve that the microearthquakes result from slip along preexisting joints, and not from tensile extension at the tip of the fracture. Orientations of the principal stresses can be estimated by using fault plane solutions of the larger microearthquakes. By using a joint earthquake location scheme, and/or calibrations with downhole detonators, rock velocities and heterogeneities thereof can be investigated in rock volumes that are far enough from the borehole to be representative of intrinsic rock properties.

Jan 1, 1986

By C. K. Jankousky

The midwestern area referred to is the Illinois basin. The coals presently worked are mainly the No. 5 and No. 6 coal seams which vary in thickness from five to eleven feet. Present average of the more important No. 6 id about nine feet. The coal can vary considerably in toughness within the same mine with some coal perhaps rashing very easily and other coal being extremely difficult to cut. Top is generally well laminated shales with some fortunate areas having limestone roof. There are local areas with troublesome top of poorly laminated shales, shale with slickensides and shale intermingled with small partings and traces of coal. The bottoms are generally one to three feet of clay which softens readily on exposure to moisture. The mines are dry although some water is released and collects from rapid penetration of the seam by continuous miners. However, there are locally wet areas. Most of this material refers to mines of the Freeman Coal Mining Corporation. The mining operations written about are underground mines in southern and central Illinois.

Jan 1, 1962

By John B. Squyres

The purpose of this paper is to describe certain features of the uranium deposits of the South San Juan Basin, and to suggest a mode of origin for the deposits which is consistent with the data. A series of photographs is included at the end of the paper to illustrate the nature of the ore bodies. Since the general geology of the Grants Region is well described in the literature, it will be only briefly reviewed, and the time will be spent instead on the morphology, spatial relations, and geochemistry of the ore deposits. Part of this material is original, but data and ideas have been taken from a variety of sources, including the literature and the personnel of the USGS, the AEC, and many of the operating companies of the South San Juan Basin. I gratefully acknowledge these sources. The accuracy of the data and the conclusions presented here are my own responsibility, however.

Jan 1, 1974

By D. M. Thayer

In the last decade public awareness of the need for pollution abatement has increased greatly. The concern that had been previously shared by local and state conservation groups has spread to create a national concern for preservation of our non-polluted environmental assets and regeneration of those that have been wasted. Because other current matters such as inflation, civil rights,' tax reform and the Vietnam situation have been the object of most national concern, an extremely strong national pressure base has not been brought to bear on the pollution control crisis. Yes, the word is crisis, for in many areas pollution is of critical concern. One has only to look at Lake Erie, the skies about our major urban areas and many of our major rivers and streams to see this crisis These are not situations that can be corrected overnight. We are faced with two basic problems that should be attacked simultaneously: (1) Cleaning up the present sources of pollution and (2) preventing the generation of new pollution sources. What approach should be taken? As in any engineering problem, the limits must be well defined before a final solution is attempted. Pollution must be defined on a national basis. This means that basic Federal legislation and control is necessary. This should reduce any competitive advantage that can presently be gained by movement of operations from one state or geographical area to another on the basis of differences in local legislation .and enforcement. By giving real numbers as guidelines, selective enforcement can be avoided. As a starting point, for a definition of pollution let us use the following - "Any change in the environment occurring from other than natural causes." This definition may not be satisfactory to all but surely we must be somewhat dramatic in our statements to counteract the present prevailing philosophy. Our statement of this philosophy - "At what level of pollution can we afford to operate?" On the basis of our general definition we would like to state what we feel should be the philosophical statement - "How little can we change our physical environment as a result of operations?"

Jan 1, 1970

By E. J. Harvey

The Ozarks has been called "a diamond in the rough". In this region streams have steep gradients, sparkling clear flows of cold water fed by many springs, and a wildness that is almost unique in the central part of the United States today. The Current River and its tributary, Jacks Fork, have been set aside for preservation by the National Park Service as a "Wild River" in the first park of its kind in the country. It is called the Ozark National Scenic Riverway. Similarly, responsibility for the preservation of the Eleven Point River has been assigned to the U. S. Forest Service. Protection of other streams in the Ozarks has been considered by State agencies. The hydrologic system of the Ozarks is a complex network of gaining and losing streams, caves, conduits, and large springs. Increased sewage loads derived from the growing towns and expanding tourist trade are a potential hazard; effluents may flow underground for long distances, polluting springs and wells. To add another dimension to the hydrologic picture a new lead industry is also flourishing in the Ozarks. Although the history of lead mining in the area goes back to 1701 (U. S. G. S., p. 43), the area has not seen a revitalization like the one that has been developing in the last 10 years; and the economic growth promises to continue indefinitely. Although this brings capital expenditures and wages into the area, it also brings potential hydrologic problems. Chemicals, wastes and other substances either stored on the surface or transported across it are subject to accidental spillage. In an area where these substances remain on the surface their effects are subject to surveillance. In the Ozarks, however, this may not be possible.

Jan 1, 1970

By George F. Weaton

During the past eight years there has been a dramatic change in the iron ore industry of Minnesota, in that its status has changed from that of a seller's market to a higly competitive buyer's market. Minnesota's natural ores must now be beneficiated and up-graded considerably to be marketed in order to compete with the higher grade foreign ores as well as with the locally produced and highly desirable taconite pellets. With the passage of the "Taconite Amendment' in the November, 1964 election, the taconite industry commenced to expand in Minnesota, which, although initiated in that state, was benefiting many other states and some foreign countries to a much greater extent than Minnesota. These other areas were actually appropriating markets that had been established and retained by Minnesota for many years. Since the approval by the state voters of this amendment, there has been a great increase in the development of taconite properties on the Mesabi Range.

Jan 1, 1966

By R. H. Weiland

The dewatering of flocculated clay suspensions by compression in a centrifugal field has been investigated. The results are evaluated with regard to both direct applicability to centrifugal dewatering, in solid-bowl centrifuges for example, and indirect applications to gravity sedimentation systems. It is well known that sediment consolidation under gravity depends on structural characteristics such as permeability and on the "self-weight" of overlying sediment layers. An important objective of the study has been to evaluate the self-weight effect using centrifugal forces to simulate consolidation in deep sediments. In this way, small-scale laboratory tests can be used to predict the rates and limits of sediment compression in industrial systems such as thickeners and settling ponds. Experiments have been conducted in which the sediment mass and initial structure were maintained constant while the effective sediment weight was varied by centrifuging at different speeds. The effects of initial structure have also been studied using controlled variations in flocculation conditions.

Jan 1, 1993

By J. Partyka

Respirable dust produced during blasting operations in underground mines exhibits both diffusion and convection properties of the airflow. However, the application of the mathematical model presently used to calculate the change in time in the concentration of blasting pollutants is mostly limited to a single drift and cannot be easily utilized for blasts taking place in stopes. This paper discusses an analytical solution based on considerations that enable us to reliably identify the initial condition. Such an approach may be used for any blasting area regardless of its position, its size, or the ventilation system in use during blasting. In addition, a test procedure using field data is established to determined those parameters not measured directly. As well, equations are derived to find the diffusion coefficient, and the position and size of a dust source from the field data. Mathematical considerations The convection-diffusion problem, for a one-dimensional case, is described by the following partial differential equation (PDE): ct. = Dcxx - Vcx + source - sink(1) where C = the concentration of a pollutant T = time V = the mean air velocity in x-direction D = the diffusion coefficient X = distance away from the pollutant source source = any additional pollutant source specified by an initial value problem sink = decay of a pollutant inside the region specified by the boundary conditions. Respirable dust produced during blasting is best considered as an initial value problem (IVP). To derive a mathematical model, the following assumptions are made: •At time zero (t = 0), the dust source is at point x = 0 of an infinite drift. •The problem is considered a one-dimensional case. •The mean velocity of air and the diffusion coefficient are constant. •There is no source or sink of dust other than specified at point x = 0 and time t = 0. We have to solve the following problem [PDE ct=Dcxx-Vcx-m<x...m;0<t<m(2)] ICc(x,0)=f(x)t=0, the initial condition Where c = dust concentration in mg/m3 V= the average mean velocity in a drift in m/s t= time in s D= the diffusion coefficient in m2 /S x = distance coordinate in m. We observe that in problem (2), we have moved the boundaries to[ -m and +m] in order to have an initial-value problem. We introduce new coordinates, s = t and z =x - Vt. To rewrite the PDE in terms of (z, s), we use the chain rule ct = czzt + csst = -Vcz + cs cx = czzx = cz cxx = (cz)x = czz. We now substitute our computed ct, cx. and cxx into the PDE to get new IVP in terms of z and s :

Jan 1, 1991

By George I. Staber

As stated by the Congress in the preamble of the act establishing the Office of Coal Research, its purpose is, "To encourage and stimulate the production and conservation of coal in the United States through research and development by authorizing the Secretary of the Interior to contract for coal research, and for other: purposes." Thus, while the overall responsibility for air pollution control from all sources rests primarily with the Department of Health, Education and Welfare, it is obvious that OCR could not perform its mandate of, increasing the utilization of our Nation&apos;s greatest energy resource if it ignored one of the greatest practical obstacles to achieving that objective. Therefore, air pollution abatement and prevention is one of the practical considerations taken into account in the selection of the OCR program. And as the severity of the air pollution problem imposes new restrictions on the use of coal, the importance of this criteria in the selection of OCR projects increases. The work done by OCR in air pollution abatement does not conflict with nor does it duplicate the program developed by HEW&apos;s National Center for Air Pollution Control. Technical members of the OCR staff maintain close formal and informal liaison with their counterparts in NCAPC. One formal agreement has been executed whereby the HEW agency has transferred funds to OCR for a practical study of the potential effectiveness of air pollution control when coal is burned in a fluidized bed comprised of inert alkaline earth material. It is hoped that this initial cooperative effort will be

Jan 1, 1968

By D. E. Ranta, M. G. Schulz

Mining of Molybdenum at Questa, New Mexico has been accomplished by block cave methods since August, 1983. As caving progresses, a periodic geologic evaluation is made of the rock types present in finger raises on the Grizzly Level of the mine. The production maturity of the cave can be monitored by relating this data to geologic cross-sections through the orebody. The draw point mapping program is a simple and effective tool that is used in making draw control decisions at Questa.

Jan 1, 1992

By L. W. Laage

MFIRE is a mine ventilation and fire interaction computer simulation program. It allows transient state ventilation simulation and features mass based flow rates, natural ventilation, air recirculation, fan curve fitting, airflow reversal and product of combustion tracking. MFIRE was designed to accommodate the needs of the mining industry for routine ventilation calculations and mine emergency planning. This paper describes recent work by the Bureau and MTU to improve MFIRE by incorporating humidity in the mass flow and heat exchange calculations, a data file preparation program and variable reference density in the network calculations. Recent bug fixes are also discussed.

Jan 1, 1993

By C. E. Jordan

The fundamental characteristics of ultrafine chalcopyrite flotation were investigated by the Bureau of Mines to establish techniques to improve recovery of ultrafine chalcopyrite. Intense agitation during conditioning was found to improve flotation recovery of the ultrafine chalcopyrite. A split-circuit flotation design, treating the plus 38-µm-size ore by the conventional method and treating the minus 38-µm-size ore with intense agitation conditioning followed by flotation, recovered 95.6 pct of the copper in a 28.3-pct-copper concentrate, This was a 5-pct increase in copper recovery over the conventional chalcopyrite flotation method.

Jan 1, 1986

By T. Reed Scollon

Major interrelated factors to be considered in assessing the impact of air pollution control regulations on coal are: (I) the fuel and fuel-related limitations of such regulations; (2) the rate of adoption and areal scope of the regulations; and (3) the availability of fuels and fuel-burning equipment to meet the requirements. A growing number of regulations contain provisions limiting the emissions of sulfur oxides or the sulfur content of fuels or both. With few exceptions, these limitations have not yet become fully effective in those areas which have already adopted regulations, and pertinent details of future regulations or legislation for most other areas are unknown at this time. Sufficient information is not avail- able to determine the availability of low-sulfur fuels at various demand and price levels, and large-scale commercial feasibility of sulfur-oxides removal processes and equipment is believed to be some years away. Accordingly, with the many uncertainties and unknowns, it is possible at best to make only a rough assessment of the impact of such regulations or legislation on coal.

Jan 1, 1969