Search Documents

1.1 DEVELOPMENT OF INDUCTANCE MATRICES The basic building block in this analytical work is the development of an equivalent circuit. The equivalent circuit for the cable depends on all of the distributed parameters of the cable although the series inductance and resistance are of primary importance. The cable resistances are generally available from handbooks or from cable manufacturers. On the other hand, the cable inductances are not usually available either from handbooks or from the manufacturer's published data. Thus, it is useful to summarize the derivation of the origin of the inductance matrix from basic principles. 1.1.1 Flux Around a Cylindrical Conductor The flux pattern around a cylindrical current carrying conductor can be found by using symmetry in conjunction with Ampere's Law. From symmetry it is clear that the flux lines which always close on themselves must be concentric circles. Thus, from symmetry alone one can get a qualitative picture of the magnetic field. This is shown in Fig. 1.1 where the inner circle represents the solid round conductor and the outer circle represents a flux line. The quantitative picture will now be developed using Ampere's Law.

Jan 1, 1973

By Harvey L. Pastan

The purpose of the investigation and analysis described in this report is to assess the data flow requirements that are required for remote supervisory control of a continuous mining system. Since these control concepts as applied to continuous underground mining are still in a formative stage at the present time during the first half of 1975, assumptions had to be made based upon engineering judgment as to what embodiment of mining machinery and control methodology seemed most feasible for achieving such a system. Based upon these assumptions and estimates of the control system's accuracy and response requirements, it was then possible to estimate the communication requirements for the assumed system configuration. 2. Approach The team members responsible for this study visited numerous coal mines to observe room and pillar mining operations in both high and low coal. The objective was to observe the methods of operating a variety of continuous mining machinery and haulage equipment with a view toward defining the problems to be overcome in the application of automation to the coal extraction process. Descriptive information concerning the mining equipment was obtained through contacts with the manufacturers. Conferences with Bureau of Mines personnel, equipment manufacturers and developers, and mine operators were held to explore the current thinking and developments being pursued toward automation and increasing both production and productivity.

Jan 1, 1975

By Philip K. Hopke

A systematic study of the mechanism of interaction of 218Po(RaA) armed by the decay of 222Rn with airborne particulate matter has been made. The rate of attachment of RaA to particles in the diameter range of 0.1 µm to 10.0 µm has been measured as a function of particle size, concentration, and composition, radon concentration, time of interaction, relative humidity and temperature. It was found that under the conditions in these experiments the attachment rate was proportional to the square of the particle diameter and varied with temperature and relative humidity. The composition of the particles apparently has no effect on the attachment. The variation in attachment rate was related to a sticking probability coefficient of approximately 0.02 that varies systematically with temperature and humidity. In addition, the rate of deposition of RaA on the wall of the attachment kinetics system was measured and also found to change with temperature and relative humidity.

Jan 1, 1980

By Gary Choate

The work presented in this report represents the background activity which led to the fabrication and testing of a greenhorn and crowd limit switch system for electric shovels. The program began With a literature search and manufacturers product review to gather material as a basis for concept generation. Visits to three open pit mines provided information from operation and maintenance managers which was useful in preparing design concepts. These concepts were evaluated through laboratory tests and engineering analysis to select a final design concept. The resultant greenhorn is four separate shock absorbing pads each enclosed in a housing which bolts to the end of a dipper handle adaptor. The plungers impact against stops mounted to the saddle block. The crowd limit control is a nonmechanical device which senses the location of the dipper and makes appropriate commands to the crowd motor to insure against impacting the greenhorns. The electronic crowd limit control is redundant and indicates malfunction modes. The greenhorn prevents shovel damage in the unlikely event of impact.

Jan 1, 1983

By N. Barton

Large scale tests were conducted on quartzitic gravel and crushed sand-stone to investigate pertinent geotechnical properties for backfill support of egress shafts. Such shafts are envisaged for rapid launching of deep-based missiles. The backfill support is designed to resist shaft closure under dynamic loading, and must also drain rapidly to a lower catch chamber to allow launching. Large scale tilt shear tests were performed to measure the internal shear strength of the two backfill materials. Shaft filling and emptying tests were conducted in a 12 ft deep, 3 ft diameter model section of shaft drilled in sandstone. One half of the model was smooth bored, the other half rough-surfaced to represent drill and blast surfaces. Vertical and horizontal pressure cells indicated that stress only built-up during the first 1 to 1 ½ diameters of filling, due to the high-sidewall friction of 38° for the rough shaft and 31° for the smooth shaft. Interface sliding tests were performed to confirm these figures. Static and dynamic deformation tests were also per-formed, and indicated moduli as high as 56,000 psi, which will give excellent shaft support. Both the shaft support characteristics and the ease of emptying of gravel look particularly promising.

Jan 1, 1983

By William M. Schafer

Forage plots were established on agricultural lands contaminated by acid mining waste. The acid produced through oxidation of pyrite and other sulfides caused elevated solubility and plant availability of copper, zinc, and arsenic which killed vegetation and polluted surface and groundwater. Soil amendments including agricultural lime (CaCO3), hydrated lime (Ca(OH)2), phosphorus, and organic matter were used to reduce the toxicity of metals. Several acid-tolerant grasses were used to vegetate the amended soils. Various soil extraction techniques were used to see which best correlated with vegetation performance. The extractions corresponded to three "forms" of metals in soil including soluble (water-saturation extract); plant-available/weakly adsorbed (DTPA extract); and total (HNO3/H202 extract). Of the extractants tested the DTPA levels appeared to correlate best with metal levels in plant tissue. The DTPA soil extractant serves as a useful tool in predicting potential phytotoxicity of mine waste materials.

Jan 1, 1989

By C. W. Morris

This Final Report describes the major technical activities that were accomplished to produce a comprehensive continuous miner training system (CMTS) for coal industry utilization. The primary product of this program was a continuous miner part-task trainer. It is composed of an interactive computer graphics system combined with the operating controls of a continuous mining machine mounted in a simulated cab. The cab contains an audio system for reproducing continuous miner operational sounds. The trainer is supplemented with a complete set of cognitive materials that provide instruction in the operation, safety and health of continuous miner operations. A complete summary of the field test and evaluation of the CMTS is provided along with a set of recommendations for further training program refinements, expansions, and utilization.

Jan 1, 1982

By C. W. Morris

The continuous miner training system provides classroom materials training aids, and a continuous miner simulator to provide a short, intensive instruction and skills development program for training or retraining continuous miner operators. This project included refinement of training objectives, revision of training aids, improvements to the simulator, and evaluation of the entire system. This report describes the revised classroom materials and the validation of the training system.

Jan 1, 1982

By Robert E. Green

This Final Report summarizes the results of work accomplished under Contract No. J0215039. It is in an executive overview or executive summary format. The number and description of the various technical reports prepared and submitted is outlined. The essential changes and reasons for the revised program schedule/contract modifications actually enacted in May 1982 are discussed in detail. The evolving mines/deposits list and the accompanying criteria classifications are explained along with the verifications/justifications for adding or deleting specific mines/deposits to the list. Difficulties and problems experienced during the different phases of the project in conjunction with the ensuing remedies are highlighted. The final section of they report is devoted to presenting Davy McKee's suggestions for improvements to future MAS commodity studies. Appendix I is comprised of three of the evolving mines/deposits lists starting with the original RFP list and ending with the final completed list. Appendices II and Ill are tabulated summaries of property data including reserves/resources, assays, production, and operating costs. The figures for the specific mines/deposits are given in "range of values" so as to protect the confidentiality of the individual owners/ operators.

Jan 1, 1983

By R. L. Mazza

This final report on methods of reducing and controlling methane in coal mine gob areas indicates that vertical degas holes are beneficial to the mines of northern West Virginia working the Pittsburgh Coal. The USBM funded project involved the drilling and testing of eight vertical holes (four over longwall panels and four over room and pillar panels) based on a review of 13 previously in existence. Areas of observation included gas production history, flow entry profile, underground methane reductions, strata separations, and casing loads (accompanying subsidence). Observations led to the drilling of successful holes drilled short of the mine. Eleven gas production response to applied vacuum tests were conducted at nine degas holes under the contract. Significant production responses were recorded over longwall gobs.

Jan 1, 1977

Mining and the related extractive and processing industries are chiefly responsible for America's high standard of living. Enormous quantities of sand and gravel, limestone, copper, iron and a myriad of other mineral commodities are required to sustain our growing nation. However, the mineral deposits, both domestic and foreign, are becoming increasingly difficult to find. Adding substantially to the problem, is the fact that the conditions are worldwide. Foreign politics are increasingly affecting mineral commodity availability. Figure 1, taken from Bureau of Mines, "Status of the Mineral industries 1976" illustrates our dependency (in some cases total) on foreign sources for vital mineral commodities. While few nations are capable of exerting an OPEC-like influence on any one mineral commodity, the threat of cartel arrangements and related control strategies is evident. Nationalization of entire industries, once they become self-sufficient, is also exerting a disruptive influence on a large portion of the mineral industries.

Jan 1, 1977

By Jose P. T. Agapito

Several underground coal mines currently operating in the Beckley District of West Virginia are experiencing serious roof and floor problems. A significant portion of the estimated two billion tons of coal resources may be lost as a result of these ground control problems. Preliminary studies by the Bureau of Mines indicated that these problems are due in part to a high horizontal stress field. During this contract study, a field program was conducted to quantify the horizontal in situ stress. A total of 14 overcoring sites (using the Bureau of Mines strain-relief overcoring technique) in five mines were drilled producing 53 data sets. Analysis of the data was done to provide in situ horizontal stresses for each of the five mine, and for the district as a whole. Stress data indicate horizontal stresses far in excess of that predicted by theory and in some cases, up to six times the estimated vertical stress. In addition to the field testing, a detailed computer modeling study was conducted using finite element and boundary integral (displacement discontinuity) methods. Verification of in situ stresses was obtained by the models and analysis of various development geometries, mining methods and remedial techniques were conducted. Recommendations for reducing ground control problems and future studies are presented.

Jan 1, 1980

By Matthew N. Rubin

This report summarizes the work performed under USBM Contract No. H0155155. The purpose of this work was to obtain operational data on retrofit noise control treatments suitable for use in coal preparation plants. This data was obtained by evaluating the performance of four categories of noise control treatments which were installed in a commercial coal preparation plant. The four categories of treatments were resilient screen decks, resilient impact pads, chute liners, and curtains. The selection, installation and initial evaluation of the treatments was documented in the Volume I report issued in 1977. This Volume II report summarizes the results of the long-term evaluation of the original treatments, as well as some additional tests which were conducted on elastomer-clad (resilient) screen decks. This project demonstrated the feasibility of a number of retrofit noise control treatments, some of which also proved to be quite durable over the long term.

Jan 1, 1982

By Piyush K. Dutta

This report describes the design, development and manufacture of production stoper drills and results of their field tests, it is shown that underground stoper drill noise level can be reduced from 118 dBA to below 100 dBA by using these pneumatic drills. The design concept of these drills is a radical departure from the standard valved rifle bar type drill machine design to a drill featuring a valveless independent rotation system, use of an integral muffler and a shroud tube. Six drills were manufactured in a standard commercial drill manufacturing setup and organization. The design and production technology proved that commercially viable quiet drills can be made available for mine use.

Jan 1, 1983

By Michael Radnor

The purpose of the study was to 1) examine the social and economic impacts of surface mine blasting in relation to variations in conditions of terrain and geology, population density and type, levels of ground motion and air blast; 2) consider technical, legal and government policy issues; and 3) examine the potential, nature and extent of surface mine blasting impacts and its regulations upon both communities and surface mining companies. Phase One designed the empirical research and technical analyses of Phase Two, focused upon surface coal mining and quarrying in the Eastern U.S. Several broad conclusions are evident: 1) blasting is not the major issue for communities or surface mine companies; 2) while the number of instances of severe cracking or annoyance are relatively small, the impact can be severe for individuals immediately involved; 3) blasting/drilling cost curves tend to rise significantly at intervals below 1.0 particle velocity, in/sec, dependent upon the size of a permit area and the size of a mine; and 4) the legal, complaint, cost and density analyses do not suggest the need for a general lowering of present regulations.

Jan 1, 1981

By H. Miller

In recognition of the need for a portable low-profile hard rock crusher, the Bureau of Mines sponsored the development of such a unit capable of moving up as the face advances. By allowing primary ore reduction at or near the mine face, the advantages of conveyor haulage From the face as demonstrated in soft ore and coal mines, could be realized for hard rock Brines as well. This report presents the results of a development and testing program for such a portable low-profile crusher, designed by Eagle Crusher Company and called the M44. The unit has an extremely low vertical profile considering its size and capacity. The crushing jaws, which form the crushing lumber, are inclined, with the lower jaw mounted for eccentric movement relative to the stationary upper jaw. This provides efficient crushing while also forcing material through the crushing chamber. As a result, the inlet feeder can be disposed horizontally. To facilitate correct processing of different materials, the size of the discharge opening and the action of the movable crushing jaw are variable. The unit also incorporates a feeder hopper and discharge conveyor that provides for efficient ore handling through the machine. Tests demonstrated the M44 Crusher's high capacity, efficiency and reliability. During testing, it crushed over 120,000 tons of materials of up to 32,000 psi compressive strength at production rates in the 200-350 tons/hour range. The unit operated smoothly under simulated low-headroom conditions, and Proved readily transportable.

Jan 1, 1983

By Gerald H. Groenewold

Reclamation of surface-mined landscapes is commonly defined only in terms of biological productivity. Other critical concerns associated with surface mining include the long-term quality of groundwater and stability of the postmining landscape. Meaningful reclamation design must address all these concerns. Reconnaissance of postmining landscapes indicates that three types of instability occur in these settings. These include: area-wide settling, localized collapse, and piping. Area-wide settling is most pronounced during the first year after contouring but appears in precontouring valley areas where frozen materials are contoured with a dozer. Although severe in some settings, development typically ends within one year. Piping appears to be a severe and long-term problem in some settings. Piping usually begins soon after contouring ceases and may continue for several years. In some postmining landscapes, piping has only started to develop after as many as five years of apparent stability. Piping is controlled by a combination of physical and chemical conditions in the spoil. A key factor is the presence of highly dispersive materials in the near surface. The design of a stable postmining landscape requires the integration of severe critical factors. These include: 1) detailed knowledge of the distribution of overburden materials with emphasis upon the delineation of highly sodic sediments; 2) proper equipment selection; and 3) a consideration of climatic factors. For reclamation to be successful, it must consider the entire landscape, not merely the soil zone. Any approach short of this will lead, at best, to temporary solutions.

Jan 1, 1980

By Larry R. Powell

As part of the Bureau of Mines effort to establish a comprehensive subsidence data base for subsidence technology development, subsidence and related data are being compiled for various mining, geological, and environmental situations. This publication presents data for two longwall mining operations in the Northern Appalachian Coal Region. Vertical displacements and relative face positions are tabulated for 104 subsidence monuments. Brief physiographic and geological descriptions of the mining sites are presented along with a general account of the mining and subsidence monitoring methods.

Jan 1, 1981

By J. A. Kost

A dust-control manual was prepared for use by mine operations personnel. The manual documents state-of-the-art control techniques, dust sampling, and use of personal protective devices. Content addresses advantages/disadvantages of control techniques, design and operating specifications, and implementation and maintenance guidelines. An indexed list of selected references is also included. In addition to the completed manual, this report documents work performed in the course of its preparation.

Jan 1, 1981

By Jacqueline V. Rich

The relationship between surface and ground water quality and copper mining in the Globe-Miami area is investigated in this three-year study. Methods to prevent, minimize, mitigate, or treat polluted waters are identified and evaluated. Best Management Practices are incorporated in a recommended plan to manage the area's water quality.

Jan 1, 1983