Results 241 - 250 of 282

• Probability of Encountering Coalbed Discontinuities During Vertical and Horizontal Borehole Drilling
  1/1/1982 - Reports of Investigations
  Probabilities of encountering coalbed discontinuities during vertical or horizontal drilling in a specific coalbed can be estimated based on analysis of mined-out areas of the coalbed where the size, shape, orientation, and distribution of discontinuiti...
• A Fail-Safe Control System for a Mine Methane Pipeline
  1/1/1980 - Reports of Investigations
  The Bureau of Mines has designed and put into operation a fail-safe control system for use in underground coal mines equipped with methane drainage pipelines. This control system can detect certain unsafe conditions and respond by automatically shutting...
• Three Coal Mine Gob Degasification Studies Using Surface Boreholes and a Bleeder System
  1/1/1980 - Reports of Investigations
  The use of vertical surface degasification boreholes with bleeder systems and the use of a timbered bleeder system to degasify gob areas were studied by the Bureau of Mines. This report describes three gob degasification studies conducted in the Pittsbu...
• Review of Horizontal Drilling Technology for Methane Drainage From U. S. Coalbeds
  1/1/1980 - Information Circulars
  Reviews underground methane drainage programs being conducted in various coalbeds. Equipment used in drainage programs such as drills, underground pipelines, and methane monitoring systems is described.
• Wireless Communications for Trackless Haulage Vehicles
  7/1/1979 - Contract reports, Open File Reports
  This report describes a complete system design for medium frequency ( MF) wireless radio systems for use in coal mines. The emphasis is on AC mines where no trolley wire exists and, for which, conventional trolley phone communications cannot be used. Th...
• Propagation of UHF Radio Waves in Limestone Room and Pillar Mines
  1/1/1979 - Contract reports
  This report presents a mathematical model for the propagation of UHF radio waves in the large cross section tunnels of a room-and-pillar limestone mine and describes the analysis of a small amount of propagation data obtained. The model and analysis is ...
• Antenna Design & Coupling Studies at Medium Frequency for lmproved Coal Mine Communications
  9/1/1978 - Contract reports
  This report covers antenna design, analysis, and development work suited for use with a wireless radio communication system operating at medium frequency. The work includes the test and evaluation of prototype vehicular antennas developed during the pro...
• Medium-Frequency Propagation in Coal Mines
  8/1/1978 - Conference papers
  Medium-frequency (MF) waves can propagate in a coal seam, bounded above and below by conducting rock, in an approximate transverse electro-magnetic (TEM) transmission-line mode with the electric field vertical and the magnetic field horizontal. The theo...
• Transmit Antennas for Portable VLF to MF Wireless Mine Communications
  9/1/1977 - Contract reports
  An investigation was made of the feasibility of developing compact transmit antennas and/or other means to efficiently couple VLF to MF band radio energy between portable wireless communication units in coal mines. The completely wireless communication ...
• Effects of Hydraulic Stimulation on Coalbeds and Associated Strata
  1/1/1977 - Reports of Investigations
  In studies conducted by the Bureau of Mines, two test areas were hydraulically stimulated and exposed by mining: one in the Pittsburgh coalbed at the Vesta No. 5 Mine, Washington County, Pennsylvania; and one in the Illinois No. 6 Coalbed at the Inland ...