An army of jumbos and intricate temporary tunneling has helped speed work on an underground powerhouse, maximize drill use and increase the contractor's overall job profit. Short stroke Copco drills were used which add 25 to 40 percent to equipment speed and adopts well to the stratified mica schist. The drill steel was changed every 1,500 ft and detachable bits every 750 ft. Three 7-boom tractor-mounted jumbos worked side-by-side in the 82 x 778 x 187-ft-high main powerhouse excavation. Other units included a 4-drill jumbo, two Atlas Copco 3-drill jumbos and 11 Gardner-Denver Model 3200 Air-Trac units plus stopers and jacklegs. The big 7-boomers and the 3-boomers added flexibility and adapted to the varying heading sizes and shapes. The observation is made that smaller drifts can be mined more efficiently with custom-built jumbos that can handle rockbolting and meshing during the drill cycle. The customized BUT 14ER booms cover twice the area and they position easier than standard units. Details of the timing and tunneling are described as well as the drilling cycle, blasting and rockbolting.

  • Corporate Authors:

    McGraw-Hill, Incorporated

    330 West 42nd Street
    New York, NY  United States  10036
  • Authors:
  • Publication Date: 1974-10

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Filing Info

  • Accession Number: 00264756
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Feb 11 1975 12:00AM