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503 EM 385-1-1 Sections 20-26
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503 EM 385-1-1 Sections 20-26

26.J Underground Blasting.

A Blasting Plan must be developed and submitted for this work. > See also Section 29.

Tunnel construction in Greece.

26.J.01 Explosives.

  1. Dynamite used in tunnel blasting must be Fume Class 1. Fume Class 2 and Fume Class 3 explosives may be used if adequate ventilation is provided.
  2. Storage of explosives, blasting agents, and detonators in tunnels or underground work areas must be prohibited.
  3. Trucks used for the transportation of explosives underground must have the electrical system checked weekly to detect any failures that may constitute an electrical hazard. A written record of such inspections must be kept on file and available for review. The installation of auxiliary lights on truck beds that are powered by the truck's electrical system must be prohibited.
  4. Explosives or blasting agents, not in original containers, must be placed in a suitable container when transported manually. Detonators, primers, and other explosives must be carried in separate containers when transported manually.

26.J.02 Blasting circuits.

  1. All underground blasts fired by external power must be by a power blasting switch system.
  2. Blasting power circuits must be separate and distinct from, and kept clear of, other power and lighting circuits and pipes, rails, and other conductive material (excluding earth) to prevent explosives initiation or employee exposure to electric current.
  3. Sectioning switches or equivalent must be installed in the firing line at 500-ft (150.4- m) intervals.

26.J.03 Loading.

  1. Prior to loading, all power, water, and air lines must be disconnected from the loading jumbo and power lines, including lighting circuits, must be moved back a minimum of 50 ft (15.2 m).
  2. The loading area must be illuminated a minimum 10 ft-candles (107.6 lx) by floodlights located 50 ft (15.2 m) from the face. If additional illumination is needed, the loading crew must be provided with head lamps approved by the United States Bureau of Mines.
  3. Equipment used for pneumatic placement of non-cap-sensitive blasting agents must be designed for that purpose and must be grounded while in use.

Knowledge Check Choose the best answer for the question.

26-13. Prior to loading, how far back do power lines, including lighting circuits have to be moved from the loading area?

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