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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.04 Blasting.

  1. The person in charge of blasting must be the last to leave the blast area, must see that no one remains in the blast area, and must operate the sectioning switches in the firing line while proceeding out of the blast area.
  2. No persons must enter the tunnel blast area until the ventilation system has cleared the heading of harmful gases, smoke, and dust.
  3. After each blast, the underground supports in the blast area must be inspected and secured as necessary work is resumed. Rock surfaces must be inspected, scaled, and if required, provided with shoring, bracing, rock bolts, shotcrete, or chain-link fabric, before mucking is started. Rock bolts within 100 ft (30.4 m) of a blast must be tested after each blast before drilling for the next round begins.
  4. The muck pile must be wet down prior to mucking and kept wet during mucking operations.

26.J.05 Blasting in excavation work under compressed air.

  1. When detonators or explosives are brought into an air lock, no employee (except the blaster, lock tender, and employees necessary for transport) shall be permitted to enter the air lock; other material, supplies, or equipment must not be locked through with the explosive materials.
  2. Detonators and explosives must be taken separately into pressure working chambers.
  3. All metal pipes, rails, air locks, and steel tunnel lining must be electrically bonded and grounded at or near the portal or shaft. Such pipes and rails must be cross-bonded at not less than 1000-ft (304.8-m) intervals throughout the length of the tunnel. In addition, each low air supply pipe must be grounded at its delivery end.
  4. The explosive suitable for use in wet holes must be water resistant and must be Fume Class 1.
  5. When tunnel excavation in rock face is approaching mixed face, and when tunnel excavation is in mixed face, blasting must be performed with less explosive per drilled hole and with less dimension in hole spacing and to the free face. Advance drilling must be performed as tunnel excavation in rock face approaches mixed face to determine the nature and extent of rock cover and the remaining distance ahead to soft ground.

Knowledge Check Choose the best answer for the question.

26-14. Who is NOT permitted to enter an air lock when detonators or explosives are brought into an air lock?

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