The GATE Grind

GATE 2021 MN – Question 17

Surface Environment, Mine Ventilation and Underground Hazards · Underground Hazards · 1 mark · Multiple choice

Why is NONEL used as a down-the-hole initiator in the context of this question?

  1. Avoid generation of air overpressure
  2. Provide precise delay
  3. Avoid deflagration of column charge
  4. Reduce ground vibration

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Correct answer: (C) Avoid deflagration of column charge

Explanation

The intended down-hole advantage is avoiding adverse initiation/deflagration of the explosive column, C. NONEL transmits an initiating signal through shock tube. Air overpressure and ground vibration depend on the full blast design, and conventional pyrotechnic NONEL delays are not inherently exact electronic delays.

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