Question

The best combination of explosive and initiation system for underwater blasting for rock breakage is

• A. ANFO and electric detonator
• B. emulsion and non-electric detonator
• C. HANFO and safety fuse
• D. PETN and electronic detonator

Hint:

Think about which explosive resists water without dissolving, and which type of detonator avoids relying on an electric current in wet ground.

Answer 1

The Correct Option is B

Step 1: Understanding the Question.
Underwater blasting means the blastholes are wet or fully submerged, so both the explosive and the way it is fired must survive water without failing or becoming a safety hazard. The question asks which explosive and initiation system pairing works best under these wet conditions.

Step 2: Key Formula or Approach.
Two properties decide the answer here. First, water resistance of the explosive: an explosive used underwater must not dissolve, desensitize or wash out while it sits in water during charging and firing. Second, safety of the initiation system: any electrical circuit lying in wet ground or water is at risk from stray currents, static charge and leakage, so a non-electric firing method is safer underwater.

Step 3: Detailed Explanation.
Option (A) ANFO and electric detonator fails on both counts. ANFO is a mixture of ammonium nitrate prills and fuel oil, and ammonium nitrate dissolves readily in water, so ANFO loses its explosive strength almost at once when wet. An electric detonator also adds stray current risk in a wet hole.
Option (B) emulsion and non-electric detonator fits both requirements. An emulsion explosive is a water in oil system, tiny droplets of ammonium nitrate solution held inside a continuous oil and wax phase, so water cannot get in to dissolve it and it keeps its strength even fully submerged. A non-electric (shock tube) detonator carries its signal as a shock wave inside a plastic tube, not as an electric current, so it is not affected by water conductivity or stray currents.
Option (C) HANFO and safety fuse is weaker. HANFO (heavy ANFO) blends some emulsion into ANFO and so resists water better than plain ANFO, but it is still not as water resistant as pure emulsion, and a plain safety fuse burns on the outside, so water can put it out or delay it unpredictably.
Option (D) PETN and electronic detonator is not the standard choice either. PETN is mainly used inside detonating cord and boosters rather than as the main column charge, and electronic detonators are costly, sensitive units, not the routine choice for rough underwater rounds.

Step 4: Final Answer.
The pairing that survives water and avoids electrical hazards is emulsion explosive fired with a non-electric detonator.
This corresponds to option (B).