When using slurry or emulsion in a wet hole, what should be used for stemming?

• A. Drill cuttings
• B. Crushed rock
• C. Wet sand
• D. Loose gravel

Answer: (B)

Using crushed rock for stemming in a wet hole when using slurry or emulsion is the most effective choice because crushed rock provides a solid and effective barrier to contain the explosive charge. Its angular shape ensures good packing and minimizes the risk of blow-by of the explosive gases during initiation. The density and weight of crushed rock help to properly confine the explosive energy, enhancing fragmentation and minimizing environmental impacts.

While other materials like drill cuttings or loose gravel may also be considered, they do not offer the same level of containment and stability. Drill cuttings can be variable in size and may not pack well, leading to air pockets that could allow gases to escape. Loose gravel, on the other hand, due to its rounded shape, lacks the friction necessary for adequate compaction, which can further compromise the effectiveness of containment. Wet sand, while providing some cohesion when wet, may not provide the necessary structural integrity needed for stemming. Crushed rock stands out for its optimal performance and safety in this application.