Question

Which one of the following is NOT a Controlled blasting technique used in Opencast mines ?

• A. Pre splitting
• B. Deck charging
• C. Cushion blasting
• D. Cast blasting

Hint:

Think of the goal:
- Controlled Blasting = Precision and care, like a surgeon's scalpel (e.g., Pre-splitting).
- Cast Blasting = Brute force and movement, like a catapult.

Answer 1

The Correct Option is D

Step 1: Recall what makes a blasting technique "controlled".
Controlled blasting techniques are all about protecting the final rock wall that will remain standing in the pit, by carefully limiting how much shock and cracking reaches beyond the intended excavation line.
Step 2: Check pre splitting and cushion blasting against this idea.
Pre splitting fires a line of closely spaced holes ahead of the main blast to create a clean fracture plane that shields the final wall, and cushion blasting fires a lightly charged trim row after the main blast to smooth the wall, both directly aim to protect the remaining rock.
Step 3: Check deck charging.
Deck charging places separated explosive charges within one hole with stemming in between, this is a technique for distributing energy more precisely, and it is commonly used as part of controlled blast designs too.
Step 4: Now test cast blasting against the same idea.
Cast blasting does the opposite of protecting a wall, its whole purpose is to use a large explosive charge to throw as much broken overburden as possible into the adjacent mined out pit for bulk material movement, so it belongs to production blasting, not controlled blasting.
\[ \boxed{\text{Cast blasting}} \]