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: Understanding the Question:
We need to distinguish between "controlled blasting" techniques and other types of blasting, and identify the option that doesn't fit the "controlled" category.

Step 2: Detailed Explanation:

Controlled Blasting refers to a set of specialized techniques used to achieve a specific outcome, usually to minimize damage to the rock that is intended to remain in place (the final wall).
These techniques aim to produce a smooth, stable, and crack-free final pit slope.
-

Pre-splitting: This involves drilling a line of closely spaced holes along the final wall line and firing them before the main production blast.
This creates a fracture plane that isolates the final wall from the shock of the main blast.
It is a key controlled blasting technique.
-

Cushion Blasting (or Trim Blasting): This involves firing a final row of lightly charged holes along the pit limit after the main blast has been completed.
It "trims" the wall to its final position with minimal damage.
It is also a key controlled blasting technique.
-

Deck Charging: This is the technique of placing multiple, separated explosive charges (decks) within a single blast hole, separated by inert stemming material.
It is used to distribute explosive energy more effectively and can be used as part of a controlled blast design to reduce damage.
-

Cast Blasting: This is a

bulk production blasting technique, not a controlled one.
Its objective is the opposite of preserving a final wall.
Cast blasting uses a large amount of explosive energy to physically throw a significant percentage of the broken overburden directly from the bench into the adjacent mined-out pit.
It is designed for maximum displacement of rock, not minimum damage.

Step 3: Final Answer:
Cast blasting is a bulk blasting method, not a controlled blasting technique.
This corresponds to option (D).