Question

Sub-level stoping method belongs to

• A. Heavily supported class
• B. Artificially supported class
• C. Caving type
• D. Open stoping type

Hint:

The key to open stoping methods is "strong rock."
If the description of a method involves creating large empty rooms without backfilling and without intentional collapse, it's an open stoping method.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
We need to classify the sub-level stoping method into one of the major categories of underground mining methods.

Step 2: Detailed Explanation:
Underground mining methods are broadly classified based on how the void created by ore extraction is supported:
1.

Artificially Supported Methods: The walls of the stope are supported using materials brought into the mine, such as waste rock, sand, or cement (e.g., Cut-and-Fill stoping).
2.

Supported by Ore (Pillars): The roof is supported by pillars of the ore itself, which are left unmined (e.g., Room and Pillar, Shrinkage Stoping).
3.

Caving Methods: The ore and/or the surrounding wall rock is intentionally collapsed in a controlled manner (e.g., Block Caving, Sub-level Caving).
4.

Open Stoping Methods: These methods are used in orebodies where both the ore and the surrounding wall rocks are strong and competent.
Large underground openings (stopes) are created and left empty (open) after the ore is removed, relying on the natural strength of the rock mass for stability.

Sub-level stoping is a classic example of an open stoping method.
It involves creating very large, open stopes, and it can only be applied in orebodies with strong ore and strong host rock that will not collapse once the ore is removed.

Step 3: Final Answer:
Sub-level stoping belongs to the open stoping type.
This corresponds to option (D).