Question

The type of explosive used for solid blasting is

• A. P1
• B. P3
• C. P4
• D. P5

Hint:

The "P" number in permitted explosives indicates the level of safety, with a higher number generally signifying a safer explosive for gassier conditions.
P5 is the "top tier" of safety, required for the most dangerous blasting scenario, which is solid blasting.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
We need to identify the specific class of permitted explosives that is suitable for "solid blasting" in underground coal mines.

Step 2: Detailed Explanation:
In underground coal mining, special "permitted" explosives are used to minimize the risk of igniting flammable methane gas or coal dust.
These explosives are classified into different categories (P1, P2, P3, P4, P5) based on their safety characteristics and intended use.

Solid Blasting is a technique where blasting is carried out in a coal face "off the solid," meaning without a pre-existing free face created by cutting or shearing.
This is a particularly hazardous operation because the explosive energy is highly confined, increasing the risk of a gas or dust ignition.
Therefore, it requires the safest category of explosives.
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P1 Explosives: General-purpose explosives for use in coal where there is minimal gas.
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P3 Explosives: For use in stone drifts or seams with higher gas content.
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P4 Explosives: This category is obsolete.
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P5 Explosives: These are "sheathed" or equivalent-to-sheathed (EQS) explosives designed with the highest degree of safety.
They produce a low-temperature, short-duration flame and are specifically approved for the most hazardous applications, including solid blasting and blasting in fractured ground.

Step 3: Final Answer:
The type of explosive used for solid blasting is the P5 category.
This corresponds to option (D).