Fractured and broken roof or back of mine workings shall be provided with laggings of at least how thick, and these shall be tightly blocked?

• A. 3 centimeters
• B. 5 centimeters
• C. 7 centimeters
• D. 10 centimeters

Answer: (B)

When roof or back rock is fractured or broken, a protective layer is needed to keep loose pieces from falling and to provide a solid surface for further support work. The required lagging thickness is five centimeters, which is just enough to cover the uneven surface and distribute the load so the rock mass isn’t concentrated on thin boards. The boards must be tightly blocked, meaning they’re pressed closely together and secured so there are no gaps. This tight blocking prevents movement and gaps through which rock could break free, giving workers a safer working face as stabilization continues.