The boreholes drilled across the course of the drive must not exceed what width?

The boreholes drilled across the course of the drive must not exceed what width?

• A. 1.5 meters
• B. 2.0 meters
• C. 2.5 meters
• D. 3.0 meters

Answer: (C)

Controlling borehole width across the drive helps balance effective rock breakage with the ability to install supports and maintain safe ground conditions as you advance. Limiting the width to 2.5 meters keeps fragmentation within a manageable range, reduces the risk of excessive overbreak, and ensures supports and ventilation can be applied effectively. Exceeding this width would make the rock more difficult to support and safer blasting harder to manage, increasing the danger of roof failure. So the maximum allowed width is 2.5 meters.

Controlling borehole width across the drive helps balance effective rock breakage with the ability to install supports and maintain safe ground conditions as you advance. Limiting the width to 2.5 meters keeps fragmentation within a manageable range, reduces the risk of excessive overbreak, and ensures supports and ventilation can be applied effectively. Exceeding this width would make the rock more difficult to support and safer blasting harder to manage, increasing the danger of roof failure. So the maximum allowed width is 2.5 meters.