Drilling and Blasting - Procedure

Procedure

As the name suggests, drilling and blasting works as follows:

• A number of holes are drilled into the rock, which are then filled with explosives.
• Detonating the explosive causes the rock to collapse.
• Rubble is removed and the new tunnel surface is reinforced.
• Repeating these steps will eventually create a tunnel.

The positions and depths of the holes (and the amount of explosive each hole receives) are determined by a carefully constructed pattern, which, together with the correct timing of the individual explosions, will guarantee that the tunnel will have an approximately circular cross-section.