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Drill & Blast Tunnels PDF Print E-mail
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Drill & Shoot
Drill and Blast tunnels vary in size from 5 to 60 feet in diameter. They are used for underground utilities, highways, railroads, water diversions, mass transit systems, and underground mineral development. Prior to the introduction of Tunnel Boring Machines, all hard rock tunnels were excavated by the Drill and Blast method.

Technique
Drill and Blast Tunneling consists of drilling a controlled number of holes into the tunnel face to a designated depth and then loading the drilled holes with an appropriate blasting agent. The loaded holes are detonated and the broken rock (muck) is removed from the tunnel. The most import aspect of the D&B method is allowing the energy created by the explosive to be directed in the correct alignment. The geological conditions of the rock, the angle of the drill holes, the size and spacing of the drill holes, and the energy factor, which is calculated in kcal/cy, accomplish this.


Equipment
Drilling equipment varies from handheld jackhammers and jack legs to large mobile jumbos and gantries, depending on the size of the heading. Hand held drills are pneumatically powered by compressed air and the large drill jumbos are hydraulically powered. The tunnel muck is removed from the tunnel by rubber tire loaders. Temporary ground support of the excavated tunnel is normally rock bolts and shotcrete.

Experience
Traylor Bros. has excavated numerous D&B tunnels. Two large cross sectional highway tunnels in Colorado and Oahu, Hawaii were completed by Traylor Bros. utilizing state-of-the-art high speed drills and mucking equipment.
 
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