Quote:
Originally Posted by dirtbanker
Les - What I saw was a 8' diameter tunnel being installed and there was not much ground above it. They had an 8' diameter arbor bit, they bored into the side of the hill while shoving a 8' diameter x 3' long section behind it. The drive shaft for the 8' diameter arbor was then disconnected, the next 3' long section of tunnel was rolled behind the already inserted piece along with a drive shaft extension, and they start boring again while shoving the now 2 sections in (the sections mated with a tongue and groove joint). They did this several times to get across 4 lanes of traffic, adding sections and lengths to the drive shaft on the boring arbor. Really neat to see.
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Wow, I never saw that. It seems to me though that the precast tunnel sections are more than 3', more like 10' feet. Also the pics I saw showed the tunnel being put in place with out a road over it. Why put in a road and then a tunnel under it when you can lay down a tunnel and cover it up with dirt?