Snyder & Associates Engineering contacted the Miller the Driller regarding jacking in a square concrete tunnel for a bike trail. Miller had previous experience with both square and round tunnels including completing a 122” OD steel tunnel in East Peoria Illinois under railroad tracks for a bike trail.

After looking at the sight, only four miles from the Miller shop, it was determined that a square tunnel would not be a good solution. The Union Pacific Railroad tracks were built on a levee. Levees are usually built on or with fill materials, which can hinder a normal trenchless operation. Because the north side of the levee (exit side) was very steep, there was nothing there for a backstop to support any jacking or resist jacking loads that would be applied.

When jacking square boxes under railroad tracks there is usually a large surface area of the box to contend with. The tracks tend to move or shift with the bore as it advances. Pipe ramming as well as the arch of the casing has a much different forward motion, which allows the casing to be advanced without movement of the tracks. Also needed was the ability to handle the old railroad ties and tree stumps that were under the tracks.

Permalok steel casing was selected and installed. The 147" OD steel casing with a 1.5" wall thickness was fabricated in 20' lengths. In a typical weld in place operation, one 147” joint would normally take a week to weld and x-ray. The time to make up a Permalok joint was less than one hour for each joint. The snap together joint makes up water tight, without an external or internal bell.

The project took 14 days from pit excavation to finish. Installation of the Permalok pipe took only four of those days.

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