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Twin Jacked Box Tunnels

Liberty University, Lynchburg, VA

Project At-a-Glance


  • Design/Build Project Delivery
  • Innovative installation of pulling not pushing to keep rail embankment in compression
  • Twin box tunnels constructed on site and installed under active rail lines
  • Four travel lanes are conveyed through the completed tunnels

Recognition


  • ENR Mid-Atlantic Region “Best Small Project Award” 2014
  • ENR Mid-Atlantic Region “Best Project Safety Award” 2014
  • ACEC Virginia “Grand Award” 2014
  • See a time-lapse video of the construction of the tunnel on our YouTube channel.

Liberty University had to overcome an access obstacle posed by absence of ingress to the westside of the campus from the intersection of Ward Road and Harvard Street. The solution was to create a new roadway under the Norfolk-Southern rail lines.

Brierley Associates was selected for this Design/Build project which consists of two 2,100 ton by 20.5‑ft high by 32-ft wide and 130-ft long cast on-site reinforced concrete box tunnels installed by box-tunnel jacking methods. The completed twin tunnel system conveys four lanes of vehicular traffic.

Although conventional construction of these types of tunnels is by jacking, a novel approach was selected to pull the boxes through the existing railroad embankment via post-tensioning tendons installed through the embankment and walls of the tunnels.  The six 765-ton capacity jacks were mounted on 4‑ft thick reinforced concrete blocks, cast against a 23-ft high soldier pile reaction wall located at the receiving side of the embankment. The second box was pulled through after placing the jacks on the back end of the tunnel with the post-tensioning strands attached to the soldier pile reaction wall on the receiving side of the embankment.