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Geotechnical Services for the Youghiogheny River Bridge

Redesigned bridge features spans exceeding 230 feet and some of the largest drilled shafts ever constructed in Pennsylvania.
  • Reinforced concrete pier bents on 9-foot-diameter drilled shafts embedded into bedrock support this structure-Gannett Fleming

    Reinforced concrete pier bents on 9-foot-diameter drilled shafts embedded into bedrock support this structure.

Client

Pennsylvania Department of Transportation, District 12-0


Location
Fayette and Somerset Counties, Pennsylvania

Our Role
Subsurface Investigation, Geotechnical Design, Construction Services, Drilling.

Data
Completed
2006
Outcomes
  • Original 12-span, prestressed-concrete bridge was redesigned to an 8-span steel structure
  • Longer spans reduced number of deep-water pier foundations, resulting in an 11-percent cost savings
  • The selected foundation elements were 9-foot-diameter, 130-foot-long drilled shafts. 

Gannett Fleming competitively bid for the project against an “as-designed,” prestressed 12-span concrete bridge. The firm’s alternate design of an eight-span steel structure, with steel girders allowing for lengthened spans, translated into significant savings for the $25 million bridge project. 

The longer spans allowed a reduced number of deep-water pier foundations, which translated into an 11 percent savings in overall project cost. The selected foundation elements were 9-foot-diameter, 130-foot-long drilled shafts.

What We Did

Our firm’s geotechnical work for the design of the drilled shafts involved a thorough subsurface investigation. Through our affiliated company, L.G. Hetager Drilling, Inc., test borings were drilled at each proposed shaft location.

Our firm installed a technique shaft prior to constructing the production shafts. We used a miniature shaft inspection device (Mini-SID) to visually inspect the shaft excavation. After the technique shaft was constructed, the team performed crosshole sonic logging to check the integrity of the shaft. Additional testing at the technique shaft included instrument installation and testing to failure with three 34-inch-diameter Osterberg Load Cells (O-Cells) to verify axial, side-shear, and end-bearing resistances.

Key Features

  • Value engineering
  • Three-dimensional finite element analysis
  • 9-foot-diameter drilled shafts, with 8-foot, 6-inch-diameter rock sockets
  • 10,000-ton O-Cell load test performed on full-scale technique shaft
  • Borings drilled from barge through 70 feet of water
  • Crosshole sonic logging of all production shafts.

Awards & Recognition

  • Susquehanna Chapter Award in the Outstanding New Multi-Span Bridge Category, 2006, Association for Bridge Construction and Design (ABCD), ABCD Susquehanna Chapter 2005/2006 Competition
  • No. 5 Bridge Project, 2005, Roads & Bridges, Top 10 Bridges.

Similar Projects: Transportation: Bridges, Geotechnical, Transportation: Operations, ITS & Traffic