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Modeling and Monitoring Scour during Bridge Replacement with Multi-Dimensional Modeling and Repeated Multi-Beam Surveys at the Tanana River near Tok, Alaska
The Alaska Highway near Tok, Alaska crosses the Tanana River via a 288 m truss bridge constructed in 1944. Due to age, damage from a 2002 earthquake, and extensive pier scour, the bridge is being replaced in 2009–2010. Since it was originally constructed, the angle of approaching flow to the bridge has changed and currently approaches the right-bank pier at 45 degrees creating a large scour hole around the pier. The new bridge is being constructed 75 meters downstream of the existing bridge and a temporary construction causeway was built in 2009 upstream of the new bridge alignment. The effect of the causeway on the channel hydraulics at the existing bridge are of concern to ADOT&PF. Several potential causeway geometries and their corresponding affect on the angle of flow approaching the existing bridge pier were simulated with a multi-dimensional model. Modeled flow angles, depths, and velocities immediately upstream of the pier did not vary significantly between the modeled scenarios, but a monitoring schedule was put in place to insure the safety of the structure until the new bridge is completed. Four multi-beam surveys completed during the summer of 2009 documented the dynamic nature of the streambed. The largest scour depths were consistently at the nose and along the right-bank side of the caisson where the flow was attacking the pier. Model results and repeated high accuracy surveys allow the state to continue operation of the bridge and avoid installing scour countermeasures until construction of the new bridge is completed.
Modeling and Monitoring Scour during Bridge Replacement with Multi-Dimensional Modeling and Repeated Multi-Beam Surveys at the Tanana River near Tok, Alaska
The Alaska Highway near Tok, Alaska crosses the Tanana River via a 288 m truss bridge constructed in 1944. Due to age, damage from a 2002 earthquake, and extensive pier scour, the bridge is being replaced in 2009–2010. Since it was originally constructed, the angle of approaching flow to the bridge has changed and currently approaches the right-bank pier at 45 degrees creating a large scour hole around the pier. The new bridge is being constructed 75 meters downstream of the existing bridge and a temporary construction causeway was built in 2009 upstream of the new bridge alignment. The effect of the causeway on the channel hydraulics at the existing bridge are of concern to ADOT&PF. Several potential causeway geometries and their corresponding affect on the angle of flow approaching the existing bridge pier were simulated with a multi-dimensional model. Modeled flow angles, depths, and velocities immediately upstream of the pier did not vary significantly between the modeled scenarios, but a monitoring schedule was put in place to insure the safety of the structure until the new bridge is completed. Four multi-beam surveys completed during the summer of 2009 documented the dynamic nature of the streambed. The largest scour depths were consistently at the nose and along the right-bank side of the caisson where the flow was attacking the pier. Model results and repeated high accuracy surveys allow the state to continue operation of the bridge and avoid installing scour countermeasures until construction of the new bridge is completed.
Modeling and Monitoring Scour during Bridge Replacement with Multi-Dimensional Modeling and Repeated Multi-Beam Surveys at the Tanana River near Tok, Alaska
Conaway, J. S. (author)
International Conference on Scour and Erosion (ICSE-5) 2010 ; 2010 ; San Francisco, California, United States
Scour and Erosion ; 978-986
2010-10-29
Conference paper
Electronic Resource
English
Numerical models , Surveys , Case studies , Slope stability , Bridges , Infrastructure , Beams , Alaska , Coastal environment , Replacement , Scour , Soil erosion , Monitoring
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