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GPR Study of Voids behind a Highway Bridge Retaining Wall
Ned Billington, PG
ESP AssociatesApril 9, 2015
April 2011
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November 2011
AOI
November 2013
AOI
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November 2015
AOI
Site Visit
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Site Visit
Construction Drawings
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Construction Drawings
Construction Photos
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Construction Photos
Construction Photos
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Locations of Slumping
GPR Data Collection on Wall
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GPR Depth Slices, 0.1’ Depth
GPR Depth Slice, 1.0’ Depth
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GPR Polarity Changes
GPR Depth Slices, 1.5’ and 4.2’ Depth
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GPR Data, EB Inside Shoulder
Conclusions
• Voids behind retaining wall formed by water flow into and around areas of slumping/flowable fill during construction before closure pour made.
• Vertical settlement of approach slab caused by loose material left in place during construction.
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ESP Mobile Mapper Data
• Two 3D lasers
• 4 to 6 cameras
• A military grade IMU
• Two GPS receivers
• Collect continuous point data clouds at highway speeds
Example Mobile LiDAR StudyI‐85, Salisbury
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Mobile LiDAR Data
TOPO SLOPE
Older LanesNewer Lanes
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Repairs ‐ 2016
• Filled voids with 20 CY of foamed concrete
• Milled down roadway to remove bumps and added asphalt overlay
• Monitoring indicates no additional movement
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Thank you