TRBâ€™s National Cooperative Highway Research Program (NCHRP) Report 717: Scour at Bridge Foundations on Rock presents a methodology for estimating the time rate of scour and the design scour depth for a bridge founded on […]
TRB’s National Cooperative Highway Research Program (NCHRP) Web-Only Document 177: Evaluation of Bridge Scour Research: Geomorphic Processes and Predictions explores the impact of long-term aggradation and degradation, and lateral river channel migration, on highway structures. […]
Severe erosion was discovered on an October 2008 inspection of Allegheny River Lock and Dam No. 6 near Pittsburgh, PA, a US Army Corps of Engineers structure. In the Q1 2009 issue of PileDriver Magazine […]
The Progressive Engineer website has an interesting article profiling Colwyn Sayers, a geotechnical engineer with the Lexington, Kentucky office of Stantec. His specialty is inspecting underwater bridge foundations which requires either wetsuit or drysuit diving using topside air sources. Occasionally a hyperbaric chamber is required as well. (Photo credit: Progressive Engineer)
On a typical dive, Sayers looks for signs of deterioration that may cause instability or even collapse of the bridge. This includes scour, undermining from flowing water that erodes the streambed, deterioration, cracks, section loss, and impact and abrasion damage from trees. Tree debris caught in the bridge leads to scour and erosion. “It depends on the construction type as well as the materials on the bridge,” he states.
[Update 2/10/08] Updated the name of the bridge. [/Update]
DelDOT is putting the new Indian River Bridge over out to bid. The current bridge is said to be in danger of failing between 2008 and 2012 according to the Army Corps of Engineers, seems to be related to scour. From what I hear, the tidal currents at that inlet being spanned over are tremendous, with water velocities on the order of 35 mph.
In 2005, Mactec, a geotechnical firm, provided a geotechnical report and associated recommendations to DelDOT for how to construct the 45-ft high approach embankments for a 1,400-ft long bridge in light of a 60-ft clay layer (sounds like pre-loading). However, the embankments are not settling as Mactec predicted (not sure if its more or less, probably less meaning slower) and are "shifting laterally" (squeezing?) so the DOT is going with a longer bridge to span the problem soil. More after the break.