Bridge abutments are commonly founded on a deep foundation and are much more rigid than the adjacent embankment fill. In some cases the abutment’s construction/soil compaction is deficient, the subgrade below the abutment does not have the adequate bearing capacity to handle the fill loading, and/or the abutment fill experiences significant post-construction settlement. This settlement is most common and severe at the embankment/abutment interface and often requires on-going maintenance with associated costs such as milling and/or new asphalt placement by maintenance crews.
Compaction grouting can be used to remediate and densify the settling embankment soils to reduce future settlements and/or increase the load carrying capacity of the soils under the embankment. The grouting operation can be conducted from one or two closed lanes while one-way or alternating traffic is maintained in adjacent lanes, thus limiting impact to the traveling public. A recently completed project for a western state’s Department of Transportation required the compaction of a soft fill zone from 10 to 25 feet below roadway grade on either side of the bridge abutment. The project required one lane to be opened to alternating traffic at all times during the work.
Pre- and post-SPT borings were done and compared in order to verify the success of the grouting program. The work resulted in significant blow-count improvement of 50% or more in the treated zone.
During the revolutionary war, General Washington burned the wooden bridge over a small brook in the Northeastern United States to delay the advance of Cornwallis’ army.