The Job
The geotechnical investigation for a double bridge replacement in Amelia County, Virginia found a layer of compressible soils below four proposed abutments.
Anticipated settlement exceeded allowable settlement, so the abutments were designed to be backfilled with expanded shale lightweight aggregate.
The two parallel bridges have an AAWDT of 14,000 and carry a rural divided highway (US-360) over Norfolk Southern Railway & Business 360 in Amelia Courthouse, Virginia.
The Challenge
Lightweight fill placement had to be unaffected by frequent rail traffic, have a limited footprint, and be economical.
The Solution
CJGeo provided a value engineering proposal to utilize 30lb/cuft cellular concrete in place of the expanded shale lightweight aggregate. This significantly reduced the unit weight of the lightweight fill, given the 70lb/cuft density used in the design, further reducing the anticipated settlement.
CJGeo mobilized a 200CY/hour cellular grout plant to the site and placed lifts ranging in size from 35 to 300CY. Wall erection crews were able to walk on the in-place cellular concrete without leaving footprints as quickly as 4 hours after each placement.
The total project volume was approximately 7200CY.
