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.
Lightweight fill placement had to be unaffected by frequent rail traffic, have a limited footprint, and be economical.
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.
A stone arch bridge constructed in the 1800s was experiencing significant scour at the bases of the arch. This caused differential settlement of the structure, and deterioration of the wing walls.
The bridge, which was adjacent to a historic mill structure, could not be removed and replaced with a modern structure, it had to be rehabilitated in a fashion which preserved its historic nature.
The bridge was constructed on shallow stone foundations.
As part of rehabilitating the structure, structural engineers designed two new mass footings in the stream bed to underpin the edges of the stone arch. Then, to strengthen the arch designed a 12″ thick reinforced concrete arch overlay on top of the stone arch for the full length/width of the bridge.
In order to compensate for this additional weight, designers determined that a lightweight fill material was needed to reduce the chances of inducing settlement.
Designers also evaluated remedial deep foundations but determined that lightweight fill was the fastest and most economical solution.
After the structure had been rehabilitated, CJGeo installed 325CY of 30lb/cuft cellular concrete to backfill the structure. Placed in lifts up to 4 feet thick, the work was completed over a period of three days.
By using 30lb/cuft non-permeable cellular concrete, the dead load on the underlying soil decreased by up to 935lbs/sqft relative to compacted soil backfill.
Because cellular concrete is self-consolidating and can easily be pumped hundreds of feet, single side access was not a problem, and no compaction equipment was necessary.
A crew of two workers completed the pour using continuous wet batch generation. Wet batch generation was chosen due to the relatively small daily volume of material placement.
With an annual throughput capacity of 48 million tons, Norfolk Southern’s Pier 6 at Lamberts Point in Norfolk, Virginia is one of the largest coal trans-loading facilities in the world. As an around-the-clock facility built around precision logistics, there’s little tolerance for disruption or downtime.
When two sinkholes opened up at the end of Pier 6 adjacent to the bulkhead, railroad personnel reached out to an onsite maintenance contractor. Steel plates were installed to provide temporary protection while a long-term solution could be implemented.
CJGeo performed DCP testing at the site in order to quantify the depth of voids below the pavement adjacent to the sinkholes. The DCP testing showed that in addition to large voids visible from the sinkholes immediately below the pavement, there were large pockets of voids down to 15’ below the surface.
CJGeo crews then used CJGrout 35NHV61, a hydro insensitive, NSF-certified geotechnical polyurethane to fill all voids and restore stability to the area. The grouting work took five hours onsite to install 3400 pounds of material, with zero disruption to operations.
As part of a 24 lane mile mill & pave rehabilitation on the Pennsylvania Turnpike, slab stabilization was required. The Turnpike’s specification for stabilization is either liquid asphalt or polyurethane.
In order to keep MOT in place continuously, work had to be done 24 hours per day. Due to work on three bridges within the repair area, undersealing also had to be phased.
CJGeo proposed undersealing with CJGrout 40NHL, a 4.0 lb/cuft free rise polyurethane grout formulated specifically for undersealing thick pavements in transportation environments. 40NHL is hydro insensitive, so performs well in wet environments, as confirmed with NYSDOT GTP-9 testing.
Using a double gang drill and single grout truck, CJGeo crews undersealed up to 1.8 lane miles per shift. Drilling was completed at night, and grouting during the day, to allow the general contractor to keep MOT in place continuously.
The George Washington Memorial Parkway connects Washington, DC with Fairfax and Alexandria Counties in Virginia. Originally designed as a scenic route, the road has transformed into a heavily used commuter route in and out of Washington. The road runs along the Potomac River, with bridges crossing deep ravines, including Windy Run.
Our biggest challenge with this project was making sure this heavily populated commuter route was completed in a timely fashion.
CJGeo proposed polyurethane compaction grouting using CJGrout 30NHL, which is specifically formulated for improving the bearing capacity of loose soils. Grouting was performed on 4’ centers, at 5’, 10’ & 15’ below grade, until surface movement was detected. Top-Down grouting was used to help ensure maximum densification of underlying soils, and approximately 25,000 pounds of grout were used over two mobilizations. Due to polyurethane grout’s nearly immediate cure, CJGeo helped ensure that ground improvement stayed out of the critical path of this accelerated project. Pre and Post Grouting DCP Testing was performed by Schnabel Engineering to quantify the soil density improvement.