The concrete slab on grade floor inside of a fire station on the North Neck of Virginia settled up to two inches. As part of the investigation into the cause, an engineer discovered voids up to 8″ below the slab, and multiple broken sanitary sewer pipes below the floor.
The affected areas included a dayroom, kitchen & meeting hall.
In order to minimize disruption to the fire station’s operations, the proposed repair had to be quick, clean, and minimize uncertainty associated with the plumbing repair slab cuts.
CJGeo performed ground improvement grouting of the underlying soils to 5′ below grade utilizing plural component polyurethane compaction grouting. Shallow voids were filled using plural component polyurethane, which was also used for settlement correction.
Because polyurethane grouts cure very quickly, the floor was repaired the day before the plumbing work was scheduled. This allowed the plumbers a stable work surface, and eliminated the risk of stuck saws or sudden collapse of the floor during floor sawing for plumbing access.
Pre & post grouting DCP testing was done to verify grout travel.
Starting immediately after construction was completed, the slab on grade floor within the cafeteria, loading dock and kitchen at a corporate headquarters building in Pittsburgh, Pennsylvania settled. Over the course of 12 years, the owner had four different grouting companies attempt to address the problem. Lime slurry injection below the slab was disruptive, and settlement always resumed shortly thereafter.
Compaction grouting was performed in one area, but was so disruptive that despite the fact that it was the only method where settlement didn’t resume, the owner kicked the contractor off the site after nearly four months of not having access to their executive dining room.
Settlement progressed over time to be as much as four inches, affecting nearly 20,000 square feet of floor. A general contractor retained by the owner reached out to CJGeo about performing low impact grouting to address the settlement.
Because settlement affected the entire kitchen, food prep, serving and majority of the dining areas, repairs had to be facilitate continuous use of the facility. Additionally, due to 24 hour staffing of the facility, noise had to be limited, and there was zero tolerance of dust.
Video inspection of the extensive gravity sanitary and floor drains below the floor revealed six defects, including a 2″ offset in a sanitary drain line for a 6 stall restroom.
CJGeo performed 17 DCP tests to determine the depth of uncontrolled fill, which was the presumed cause of settlement. DCP testing showed pockets of WOH fill down to 35′ below finish floor, and voids ranging from 2″ to 18″ immediately below the floor.
Over the course of 7 nights onsite, CJGeo crews installed 12,000 pounds of CJGrout 20SDB into voids immediately below the floor, and 53,000 pounds of CJGrout 35NHV61 for polyurethane compaction grouting. Compaction grouting was performed up to 35′ deep, but to an average depth of 15′ over the entire area.
All work was completed off hours. As soon as the kitchen shut down for the evening, CJGeo crews swung into action, grouting through the night until wrapping up in time for the food prep crews to get ready for breakfast at 0500.
To facilitate grouting under four walk-in freezers and refrigerators, over the course of a 24 hour shift, all cold contents were moved to reefer trailers, CJGeo grouted to 30′ under the freezers and refrigerators, which were then immediately turned back on, and then refilled.
Through careful coordination with multiple operational divisions for the owner, general contractor, flooring restoration contractors, plumbers, and remediation contractors, CJGeo successfully completed the project under budget and on time.
When the operators of a tire and auto shop noticed a sinkhole developing next to their building, they weren’t sure what to do. After an employee crawled into the hole and discovered that he could stand up underneath their building, the owner reached out to the city. City crews determined that a 20″ VCP combined sewer & storm pipe had collapsed under the structure, roughly 25′ below grade.
An on call contractor for the city installed a new manhole and rerouted the pipe around the building, but addressing the sinkhole was out of their businesses’s scope. The project manager reached out to CJGeo, who visited the site and recommended DCP testing to better quantify the extent of the problem.
DCP testing showed that outside of the large hole on the surface, there was little deep disturbance. Working with the city’s consulting engineer, CJGeo developed a grouting plan to install two different CJGrouts; 20SDB in the bulk voids near the surface, and 35NHV61 for soil grouting to address voids within the underlying ground near the failed sewer line.
While onsite for just 6 hours, a CJGeo crew completed the work with zero disruption to the businesses’s operations.
As part of renovation of a storage/logistics building at the Norfolk Naval Shipyard, underpinning was required due to settlement of a column footing pile cap. In addition to settlement of the pile-supported pile cap under an exterior wall, two adjacent pile caps had settled on the outside of the loading dock.
Due to a limited overhead environment on the interior, but high torque requirement, piles had to be installed with a large machine from the exterior only. The bottom of footing elevation was nearly 6 feet below finish floor elevation, so extensive excavation was required on the interior, as well, further complicating the installation.
CJGeo provided a turnkey design-build package for the piles. Due to the low count, 3.0FOS was used to avoid the load testing requirement associated with 2.0FOS.
CJGeo installed four underpinning piles and four new construction piles over two days. The 3.5″, grout-filled 10-12-14-14-14 helical piles were installed to an average depth of 57 feet, at 12,000ft-lbs. A small excavator was used inside for access excavation, while the install machine reached through the demolished wall.