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.
The Princeton Middle School in Princeton, West Virginia is a slab on grade masonry structure, and serves approximately 550 students in grades 6 through 8.
The corridor floor in the arts wing settled up to 3.5 inches. A geotechnical investigation was performed, and identified voids up to 2.5 inches below the settled slab. Due to budgetary constraints, the repair needed to address the settlement & instability without requiring flooring replacement.
CJGeo mobilized a two person polyurethane grouting crew to the site. Over a few hours they filled all the voids utilizing CJGrout geotechnical polyurethanes, and corrected the settlement. After the floor was lifted back into position and the voids all filled, the custodian reinstalled the cove base at the correct height. CJGeo patched the injection holes with off-white stained grout to match the VCT flooring.
A plumbing contractor hand tunneled 140LF of 4’x5′ tunnel under two apartment buildings near Boston, Massachusetts. In preparation for a renovation project, a structural inspection was performed. The structural inspection revealed the slab floors which were tunneled under were not designed as structural slabs. The structural engineer directed the property owner to immediately fill the tunnels to restore structural integrity.
The tunnel abandonment work had to be completed during the winter, and while one of the two affected buildings was occupied. The non-occupied building was also in the process of asbestos abatement and a full gut renovation.
Due to the plumbing run through the tunnels, an excavatable grout was required. Also, grout had to be low exotherm in order to not affect the new PVC plumbing.
CJGeo proposed polyurethane grouting for the tunnel abandonment. Polyurethane grouting can be performed in any weather, is low exotherm, and can be placed in very thick lifts. The specific grout chosen was a low exotherm bulk void filling polyurethane.
CJGeo mobilized a polyurethane grouting truck with more than 9000 pounds of polyurethane grout, due to the unknown exact volume of the tunnels. During a 8″ snowstorm, CJGeo abandoned both tunnels in a single day. The unoccupied building was grouted via holes drilled through the floor. The tunnel below the occupied building was free sprayed from inside the tunnel. All tunnels were kept under negative pressure ventilation in order to address installation odors.
CJGeo placed 4100 pounds of polyurethane grout into the two tunnels.
The slab floor inside of a grain import/export facility office settled. All exterior walls were pile-supported, but the floor was poured as slab on grade. Slab settlement up to 3 inches affected approximately half of the building footprint.
Over the years the floor settled, extensive cosmetic repairs were done to the walls, including tuck pointing CMU walls, moving/shimming HVAC ducting, and rerouting water lines. Scheduling for the slab foundation repair had to be done around the busy grain season, when the office building was continuously occupied.
CJGeo proposed polyurethane grouting for the settlement repair. Polyurethane grouting is safe, fast, and economical for floor settlement repair.
CJGeo mobilized two polyurethane grouting crews to the facility on a Saturday morning. The entire 4,000 square foot area was lifted over a period of 9 hours, with no disruption to operations. During lifting, previous cosmetic repairs were undone to facilitate lifting. This included removing extensive patch material from the CMU walls, loosening plumbing connections and adjusting HVAC ductwork.
By mobilizing multiple crews with multiple equipment redundancies, CJGeo was able to ensure that the repair had zero disruptions to the facility and its operations.
The 11″ thick slab floor of a storage shed at a port facility settled up to 6 inches. Exploratory coring & non-destructive imaging (GPR & microgravity) indicated there were extensive voids below the floor.
Previous work on the adjacent bulkhead uncovered extensive voids below the exterior footings (pile-supported) and multiple abandoned, but unfilled, pipes under the floor.
Due to relatively thin voids, which were all less than 6 inches, any void filling grout had to be highly mobile. However, this posed environmental challenges due should the grout make its way into an unfilled abandoned pipe and into the adjacent waterway. The owner did not want to lift the floor, so grouting had to be sufficiently low mobility to prevent runaways, but also fill all voids at an economical hole spacing.
CJGeo proposed polyurethane grouting for this slab foundation repair project. The original design was for a 50/50 mix of polyurethane and cement grouting, CJGeo proposed a valued engineering proposal to perform all grouting with polyurethane. A high density (3.3PCF free rise, 4PCF in place) TerraThane grout was proposed to balance mobility for completeness of fill and reaction time to avoid any runaway loss into the adjacent waterway.
CJGeo mobilized a two reactor polyurethane grouting rig and installed approximately 6300lbs of polyurethane grout over a three day period. Pneumatic rock drills were used to speed drilling.
During a Local Law 11 inspection, the owner of a coop building’s first floor asked the GC to investigate a settled slab floor inside part of the building. The contractor started to open up a 2′ square hole in the floor, and noticed that all the debris was disappearing. After opening the hole it was apparent why–a 2′ to 3′ deep void around the entire perimeter of the building footprint.
Filling a 90CY void under the floor of an operation business can be a challenge anywhere. Complicate it with a 40′ x 10′ laydown area, Mid-Town Manhattan traffic, and cold winter temperatures, and you’ve got quite the challenge.
The presumed cause of settlement was consolidation of poorly placed fill, which was primarily construction debris. Lightweight void filling material was required to minimize future settlement of the underlying fill material.
At the suggestion of an on-staff structural engineer, the general contractor’s project manager reached out to CJGeo about performing polyurethane grouting to fill the voids. CJGeo proposed using a low-exotherm, high mobility bulk void filling foam to fill the voids. 3′ deep voids are too deep to be filled with most polyurethane grouts; a true low exotherm foam is needed for efficiently and safely filling any voids thicker than about 6″. High mobility foams are also critical when filling voids in order to ensure complete coverage.
CJGeo mobilized a two reactor polyurethane grouting rig and installed approximately 4800lbs of 2PCF polyurethane grout over a two day period. CJGeo pulled continuous negative pressure on the void through the floor in order to allow for continuous operation of the facility during grouting. There was zero disruption to the facility’s operations, and the voids were filled completely.
An area of floor inside of a produce processing facility experienced water intrusion through joints in the floor. Considerable amounts of process water were dumped on the floor each day, and unsealed joints in the floor allowed water to collect under the floor slab. With dynamic loading from material handling equipment, water was displaced through the joint onto the floor. The facility’s health & safety staff was concerned that the water could introduce contaminants to the food processing area.
The proposed repair had to perform well in saturated conditions, allow for near immediate resumption of material handler equipment, and ensure a longterm fix. Since no settlement had occurred, the grout material had to be able to seal the very small voids, displace water, and not exert any lifting forces on the floor.
The material & process also had to be performed at cold temperatures–the facility is maintained at 34 degrees year-round.
CJGeo proposed chemical grouting using a hydrophilic prepolymer grout. Chemical grouting is ideal for saturated environments and helps to ensure complete stabilization and sealing of floors.
A single CJGeo chemical grouting crew mobilized to the site and performed the work in a few hours. The work started after second shift, and was completed in time for the grout to set and tolerate material handling equipment at the start of first shift.
The following day, the facility reported no water extrusion under material handler traffic.
The floor of a 105′ diameter grain bin settled. The floor had a bin sweep installed, that was mounted on the top of the unloading tunnel, which ran down the center of the structure. Where the slab floor butted up to the tunnel walls, the floor had settled 2″ on one half, and 3.5″ on the other half. This caused issues with operating the bin sweep, because it was designed for a smooth, level floor.
The owner’s alternative was to remove the entire floor and pour a new floor. This would have been incredibly expensive, and take a very long time. The only access into the bin was two 2′ wide by 4′ tall doors, located 5′ above exterior finish grade, and 2′ above the bin floor elevation.
Due to the nature of the commodity business, mobilization and completion of the grain bin floor repair had to be fast. Additionally, the repair had to return the floor to its original profile, along with the turned down ventilation trenches in the floor. The extensive turned down ventilation troughs made this floor very susceptible to cracking. The floor was 6″ thick, but then went to 24″ thick at the ventilation troughs. Slabs with non-uniform thickness require extreme care and attention to avoid differential lifting.
The design loads for the floor are approximately 3500psf, so the material used for lifting the floor had to be relatively high strength.
CJGeo proposed polyurethane grouting for filling the voids below the floor and lifting it back into place. The minimum bearing capacity of the proposed materials was 5500PSF, ensuring adequate bearing capacity even under full load.
CJGeo mobilized two polyurethane grouting crews to the site. The work was completed over a period of two days, during which more than 7,000 pounds of polyurethane grout were installed using three reactors running simultaneously. Multiple reactors (pumps) helped to ensure thorough lifting of the slab and the ventilation troughs. The crews that completed this job have collectively performed millions of pounds of polyurethane grouting, ensuring successful completion of this grain bin floor repair job.