School Floor Leveling
The Job
This school floor leveling project is located in Princeton, West Virginia. The Princeton Middle School is a slab-on-grade masonry structure and serves approximately 550 students in grades 6 through 8.
The Challenge
The corridor floor in the arts wing settled up to 3.5 inches. A geotechnical investigation found 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.
A hand auger confirmed that the fill material below the slab had consolidated to the point of providing sufficient capacity. So, there was no need for polyurethane compaction grouting, which would have been useful if the soils were still loose.
The Solution
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.
CJGeo used CJGrout 28FDL for this repair. 28FDL is a fast, dry environment lifting foam that works great for lifting bellies out of lightly loaded slabs. There were no water leaks below the slab, there was a significant belly, and the loads were less than one tenth of the grout’s capacity, so it was a great fit. To make sure there weren’t any remaining voids, the crew installed CJGrout 20SDB, which is higher mobility than 28FDL.
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Railroad Sinkhole Stabilization
The Job
This railroad sinkhole stabilization project is located in Martinsburg, West Virginia. During the installation of a 42″ jack & bore casing below a three-track Class 1 railroad, ballast started showing in the spoils. Soon afterward a sinkhole appeared between tracks 2 & 3, 15 feet above the casing. The jack & bore installation was stopped, and the contractor reached out CJGeo requesting an emergency mobilization.
The Challenge
CJGeo had to mobilize with very little notice, and work had to be performed adjacent to an operational track.
The Solution
CJGeo mobilized two polyurethane compaction grouting crews, who were on the road in less than an hour. Within four hours of the sinkhole formation, CJGeo was onsite with more than 250CY of material placement capacity.
CJGeo successfully grouted the sinkhole, using CJGrout 20SDB. Rail traffic continued on adjacent tracks, and the face of the bore was restored, allowing the jack & bore operation to safely restart. CJGeo performed this repair using a polyurethane grout with an elastic modulus similar to the existing soil in order to prevent creating a hard spot in the rail. CJGrout 20SDB was the best fit grout for railroad sinkhole stabilization project because:
- it cures to 95% strength within 15 minutes
- doesn’t impede auger boring
- is highly mobile, so will pass through ballast easily
- doesn’t have lifting capacity, so wouldn’t move the adjacent tracks
- is formulated for bulk placements without charring
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Tunnel Abandonment – Boston
THE JOB
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 CHALLENGE
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 running through the tunnels, an excavatable grout was required. Also, the grout had to be low exotherm in order to not affect the new PVC plumbing.
THE SOLUTION
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 an 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.
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Mine Shaft Abandonment
The Job
This mine shaft abandonment project is located in an area with a significant number of abandoned coal mines. The inverted pyramid concrete cap on a Civil War-era coal mine shaft collapsed catastrophically. The mine shaft was located in the middle of a suburban golf course in Richmond, Virginia. The collapse was due to the deterioration of timbers lining the shaft through soft sandy soils. The soft sandy soils extended approximately 25VF down to rock. As the timbers deteriorated with time, they lost the ability to support the cap.
The Challenge
The tunnel shaft was completely full of water, which was approximately 60 degrees. The area around the cap was very unstable and did not facilitate top-down access over the mine shaft.
The Solution
The repair was designed around drilling well casing at an angle to intercept the mine shaft at various elevations between the bottom of the cap and socketed down into the underlying rock. 3.5PCF hydro insensitive polyurethane grout was chosen for its ability to provide the necessary structural support to the cap.
CJGeo performed pre-mobilization testing at our facility in collaboration with the design engineer to ensure that the grout would perform as desired. CJGeo placed CJGrout 35NHV geotechnical polyurethane through approximately 15 different injection points, grouting from the top down. The end result was a plug extending at least 5′ into the shaft through rock. This plug ensures that the shaft through soft soils is completely stable.
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Office Floor Settlement Repair
The Job
This office floor settlement repair project is located near Norfolk, Virginia. The slab floor inside of a grain import/export facility office sank both differentially and globally. All exterior walls are on driven timber piles, but the floor floats independently of the foundations. Slab settlement up to 3 inches affected approximately half of the building footprint.
The Challenge
Over the roughly 15 years that the floor was settling, maintenance crews were constantly repairing various systems. These repairs were including tuckpointing CMU walls, moving/shimming HVAC ducting, and rerouting water lines.
The foundation repair work on this building couldn’t impact operations. Ship loading and unloading could not be disrupted for any reason. The settled building houses many operations critical to ensuring timely loading and unloading.
The Solution
CJGeo proposed polyurethane grouting for this slab foundation repair project. Polyurethane grouting is safe, fast, and economical for floor settlement repair. Structural polymer grouting is another name for polyurethane grouting. The material of choice was CJGrout 28FDL. 28FDL is optimal for lifting light duty commercial floors experiencing both global and differential settlement.
CJGeo mobilized two polyurethane grouting crews to the facility on a Saturday morning. The 4,000 square foot repair only took nine hours start to finish. There were zero 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.
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Port Shed Floor Stabilization
THE JOB
This port shed floor stabilization project is located in Baltimore, Maryland. 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.
THE CHALLENGE
Due to relatively thin voids, which were all less than 6 inches, and 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.
THE SOLUTION
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. CJGrout 35NHV geotechnical polyurethane 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.
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Commercial Floor Void Fill
THE JOB
This commercial floor void fill project is located in Manhattan. 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 began opening up a 2′ square hole in the floor. During this, all the debris was disappearing. After opening the hole it was apparent why. There was a 2′ to 3′ deep void around the entire perimeter of the building footprint.
THE CHALLENGE
Filling a 90CY void under the floor of an operating 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 cause of settlement was the consolidation of poorly placed fill, which was primarily construction debris. Lightweight void filling material is best to minimize future settlement of the underlying fill material.
THE SOLUTION
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 fill 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. The CJGeo crew installed approximately 4800lbs of CJGrout 20SDB geotechnical polyurethane grout over a two-day period. CJGeo pulled continuous negative pressure on the void through the floor. This was to allow for continuous operation of the facility during grouting. CJGeo’s work didn’t disturb operations at all. All of the voids were completely full of grout at the end of the project. The polyurethane grouting process used here for slab foundation repair is sometimes also called slab jacking or structural polymer grouting.
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Bridge Approach Polymer Grouting
The Job
This bridge approach polymer grouting project is located just outside of Washington, DC. 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.
The Challenge
Our biggest challenge with this project was making sure this heavily populated commuter route was completed in a timely fashion.
The Solution
CJGeo proposed polyurethane compaction grouting using CJGrout 30NHL. CJGrout 30NHL’s design is for improving the bearing capacity of loose soils similarly to cementitious compaction grouting. Grouting is done on 4’ centers, at 5’, 10’ & 15’ below grade. Top-down grouting ensured maximum densification of underlying soils. This grouting program was generally prescriptive, but with ground movement of 0.5 inches cutoff criteria.
CJGeo installed approximately 25,000 pounds of CJGrout 30NHL to increase the bearing capacity of the embankment soils. 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 & post grouting DCP testing showed improvement in soil density.
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Chemical Underpinning
The Job
This chemical underpinning project is located outside of Pittsburgh, Pennsylvania at a manufacturing facility. Water began to seep through the floor of the shop, break room, and bathrooms inside a manufacturing facility. The investigation determined that a water line had broken, and weekend soils below the floor, causing the settlement. Voids were also present below the floor.
The Challenge
The client’s primary concern was addressing the stability of the area without affecting normal usage.
The Solution
CJGeo proposed chemical grouting to stabilize the weakened soils, along with structural polyurethane grouting to fill voids. Previous repairs to address floor settlement had been completed, so a hydro-insensitive undersealing polyurethane grout was used to ensure stability without lifting the slab.
Due to saturated soils, CJGrout 35NHV was the best material for filling voids immediately below the floor. 35NHV is a normal speed, hydro-insensitive geotechnical polyurethane, specifically formulated for void filling applications. It provides high bearing capacity, and minimizes the chance of undesirable lifting during installation.
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RCP Pipe Sealing
THE JOB
This RCP pipe sealing project is located in Wake Forest, North Carolina. The asphalt parking lot over a 300′ run of 54″ RCP culvert kept collapsing. The public works department of the locality determined that the joints between the 4′ sticks of pipe had not been properly gasketed or seated during installation. The pipe saw the continuous flow of a small stream. Flow enters at an end wall and discharges into a box culvert that crosses a public street. The drop inlet at the downstream junction between the RCP culvert and box culvert also had a failed 18″ RCP culvert feeding it. This had been repaired multiple times using open trench excavation.
THE CHALLENGE
The municipality was looking for an affordable, proven, and non-disruptive solution. Replacement would have required removal of a structure, and prevented adjacent businesses from using their parking lot during the work. Relining was not practical due to multiple sewers and water utility lines crossing through the pipe. Significant joint offsets would have also made lining difficult.
Extensive voids were identified around the pipe through an inspection. Much of the water flow from the stream was passing under/outside of the pipe, causing the erosion and collapse of the overhead parking lot, and the floor of a storage building built over the pipe. Previous attempts at sealing the joints and filling voids around the pipe with concrete had failed.
THE SOLUTION
Polyurethane grouting fill voids around the pipe and seal the joints between the individual pieces of pipe, end wall and drop inlet. And, chemical grouting to treat a curtain at the upstream end to reduce subsurface flow, and at the downhill end to stabilize a joint in the failed small diameter RCP culvert entering the drop inlet.
CJGeo polyurethane grouting crews placed 50 cubic yards of CJGrout 35NHV61, hydro insensitive polyurethane and 45 gallons of polyurethane resin chemical grout for an upstream grout curtain over a period of three days to complete the repair. The repairs were all completed without disruption to the adjacent businesses or streets.
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