Fairfax Polyurethane Grouting
The Job
This Fairfax polyurethane grouting project is located at a commercial building used for medical office space in Merrifield, Virginia. The facility is a clinical site for a large regional hospital operator. It houses a primary care and community outreach practice.
The Challenge
The building was built in the 1980s, and will eventually be torn down. However, over the past few years after build out, the floor along the exterior wall settled about 0.75 inches. As the floor settled, the interior finishes along the wall started to cause functional issues for the users. Most of the cabinet and desk drawers were racked and unable to completely close, and office chairs were always trying to roll towards the wall.
The tenant reached out to the owner/property manager, who brought in a forensic structural engineer to investigate the problem and recommend a repair. The structural engineer reached out to CJGeo for recommendations.
Due to the clinic schedule, all demo, grouting, and finish restoration had to be completed in no more than two days. The area of impact is about 1200 square feet.
The Solution
CJGeo recommended CJGrout 28FDL to the structural engineer due to the relatively narrow zone of settlement, and nominal loads due to the light duty use of the space.
A single CJGeo polyurethane grouting crew filled the voids below the floor, lifted back into place and turned it over to the general contractor in fewer than four hours onsite. The general contractor then replaced the VCT and LVP floor tiles that CJGeo drilled through to perform the grouting. The space returned to normal use the following day, without the chairs moving on their own.
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Seawall curtain grouting
The Job
This seawall curtain grouting project is located at a secure facility in North Carolina. It is owned and maintained by the federal government.
The Challenge
The facility is located along a tidal waterway, and has a pre-cast concrete panel seawall protecting it from the adjacent waterway. The soils in the area are beach sand. Numerous sinkholes developed over time at the top of the seawall, which is just over half a mile long. The structure extends up to 17 feet from the cast-in-place cap down to the mud line, with mean high tide roughly six feet below grade. In other areas, the mud line is as close as five feet to below water. The seawall retains an airfield taxiway, runway, and extensive sensitive other infrastructure elements.
The original design for the seawall repair called for performing jet grouting along the entire length of the wall. This caused concerns from an environmental perspective, due to the difficulty in containing highly mobile material behind the wall, and also the equipment required for jet grouting, given extensive sensitive structures adjacent to the wall.
The Solution
CJGeo worked with the general contractor to analyze two different alternative repairs:
- permeation grouting with an acrylic grout
- curtain grouting with geotechnical polyurethane
Based on cost, timeline, and environmental concerns, CJGeo and the general contractor determined that curtain grouting with geotechnical polyurethane was the best alternative to jet grouting. Fundamentally, curtain grouting effectively coats the backside of a wall or structure with plastic, kind of like a waterproofing membrane, but without having to excavate.
Working together, the solution was presented to the owner. The owner determined that the value engineer alternative was preferable to the original design based on:
- water quality risk management – CJGrout 22SHV is certified for potable water contact, and does not contain PFAS. CJGrout 22SHV does not contain any cement, which can quickly change the pH of water, affecting aquatic life
- top side footprint – no drilling equipment is needed in this case. This eliminates obstructions for the airfield operation, and eliminating surface disturbances and surcharge loads on the wall
- cost – the value engineer alternative was accompanied by a savings of approximately $1.7 million
CJGeo mobilized a single polyurethane grouting crew to the site. Over a period of three months, CJGeo successfully performed the seawall curtain grouting work.
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Paved Slope Void Filling
The Job
This paved slope void filling project is located in Interstate 95, near Rocky Mount, North Carolina. The work is part of a bridge rehabilitation for the North Carolina Department of Transportation.
The Challenge
One of the bid items for the project is filling voids below the paved slopes protecting the embankments below the bridge structures. There are two bridges; each carrying two travel lanes over a set of railroad tracks and a rural roadway.
The slopes are quite steep; effectively 1:1. Specifications call for a 3lb/cuft geotechnical polyurethane for the void filling.
The Solution
The general contractor awarded the polyurethane grouting work to CJGeo due to our extensive experience performing geotechnical polyurethane grouting on transportation projects.
CJGeo mobilized a single polyurethane grouting crew to execute the paved slope void filling work. The crew used CJGrout 35NHV geotechnical polyurethane to completely fill all of the voids. Cutoff criteria for the project was cross-hole communication.
Due to the very steep slope, CJGeo installed working platforms and used tie-offs to ensure safety of our crew.
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Jersey Turnpike Polyurethane Grouting
The Job
This Jersey Turnpike polyurethane grouting project is located next to Secaucus Junction in North Jersey. It is part of a larger paving and rehabilitation project. The work location is the exit departure slabs for the 15X tollbooth over Penhorn Creek.
The Challenge
The departure slab (closest to the toll booth) for this structure settled about six inches. The adjacent barrier walls are integrated into an MSE wall, which has an open graded stone reinforced zone. The cause of the settlement is due to consolidation of underlying soft soils, which are prevalent in the area.
Before CJGeo’s involvement in the project, the design engineer consulted with a chemical grout manufacturer representative. This person designed a grouting program to address voids below the pavement and within the underlying soils, up to eight feet below grade.
The Solution
The general contractor awarded the polyurethane grouting work to CJGeo due to our extensive experience performing geotechnical polyurethane grouting on transportation projects.
CJGeo mobilized a single polyurethane grouting crew to execute the plan designed by the chemical grouting manufacturer representative. It took a single crew two onsite shifts to perform about 7200 pounds of polyurethane grouting. The material was equivalent to CJGrout 48NHL.
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North Carolina Polyurethane Grouting
The Job
This North Carolina polyurethane grouting project is located at Elon University. It is part of the Innovation Quad project, being built by Whiting Turner.
The Challenge
The site concrete contractor poured a large set of steps near the entrance of the new building. The steps are approximately thirty feet wide, and have roughly eight feet in rise. The steps are constructed over fill material, including site soils and dense graded crushed aggregate.
During a precipitation event, the grading at the top of the steps directed a significant amount of water towards the top of the steps. The water had nowhere to go other than below the steps. This washed out a significant amount of material, and also caused consolidation of some backfill material.
The Solution
The project’s geotechnical consultant recommended the general contractor reach out to CJGeo to address the voids below the steps. They also recommended performing DCP testing as a minimally invasive way to check the bearing capacity of the underlying materials after the erosion event.
The most suitable polyurethane grout for this project was CJGrout 20SDB. CJGrout 20SDB is a high mobility grout designed specifically for undersealing and bulk void filling, with lifting ability designed out in order to manage risk of displacing the brand new structure.
CJGeo mobilized a single polyurethane grouting crew to the site. They started by performing DCP testing, which uncovered voids within the top three feet of fill material immediately below the steps. The crew used sacrificial tubing to ensure that these voids were completely full, along with the voids immediately below the steps.
Confirmation of fill was material returning to the surface.
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Spillway Undersealing
The Job
This spillway undersealing project is located at a dam in Tuckahoe, Virginia. The dam is owned and maintained by a home owner association, and is approximately 45 years old.
The Challenge
The lake, which is is approximately 7.5 acres, drains through a 24′ RCP pipe that maintains the lake at the lip of a large concrete spillway that only occasionally sees flow. The lake dropped about two feet, which was an immediate cause for concern. A consulting engineer specializing in dams inspected the structure, and determined that a flowpath had opened under the spillway. This flowpath allowed water to drain under the structure at an elevation below the primary outlet.
This obviously caused concerns about the stability of the earthen structure. The consultant recommended that the owner work with CJGeo to perform polyurethane grouting to address the voids and restore flow to its designed routes.
The Solution
CJGeo worked with the consultant to design a polyurethane grouting program to address two different problems:
- water piping along the outside of the concrete-encased 24″ RCP outfall
- bulk voids under the 6″ thick concrete secondary spillway structure
To address the piping along the pipe, CJGeo proposed injecting CJGrout 22SHV geotechnical polyurethane grout along the entire pipe alignment using driven sacrificial tubing. Because the pipe was relatively shallow and the soils relatively soft and uniform, percussion installation of tubing was sufficient, and no sonic drilling was needed.
To address the voids under the larger surface spillway structure, CJGeo also proposed grouting with CJGrout 22SHV geotechnical polyurethane grout. Here, grout installation was through mechanical packers installed in 5/8″ holes drilled through the concrete.
A three person polyurethane grouting crew took less than a day to perform all of the grouting. Confirmation of fill was grout extruding from numerous points at the top and bottom of the spillway, as well as cross-hole communication.
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Collapsed CMP Abandonment
The Job
This collapsed CMP abandonment project is located at a paper mill near Richmond, Virginia. The pipe drains a relatively large area of the site under the primary road into the facility. Onsite personnel noticed that flow through the structure diminished significantly with time.
The Challenge
The first thought was that the pipe had just filled slowly with sediment. To address this, the mill hired a jetting contractor to clean the pipe. The jetting equipment ran into an obstruction inside the 36″ corrugated metal pipe. The obstruction turned out to be a nearly complete collapse.
The mill hired a consulting civil firm to design a replacement crossing, who then reached out to CJGeo for options to abandon the collapsed pipe.
The Solution
The first thought from the consultant was to sonic drill down to the pipe at three locations, drop and grout 2″ PVC pipes in, and install cellular grout through the pipes.
CJGeo thought this could work, but had concerns about the environmental risks. The pipe has quite a bit of fall, so the low end would see quite a bit of head, which increases the likelihood of leaks out of the embankment. These leaks can be hard to predict, and if they occur, very difficult to contain.
CJGeo recommended abandoning the CMP with CJGrout 22SHV geotechnical polyurethane as a lower risk, faster alternative. The consultant agreed with CJGeo’s recommendation to use polyurethane grouting to reduce costs and environmental risks.
CJGeo mobilized a geotechnical polyurethane grouting crew to the site. It took a few hours to fill the pipe. Despite being significantly lighter than the water & muck in the pipe, the CJGrout 22SHV still displaced all of this material because it expands and is only moderately mobile.
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Yonkers Polyurethane Grouting
The Job
This Yonkers polyurethane grouting project is located in Yonkers, New York. The project is part of a renovation of a multi-tenant strip center into a single discount grocery tenant.
The Challenge
During construction, someone on the general contractor’s team thought that areas of the floor sounded hollow. Tapping on the floor, it sounded like a drum. The contractor reached out to CJGeo, and we recommended performing a few cores in the hollow sounding areas.
Coring revealed extensive voids in two areas of the building footprint. Both were along the side exterior walls. In one area of the floor, the voids were up to 4′ deep. The apparent cause for the voids was a longstanding problem with below slab plumbing when the space was a deli and dry cleaner.
The Solution
After the cores were used to confirm the size and extent of the voids, CJGeo recommended CJGrout 20SDB geotechnical polyurethane grout to fill the voids.
CJGrout 20SDB is ideal for filling large voids below floors because it is low exotherm. Many foams used for polyurethane grout are not well suited for filling very large voids.
A plumber installed new sanitary lines below the floor after CJGeo completed the void filling. The void filling only took a single day onsite. It’s important to fill voids first so that cutting new plumbing trenches doesn’t cause catastrophic, unexpected settlement.
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Tunnel Shaft Sinkhole Grouting
The Job
This tunnel shaft sinkhole grouting project is located in Newport News, Virginia. It is located outside the gate for Pier 2 at Newport News Shipbuilding, home to the deactivated USS Enterprise (CVN-65). As part of water and sewer upgrades in the area, multiple shafts were excavated to facilitate guided pilot tube bores.
The Challenge
At a shaft in the middle of an intersection, the dewatering well driller was unable to maintain circulation. This resulted in incomplete dewatering points. During excavation of the ring beam and liner plate shaft, the floor blew out after excavating through a fat clay layer. The fat clay is underlain by a highly permeable flowing sand.
When the floor blew out, the shaft, which is roughly 30 feet diameter, settled up to a foot on one side, and the shaft flooded in a few minutes. Multiple large sinkholes opened up around the perimeter of the shaft.
The Solution
The utility contractor, who was sinking the shaft, reached out to CJGeo for a solution. The only way to salvage the situation was to adequately dewater the site, which was even less possible due to the extensive voids around the shaft.
CJGeo visited the site, and made a few recommendations. First was to grade the site to direct the surface water away from the structure. There were multiple blocks of surface stormwater flowing directly into the area around the shaft. Second was to perform polyurethane compaction grouting around the entire structure to fill voids under the pavement and around the liner plates.
CJGeo mobilized a geotechnical polyurethane grouting crew to the site the following day. Using CJGrout 35NHV61, the crew filled approximately 70 cubic yards of sinkholes. Grout uniformly migrated through the liner plates, indicating that voids were continuous around the perimeter, and across the full depth of the shaft.
After CJGeo completed the grouting work, the dewatering contractor was able to successfully drop four wells around the shaft. By dewatering the underlying flowing sands, the contractor was able to resume excavating the shaft.
A few weeks after stabilizing the shaft, the two tunnels were successfully completed from the shaft. A CJGeo cellular grouting crew then grouted the annular space on both tunnels.
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Penstock Void Grouting
The Job
This penstock void grouting project is located near Hopkinton, New Hampshire. It is located at a small hydroelectric power plant that has been in service for more than 40 years.
The Challenge
This hydro-electric plant’s two original parallel penstocks are wooden. Sometime after original construction, 6.5′ ID steel liners were installed inside the original wooden penstocks.
Typically, when pipes are slip lined, the annular space between the ID of the original pipe and OD of the liner is grouted. However, in this case, the annulus was left open.
The steel pipes are nearing the end of their service life, and require rehabilitation. Plans called for installing a shotcrete liner. Specs called for a cementitious grout with 30 minute working time placement behind the steel pipes prior to spraying shotcrete.
The Solution
The marine contractor performing the shotcrete lining reached out to CJGeo about performing the annular space grouting with cementitious grout. CJGeo’s engineering & operations teams evaluated the project documents and site conditions and determined that there was a very high risk of grout escaping the annulus and making it to the adjacent waterway. This was due to the unknown condition of the original wood penstock, minimal cover over the pipes, and unknown, but potentially open graded backfill material.
CJGeo proposed an alternative, using CJGrout 22SHV geotechnical polyurethane grout to perform the penstock void grouting. CJGeo’s alternative material proposal was accompanied by load calculations from our geotechnical professional engineer confirming that despite strength significantly less than the specification requirement, that CJGrout 22SHV provided multiple factors of safety beyond the actual loads the annulus would see.
Upon approval by the owner’s consulting engineering team, CJGeo mobilized a confined space polyurethane grouting crew to the site. Over two days, the crew successfully grouted the annular space between the steel and wood penstocks. The following day, the contractor began installing reinforcement and prepping the steel pipe surface for shotcrete application.
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