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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Slurry Wall Gap Closure Grouting
The Job
This slurry wall gap closure grouting work is part of CJGeo’s continuing permeation and water control work at the RiverRenew project in Alexandria, Virginia. At an outfall structure that will pull wet weather flow from an existing CSO, which is a roughly 8’x8′ box culvert. It is currently suspended from a large beam and webbing. The beam spans a roughly 40′ wide excavation between two parallel slurry walls. The slurry wall gap is approximately 20 feet wide.
The Challenge
Excavation at this location has continued to uncover seams of highly permeable sand and gravel. The material is quickly recharging due to close proximity to the Potomac River. It also recharges with ground water flowing through the bedding stone below the box culvert from the uphill catchment area.
The Solution
Due to ground-level obstructions, drilling from the surface into the grouting zone isn’t possible. CJGeo designed a percussion-driven sacrificial tubing plan to install the grout. No sonic drilling needed.
The grout curtain is approximately two feet thick. It is fourteen feet deep. It is located about two feet behind the desired face of excavation.
All of the work was done from a mud mat installed by the contractor. Evaluated grouts included:
- colloidal silica grout, which would perform well from a permeation perspective, but likely be susceptible to washout. Colloidal silica would also potentially not perform well during lagging installation due to the friable nature of treated soils, and high groundwater head
- acrylic grout, which has performed very well onsite in previous work.
CJGeo mobilized to the site and completed the permeation grouting over a period of a few daytime shifts. This allowed the contractor to resume excavation within the structure.
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Fort Lauderdale Permeation Grouting
The Job
This Fort Lauderdale permeation grouting project is located next to Port Everglades. Port Everglades is a crucial piece of Florida’s infrastructure, with annual economic impact exceeding $30 billion dollars per year. The tunnel, which is being mined with a 72″ MTBM, crosses under Eisenhower Boulevard from the George T Lohmeyer Wastewater Treatment Plant towards the Broward County Convention Center.
The tunnel is more than 20′ below grade, below the water table, in limestone with pockets of silty sand.
The Challenge
On this project, the microtunneling contractor had two tunnel crossings. On the first, they elected to not pre-grout their break in & break outs through the SOE. This resulted in a significant water and soil inflow event during the first break in. This crossing, under the entrance to the cruise port and between two other pieces of critical infrastructure, would not tolerate any surface disturbances associated with a flooding event.
The contractor reached out to CJGeo about stabilizing the launch & retrieval shafts to ensure stability during the launch & retrieval processes, by performing permeation grouting.
The Solution
CJGeo proposed permeation grouting of the limestone with an acrylic grout to ensure stability of the launch & retrieval shafts. Permeation grouting with acrylic grout ensures uniform permeation, and displacement of groundwater. It also ensures that the soils are sufficiently bound together to not fail while cutting the launch & retrieval holes in the sheet pile.
CJGeo installed the sacrificial tubing for this installation from the shaft. Occasionally, sonic drilling is useful for pre-grouting, but in this case, it was more economical and less disruptive to go through the shaft walls.
CJGeo performed the permeation grouting work in a single shift at each shaft.
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T Wall Lightweight Backfill
The Job
This T wall lightweight backfill project is located in Boston, Massachusetts. The bridge is located on the Lowell Line, within the MBTA‘s Commuter Rail Maintenance Facility.
The Challenge
CJGeo has been involved in this alternative delivery project since 2020, helping to optimize the use of CJFill-Ultra Lightweight fill to facilitate constructing a new embankment over underlying compressible soils.
In this specific location on the project, curved T walls were installed along the curved alignment (different radius) of the existing embankment. A sheet pile SOE retains the existing embankment. Due to highly irregular spaces, limited access, lightweight aggregate, such as foamed glass, would be exceptionally difficult to install and ensure adequate compaction.
The Solution
CJGeo proposed 26lb/cuft CJFill-Ultra Lightweight as the optimal material for the T wall lightweight backfill. The lowest 4′ is CJFill-High Permeability. Because CJFill is a self consolidating fill, there’s no compaction required. This practically eliminates chances of backfill consolidation. On a curved, relatively high speed commuter rail alignment, settlement could be quite risky if it were to occur.
For the first phase, CJGeo mobilized a single dry batch cellular grout plant. The work took a total of five days.
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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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TBM Intervention Permeation Grouting
The Job
This TBM intervention permeation grouting project is located in Virginia. It is part of a highway tunnel installation project to increase capacity on a bridge tunnel.
The Challenge
During mining, the TBM, which is more than 40′ in diameter, began to pull pieces of sheet pile & wire rope through the face. To prevent further damage to the machine, tunneling was stopped. The machine encountered the debris approximately 250 feet short of the exit structure, underneath a constructed island.
The island is built out of relatively loose beach sand that’s commonly available in the area. The crown of the machine is approximately 25′ below grade, with the invert of the machine being about 70 feet below grade. Mean high tide is also about 25′ below grade.
In order to facilitate a hyperbaric intervention, the contractor needed a solid plug in front of and around the machine face. The criteria for the plug included:
- easily excavatable, to prevent issues for the TBM upon resumption of mining, and also to ensure that divers doing the hyperbaric intervention wouldn’t have issues removing grouted material in the case of grout entry into the machine face.
- low viscosity, to ensure uniform permeation into the soils in front of the machine, though they were relatively course (only 1% fines)
- readily available, in order to meet the incredibly short schedule requirement
The Solution
CJGeo proposed permeation grouting to create the plug using acrylic grout. Acrylic grout is:
- readily available through the mining supply chain
- very low viscosity, so well suited for permeating sands
- forms a stiff gel that’s stable, but still easily hand-excavatable
To perform permeation grouting up to 75 feet below grade, CJGeo proposed sonic drilling to install Tube-a-Manchette (TAM) pipes.
Due to the compressed timeframe, CJGeo subcontracted a sonic driller to install 86 different TAM wells, ranging from 25 to 75 feet deep. Once the first 10 TAM tubes were in place, CJGeo started placing acrylic grout through up to 10 simultaneous TAM pipes, using straddle packers and a PLC-controlled grouting system.
CJGeo was onsite within 10 days of the first call. Then, over 23 calendar days, CJGeo successfully installed more than 85,000 gallons of acrylic grout, at rates of nearly 15 gallons per minute.
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Hobas Pipe Backfilling
The Job
This Hobas pipe backfilling project is located in Baltimore, Maryland. It is one of the last steps in an emergency storm drain collapse project.
The Challenge
The original design for this project was to slip line a roughly 100 linear foot length of 108″ brick sewer that had collapsed. There was a massive void above the pipe, which was going to be filled with CJFill-Ultra Lightweight after the new pipe was slid in. However, the soil collapsed and the repair turned into an open cut repair.
The pipe is more than 100 years old, and was installed in a rock trench, the walls of which were uneven and unstable. Extensive rock bolting and stabilization was installed to facilitate the installation of the pipe. In order to ensure uniform bedding and stability of the new pipe, Hobas and the EOR recommended backfilling the pipe to at least 1′ above the crown with self-consolidating fill.
150lb/cuft flowable fill would have resulted in tremendous uplift forces on the pipe, unless installed in impracticably thin layers.
The Solution
CJGeo proposed cellular grout as an alternative, in order to reduce the uplift while decreasing the number of lifts.
Due to water infiltration near the invert, the first lift was done using 65lb/cuft CJFill-Under Water. Once the first lift was in place, the placement was switched to CJFill-Standard.
All material was generated onsite from bulk cement using CJGeo’s colloidal dry batch generation process.
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